# ============================================================
# 混合嵌入（moduleId: knowledge-embedding, 可重生 ✅）
# 本地 sentence-transformers → API embeddings → None（检索降级 bigram）
# ============================================================
from __future__ import annotations

import json
import math
import os
import tempfile
import threading
from typing import Any

import httpx

_PATH_ENV = "APS_EMBEDDINGS_PATH"


def _cosine(a: list[float], b: list[float]) -> float:
    if not a or not b or len(a) != len(b):
        return 0.0
    dot = sum(x * y for x, y in zip(a, b))
    na = math.sqrt(sum(x * x for x in a))
    nb = math.sqrt(sum(y * y for y in b))
    if na <= 0 or nb <= 0:
        return 0.0
    return dot / (na * nb)


class EmbeddingProvider:
    """混合嵌入：local → api → disabled（检索走 bigram）。"""

    def __init__(self) -> None:
        self.mode = (os.environ.get("EMBEDDING_PROVIDER") or "auto").strip().lower()
        self.api_key = os.environ.get("EMBEDDING_API_KEY") or os.environ.get("LLM_API_KEY") or ""
        self.base_url = (os.environ.get("EMBEDDING_BASE_URL")
                         or os.environ.get("LLM_BASE_URL") or "").strip()
        self.model = (os.environ.get("EMBEDDING_MODEL") or "text-embedding-3-small").strip()
        self.local_model = os.environ.get("EMBEDDING_LOCAL_MODEL") or "BAAI/bge-small-zh-v1.5"
        self._local = None
        self._backend = self._resolve_backend()

    def _resolve_backend(self) -> str:
        want = self.mode
        if want in ("off", "none", "bigram"):
            return "none"
        if want in ("local", "auto"):
            try:
                from sentence_transformers import SentenceTransformer  # noqa: F401
                return "local"
            except Exception:
                if want == "local":
                    return "none"
        if want in ("api", "auto") and self.api_key and self.base_url:
            return "api"
        return "none"

    @property
    def enabled(self) -> bool:
        return self._backend in ("local", "api")

    @property
    def backend(self) -> str:
        return self._backend

    def _ensure_local(self):
        if self._local is None:
            from sentence_transformers import SentenceTransformer
            self._local = SentenceTransformer(self.local_model)
        return self._local

    def embed(self, texts: list[str]) -> list[list[float]] | None:
        """批量嵌入；不可用返回 None。"""
        if not texts:
            return []
        if self._backend == "local":
            model = self._ensure_local()
            vecs = model.encode(texts, normalize_embeddings=True)
            return [v.tolist() for v in vecs]
        if self._backend == "api":
            try:
                with httpx.Client(timeout=30.0) as client:
                    resp = client.post(
                        f"{self.base_url.rstrip('/')}/embeddings",
                        headers={"Authorization": f"Bearer {self.api_key}"},
                        json={"model": self.model, "input": texts},
                    )
                    resp.raise_for_status()
                    data = resp.json().get("data") or []
                    data = sorted(data, key=lambda x: x.get("index", 0))
                    return [d["embedding"] for d in data]
            except Exception:
                return None
        return None

    def embed_one(self, text: str) -> list[float] | None:
        out = self.embed([text])
        return out[0] if out else None


class EmbeddingStore:
    """向量仓：chunk/asset id → vector，JSON 落盘。"""

    def __init__(self, path: str | None = None) -> None:
        self.path = path or os.environ.get(_PATH_ENV, "server/data/embeddings.json")
        self._lock = threading.Lock()
        self.vectors: dict[str, list[float]] = self._load()

    def _load(self) -> dict[str, list[float]]:
        try:
            with open(self.path, "r", encoding="utf-8") as f:
                return json.load(f).get("vectors", {})
        except (FileNotFoundError, json.JSONDecodeError):
            return {}

    def _write(self) -> None:
        os.makedirs(os.path.dirname(self.path) or ".", exist_ok=True)
        fd, tmp = tempfile.mkstemp(dir=os.path.dirname(self.path) or ".", suffix=".tmp")
        try:
            with os.fdopen(fd, "w", encoding="utf-8") as f:
                json.dump({"vectors": self.vectors}, f, ensure_ascii=False)
            os.replace(tmp, self.path)
        except BaseException:
            if os.path.exists(tmp):
                os.unlink(tmp)
            raise

    def upsert_many(self, items: dict[str, list[float]]) -> None:
        with self._lock:
            self.vectors.update(items)
            self._write()

    def search(self, query_vec: list[float], top_k: int = 5) -> list[tuple[str, float]]:
        scored = [(_id, _cosine(query_vec, vec)) for _id, vec in self.vectors.items()]
        scored.sort(key=lambda x: -x[1])
        return scored[:top_k]


_provider: EmbeddingProvider | None = None
_stores: dict[str, EmbeddingStore] = {}
_stores_lock = threading.Lock()


def get_embedding_provider() -> EmbeddingProvider:
    global _provider
    if _provider is None:
        _provider = EmbeddingProvider()
    return _provider


def get_embedding_store() -> EmbeddingStore:
    from server.auth.context import get_identity
    from server.state.store import world_path_for

    tenant_uuid = get_identity().tenant_uuid
    with _stores_lock:
        store = _stores.get(tenant_uuid)
        if store is None:
            if tenant_uuid == "platform":
                path = os.environ.get(_PATH_ENV, "server/data/embeddings.json")
            else:
                world_path = world_path_for("knowledge", tenant_uuid)
                path = os.path.join(os.path.dirname(os.path.dirname(world_path)), "embeddings.json")
            store = EmbeddingStore(path)
            _stores[tenant_uuid] = store
        return store


def index_units(units: list[dict[str, Any]]) -> int:
    """为检索单元生成/更新向量；返回成功条数。"""
    prov = get_embedding_provider()
    if not prov.enabled:
        return 0
    store = get_embedding_store()
    texts, keys = [], []
    for u in units:
        key = u.get("chunkId") or u["assetId"]
        if key in store.vectors:
            continue
        texts.append((u.get("title") or "") + "\n" + (u.get("content") or ""))
        keys.append(f"{u['assetId']}:{key}")
    if not texts:
        return 0
    # 分批
    added = 0
    batch = 16
    for i in range(0, len(texts), batch):
        vecs = prov.embed(texts[i:i + batch])
        if not vecs:
            break
        store.upsert_many({keys[i + j]: vecs[j] for j in range(len(vecs))})
        added += len(vecs)
    return added