"""Analyze a knowledge graph built from OCR pipeline output."""

from __future__ import annotations

from dataclasses import dataclass
from typing import Any

LOW_CONFIDENCE_THRESHOLD = 0.4
HUB_MENTIONS_THRESHOLD = 20


@dataclass(frozen=True)
class Anomaly:
    kind: str
    node: str
    detail: str


def _nodes_of_kind(graph: Any, kind: str) -> list[tuple[str, dict]]:
    return [(n, d) for n, d in graph.nodes(data=True) if d.get("kind") == kind]


def summary(graph: Any) -> dict[str, int]:
    """Node and edge counts grouped by kind."""
    counts: dict[str, int] = {}
    for _, data in graph.nodes(data=True):
        kind = data.get("kind", "unknown")
        counts[f"nodes:{kind}"] = counts.get(f"nodes:{kind}", 0) + 1
    for _, _, data in graph.edges(data=True):
        kind = data.get("kind", "unknown")
        counts[f"edges:{kind}"] = counts.get(f"edges:{kind}", 0) + 1
    return counts


def top_entities(graph: Any, limit: int = 10) -> list[tuple[str, int]]:
    """Most-mentioned entities as (text, mentions), descending."""
    entities = [
        (data.get("text", ""), int(data.get("mentions", 0)))
        for _, data in _nodes_of_kind(graph, "entity")
    ]
    entities.sort(key=lambda item: item[1], reverse=True)
    return entities[:limit]


def top_cooccurrences(graph: Any, limit: int = 10) -> list[tuple[str, str, int]]:
    """Strongest entity co-occurrence pairs as (left, right, weight)."""
    pairs = []
    for left, right, data in graph.edges(data=True):
        if data.get("kind") != "CO_OCCURS":
            continue
        left_text = graph.nodes[left].get("text", left)
        right_text = graph.nodes[right].get("text", right)
        pairs.append((left_text, right_text, int(data.get("weight", 1))))
    pairs.sort(key=lambda item: item[2], reverse=True)
    return pairs[:limit]


def top_citations(graph: Any, limit: int = 10) -> list[tuple[str, str, int]]:
    """Most-cited identifiers as (type, identifier, citing chunks)."""
    rows = []
    for node, data in _nodes_of_kind(graph, "citation"):
        citing = sum(
            1 for _, _, edge in graph.in_edges(node, data=True) if edge.get("kind") == "CITES"
        )
        rows.append((data.get("citation_type", ""), data.get("identifier", node), citing))
    rows.sort(key=lambda item: item[2], reverse=True)
    return rows[:limit]


def detect_anomalies(
    graph: Any,
    low_confidence: float = LOW_CONFIDENCE_THRESHOLD,
    hub_mentions: int = HUB_MENTIONS_THRESHOLD,
) -> list[Anomaly]:
    """Flag suspicious graph regions worth re-checking.

    - documents with very low OCR confidence (likely OCR failure)
    - chunks with empty extracted text
    - documents with zero entities and zero citations (nothing extracted)
    - entity hubs (mentioned everywhere; often a junk pattern)
    """
    anomalies: list[Anomaly] = []

    documents = _nodes_of_kind(graph, "document")
    for node, data in documents:
        confidence = float(data.get("ocr_confidence_mean") or 0.0)
        if confidence < low_confidence:
            anomalies.append(
                Anomaly(
                    "low_confidence",
                    node,
                    f"ocr_confidence_mean={confidence:.2f} < {low_confidence}",
                )
            )

        meaningful_out = 0
        for _, target, edge in graph.out_edges(node, data=True):
            if edge.get("kind") != "CONTAINS":
                continue
            for _, _, chunk_edge in graph.out_edges(target, data=True):
                if chunk_edge.get("kind") in ("MENTIONS", "CITES"):
                    meaningful_out += 1
        if meaningful_out == 0:
            anomalies.append(Anomaly("empty_document", node, "no entities or citations extracted"))

    for node, data in _nodes_of_kind(graph, "chunk"):
        if not (data.get("text") or "").strip():
            anomalies.append(Anomaly("empty_chunk", node, "extracted text is empty"))

    for node, data in _nodes_of_kind(graph, "entity"):
        mentions = int(data.get("mentions", 0))
        if mentions >= hub_mentions:
            anomalies.append(
                Anomaly("entity_hub", node, f"mentioned {mentions} times; possible junk pattern")
            )

    return anomalies