"""Graph data services shared by the REST route and the AI tool layer.

Builds the nodes/edges structure consumed by the graph view. The route
``/api/graph/{vault}`` and the tool ``get_graph`` both delegate here so the
graph semantics (parent/child edges, wikilinks, tag filter) stay identical.
Permission checks are the caller's responsibility.
"""

from __future__ import annotations

import re
from pathlib import Path
from typing import Any

from backend.indexer import SUPPORTED_EXTENSIONS, index
from backend.services.errors import ServiceError
from backend.services.paths import resolve_safe_path
from backend.services.vaults import get_vault_root

_WIKILINK_PATTERN = re.compile(r"\[\[([^\]|#]+)(?:[|#][^\]]+)?\]\]")


def get_graph(
    vault_name: str,
    path: str = "",
    depth: int = 1,
    scope: str = "directory",
    tag: str = "",
) -> dict[str, Any]:
    """Return graph data (nodes and edges) for a vault or directory.

    Args:
        vault_name: Name of the vault.
        path: Relative directory path to focus on (empty = root).
        depth: Expansion depth (0 = only direct children, 1-3 = deeper).
        scope: ``"directory"`` for a subtree, ``"full"`` for the whole vault.
        tag: Optional tag filter (only files with this tag appear).

    Returns:
        Dict with ``vault``, ``path``, ``scope``, ``nodes`` and ``edges``.

    Raises:
        ServiceError: ``not_found`` (404) when the vault or path is missing.
    """
    from backend.vault_settings import get_vault_setting

    vault_root = get_vault_root(vault_name)
    target = resolve_safe_path(vault_root, path) if path else vault_root.resolve()

    if not target.exists():
        raise ServiceError(
            f"Path not found: {path}",
            code="not_found",
            status=404,
            details={"vault": vault_name, "path": path},
        )

    nodes: list[dict[str, Any]] = []
    edges: list[dict[str, Any]] = []
    node_ids: set[str] = set()

    def _add_node(name: str, ntype: str, npath: str, size: int = 0,
                  tags: list[str] | None = None, incoming: int = 0, outgoing: int = 0) -> str:
        nid = f"{vault_name}:{npath}"
        if nid not in node_ids:
            node_ids.add(nid)
            nodes.append({
                "id": nid, "name": name, "type": ntype, "path": npath,
                "size": size, "tags": tags or [],
                "incoming_count": incoming, "outgoing_count": outgoing,
            })
        return nid

    def _add_edge(source: str, target_id: str, relation: str) -> None:
        edges.append({"source": source, "target": target_id, "relation": relation})

    settings = get_vault_setting(vault_name) or {}
    hide_hidden = settings.get("hideHiddenFiles", False)

    # Build tag index from the in-memory index for fast lookups.
    _tag_index: dict[str, list[str]] = {}
    for doc_key, info in index.items():
        vn, fp = doc_key.split("::", 1) if "::" in doc_key else ("", "")
        if vn == vault_name:
            for t in info.get("tags", []):
                _tag_index.setdefault(t.lower(), []).append(fp)

    if scope == "full":
        target = vault_root.resolve()
        effective_depth = depth if depth > 0 else 2
    else:
        target = resolve_safe_path(vault_root, path) if path else vault_root.resolve()
        effective_depth = depth

    if not target.exists():
        raise ServiceError(
            f"Path not found: {path}",
            code="not_found",
            status=404,
            details={"vault": vault_name, "path": path},
        )

    focus_name = path.split("/")[-1] if path else vault_name
    focus_type = "directory" if path else "vault"
    focus_id = _add_node(focus_name, focus_type, path)

    def _walk_dir(dir_path: Path, parent_id: str, current_depth: int) -> None:
        if current_depth > effective_depth:
            return
        try:
            for entry in sorted(dir_path.iterdir(), key=lambda e: (not e.is_dir(), e.name.lower())):
                if hide_hidden and entry.name.startswith("."):
                    continue
                rel = str(entry.relative_to(vault_root)).replace("\\", "/")

                if tag and entry.is_file():
                    file_tags = [t.lower() for t in _tag_index.get(rel, [])]
                    if tag.lower() not in file_tags:
                        continue

                if entry.is_dir():
                    did = _add_node(entry.name, "directory", rel)
                    _add_edge(parent_id, did, "parent")
                    if current_depth < effective_depth:
                        _walk_dir(entry, did, current_depth + 1)
                elif entry.suffix.lower() in SUPPORTED_EXTENSIONS or entry.name.lower() in ("dockerfile", "makefile"):
                    file_tags = _tag_index.get(rel, [])
                    fid = _add_node(entry.name, "file", rel, entry.stat().st_size, tags=file_tags)
                    _add_edge(parent_id, fid, "parent")
        except PermissionError:
            pass

    if target.is_dir():
        _walk_dir(target, focus_id, 0)
    elif target.is_file():
        _walk_dir(target.parent, focus_id, 0)

    _add_wikilink_edges(nodes, edges, vault_name)

    edge_counts: dict[str, dict[str, int]] = {}
    for node in nodes:
        edge_counts[node["id"]] = {"incoming": 0, "outgoing": 0}
    for edge in edges:
        if edge["relation"] in ("wikilink", "backlink"):
            src = edge["source"]
            tgt = edge["target"]
            if src in edge_counts:
                edge_counts[src]["outgoing"] += 1
            if tgt in edge_counts:
                edge_counts[tgt]["incoming"] += 1
    for node in nodes:
        counts = edge_counts.get(node["id"], {"incoming": 0, "outgoing": 0})
        node["incoming_count"] = counts["incoming"]
        node["outgoing_count"] = counts["outgoing"]

    return {"vault": vault_name, "path": path, "scope": scope, "nodes": nodes, "edges": edges}


def _add_wikilink_edges(nodes: list[dict[str, Any]], edges: list[dict[str, Any]], vault_name: str) -> None:
    """Add edges for wikilinks between markdown files in the current graph scope."""
    file_nodes = [n for n in nodes if n["type"] == "file" and n["path"].endswith(".md")]
    if len(file_nodes) < 2:
        return

    path_to_id = {n["path"]: n["id"] for n in file_nodes}
    existing = {(e["source"], e["target"]) for e in edges}

    for node in file_nodes:
        vault_data = index.get(vault_name)
        if not vault_data:
            continue
        file_entry = None
        for f in vault_data.get("files", []):
            if f["path"] == node["path"]:
                file_entry = f
                break
        if not file_entry:
            continue

        content = file_entry.get("content", "")
        if not content:
            continue

        for match in _WIKILINK_PATTERN.finditer(content):
            target = match.group(1).strip()
            target_lower = target.lower()
            if not target_lower.endswith(".md"):
                target_lower += ".md"

            for target_path, target_id in path_to_id.items():
                if target_id == node["id"]:
                    continue
                target_name = target_path.rsplit("/", 1)[-1].lower()
                if target_name == target_lower or target_path.lower() == target_lower:
                    edge_key = tuple(sorted([node["id"], target_id]))
                    if edge_key not in existing and (edge_key[1], edge_key[0]) not in existing:
                        edges.append({"source": node["id"], "target": target_id, "relation": "wikilink"})
                        existing.add((node["id"], target_id))
                    break