from __future__ import annotations

import json
import os
import hashlib
from pathlib import Path
from typing import List

import chromadb
from chromadb.config import Settings
from sentence_transformers import SentenceTransformer

from src.utils.logger import get_logger
from config.settings import settings

logger = get_logger(__name__)


class ChromaVectorDBManager:
    """Corporate-friendly ChromaDB manager - completely offline."""

    def __init__(self, model_name: str = None, db_path: str = None):
        self.model_name = model_name or getattr(
            settings, 'EMBEDDING_MODEL', 'sentence-transformers/all-MiniLM-L6-v2'
        )
        self.embedding_model = SentenceTransformer(self.model_name)

        self.db_path = db_path or getattr(settings, 'CHROMADB_PATH', './chroma_db')
        os.makedirs(self.db_path, exist_ok=True)

        self.client = chromadb.PersistentClient(
            path=self.db_path,
            settings=Settings(
                anonymized_telemetry=False,
                allow_reset=True,
                is_persistent=True
            )
        )

        self.collection_name = getattr(settings, 'COLLECTION_NAME', 'rag_chunks')
        self.collection = self._get_collection()

        logger.info(f"ChromaDB initialized at: {self.db_path}")

    def _get_collection(self):
        """Get or create collection without embedding function."""
        try:
            return self.client.get_collection(name=self.collection_name)
        except Exception:
            try:
                self.client.delete_collection(name=self.collection_name)
            except Exception:
                pass
            return self.client.create_collection(
                name=self.collection_name,
                metadata={"description": "RAG chunks"}
            )

    def generate_embeddings(self, texts: List[str]) -> List[List[float]]:
        """Generate embeddings using local sentence-transformers."""
        embeddings = self.embedding_model.encode(
            texts,
            batch_size=32,
            show_progress_bar=len(texts) > 100,
            convert_to_tensor=False
        )
        return embeddings.tolist()

    def add_chunks_to_db(self, chunks: list, source_file: str) -> bool:
        """Add chunks (list of dicts) to ChromaDB with manual embedding generation."""
        if not chunks:
            return True

        texts, ids, metadatas = [], [], []
        seen_hashes = set()

        for chunk in chunks:
            text = chunk.get("text", "").strip()
            if not text:
                continue

            text_hash = hashlib.md5(text.encode()).hexdigest()
            if text_hash in seen_hashes:
                continue
            seen_hashes.add(text_hash)

            chunk_id = f"{source_file}_{chunk.get('chunk_id', 0)}_{text_hash[:8]}"
            try:
                if self.collection.get(ids=[chunk_id])['ids']:
                    continue
            except Exception:
                pass

            texts.append(text)
            ids.append(chunk_id)

            metadata = {
                "source_file": source_file,
                "chunk_index": chunk.get("chunk_id", 0),
                "char_length": len(text),
                "text_hash": text_hash
            }
            metadatas.append(metadata)

        if not texts:
            return True

        embeddings = self.generate_embeddings(texts)
        self.collection.add(
            embeddings=embeddings,
            documents=texts,
            metadatas=metadatas,
            ids=ids
        )

        logger.info(f"Added {len(texts)} chunks from {source_file} to ChromaDB")
        return True

    def search_for_rag(
        self,
        query: str,
        n_results: int = 5,
        use_truncated: bool = False,
        filter_128_context: bool = False
    ) -> List[dict]:
        """Search using manual query embedding generation - completely offline."""
        query_embedding = self.generate_embeddings([query])[0]

        results = self.collection.query(
            query_embeddings=[query_embedding],
            n_results=min(n_results * 2, 20),
            include=["documents", "metadatas", "distances"]
        )

        search_results = []
        for i, (doc, metadata, distance) in enumerate(zip(
            results['documents'][0], results['metadatas'][0], results['distances'][0]
        )):
            if len(search_results) >= n_results:
                break

            similarity_score = 1 / (1 + distance)
            result = {
                "id": results['ids'][0][i],
                "score": similarity_score,
                "distance": distance,
                "text": doc,
                "source_file": metadata["source_file"],
                "chunk_index": metadata["chunk_index"]
            }
            search_results.append(result)

        return search_results

    def reset_database(self):
        """Reset/delete existing collection."""
        try:
            self.client.delete_collection(name=self.collection_name)
            self.collection = self._get_collection()
            logger.info(f"Reset collection: {self.collection_name}")
            return True
        except Exception as e:
            logger.error(f"Failed to reset database: {e}")
            return False

    def get_collection_stats(self) -> dict:
        """Get collection statistics."""
        count = self.collection.count()

        db_size_mb = 0
        try:
            for file_path in Path(self.db_path).rglob("*"):
                if file_path.is_file():
                    db_size_mb += file_path.stat().st_size
            db_size_mb /= (1024 * 1024)
        except Exception:
            db_size_mb = 0

        return {
            "total_chunks": count,
            "collection_name": self.collection_name,
            "embedding_model": self.model_name,
            "db_path": self.db_path,
            "db_size_mb": db_size_mb
        }

    def process_all_chunks(self, chunks_dir: str = None) -> bool:
        """Process all *_extracted.json files and build ChromaDB."""
        if not chunks_dir:
            chunks_dir = getattr(settings, 'PROCESSED_TEXT_DIR', './data/processed_text')

        chunk_files = list(Path(chunks_dir).glob("*_extracted.json"))
        logger.info(f"Found {len(chunk_files)} extracted JSON files to process")

        total_processed = 0
        for chunk_file in chunk_files:
            try:
                with open(chunk_file, "r", encoding="utf-8") as f:
                    data = json.load(f)

                # Handle the actual structure of extracted JSON files
                if isinstance(data, dict) and "initial_chunks" in data:
                    # New format: { "source_info": {...}, "initial_chunks": [...] }
                    chunks = data["initial_chunks"]
                elif isinstance(data, list):
                    # Old format: list of chunks directly
                    chunks = data
                else:
                    logger.warning(f"Unexpected format in {chunk_file.name}")
                    continue

                if chunks and self.add_chunks_to_db(chunks, source_file=chunk_file.name):
                    total_processed += len(chunks)
                    logger.info(f"Processed {chunk_file.name}: {len(chunks)} chunks")

            except Exception as e:
                logger.error(f"Error processing {chunk_file}: {e}")
                continue

        logger.info(f"Successfully processed {total_processed} total chunks")
        return total_processed > 0