"""Project-bound, read-only graph visualization over a validated DocForge index."""

from __future__ import annotations

import atexit
import json
import os
import secrets
import socket
import sqlite3
import subprocess
import sys
import threading
import urllib.parse
from collections.abc import Generator
from contextlib import contextmanager
from http import HTTPStatus
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
from pathlib import Path
from time import monotonic

from .errors import DocForgeError
from .index import APPLICATION_ID, INDEX_SCHEMA_VERSION, ProjectIndex, re_tokenize

VISUALIZATION_TEMPLATE = "graph-browser@5"
DEFAULT_EDGE_LIMIT = 100
MAX_EDGE_LIMIT = 400
DEFAULT_INITIAL_GRACE_SECONDS = 120.0
DEFAULT_LEASE_SECONDS = 180.0
LEASE_MONITOR_INTERVAL_SECONDS = 1.0


class _VisualizationHttpServer(ThreadingHTTPServer):
    daemon_threads = True
    allow_reuse_address = False


class VisualizationIndexSnapshot:
    """Fast read model pinned to one index file validated by ``ProjectIndex.check``."""

    _IDENTITY_KEYS = (
        "project_id",
        "project_root_fingerprint",
        "revision",
        "source_hash",
        "adapter",
        "node_count",
        "edge_count",
    )

    def __init__(self, index: ProjectIndex, checked: dict[str, object]) -> None:
        self.path = index.path
        self.title = index.project.descriptor.title
        self.max_query_chars = index.project.descriptor.limits.max_query_chars
        self.max_results = index.project.descriptor.limits.max_results
        self.max_depth = index.project.descriptor.limits.max_traversal_depth
        self.identity = {key: checked[key] for key in self._IDENTITY_KEYS}
        self._stat = self._safe_stat()

    @classmethod
    def from_spec(cls, spec: dict[str, object]) -> VisualizationIndexSnapshot:
        snapshot = cls.__new__(cls)
        snapshot.path = Path(str(spec["path"]))
        snapshot.title = str(spec["title"])
        snapshot.max_query_chars = int(spec["max_query_chars"])
        snapshot.max_results = int(spec["max_results"])
        snapshot.max_depth = int(spec["max_depth"])
        identity = spec["identity"]
        if not isinstance(identity, dict):
            raise DocForgeError("invalid_index", "Visualization identity is invalid")
        snapshot.identity = {key: identity[key] for key in cls._IDENTITY_KEYS}
        snapshot._stat = snapshot._safe_stat()
        return snapshot

    def spec(self) -> dict[str, object]:
        return {
            "path": str(self.path),
            "title": self.title,
            "max_query_chars": self.max_query_chars,
            "max_results": self.max_results,
            "max_depth": self.max_depth,
            "identity": dict(self.identity),
        }

    def overview(self) -> dict[str, object]:
        with self._connection() as connection:
            return self._result(
                title=self.title,
                node_count=connection.execute("SELECT COUNT(*) FROM nodes").fetchone()[0],
                edge_count=connection.execute("SELECT COUNT(*) FROM edges").fetchone()[0],
                families=_facet_rows(connection, "nodes", "family"),
                authorities=_facet_rows(connection, "nodes", "authority"),
                statuses=_facet_rows(connection, "nodes", "status"),
                relations=_facet_rows(connection, "edges", "relation"),
                max_results=self.max_results,
                snapshot=True,
            )

    def search(
        self,
        *,
        query: str,
        family: str | None,
        limit: int,
    ) -> dict[str, object]:
        bounded = self._bounded_limit(limit)
        with self._connection() as connection:
            if query:
                if len(query) > self.max_query_chars:
                    raise DocForgeError(
                        "invalid_query", "Search query exceeds the configured limit"
                    )
                terms = re_tokenize(query)
                if not terms:
                    raise DocForgeError("invalid_query", "Search query contains no searchable text")
                expression = " AND ".join(
                    f'"{term.replace(chr(34), chr(34) * 2)}"' for term in terms
                )
                family_clause = "AND nodes.family = ?" if family else ""
                values: tuple[object, ...] = (
                    (expression, family, bounded) if family else (expression, bounded)
                )
                rows = connection.execute(
                    """
                    SELECT nodes.*, bm25(node_fts) AS rank,
                           snippet(node_fts, 3, '[', ']', ' … ', 18) AS snippet
                    FROM node_fts JOIN nodes USING(node_id)
                    WHERE node_fts MATCH ?
                    """
                    + family_clause
                    + " ORDER BY rank, nodes.node_id LIMIT ?",
                    values,
                ).fetchall()
                results = []
                for row in rows:
                    item = _node_dict(row, include_content=False)
                    item.update({"rank": row["rank"], "snippet": row["snippet"]})
                    results.append(item)
            else:
                family_clause = "WHERE family = ?" if family else ""
                values = (family, bounded) if family else (bounded,)
                rows = connection.execute(
                    f"SELECT * FROM nodes {family_clause} ORDER BY node_id LIMIT ?",
                    values,
                ).fetchall()
                results = [_node_dict(row, include_content=False) for row in rows]
        return self._result(
            query=query,
            family=family,
            count=len(results),
            results=results,
            snapshot=True,
        )

    def node(self, node_id: str, *, depth: int, limit: int) -> dict[str, object]:
        if type(depth) is not int or depth < 1 or depth > self.max_depth:
            raise DocForgeError("invalid_depth", "Traversal depth is outside the configured limit")
        if type(limit) is not int or limit < 1 or limit > MAX_EDGE_LIMIT:
            raise DocForgeError(
                "invalid_limit",
                "Visualization edge limit exceeds the fixed safety boundary",
                maximum=MAX_EDGE_LIMIT,
            )
        with self._connection() as connection:
            root_row = connection.execute(
                "SELECT * FROM nodes WHERE node_id = ?", (node_id,)
            ).fetchone()
            if root_row is None:
                raise DocForgeError(
                    "missing_node",
                    "No node has the requested stable ID",
                    node_id=node_id,
                )
            visited = {node_id}
            frontier = {node_id}
            selected: list[dict[str, str]] = []
            selected_keys: set[tuple[str, str, str]] = set()
            truncated = False
            for _ in range(depth):
                if not frontier or len(selected) >= limit:
                    break
                placeholders = ",".join("?" for _ in frontier)
                values = tuple(sorted(frontier))
                rows = connection.execute(
                    "SELECT source_id, relation, target_id FROM edges "
                    f"WHERE source_id IN ({placeholders}) OR target_id IN ({placeholders}) "
                    "ORDER BY source_id, relation, target_id LIMIT ?",
                    (*values, *values, limit + 1),
                ).fetchall()
                next_frontier: set[str] = set()
                for row in rows:
                    key = (row["source_id"], row["relation"], row["target_id"])
                    if key in selected_keys:
                        continue
                    if len(selected) >= limit:
                        truncated = True
                        break
                    selected_keys.add(key)
                    edge = {
                        "source_id": row["source_id"],
                        "relation": row["relation"],
                        "target_id": row["target_id"],
                    }
                    selected.append(edge)
                    for candidate in (edge["source_id"], edge["target_id"]):
                        if candidate not in visited:
                            visited.add(candidate)
                            next_frontier.add(candidate)
                frontier = next_frontier
            placeholders = ",".join("?" for _ in visited)
            node_rows = connection.execute(
                f"SELECT * FROM nodes WHERE node_id IN ({placeholders}) ORDER BY node_id",
                tuple(sorted(visited)),
            ).fetchall()
        return self._result(
            root=node_id,
            depth=depth,
            edge_limit=limit,
            truncated=truncated,
            node=_node_dict(root_row),
            nodes=[_node_dict(row, include_content=False) for row in node_rows],
            edges=selected,
            snapshot=True,
        )

    def require_node(self, node_id: str) -> None:
        with self._connection() as connection:
            row = connection.execute("SELECT 1 FROM nodes WHERE node_id = ?", (node_id,)).fetchone()
        if row is None:
            raise DocForgeError(
                "missing_node",
                "No node has the requested stable ID",
                node_id=node_id,
            )

    def _bounded_limit(self, value: int) -> int:
        if type(value) is not int or value < 1 or value > self.max_results:
            raise DocForgeError("invalid_limit", "Result limit is outside the configured range")
        return value

    def _safe_stat(self) -> tuple[int, int, int, int]:
        if (
            self.path.is_symlink()
            or not self.path.is_file()
            or self.path.resolve(strict=True) != self.path
        ):
            raise DocForgeError("missing_index", "Validated visualization index is unavailable")
        stat = self.path.stat()
        return (stat.st_dev, stat.st_ino, stat.st_size, stat.st_mtime_ns)

    @contextmanager
    def _connection(self) -> Generator[sqlite3.Connection, None, None]:
        if self._safe_stat() != self._stat:
            raise DocForgeError(
                "visualization_stale",
                "The validated index changed; invoke docforge_visualize again",
            )
        connection: sqlite3.Connection | None = None
        try:
            connection = sqlite3.connect(f"file:{self.path}?mode=ro", uri=True)
            connection.row_factory = sqlite3.Row
            application_id = connection.execute("PRAGMA application_id").fetchone()[0]
            schema_version = connection.execute("PRAGMA user_version").fetchone()[0]
            if application_id != APPLICATION_ID or schema_version != INDEX_SCHEMA_VERSION:
                raise DocForgeError(
                    "invalid_index", "Visualization index has an unsupported schema"
                )
            metadata = dict(connection.execute("SELECT key, value FROM metadata"))
            if any(metadata.get(key) != str(value) for key, value in self.identity.items()):
                raise DocForgeError(
                    "visualization_stale",
                    "The validated index identity changed; invoke docforge_visualize again",
                )
            yield connection
            if self._safe_stat() != self._stat:
                raise DocForgeError(
                    "visualization_stale",
                    "The validated index changed during the request",
                )
        except DocForgeError:
            raise
        except (json.JSONDecodeError, KeyError, sqlite3.Error, TypeError) as error:
            raise DocForgeError(
                "invalid_index", "Visualization index is corrupt or unreadable"
            ) from error
        finally:
            if connection is not None:
                connection.close()

    def _result(self, **payload: object) -> dict[str, object]:
        return {
            "status": "ok",
            **self.identity,
            **payload,
        }


class VisualizationRunner:
    """Start one token-protected loopback reader for one immutable project binding."""

    def __init__(
        self,
        index: ProjectIndex | None,
        *,
        snapshot_spec: dict[str, object] | None = None,
        token: str | None = None,
        register_atexit: bool = True,
        initial_grace_seconds: float = DEFAULT_INITIAL_GRACE_SECONDS,
        lease_seconds: float = DEFAULT_LEASE_SECONDS,
        monitor_interval_seconds: float = LEASE_MONITOR_INTERVAL_SECONDS,
    ) -> None:
        if (index is None) == (snapshot_spec is None):
            raise ValueError("Provide exactly one visualization index or snapshot")
        if initial_grace_seconds <= 0 or lease_seconds <= 0 or monitor_interval_seconds <= 0:
            raise ValueError("Visualization lease durations must be positive")
        self.index = index
        self._snapshot_spec = snapshot_spec
        self._register_atexit = register_atexit
        self.initial_grace_seconds = initial_grace_seconds
        self.lease_seconds = lease_seconds
        self.monitor_interval_seconds = monitor_interval_seconds
        self._lock = threading.Lock()
        self._token = token or secrets.token_urlsafe(24)
        self._server: _VisualizationHttpServer | None = None
        self._thread: threading.Thread | None = None
        self._lease_thread: threading.Thread | None = None
        self._lease_stop = threading.Event()
        self._lease_last_activity = monotonic()
        self._lease_connected = False
        self._atexit_registered = False
        self._reader: VisualizationIndexSnapshot | None = None

    def start(
        self,
        *,
        node_id: str | None = None,
        query: str | None = None,
        depth: int = 1,
    ) -> dict[str, object]:
        if node_id is not None and query is not None:
            raise DocForgeError(
                "invalid_visualization_target",
                "Choose either one exact node ID or one search query",
            )
        reader = (
            VisualizationIndexSnapshot(self.index, self.index.check())
            if self.index is not None
            else VisualizationIndexSnapshot.from_spec(self._snapshot_spec or {})
        )
        maximum_depth = reader.max_depth
        if type(depth) is not int or depth < 1 or depth > maximum_depth:
            raise DocForgeError(
                "invalid_depth",
                "Visualization depth is outside the configured traversal limit",
            )
        if node_id is not None:
            reader.require_node(node_id)
        elif query is not None:
            reader.search(query=query, family=None, limit=1)

        with self._lock:
            self._reader = reader
            if self._server is None:
                runner = self

                class Handler(BaseHTTPRequestHandler):
                    def do_GET(self) -> None:  # noqa: N802
                        runner._handle_get(self)

                    def do_HEAD(self) -> None:  # noqa: N802
                        runner._handle_get(self, include_body=False)

                    def do_POST(self) -> None:  # noqa: N802
                        runner._respond_error(
                            self,
                            HTTPStatus.METHOD_NOT_ALLOWED,
                            "method_not_allowed",
                            "The visualization service is read-only",
                        )

                    def do_PUT(self) -> None:  # noqa: N802
                        self.do_POST()

                    def do_PATCH(self) -> None:  # noqa: N802
                        self.do_POST()

                    def do_DELETE(self) -> None:  # noqa: N802
                        self.do_POST()

                    def log_message(self, _format: str, *_args: object) -> None:
                        return

                self._server = _VisualizationHttpServer(("127.0.0.1", 0), Handler)
                self._lease_last_activity = monotonic()
                self._lease_connected = False
                self._lease_stop.clear()
                self._thread = threading.Thread(
                    target=self._server.serve_forever,
                    name="docforge-visualization",
                    daemon=False,
                )
                self._thread.start()
                self._lease_thread = threading.Thread(
                    target=self._monitor_lease,
                    name="docforge-visualization-lease",
                    daemon=True,
                )
                self._lease_thread.start()
                if self._register_atexit and not self._atexit_registered:
                    atexit.register(self.stop)
                    self._atexit_registered = True

            server = self._server
            assert server is not None
            port = int(server.server_address[1])

        parameters: dict[str, str] = {"depth": str(depth)}
        if node_id is not None:
            parameters["node"] = node_id
        if query is not None:
            parameters["q"] = query
        query_string = urllib.parse.urlencode(parameters)
        url = f"http://127.0.0.1:{port}/{self._token}/"
        if query_string:
            url = f"{url}?{query_string}"
        return {
            "state": "running",
            "url": url,
            "bind": "127.0.0.1",
            "port": port,
            "template": VISUALIZATION_TEMPLATE,
            "read_only": True,
            "project_bound": True,
            "lifetime": {
                "policy": "browser_lease",
                "initial_grace_seconds": self.initial_grace_seconds,
                "lease_seconds": self.lease_seconds,
            },
            "target": {
                "node_id": node_id,
                "query": query,
                "depth": depth,
            },
            "snapshot": dict(reader.identity),
        }

    def stop(self) -> None:
        with self._lock:
            server = self._server
            thread = self._thread
            self._server = None
            self._thread = None
            self._lease_thread = None
            self._reader = None
            self._lease_stop.set()
        if server is None:
            return
        server.shutdown()
        server.server_close()
        if thread is not None and thread is not threading.current_thread():
            thread.join(timeout=2)

    def is_running(self) -> bool:
        with self._lock:
            return self._server is not None

    def _touch_lease(self) -> None:
        with self._lock:
            if self._server is None:
                return
            self._lease_last_activity = monotonic()
            self._lease_connected = True

    def _monitor_lease(self) -> None:
        while not self._lease_stop.wait(self.monitor_interval_seconds):
            with self._lock:
                if self._server is None:
                    return
                timeout = (
                    self.lease_seconds if self._lease_connected else self.initial_grace_seconds
                )
                expired = monotonic() - self._lease_last_activity >= timeout
            if expired:
                self.stop()
                return

    def _handle_get(self, handler: BaseHTTPRequestHandler, *, include_body: bool = True) -> None:
        parsed = urllib.parse.urlparse(handler.path)
        prefix = f"/{self._token}"
        if parsed.path not in {prefix, f"{prefix}/"} and not parsed.path.startswith(
            f"{prefix}/api/"
        ):
            self._respond_error(
                handler,
                HTTPStatus.NOT_FOUND,
                "not_found",
                "Not found",
                include_body=include_body,
            )
            return
        self._touch_lease()
        if parsed.path in {prefix, f"{prefix}/"}:
            self._respond(
                handler,
                _GRAPH_BROWSER_HTML.encode("utf-8"),
                "text/html; charset=utf-8",
                include_body=include_body,
            )
            return

        try:
            params = urllib.parse.parse_qs(parsed.query, keep_blank_values=True)
            reader = self._current_reader()
            if parsed.path == f"{prefix}/api/overview":
                payload = reader.overview()
            elif parsed.path == f"{prefix}/api/heartbeat":
                payload = reader._result(
                    viewer="alive",
                    lease_seconds=self.lease_seconds,
                )
            elif parsed.path == f"{prefix}/api/search":
                payload = self._search(reader, params)
            elif parsed.path == f"{prefix}/api/node":
                payload = self._node(reader, params)
            else:
                self._respond_error(
                    handler,
                    HTTPStatus.NOT_FOUND,
                    "not_found",
                    "Not found",
                    include_body=include_body,
                )
                return
        except DocForgeError as error:
            status = {
                "missing_node": HTTPStatus.NOT_FOUND,
                "stale_index": HTTPStatus.CONFLICT,
                "source_changed": HTTPStatus.CONFLICT,
                "stale_adapter_source": HTTPStatus.CONFLICT,
                "visualization_stale": HTTPStatus.CONFLICT,
                "invalid_query": HTTPStatus.BAD_REQUEST,
                "invalid_depth": HTTPStatus.BAD_REQUEST,
                "invalid_limit": HTTPStatus.BAD_REQUEST,
            }.get(error.code, HTTPStatus.SERVICE_UNAVAILABLE)
            self._respond_json(
                handler,
                {"status": "error", "error": error.as_dict()},
                status=status,
                include_body=include_body,
            )
            return
        except (TypeError, ValueError):
            self._respond_error(
                handler,
                HTTPStatus.BAD_REQUEST,
                "invalid_request",
                "Request parameters are invalid",
                include_body=include_body,
            )
            return
        self._respond_json(handler, payload, include_body=include_body)

    def _search(
        self,
        reader: VisualizationIndexSnapshot,
        params: dict[str, list[str]],
    ) -> dict[str, object]:
        query = _one(params, "q").strip()
        family = _one(params, "family").strip() or None
        limit = _integer(_one(params, "limit") or "50")
        return reader.search(query=query, family=family, limit=limit)

    def _node(
        self,
        reader: VisualizationIndexSnapshot,
        params: dict[str, list[str]],
    ) -> dict[str, object]:
        node_id = _one(params, "id").strip()
        if not node_id:
            raise DocForgeError("missing_node", "One exact node ID is required")
        depth = _integer(_one(params, "depth") or "1")
        limit = _integer(_one(params, "limit") or str(DEFAULT_EDGE_LIMIT))
        if limit > MAX_EDGE_LIMIT:
            raise DocForgeError(
                "invalid_limit",
                "Visualization edge limit exceeds the fixed safety boundary",
                maximum=MAX_EDGE_LIMIT,
            )
        return reader.node(node_id, depth=depth, limit=limit)

    def _current_reader(self) -> VisualizationIndexSnapshot:
        with self._lock:
            reader = self._reader
        if reader is None:
            raise DocForgeError(
                "visualization_unavailable",
                "The visualization snapshot is unavailable",
            )
        return reader

    @staticmethod
    def _respond(
        handler: BaseHTTPRequestHandler,
        payload: bytes,
        content_type: str,
        *,
        status: HTTPStatus = HTTPStatus.OK,
        include_body: bool = True,
    ) -> None:
        handler.send_response(status)
        handler.send_header("Content-Type", content_type)
        handler.send_header("Content-Length", str(len(payload)))
        handler.send_header("Cache-Control", "no-store")
        handler.send_header(
            "Content-Security-Policy",
            "default-src 'none'; script-src 'unsafe-inline'; style-src 'unsafe-inline'; "
            "connect-src 'self'; img-src 'self' data:; base-uri 'none'; form-action 'none'; "
            "frame-ancestors 'none'",
        )
        handler.send_header("X-Content-Type-Options", "nosniff")
        handler.send_header("X-Frame-Options", "DENY")
        handler.send_header("Referrer-Policy", "no-referrer")
        handler.end_headers()
        if include_body:
            handler.wfile.write(payload)

    @classmethod
    def _respond_json(
        cls,
        handler: BaseHTTPRequestHandler,
        body: dict[str, object],
        *,
        status: HTTPStatus = HTTPStatus.OK,
        include_body: bool = True,
    ) -> None:
        cls._respond(
            handler,
            json.dumps(body, sort_keys=True, separators=(",", ":")).encode("utf-8"),
            "application/json; charset=utf-8",
            status=status,
            include_body=include_body,
        )

    @classmethod
    def _respond_error(
        cls,
        handler: BaseHTTPRequestHandler,
        status: HTTPStatus,
        code: str,
        message: str,
        *,
        include_body: bool = True,
    ) -> None:
        cls._respond_json(
            handler,
            {
                "status": "error",
                "error": {"code": code, "message": message, "details": {}},
            },
            status=status,
            include_body=include_body,
        )


class DetachedVisualizationRunner:
    """Launch a viewer worker that survives a short-lived MCP transport process."""

    def __init__(
        self,
        index: ProjectIndex,
        *,
        initial_grace_seconds: float = DEFAULT_INITIAL_GRACE_SECONDS,
        lease_seconds: float = DEFAULT_LEASE_SECONDS,
        monitor_interval_seconds: float = LEASE_MONITOR_INTERVAL_SECONDS,
    ) -> None:
        self.index = index
        self.initial_grace_seconds = initial_grace_seconds
        self.lease_seconds = lease_seconds
        self.monitor_interval_seconds = monitor_interval_seconds
        self._process: subprocess.Popen[bytes] | None = None

    def start(
        self,
        *,
        node_id: str | None = None,
        query: str | None = None,
        depth: int = 1,
    ) -> dict[str, object]:
        if node_id is not None and query is not None:
            raise DocForgeError(
                "invalid_visualization_target",
                "Choose either one exact node ID or one search query",
            )
        snapshot = VisualizationIndexSnapshot(self.index, self.index.check())
        if type(depth) is not int or depth < 1 or depth > snapshot.max_depth:
            raise DocForgeError(
                "invalid_depth",
                "Visualization depth is outside the configured traversal limit",
            )
        if node_id is not None:
            snapshot.require_node(node_id)
        elif query is not None:
            snapshot.search(query=query, family=None, limit=1)

        self.stop()
        parent_socket, child_socket = socket.socketpair()
        try:
            command = (
                sys.executable,
                "-m",
                "docforge.visualization_worker",
                "--control-fd",
                str(child_socket.fileno()),
            )
            process = subprocess.Popen(
                command,
                stdin=subprocess.DEVNULL,
                stdout=subprocess.DEVNULL,
                stderr=subprocess.DEVNULL,
                close_fds=True,
                pass_fds=(child_socket.fileno(),),
                start_new_session=True,
            )
            self._process = process
            child_socket.close()
            request = {
                "snapshot": snapshot.spec(),
                "token": secrets.token_urlsafe(24),
                "initial_grace_seconds": self.initial_grace_seconds,
                "lease_seconds": self.lease_seconds,
                "monitor_interval_seconds": self.monitor_interval_seconds,
                "owner_pid": os.getppid(),
                "target": {
                    "node_id": node_id,
                    "query": query,
                    "depth": depth,
                },
            }
            parent_socket.settimeout(10)
            parent_socket.sendall(
                json.dumps(request, sort_keys=True, separators=(",", ":")).encode("utf-8") + b"\n"
            )
            response = _receive_worker_response(parent_socket)
        except (OSError, subprocess.SubprocessError, ValueError) as error:
            self.stop()
            raise DocForgeError(
                "visualization_unavailable",
                "The detached visualization worker failed to start",
            ) from error
        finally:
            child_socket.close()
            parent_socket.close()

        if response.get("status") != "ok" or not isinstance(response.get("visualization"), dict):
            self.stop()
            raise DocForgeError(
                "visualization_unavailable",
                "The detached visualization worker rejected the snapshot",
            )
        return response["visualization"]

    def stop(self) -> None:
        process = self._process
        self._process = None
        if process is None or process.poll() is not None:
            return
        process.terminate()
        try:
            process.wait(timeout=2)
        except subprocess.TimeoutExpired:
            process.kill()
            process.wait(timeout=2)


def _receive_worker_response(control: socket.socket) -> dict[str, object]:
    chunks: list[bytes] = []
    size = 0
    while True:
        chunk = control.recv(65536)
        if not chunk:
            break
        chunks.append(chunk)
        size += len(chunk)
        if size > 1_000_000:
            raise ValueError("Visualization worker response exceeded its fixed boundary")
        if b"\n" in chunk:
            break
    payload = b"".join(chunks).split(b"\n", 1)[0]
    result = json.loads(payload)
    if not isinstance(result, dict):
        raise ValueError("Visualization worker returned an invalid response")
    return result


def _one(params: dict[str, list[str]], name: str) -> str:
    values = params.get(name) or [""]
    return values[0]


def _integer(value: str) -> int:
    return int(value)


def _node_dict(row: sqlite3.Row, *, include_content: bool = True) -> dict[str, object]:
    result = {
        "node_id": row["node_id"],
        "title": row["title"],
        "family": row["family"],
        "authority": row["authority"],
        "status": row["status"],
        "tags": json.loads(row["tags_json"]),
        "summary": row["summary"],
        "source_path": row["source_path"],
        "source_anchor": row["source_anchor"],
        "content_hash": row["content_hash"],
    }
    if include_content:
        result["content"] = row["content"]
    return result


def _facet_rows(connection: sqlite3.Connection, table: str, column: str) -> list[dict[str, object]]:
    allowed = {
        ("nodes", "family"),
        ("nodes", "authority"),
        ("nodes", "status"),
        ("edges", "relation"),
    }
    if (table, column) not in allowed:
        raise DocForgeError("invalid_index", "Unsupported visualization facet")
    rows = connection.execute(
        f"SELECT {column}, COUNT(*) AS count FROM {table} "
        f"GROUP BY {column} ORDER BY count DESC, {column}"
    ).fetchall()
    return [{"value": row[0], "count": row[1]} for row in rows]


_GRAPH_BROWSER_HTML = r"""<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>DocForge graph</title>
  <style>
    :root {
      color-scheme: dark;
      --bg: #07101a;
      --panel: #0c1825;
      --panel-2: #111f2f;
      --line: #263b51;
      --text: #ecf5ff;
      --muted: #93abc3;
      --accent: #51d7ff;
      --accent-2: #8fffc5;
      --warn: #ffd27a;
      --left-width: 310px;
      --right-width: 350px;
      --primary-fill: #176b7d;
      --primary-stroke: #83e8ff;
      --child-fill: #216c51;
      --child-stroke: #91f2bd;
      --edge-fill: #634580;
      --edge-stroke: #d0a7ff;
      font: 14px/1.45 Inter, ui-sans-serif, system-ui, sans-serif;
    }
    * { box-sizing: border-box; }
    body { margin: 0; min-height: 100vh; background: var(--bg); color: var(--text); }
    button, input, select { font: inherit; }
    button { cursor: pointer; }
    code, pre { font-family: ui-monospace, SFMono-Regular, Consolas, monospace; }
    .app { display: grid; grid-template-rows: auto 1fr; min-height: 100vh; }
    header {
      display: flex; gap: 18px; align-items: center; padding: 14px 18px;
      border-bottom: 1px solid var(--line); background: rgba(8, 18, 30, .96);
    }
    header h1 { margin: 0; font-size: 17px; }
    .stats { display: flex; gap: 14px; color: var(--muted); }
    .status { margin-left: auto; color: var(--muted); }
    .layout {
      min-height: 0; display: grid;
      grid-template-columns: var(--left-width) 7px minmax(360px, 1fr) 7px var(--right-width);
    }
    aside { min-height: 0; overflow: auto; padding: 16px; background: var(--panel); }
    .panel-resizer {
      position: relative; z-index: 4; min-height: 0; background: #0a1521;
      cursor: col-resize; touch-action: none;
    }
    .panel-resizer::after {
      content: ""; position: absolute; inset: 0 2px; background: var(--line);
      transition: background .15s;
    }
    .panel-resizer:hover::after, .panel-resizer:focus-visible::after,
    .panel-resizer.resizing::after { background: var(--accent); }
    .panel-resizer:focus-visible { outline: 1px solid var(--accent); outline-offset: -1px; }
    form { display: grid; gap: 8px; }
    input, select {
      width: 100%; border: 1px solid var(--line); border-radius: 8px;
      padding: 9px 10px; background: var(--panel-2); color: var(--text);
    }
    .search-row { display: grid; grid-template-columns: 1fr auto; gap: 8px; }
    .button {
      border: 1px solid #277fa0; border-radius: 8px; padding: 8px 12px;
      background: #12384a; color: var(--text);
    }
    .results { display: grid; gap: 7px; margin-top: 14px; }
    .section-label {
      display: flex; align-items: center; justify-content: space-between; gap: 8px;
      margin: 18px 0 8px; color: var(--muted); font-size: 11px;
      font-weight: 700; letter-spacing: .08em; text-transform: uppercase;
    }
    .section-label span {
      min-width: 24px; border: 1px solid var(--line); border-radius: 999px;
      padding: 1px 6px; text-align: center; letter-spacing: 0;
    }
    .neighborhood { margin-top: 18px; padding-top: 2px; border-top: 1px solid var(--line); }
    .node-list { display: grid; gap: 6px; }
    .node-list-item {
      width: 100%; display: grid; grid-template-columns: 8px minmax(0, 1fr);
      gap: 9px; align-items: center; text-align: left; border: 1px solid var(--line);
      border-radius: 9px; padding: 8px; background: rgba(17, 31, 47, .72); color: var(--text);
    }
    .node-list-item:hover, .node-list-item:focus-visible {
      border-color: var(--item-color, var(--accent)); outline: none;
      background: rgba(24, 43, 62, .9);
    }
    .node-swatch {
      width: 8px; height: 28px; border-radius: 999px;
      background: var(--item-color, var(--accent));
      box-shadow: 0 0 12px color-mix(in srgb, var(--item-color, var(--accent)) 35%, transparent);
    }
    .node-list-copy { min-width: 0; }
    .node-list-copy strong, .node-list-copy span {
      display: block; overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
    }
    .node-list-copy span { color: var(--muted); font-size: 11px; }
    .legend {
      display: grid; grid-template-columns: repeat(3, 1fr); gap: 6px; margin-top: 14px;
    }
    .legend span {
      display: flex; align-items: center; gap: 5px; color: var(--muted); font-size: 10px;
    }
    .legend i { width: 8px; height: 8px; border-radius: 50%; }
    .result {
      width: 100%; text-align: left; border: 1px solid var(--line); border-radius: 9px;
      padding: 9px; background: var(--panel-2); color: var(--text);
    }
    .result:hover, .result:focus { border-color: var(--accent); }
    .result strong, .result span { display: block; overflow: hidden; text-overflow: ellipsis; }
    .result span { color: var(--muted); font-size: 12px; white-space: nowrap; }
    .canvas { position: relative; min-height: 0; overflow: hidden; }
    svg { width: 100%; height: 100%; min-height: 620px; background:
      radial-gradient(circle at center, #10243a 0, #07101a 64%);
      cursor: grab; touch-action: none; user-select: none;
    }
    .canvas.dragging svg { cursor: grabbing; }
    .viewport-controls {
      position: absolute; z-index: 2; top: 12px; right: 12px;
      display: grid; grid-template-columns: repeat(3, 36px) auto;
      align-items: center; gap: 6px; padding: 6px;
      border: 1px solid var(--line); border-radius: 10px;
      background: rgba(7, 16, 26, .9); box-shadow: 0 5px 18px rgba(0, 0, 0, .28);
    }
    .viewport-control {
      width: 36px; height: 34px; border: 1px solid #31526d; border-radius: 7px;
      background: #102b3d; color: var(--text); font-weight: 700;
    }
    .viewport-control:hover, .viewport-control:focus-visible {
      border-color: var(--accent); outline: 2px solid transparent;
    }
    .zoom-level {
      min-width: 48px; padding: 0 5px; color: var(--muted);
      font-variant-numeric: tabular-nums; text-align: right;
    }
    .viewport-hint {
      position: absolute; z-index: 1; left: 12px; bottom: 12px;
      padding: 5px 8px; border: 1px solid var(--line); border-radius: 7px;
      background: rgba(7, 16, 26, .78); color: var(--muted); font-size: 11px;
      pointer-events: none;
    }
    .edge { stroke-opacity: .68; stroke-width: 1.4; }
    .edge.child-edge { stroke: #4cbe8a; }
    .edge.context-edge { stroke: #a77bd6; }
    .edge.boundary-edge { stroke: #52718b; stroke-dasharray: 5 4; }
    .edge-label { fill: #8198ae; font-size: 9px; pointer-events: none; }
    .node { cursor: pointer; }
    .node circle { stroke-width: 1.8; transition: stroke-width .15s, filter .15s; }
    .node.root circle { stroke-width: 3; filter: drop-shadow(0 0 8px rgba(81, 215, 255, .24)); }
    .node:hover circle { stroke: #fff; stroke-width: 3; }
    .node text { fill: var(--text); font-size: 10px; pointer-events: none; }
    .node .family { fill: var(--muted); font-size: 8px; }
    .empty {
      position: absolute; inset: 0; display: grid; place-items: center;
      color: var(--muted); pointer-events: none;
    }
    .empty[hidden] { display: none; }
    .connection-state {
      position: absolute; z-index: 6; inset: 50% auto auto 50%; transform: translate(-50%, -50%);
      width: min(440px, calc(100% - 40px)); border: 1px solid #9a4b59; border-radius: 12px;
      padding: 18px; background: rgba(32, 13, 20, .96); color: #ffd4dc;
      box-shadow: 0 18px 60px rgba(0, 0, 0, .45); text-align: center;
    }
    .connection-state[hidden] { display: none; }
    .connection-state strong { display: block; margin-bottom: 5px; }
    .detail-head { display: flex; align-items: start; gap: 10px; }
    .detail-head h2 { margin: 0; font-size: 18px; overflow-wrap: anywhere; }
    .badge {
      display: inline-block; margin: 4px 5px 0 0; border: 1px solid var(--line);
      border-radius: 999px; padding: 3px 7px; color: var(--muted); font-size: 11px;
    }
    .meta { display: grid; gap: 8px; margin: 14px 0; }
    .meta div { display: grid; grid-template-columns: 82px 1fr; gap: 8px; }
    .meta dt { color: var(--muted); }
    .meta dd { margin: 0; overflow-wrap: anywhere; }
    .summary { color: #c9d9e8; }
    pre {
      white-space: pre-wrap; overflow-wrap: anywhere; max-height: 44vh; overflow: auto;
      padding: 12px; border: 1px solid var(--line); border-radius: 9px;
      background: #07111c; color: #d6e6f5;
    }
    dialog {
      width: min(760px, calc(100vw - 32px)); height: min(680px, calc(100vh - 32px));
      min-width: min(360px, calc(100vw - 20px)); min-height: 280px;
      max-width: calc(100vw - 16px); max-height: calc(100vh - 16px);
      padding: 0; overflow: hidden; border: 1px solid #36536e; border-radius: 14px;
      background: var(--panel); color: var(--text);
      box-shadow: 0 24px 80px rgba(0, 0, 0, .58); resize: both;
    }
    dialog::backdrop { background: rgba(2, 8, 14, .48); }
    .dialog-shell {
      display: grid; grid-template-rows: auto minmax(0, 1fr) auto; width: 100%; height: 100%;
    }
    .dialog-head {
      display: flex; align-items: center; justify-content: space-between; gap: 12px;
      padding: 12px 16px; border-bottom: 1px solid var(--line); background: var(--panel-2);
      cursor: move; touch-action: none; user-select: none;
    }
    .dialog-head strong { font-size: 15px; }
    .dialog-close {
      width: 34px; height: 34px; border: 1px solid var(--line); border-radius: 8px;
      background: #102b3d; color: var(--text); font-size: 21px; line-height: 1;
    }
    .dialog-close:hover, .dialog-close:focus-visible {
      border-color: var(--accent); outline: 2px solid transparent;
    }
    .dialog-body { min-height: 0; overflow: auto; padding: 18px; }
    .dialog-body pre { max-height: none; }
    .dialog-actions {
      display: flex; justify-content: flex-end; gap: 8px; padding: 12px 16px;
      border-top: 1px solid var(--line); background: var(--panel-2);
    }
    .error { color: #ff9aac; }
    @media (max-width: 980px) {
      .layout { grid-template-columns: 240px 1fr; }
      .panel-resizer { display: none; }
      .right { grid-column: 1 / -1; border-left: 0; border-top: 1px solid var(--line); }
    }
    @media (max-width: 700px) {
      .layout { display: block; }
      aside { max-height: none; }
      svg { min-height: 520px; }
      header { flex-wrap: wrap; }
      .status { width: 100%; margin-left: 0; }
    }
  </style>
</head>
<body>
  <div class="app">
    <header>
      <h1 id="project-title">DocForge graph</h1>
      <div class="stats">
        <span><strong id="node-count">—</strong> nodes</span>
        <span><strong id="edge-count">—</strong> edges</span>
      </div>
      <div class="status" id="status">Loading validated index snapshot…</div>
    </header>
    <div class="layout">
      <aside class="left">
        <form id="search-form">
          <label for="search">Find nodes</label>
          <div class="search-row">
            <input id="search" name="q" autocomplete="off" placeholder="title, symbol, path…">
            <button class="button" type="submit">Find</button>
          </div>
          <label for="family">Family</label>
          <select id="family" name="family"><option value="">All families</option></select>
        </form>
        <div class="results" id="results"></div>
        <div class="neighborhood" id="neighborhood" hidden>
          <div class="legend" aria-label="Node role colors">
            <span><i style="background: var(--primary-stroke)"></i>Primary</span>
            <span><i style="background: var(--child-stroke)"></i>Children</span>
            <span><i style="background: var(--edge-stroke)"></i>Edge</span>
          </div>
          <div id="neighborhood-sections"></div>
        </div>
      </aside>
      <div class="panel-resizer" id="left-resizer" role="separator" tabindex="0"
           aria-label="Resize navigation panel" aria-orientation="vertical"
           aria-valuemin="220" aria-valuemax="900" aria-valuenow="310"></div>
      <main class="canvas">
        <div class="viewport-controls" aria-label="Graph viewport controls">
          <button class="viewport-control" id="zoom-in" type="button"
                  title="Zoom in" aria-label="Zoom in">+</button>
          <button class="viewport-control" id="zoom-out" type="button"
                  title="Zoom out" aria-label="Zoom out">−</button>
          <button class="viewport-control" id="reset-view" type="button"
                  title="Reset view" aria-label="Reset graph view">⌂</button>
          <output class="zoom-level" id="zoom-level" aria-live="polite">100%</output>
        </div>
        <svg id="graph" viewBox="-600 -410 1200 820"
             role="img" aria-label="Node neighborhood"></svg>
        <div class="empty" id="empty">Search for a node to inspect its neighborhood.</div>
        <div class="connection-state" id="connection-state" role="alert" hidden>
          <strong>Visualization disconnected</strong>
          <span>The project-bound listener is unavailable. Invoke docforge_visualize again.</span>
        </div>
        <div class="viewport-hint">
          Click node to inspect · mouse wheel to zoom · left-drag to pan
        </div>
      </main>
      <div class="panel-resizer" id="right-resizer" role="separator" tabindex="0"
           aria-label="Resize details panel" aria-orientation="vertical"
           aria-valuemin="240" aria-valuemax="900" aria-valuenow="350"></div>
      <aside class="right">
        <div id="details">
          <p class="summary">Choose a search result to load its neighborhood.</p>
        </div>
      </aside>
    </div>
  </div>
  <dialog id="node-dialog" aria-labelledby="node-dialog-label">
    <div class="dialog-shell">
      <div class="dialog-head">
        <strong id="node-dialog-label">Inspect node</strong>
        <button class="dialog-close" id="close-node-dialog" type="button"
                aria-label="Close node inspection">×</button>
      </div>
      <div class="dialog-body" id="node-dialog-details"></div>
      <div class="dialog-actions">
        <button class="button" id="explore-node" type="button">Explore neighborhood</button>
        <button class="button" id="dismiss-node-dialog" type="button">Close</button>
      </div>
    </div>
  </dialog>
  <script>
    const base = location.pathname.replace(/\/?$/, "/");
    const defaultViewport = Object.freeze({x: -600, y: -410, width: 1200, height: 820});
    const state = {
      overview: null,
      graph: null,
      root: null,
      depth: 1,
      searchLimit: 1,
      viewport: {...defaultViewport},
      pointer: null,
      suppressClick: false,
      inspectedNode: null,
      dialogDrag: null,
      leaseTimer: null,
    };
    const $ = (id) => document.getElementById(id);
    const api = async (path) => {
      let response;
      try {
        response = await fetch(`${base}api/${path}`, {cache: "no-store"});
      } catch (_error) {
        $("connection-state").hidden = false;
        throw new Error("Visualization listener disconnected; invoke docforge_visualize again");
      }
      const body = await response.json();
      if (!response.ok || body.status === "error") {
        throw new Error(body.error?.message || "DocForge request failed");
      }
      $("connection-state").hidden = true;
      return body;
    };
    const escapeText = (value) => String(value ?? "");
    const short = (value, length = 34) => {
      const text = escapeText(value);
      return text.length > length ? `${text.slice(0, length - 1)}…` : text;
    };
    function applyViewport() {
      const view = state.viewport;
      $("graph").setAttribute("viewBox", `${view.x} ${view.y} ${view.width} ${view.height}`);
      const zoom = Math.round((defaultViewport.width / view.width) * 100);
      $("zoom-level").textContent = `${zoom}%`;
    }
    function resetViewport() {
      state.viewport = {...defaultViewport};
      applyViewport();
    }
    function zoomAt(factor, clientX = null, clientY = null) {
      const svg = $("graph");
      const rect = svg.getBoundingClientRect();
      if (!rect.width || !rect.height) return;
      const current = state.viewport;
      const nextWidth = Math.min(
        defaultViewport.width * 4,
        Math.max(defaultViewport.width * .2, current.width * factor),
      );
      const nextHeight = nextWidth * (defaultViewport.height / defaultViewport.width);
      const ratioX = clientX === null ? .5 : (clientX - rect.left) / rect.width;
      const ratioY = clientY === null ? .5 : (clientY - rect.top) / rect.height;
      const anchorX = current.x + ratioX * current.width;
      const anchorY = current.y + ratioY * current.height;
      state.viewport = {
        x: anchorX - ratioX * nextWidth,
        y: anchorY - ratioY * nextHeight,
        width: nextWidth,
        height: nextHeight,
      };
      applyViewport();
    }
    function setStatus(message, error = false) {
      $("status").textContent = message;
      $("status").classList.toggle("error", error);
    }
    async function renewViewerLease() {
      try {
        await api("heartbeat");
      } catch (error) {
        setStatus(error.message, true);
        if (state.leaseTimer !== null) clearInterval(state.leaseTimer);
        state.leaseTimer = null;
      }
    }
    function startViewerLease() {
      if (state.leaseTimer !== null) clearInterval(state.leaseTimer);
      state.leaseTimer = setInterval(renewViewerLease, 15000);
      document.addEventListener("visibilitychange", () => {
        if (!document.hidden) renewViewerLease();
      });
    }
    function renderOverview(data) {
      state.overview = data;
      state.searchLimit = Math.max(1, Number(data.max_results) || 1);
      $("project-title").textContent = data.title || data.project_id;
      $("node-count").textContent = Number(data.node_count).toLocaleString();
      $("edge-count").textContent = Number(data.edge_count).toLocaleString();
      const family = $("family");
      for (const item of data.families) {
        const option = document.createElement("option");
        option.value = item.value;
        option.textContent = `${item.value} (${item.count})`;
        family.append(option);
      }
    }
    function renderResults(items) {
      const results = $("results");
      results.replaceChildren();
      if (!items.length) {
        const note = document.createElement("p");
        note.className = "summary";
        note.textContent = "No matching nodes.";
        results.append(note);
        return;
      }
      for (const item of items) {
        const button = document.createElement("button");
        button.type = "button";
        button.className = "result";
        const title = document.createElement("strong");
        title.textContent = item.title;
        const id = document.createElement("span");
        id.textContent = item.node_id;
        const family = document.createElement("span");
        family.textContent = `${item.family} · ${item.source_path}`;
        button.append(title, id, family);
        button.addEventListener("click", () => loadNode(item.node_id));
        results.append(button);
      }
    }
    function analyzeTopology(data) {
      const nodeIds = new Set(data.nodes.map((node) => node.node_id));
      const adjacency = new Map([...nodeIds].map((nodeId) => [nodeId, new Set()]));
      const outgoing = new Map([...nodeIds].map((nodeId) => [nodeId, new Set()]));
      for (const edge of data.edges) {
        if (!nodeIds.has(edge.source_id) || !nodeIds.has(edge.target_id)) continue;
        adjacency.get(edge.source_id).add(edge.target_id);
        adjacency.get(edge.target_id).add(edge.source_id);
        outgoing.get(edge.source_id).add(edge.target_id);
      }
      const hops = new Map([[data.root, 0]]);
      let frontier = [data.root];
      while (frontier.length) {
        const next = [];
        for (const nodeId of frontier) {
          for (const neighbor of adjacency.get(nodeId) || []) {
            if (hops.has(neighbor)) continue;
            hops.set(neighbor, hops.get(nodeId) + 1);
            next.push(neighbor);
          }
        }
        frontier = next;
      }
      const children = new Set();
      frontier = [...(outgoing.get(data.root) || [])];
      for (const nodeId of frontier) children.add(nodeId);
      while (frontier.length) {
        const next = [];
        for (const nodeId of frontier) {
          for (const candidate of outgoing.get(nodeId) || []) {
            if (candidate === data.root || children.has(candidate)) continue;
            children.add(candidate);
            next.push(candidate);
          }
        }
        frontier = next;
      }
      return new Map(data.nodes.map((node) => [
        node.node_id,
        {
          hop: hops.get(node.node_id) ?? data.depth + 1,
          role: node.node_id === data.root
            ? "primary"
            : children.has(node.node_id) ? "child" : "edge",
        },
      ]));
    }
    function layoutNodes(nodes, rootId, topology) {
      const ordered = [...nodes].sort((a, b) => {
        const first = topology.get(a.node_id);
        const second = topology.get(b.node_id);
        return first.hop - second.hop
          || first.role.localeCompare(second.role)
          || a.node_id.localeCompare(b.node_id);
      });
      const root = ordered.find((node) => node.node_id === rootId);
      const positions = new Map();
      if (root) positions.set(root.node_id, {x: 0, y: 0});
      const rings = new Map();
      for (const node of ordered) {
        if (node.node_id === rootId) continue;
        const hop = Math.max(1, topology.get(node.node_id).hop);
        if (!rings.has(hop)) rings.set(hop, []);
        rings.get(hop).push(node);
      }
      for (const [hop, ringNodes] of rings) {
        ringNodes.forEach((node, index) => {
          const angle = (index / Math.max(1, ringNodes.length)) * Math.PI * 2 - Math.PI / 2;
          const radius = 165 + (hop - 1) * 145;
          positions.set(node.node_id, {
            x: Math.cos(angle) * radius,
            y: Math.sin(angle) * radius,
          });
        });
      }
      return positions;
    }
    function darken(hex, amount) {
      const value = Number.parseInt(hex.slice(1), 16);
      const factor = 1 - Math.min(.5, Math.max(0, amount));
      const channels = [
        (value >> 16) & 255,
        (value >> 8) & 255,
        value & 255,
      ].map((channel) => Math.round(channel * factor).toString(16).padStart(2, "0"));
      return `#${channels.join("")}`;
    }
    function nodePalette(role, hop) {
      const colors = {
        primary: {fill: "#176b7d", stroke: "#83e8ff"},
        child: {fill: "#216c51", stroke: "#91f2bd"},
        edge: {fill: "#634580", stroke: "#d0a7ff"},
      }[role];
      const distanceShade = Math.min(.5, Math.max(0, hop - 1) * .17);
      return {
        fill: darken(colors.fill, distanceShade),
        stroke: darken(colors.stroke, distanceShade),
      };
    }
    function renderNeighborhood(data, topology) {
      const sections = [
        {role: "primary", label: "Primary focus"},
        {role: "child", label: "Children"},
        {role: "edge", label: "Edge & context"},
      ];
      const container = $("neighborhood-sections");
      container.replaceChildren();
      for (const section of sections) {
        const nodes = data.nodes
          .filter((node) => topology.get(node.node_id).role === section.role)
          .sort((a, b) => topology.get(a.node_id).hop - topology.get(b.node_id).hop
            || a.node_id.localeCompare(b.node_id));
        if (!nodes.length) continue;
        const heading = document.createElement("div");
        heading.className = "section-label";
        heading.append(document.createTextNode(section.label));
        const count = document.createElement("span");
        count.textContent = String(nodes.length);
        heading.append(count);
        const list = document.createElement("div");
        list.className = "node-list";
        for (const node of nodes) {
          const topologyNode = topology.get(node.node_id);
          const palette = nodePalette(topologyNode.role, topologyNode.hop);
          const button = document.createElement("button");
          button.type = "button";
          button.className = "node-list-item";
          button.style.setProperty("--item-color", palette.stroke);
          button.title = `Focus ${node.title}`;
          const swatch = document.createElement("i");
          swatch.className = "node-swatch";
          const copy = document.createElement("span");
          copy.className = "node-list-copy";
          const title = document.createElement("strong");
          title.textContent = node.title;
          const meta = document.createElement("span");
          const hopLabel = `${topologyNode.hop} hop${topologyNode.hop === 1 ? "" : "s"}`;
          meta.textContent = `${node.family} · ${hopLabel}`;
          copy.append(title, meta);
          button.append(swatch, copy);
          button.addEventListener("click", () => loadNode(node.node_id));
          list.append(button);
        }
        container.append(heading, list);
      }
      $("neighborhood").hidden = false;
    }
    function svgElement(name, attributes = {}) {
      const element = document.createElementNS("http://www.w3.org/2000/svg", name);
      for (const [key, value] of Object.entries(attributes)) element.setAttribute(key, value);
      return element;
    }
    function renderGraph(data) {
      state.graph = data;
      state.root = data.root;
      resetViewport();
      const svg = $("graph");
      svg.replaceChildren();
      $("empty").hidden = data.nodes.length > 0;
      const topology = analyzeTopology(data);
      const positions = layoutNodes(data.nodes, data.root, topology);
      renderNeighborhood(data, topology);
      const edgeLayer = svgElement("g");
      const nodeLayer = svgElement("g");
      for (const edge of data.edges) {
        const source = positions.get(edge.source_id);
        const target = positions.get(edge.target_id);
        if (!source || !target) continue;
        const targetRole = topology.get(edge.target_id)?.role || "edge";
        const edgeRole = edge.source_id === data.root && targetRole === "child"
          ? "child-edge"
          : edge.target_id === data.root || targetRole === "edge"
            ? "context-edge"
            : "boundary-edge";
        edgeLayer.append(svgElement("line", {
          x1: source.x, y1: source.y, x2: target.x, y2: target.y,
          class: `edge ${edgeRole}`
        }));
        const label = svgElement("text", {
          x: (source.x + target.x) / 2,
          y: (source.y + target.y) / 2,
          class: "edge-label",
          "text-anchor": "middle"
        });
        label.textContent = edge.relation;
        edgeLayer.append(label);
      }
      for (const node of data.nodes) {
        const point = positions.get(node.node_id);
        if (!point) continue;
        const topologyNode = topology.get(node.node_id);
        const palette = nodePalette(topologyNode.role, topologyNode.hop);
        const group = svgElement("g", {
          class: `node ${topologyNode.role}${node.node_id === data.root ? " root" : ""}`,
          transform: `translate(${point.x} ${point.y})`,
          "data-hop": String(topologyNode.hop),
          tabindex: "0",
          role: "button",
          "aria-label": [
            node.title, node.family, topologyNode.role, `${topologyNode.hop} hops`
          ].join(", ")
        });
        group.append(svgElement("circle", {
          r: node.node_id === data.root ? 25 : 18,
          fill: palette.fill,
          stroke: palette.stroke,
        }));
        const title = svgElement("text", {y: 35, "text-anchor": "middle"});
        title.textContent = short(node.title, 26);
        const family = svgElement("text", {y: 48, "text-anchor": "middle", class: "family"});
        family.textContent = short(node.family, 22);
        group.append(title, family);
        group.addEventListener("click", () => {
          if (!state.suppressClick) inspectNode(node.node_id);
        });
        group.addEventListener("keydown", (event) => {
          if (event.key === "Enter" || event.key === " ") {
            event.preventDefault();
            inspectNode(node.node_id);
          }
        });
        nodeLayer.append(group);
      }
      svg.append(edgeLayer, nodeLayer);
    }
    function renderDetails(details, node, data) {
      details.replaceChildren();
      const heading = document.createElement("div");
      heading.className = "detail-head";
      const title = document.createElement("h2");
      title.textContent = node.title;
      heading.append(title);
      const badges = document.createElement("div");
      for (const value of [node.family, node.authority, node.status, ...node.tags]) {
        const badge = document.createElement("span");
        badge.className = "badge";
        badge.textContent = value;
        badges.append(badge);
      }
      const summary = document.createElement("p");
      summary.className = "summary";
      summary.textContent = node.summary;
      const dl = document.createElement("dl");
      dl.className = "meta";
      for (const [label, value] of [
        ["ID", node.node_id],
        ["Source", node.source_path],
        ["Anchor", node.source_anchor || "—"],
        ["Neighbors", `${data.nodes.length - 1} nodes · ${data.edges.length} edges`],
      ]) {
        const row = document.createElement("div");
        const dt = document.createElement("dt");
        const dd = document.createElement("dd");
        dt.textContent = label;
        dd.textContent = escapeText(value);
        row.append(dt, dd);
        dl.append(row);
      }
      const content = document.createElement("pre");
      content.textContent = node.content;
      details.append(heading, badges, summary, dl, content);
    }
    function closeNodeDialog() {
      const dialog = $("node-dialog");
      if (dialog.open) dialog.close();
      else state.inspectedNode = null;
    }
    async function inspectNode(nodeId) {
      try {
        setStatus(`Inspecting ${nodeId}…`);
        const params = new URLSearchParams({id: nodeId, depth: String(state.depth), limit: "100"});
        const data = await api(`node?${params}`);
        state.inspectedNode = nodeId;
        renderDetails($("node-dialog-details"), data.node, data);
        $("node-dialog-label").textContent = short(data.node.title, 72);
        const dialog = $("node-dialog");
        if (!dialog.open) dialog.showModal();
        $("close-node-dialog").focus();
        setStatus(`Inspecting ${nodeId}`);
      } catch (error) {
        setStatus(error.message, true);
      }
    }
    async function search() {
      const params = new URLSearchParams({
        q: $("search").value.trim(),
        family: $("family").value,
        limit: String(state.searchLimit),
      });
      try {
        setStatus("Searching validated index…");
        const data = await api(`search?${params}`);
        renderResults(data.results || []);
        setStatus(`${data.count} matching node${data.count === 1 ? "" : "s"}`);
      } catch (error) {
        setStatus(error.message, true);
      }
    }
    async function loadNode(nodeId) {
      try {
        setStatus(`Loading ${nodeId}…`);
        const params = new URLSearchParams({id: nodeId, depth: String(state.depth), limit: "100"});
        const data = await api(`node?${params}`);
        renderGraph(data);
        renderDetails($("details"), data.node, data);
        setStatus(`${data.nodes.length} nodes · ${data.edges.length} edges in neighborhood`);
        history.replaceState(null, "", `?node=${encodeURIComponent(nodeId)}&depth=${state.depth}`);
      } catch (error) {
        setStatus(error.message, true);
      }
    }
    function clamp(value, minimum, maximum) {
      return Math.min(maximum, Math.max(minimum, value));
    }
    function setPanelWidth(side, width) {
      const maximum = Math.max(260, Math.floor(window.innerWidth * .46));
      const bounded = clamp(width, side === "left" ? 220 : 240, maximum);
      document.documentElement.style.setProperty(`--${side}-width`, `${bounded}px`);
      $(`${side}-resizer`).setAttribute("aria-valuenow", String(Math.round(bounded)));
    }
    function setupPanelResizer(side) {
      const handle = $(`${side}-resizer`);
      handle.addEventListener("pointerdown", (event) => {
        if (event.button !== 0) return;
        const property = getComputedStyle(document.documentElement)
          .getPropertyValue(`--${side}-width`);
        const startWidth = Number.parseFloat(property) || (side === "left" ? 310 : 350);
        const startX = event.clientX;
        handle.classList.add("resizing");
        handle.setPointerCapture(event.pointerId);
        const move = (moveEvent) => {
          const delta = moveEvent.clientX - startX;
          setPanelWidth(side, startWidth + (side === "left" ? delta : -delta));
        };
        const end = (endEvent) => {
          if (handle.hasPointerCapture(endEvent.pointerId)) {
            handle.releasePointerCapture(endEvent.pointerId);
          }
          handle.classList.remove("resizing");
          handle.removeEventListener("pointermove", move);
          handle.removeEventListener("pointerup", end);
          handle.removeEventListener("pointercancel", end);
        };
        handle.addEventListener("pointermove", move);
        handle.addEventListener("pointerup", end);
        handle.addEventListener("pointercancel", end);
      });
      handle.addEventListener("keydown", (event) => {
        if (event.key !== "ArrowLeft" && event.key !== "ArrowRight") return;
        event.preventDefault();
        const property = getComputedStyle(document.documentElement)
          .getPropertyValue(`--${side}-width`);
        const width = Number.parseFloat(property) || (side === "left" ? 310 : 350);
        const direction = event.key === "ArrowRight" ? 16 : -16;
        setPanelWidth(side, width + (side === "left" ? direction : -direction));
      });
      handle.addEventListener("dblclick", () => setPanelWidth(side, side === "left" ? 310 : 350));
    }
    function beginDialogDrag(event) {
      if (event.button !== 0 || event.target.closest("button")) return;
      const dialog = $("node-dialog");
      const header = event.currentTarget;
      const bounds = dialog.getBoundingClientRect();
      dialog.style.margin = "0";
      dialog.style.right = "auto";
      dialog.style.bottom = "auto";
      dialog.style.left = `${bounds.left}px`;
      dialog.style.top = `${bounds.top}px`;
      dialog.style.width = `${bounds.width}px`;
      dialog.style.height = `${bounds.height}px`;
      state.dialogDrag = {
        id: event.pointerId,
        startX: event.clientX,
        startY: event.clientY,
        left: bounds.left,
        top: bounds.top,
      };
      header.setPointerCapture(event.pointerId);
    }
    function moveDialog(event) {
      const drag = state.dialogDrag;
      if (!drag || drag.id !== event.pointerId) return;
      const dialog = $("node-dialog");
      const maximumLeft = Math.max(8, window.innerWidth - dialog.offsetWidth - 8);
      const maximumTop = Math.max(8, window.innerHeight - dialog.offsetHeight - 8);
      dialog.style.left = `${clamp(drag.left + event.clientX - drag.startX, 8, maximumLeft)}px`;
      dialog.style.top = `${clamp(drag.top + event.clientY - drag.startY, 8, maximumTop)}px`;
    }
    function endDialogDrag(event) {
      const drag = state.dialogDrag;
      if (!drag || drag.id !== event.pointerId) return;
      const header = $("node-dialog").querySelector(".dialog-head");
      if (header.hasPointerCapture(event.pointerId)) header.releasePointerCapture(event.pointerId);
      state.dialogDrag = null;
    }
    $("search-form").addEventListener("submit", (event) => { event.preventDefault(); search(); });
    $("family").addEventListener("change", search);
    $("zoom-in").addEventListener("click", () => zoomAt(.8));
    $("zoom-out").addEventListener("click", () => zoomAt(1.25));
    $("reset-view").addEventListener("click", resetViewport);
    $("close-node-dialog").addEventListener("click", closeNodeDialog);
    $("dismiss-node-dialog").addEventListener("click", closeNodeDialog);
    setupPanelResizer("left");
    setupPanelResizer("right");
    $("node-dialog").querySelector(".dialog-head").addEventListener("pointerdown", beginDialogDrag);
    $("node-dialog").querySelector(".dialog-head").addEventListener("pointermove", moveDialog);
    $("node-dialog").querySelector(".dialog-head").addEventListener("pointerup", endDialogDrag);
    $("node-dialog").querySelector(".dialog-head").addEventListener("pointercancel", endDialogDrag);
    $("explore-node").addEventListener("click", async () => {
      const nodeId = state.inspectedNode;
      closeNodeDialog();
      if (nodeId) await loadNode(nodeId);
    });
    $("node-dialog").addEventListener("click", (event) => {
      if (event.target !== $("node-dialog")) return;
      const bounds = $("node-dialog").getBoundingClientRect();
      const inside = event.clientX >= bounds.left && event.clientX <= bounds.right
        && event.clientY >= bounds.top && event.clientY <= bounds.bottom;
      if (!inside) closeNodeDialog();
    });
    $("node-dialog").addEventListener("close", () => {
      state.inspectedNode = null;
      if (state.graph) {
        const nodeCount = state.graph.nodes.length;
        const edgeCount = state.graph.edges.length;
        setStatus(`${nodeCount} nodes · ${edgeCount} edges in neighborhood`);
      }
    });
    $("graph").addEventListener("wheel", (event) => {
      event.preventDefault();
      zoomAt(event.deltaY < 0 ? .85 : 1.18, event.clientX, event.clientY);
    }, {passive: false});
    $("graph").addEventListener("pointerdown", (event) => {
      if (event.button !== 0) return;
      const svg = $("graph");
      state.suppressClick = false;
      state.pointer = {
        id: event.pointerId,
        startX: event.clientX,
        startY: event.clientY,
        viewport: {...state.viewport},
        moved: false,
      };
    });
    $("graph").addEventListener("pointermove", (event) => {
      const pointer = state.pointer;
      if (!pointer || pointer.id !== event.pointerId) return;
      const svg = $("graph");
      const rect = svg.getBoundingClientRect();
      if (!rect.width || !rect.height) return;
      const deltaX = event.clientX - pointer.startX;
      const deltaY = event.clientY - pointer.startY;
      if (!pointer.moved && Math.hypot(deltaX, deltaY) < 4) return;
      pointer.moved = true;
      state.suppressClick = true;
      if (!svg.hasPointerCapture(event.pointerId)) svg.setPointerCapture(event.pointerId);
      svg.closest(".canvas").classList.add("dragging");
      state.viewport = {
        ...pointer.viewport,
        x: pointer.viewport.x - deltaX * (pointer.viewport.width / rect.width),
        y: pointer.viewport.y - deltaY * (pointer.viewport.height / rect.height),
      };
      applyViewport();
    });
    function endPan(event) {
      const pointer = state.pointer;
      if (!pointer || pointer.id !== event.pointerId) return;
      const svg = $("graph");
      if (svg.hasPointerCapture(event.pointerId)) svg.releasePointerCapture(event.pointerId);
      svg.closest(".canvas").classList.remove("dragging");
      state.pointer = null;
      if (pointer.moved) {
        setTimeout(() => { state.suppressClick = false; }, 0);
      }
    }
    $("graph").addEventListener("pointerup", endPan);
    $("graph").addEventListener("pointercancel", endPan);
    applyViewport();
    (async () => {
      try {
        const params = new URLSearchParams(location.search);
        state.depth = Math.max(1, Number(params.get("depth")) || 1);
        const overview = await api("overview");
        renderOverview(overview);
        startViewerLease();
        const nodeId = params.get("node");
        const query = params.get("q");
        if (nodeId) {
          await loadNode(nodeId);
        } else {
          if (query) $("search").value = query;
          await search();
        }
      } catch (error) {
        setStatus(error.message, true);
      }
    })();
  </script>
</body>
</html>
"""