#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Modul: app/core/edges.py
Version: 1.0.0
Datum: 2025-09-09

Zweck
-----
Zentrale, konsistente Erzeugung von Edge-Payloads im **neuen Schema**:
  - kind        : "belongs_to" | "next" | "prev" | "references" | "backlink"
  - source_id   : ID des Quellknotens (Chunk- oder Note-ID)
  - target_id   : ID des Zielknotens
  - scope       : "chunk" | "note"
  - note_id     : Owner-Note (für performantes Filtern/Löschen)
  - seq         : optional (z. B. Reihenfolge von Vorkommen)

Hinweise
--------
- Edges werden dedupliziert (key=(kind,source_id,target_id,scope)).
- Für Chunk-Edges wird `note_id` aus dem Chunk-Payload entnommen.
- Für Note-Scope-Edges ist `note_id` die Quell-Note-ID.
"""

from __future__ import annotations
from typing import Dict, List

def build_edges_for_note(
    note_id: str,
    chunk_payloads: List[Dict],
    note_level_refs: List[str] | None,
    *,
    include_note_scope_refs: bool = False,
) -> List[Dict]:
    edges: List[Dict] = []

    # Chunk-Scope: belongs_to / prev / next / references
    for ch in chunk_payloads:
        cid = ch["id"]
        owner = ch.get("note_id") or note_id
        # belongs_to
        edges.append({
            "kind": "belongs_to",
            "source_id": cid,
            "target_id": note_id,
            "scope": "chunk",
            "note_id": owner,
        })
        # Nachbarn
        nb = ch.get("neighbors") or {}
        prev_id = nb.get("prev")
        next_id = nb.get("next")
        if prev_id:
            edges.append({
                "kind": "prev",
                "source_id": cid,
                "target_id": prev_id,
                "scope": "chunk",
                "note_id": owner,
            })
            edges.append({
                "kind": "next",
                "source_id": prev_id,
                "target_id": cid,
                "scope": "chunk",
                "note_id": owner,
            })
        if next_id:
            edges.append({
                "kind": "next",
                "source_id": cid,
                "target_id": next_id,
                "scope": "chunk",
                "note_id": owner,
            })
            edges.append({
                "kind": "prev",
                "source_id": next_id,
                "target_id": cid,
                "scope": "chunk",
                "note_id": owner,
            })
        # references aus Chunk
        for ref in (ch.get("references") or []):
            tid = ref.get("target_id")
            if not tid:
                continue
            edges.append({
                "kind": "references",
                "source_id": cid,
                "target_id": tid,
                "scope": "chunk",
                "note_id": owner,
            })

    # Note-Scope: backlink (immer); references (optional)
    unique_refs = list(dict.fromkeys(note_level_refs or []))
    for tid in unique_refs:
        if include_note_scope_refs:
            edges.append({
                "kind": "references",
                "source_id": note_id,
                "target_id": tid,
                "scope": "note",
                "note_id": note_id,
            })
        edges.append({
            "kind": "backlink",
            "source_id": tid,
            "target_id": note_id,
            "scope": "note",
            "note_id": note_id,
        })

    # Dedupe
    dedup = {}
    for e in edges:
        k = (e["kind"], e["source_id"], e["target_id"], e.get("scope", ""))
        dedup[k] = e
    return list(dedup.values())