from __future__ import annotations

from collections import Counter
from datetime import datetime, timezone
from typing import Any

from news_mcp.entity_normalize import normalize_entity
from news_mcp.storage.sqlite_store import SQLiteClusterStore
from news_mcp.trends_resolution import resolve_entity_via_trends
from news_mcp.trends_related import get_related_topics


def _now_iso() -> str:
    return datetime.now(timezone.utc).isoformat()


def _collect_local_related(
    store: SQLiteClusterStore,
    subject_norm: str,
    subject_resolution: dict[str, Any],
    timeframe_hours: float,
    limit: int,
) -> list[tuple[str, int]]:
    clusters = store.get_latest_clusters_all_topics(
        ttl_hours=float(timeframe_hours),
        limit=max(limit * 20, 200),
    )
    counter: Counter[str] = Counter()
    subject_terms = {
        subject_norm.strip().lower(),
        str(subject_resolution.get("normalized") or "").strip().lower(),
        str(subject_resolution.get("canonical_label") or "").strip().lower(),
        str(subject_resolution.get("mid") or "").strip().lower(),
    }
    subject_terms = {t for t in subject_terms if t}
    for cluster in clusters:
        # Match clusters by any of the resolved identity terms.
        haystack: list[str] = []
        for ent in cluster.get("entities", []) or []:
            haystack.append(str(ent).strip().lower())
        for res in cluster.get("entityResolutions", []) or []:
            if not isinstance(res, dict):
                continue
            for key in ("normalized", "canonical_label", "mid"):
                val = res.get(key)
                if val:
                    haystack.append(str(val).strip().lower())

        haystack_set = set([h for h in haystack if h])
        if not (haystack_set & subject_terms):
            continue

        # Count other entities normalized.
        for ent in cluster.get("entities", []) or []:
            ent_norm = normalize_entity(ent)
            if not ent_norm:
                continue
            ent_key = ent_norm.strip().lower()
            if ent_key in subject_terms:
                continue
            counter[ent_norm] += 1
    return counter.most_common(limit)


def _collect_trends_related(subject_norm: str, subject_resolution: dict[str, Any], limit: int) -> list[dict[str, Any]]:
    topics = get_related_topics(subject_norm, limit=limit)
    if topics:
        return topics

    # Fallback to autocomplete candidates if related topics are unavailable.
    candidates = subject_resolution.get("candidates") or []
    out = []
    for cand in candidates:
        title = cand.get("title")
        if not title:
            continue
        out.append(
            {
                "canonical_label": title,
                "normalized": normalize_entity(title),
                "mid": cand.get("mid"),
                "type": cand.get("type"),
            }
        )
        if len(out) >= limit:
            return out
    return out


def related_recent_entities(
    store: SQLiteClusterStore,
    subject: str,
    timeframe_hours: float,
    limit: int,
    include_trends: bool = True,
) -> dict[str, Any]:
    subject_norm = normalize_entity(subject)
    if not subject_norm:
        return {
            "subject": {"raw": subject, "normalized": ""},
            "related": [],
        }

    subject_resolution = resolve_entity_via_trends(subject_norm)
    store.record_entity_request(subject_norm, subject_resolution.get("mid"))
    store.upsert_entity_metadata(
        normalized_label=subject_norm,
        canonical_label=subject_resolution.get("canonical_label"),
        mid=subject_resolution.get("mid"),
        sources=[subject_resolution.get("source") or "resolver"],
    )

    local_related = _collect_local_related(
        store=store,
        subject_norm=subject_norm,
        subject_resolution=subject_resolution,
        timeframe_hours=timeframe_hours,
        limit=limit,
    )
    trends_related = _collect_trends_related(subject_norm, subject_resolution, limit) if include_trends else []

    related_map: dict[str, dict[str, Any]] = {}

    def _entry(label: str) -> dict[str, Any]:
        key = label.strip().lower()
        if key not in related_map:
            related_map[key] = {
                "normalized": label,
                "canonical_label": label,
                "mid": None,
                "sources": set(),
                "scores": {},
            }
        return related_map[key]

    for label, count in local_related:
        if not label:
            continue
        entry = _entry(label)
        entry["sources"].add("local")
        entry["scores"]["local_count"] = int(count)
        store.upsert_entity_metadata(
            normalized_label=label,
            canonical_label=label,
            mid=None,
            sources=["local"],
        )

    # Only use enough trends results to fill remaining slots.
    remaining = max(0, limit - len(related_map))
    for idx, cand in enumerate(trends_related[:remaining], start=1):
        label = cand.get("normalized")
        if not label:
            continue
        entry = _entry(label)
        entry["sources"].add("trends")
        entry["canonical_label"] = cand.get("canonical_label") or entry["canonical_label"]
        entry["mid"] = cand.get("mid") or entry["mid"]
        entry["scores"]["trends_rank"] = idx
        store.upsert_entity_metadata(
            normalized_label=label,
            canonical_label=cand.get("canonical_label"),
            mid=cand.get("mid"),
            sources=["trends"],
        )

    results = list(related_map.values())
    for item in results:
        item["sources"] = sorted(item["sources"])

    results.sort(
        key=lambda item: (
            -int(item["scores"].get("local_count", 0)),
            item["scores"].get("trends_rank", 9999),
            item["canonical_label"].lower(),
        )
    )

    return {
        "subject": {
            "raw": subject,
            "normalized": subject_norm,
            "canonical_label": subject_resolution.get("canonical_label") or subject_norm,
            "mid": subject_resolution.get("mid"),
            "resolved_at": subject_resolution.get("resolved_at") or _now_iso(),
            "source": subject_resolution.get("source"),
        },
        "related": results[: max(1, limit)],
    }