"""
FILE: app/core/graph/graph_subgraph.py
DESCRIPTION: In-Memory Repräsentation eines Graphen für Scoring und Analyse.
"""
import math
from collections import defaultdict
from typing import Dict, List, Optional, DefaultDict, Any, Set
from qdrant_client import QdrantClient
from .graph_weights import EDGE_BASE_WEIGHTS, calculate_edge_weight
from .graph_db_adapter import fetch_edges_from_qdrant

class Subgraph:
    """Leichtgewichtiger Subgraph mit Adjazenzlisten & Kennzahlen."""

    def __init__(self) -> None:
        self.adj: DefaultDict[str, List[Dict]] = defaultdict(list)
        self.reverse_adj: DefaultDict[str, List[Dict]] = defaultdict(list)
        self.in_degree: DefaultDict[str, int] = defaultdict(int)
        self.out_degree: DefaultDict[str, int] = defaultdict(int)

    def add_edge(self, e: Dict) -> None:
        """Fügt eine Kante hinzu und aktualisiert Indizes."""
        src = e.get("source")
        tgt = e.get("target")
        kind = e.get("kind")
        weight = e.get("weight", EDGE_BASE_WEIGHTS.get(kind, 0.0))
        owner = e.get("note_id")

        if not src or not tgt:
            return

        # 1. Forward
        self.adj[src].append({"target": tgt, "kind": kind, "weight": weight})
        self.out_degree[src] += 1
        self.in_degree[tgt] += 1

        # 2. Reverse (WP-04b Explanation)
        self.reverse_adj[tgt].append({"source": src, "kind": kind, "weight": weight})

        # 3. Kontext-Note Handling
        if owner and owner != src:
            self.adj[owner].append({"target": tgt, "kind": kind, "weight": weight})
            self.out_degree[owner] += 1
            if owner != tgt:
                self.reverse_adj[tgt].append({"source": owner, "kind": kind, "weight": weight, "via_context": True})
                self.in_degree[owner] += 1

    def aggregate_edge_bonus(self, node_id: str) -> float:
        """Summe der ausgehenden Kantengewichte (Hub-Score)."""
        return sum(edge["weight"] for edge in self.adj.get(node_id, []))

    def edge_bonus(self, node_id: str) -> float:
        """API für Retriever (WP-04a Kompatibilität)."""
        return self.aggregate_edge_bonus(node_id)

    def centrality_bonus(self, node_id: str) -> float:
        """Log-gedämpfte Zentralität (In-Degree)."""
        indeg = self.in_degree.get(node_id, 0)
        if indeg <= 0:
            return 0.0
        return min(math.log1p(indeg) / 10.0, 0.15)

    def get_outgoing_edges(self, node_id: str) -> List[Dict[str, Any]]:
        return self.adj.get(node_id, [])

    def get_incoming_edges(self, node_id: str) -> List[Dict[str, Any]]:
        return self.reverse_adj.get(node_id, [])


def expand(
    client: QdrantClient,
    prefix: str,
    seeds: List[str],
    depth: int = 1,
    edge_types: Optional[List[str]] = None,
) -> Subgraph:
    """Expandiert ab Seeds entlang von Edges bis zu einer bestimmten Tiefe."""
    sg = Subgraph()
    frontier = set(seeds)
    visited = set()

    for _ in range(max(depth, 0)):
        if not frontier:
            break

        payloads = fetch_edges_from_qdrant(client, prefix, list(frontier), edge_types)
        next_frontier: Set[str] = set()

        for pl in payloads:
            src, tgt = pl.get("source_id"), pl.get("target_id")
            if not src or not tgt: continue

            sg.add_edge({
                "source": src, "target": tgt,
                "kind": pl.get("kind", "edge"),
                "weight": calculate_edge_weight(pl),
                "note_id": pl.get("note_id"),
            })

            if tgt not in visited:
                next_frontier.add(str(tgt))

        visited |= frontier
        frontier = next_frontier - visited

    return sg