from uuid import NAMESPACE_URL, uuid5

from backend.database.schemas import Chunk
from backend.embeddings.embedder import embedder
from backend.core.config import settings


def cosine(a: list[float], b: list[float]) -> float:
    return sum(x * y for x, y in zip(a, b))


class InMemoryVectorStore:
    def __init__(self) -> None:
        self._vectors: dict[str, list[tuple[Chunk, list[float]]]] = {}

    def index(self, repo_id: str, chunks: list[Chunk]) -> None:
        self._vectors[repo_id] = [(chunk, embedder.embed(chunk.content)) for chunk in chunks]

    def search(self, repo_id: str, query: str, top_k: int = 8) -> list[tuple[Chunk, float]]:
        query_vector = embedder.embed(query)
        scored = [
            (chunk, cosine(query_vector, vector))
            for chunk, vector in self._vectors.get(repo_id, [])
        ]
        return sorted(scored, key=lambda item: item[1], reverse=True)[:top_k]


class QdrantVectorStore:
    def __init__(self) -> None:
        if not settings.qdrant_url:
            raise ValueError("Qdrant URL is required when use_qdrant=True")
        try:
            from qdrant_client import QdrantClient
            from qdrant_client.http import models as rest
        except ImportError as exc:
            raise ImportError(
                "qdrant-client is required for Qdrant vector storage. Install qdrant-client."
            ) from exc

        self.rest = rest
        self.client = QdrantClient(
            url=settings.qdrant_url,
            api_key=settings.qdrant_api_key,
            prefer_grpc=False,
            timeout=settings.qdrant_timeout_seconds,
        )
        self.collection_name = settings.qdrant_collection
        self._ensure_collection()

    def _ensure_collection(self) -> None:
        try:
            collections = self.client.get_collections().collections
            existing = [collection.name for collection in collections]
        except Exception:
            existing = []

        if self.collection_name not in existing:
            self.client.recreate_collection(
                collection_name=self.collection_name,
                vectors_config=self.rest.VectorParams(
                    size=settings.embedding_dimensions,
                    distance=self.rest.Distance.COSINE,
                ),
            )
        self._ensure_payload_indexes()

    def _ensure_payload_indexes(self) -> None:
        try:
            self.client.create_payload_index(
                collection_name=self.collection_name,
                field_name="repo_id",
                field_schema=self.rest.PayloadSchemaType.KEYWORD,
            )
        except Exception as exc:
            message = str(exc).lower()
            if "already exists" not in message and "conflict" not in message:
                raise

    def _point_id(self, chunk_id: str) -> str:
        return str(uuid5(NAMESPACE_URL, chunk_id))

    def index(self, repo_id: str, chunks: list[Chunk]) -> None:
        points = []
        for chunk in chunks:
            points.append(
                self.rest.PointStruct(
                    id=self._point_id(chunk.id),
                    vector=embedder.embed(chunk.content),
                    payload={
                        "chunk_id": chunk.id,
                        "repo_id": repo_id,
                        "path": chunk.path,
                        "language": chunk.language,
                        "symbol": chunk.symbol,
                        "kind": chunk.kind,
                        "start_line": chunk.start_line,
                        "end_line": chunk.end_line,
                        "content": chunk.content,
                    },
                )
            )
        batch_size = max(settings.qdrant_upsert_batch_size, 1)
        for start in range(0, len(points), batch_size):
            batch = points[start : start + batch_size]
            self.client.upsert(collection_name=self.collection_name, points=batch)

    def search(self, repo_id: str, query: str, top_k: int = 8) -> list[tuple[Chunk, float]]:
        query_vector = embedder.embed(query)
        query_filter = self.rest.Filter(
            must=[
                self.rest.FieldCondition(
                    key="repo_id",
                    match=self.rest.MatchValue(value=repo_id),
                )
            ]
        )
        if hasattr(self.client, "search"):
            response = self.client.search(
                collection_name=self.collection_name,
                query_vector=query_vector,
                limit=top_k,
                query_filter=query_filter,
            )
        else:
            query_response = self.client.query_points(
                collection_name=self.collection_name,
                query=query_vector,
                limit=top_k,
                query_filter=query_filter,
            )
            response = query_response.points

        results: list[tuple[Chunk, float]] = []
        for point in response:
            payload = point.payload or {}
            chunk = Chunk(
                id=payload.get("chunk_id", str(point.id)),
                repo_id=repo_id,
                path=payload.get("path", ""),
                language=payload.get("language", ""),
                symbol=payload.get("symbol", "file"),
                kind=payload.get("kind", "text"),
                start_line=int(payload.get("start_line", 1)),
                end_line=int(payload.get("end_line", 1)),
                content=payload.get("content", ""),
            )
            score = float(point.score or 0.0)
            results.append((chunk, score))
        return results


vector_store = QdrantVectorStore() if settings.use_qdrant else InMemoryVectorStore()