"""FastAPI application for EyeWiki RAG system."""

import logging
import time
from contextlib import asynccontextmanager
from pathlib import Path
from typing import Optional

from fastapi import FastAPI, HTTPException, Request, status
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import StreamingResponse
from pydantic import BaseModel, Field
import gradio as gr

from src.api.gradio_ui import create_gradio_interface
from config.settings import LLMProvider, Settings
from src.llm.llm_client import LLMClient
from src.llm.ollama_client import OllamaClient
from src.llm.openai_client import OpenAIClient
from src.llm.sentence_transformer_client import SentenceTransformerClient
from src.rag.query_engine import EyeWikiQueryEngine, QueryResponse
from src.rag.reranker import CrossEncoderReranker
from src.rag.retriever import HybridRetriever
from src.vectorstore.qdrant_store import QdrantStoreManager


# Configure logging
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s - %(name)s - %(levelname)s - %(message)s"
)
logger = logging.getLogger(__name__)


# ============================================================================
# Request/Response Models
# ============================================================================

class QueryRequest(BaseModel):
    """
    Request model for query endpoint.

    Attributes:
        question: User's question
        include_sources: Whether to include source information
        filters: Optional metadata filters (disease_name, icd_codes, etc.)
    """
    question: str = Field(..., min_length=3, description="User's question")
    include_sources: bool = Field(default=True, description="Include source documents")
    filters: Optional[dict] = Field(default=None, description="Metadata filters")


class StreamQueryRequest(BaseModel):
    """
    Request model for streaming query endpoint.

    Attributes:
        question: User's question
        filters: Optional metadata filters
    """
    question: str = Field(..., min_length=3, description="User's question")
    filters: Optional[dict] = Field(default=None, description="Metadata filters")


class HealthResponse(BaseModel):
    """
    Response model for health check.

    Attributes:
        status: Overall status (healthy/unhealthy)
        llm: LLM service status
        qdrant: Qdrant service status
        query_engine: Query engine initialization status
        timestamp: Check timestamp
    """
    status: str = Field(..., description="Overall status")
    llm: dict = Field(..., description="LLM service status")
    qdrant: dict = Field(..., description="Qdrant service status")
    query_engine: dict = Field(..., description="Query engine status")
    timestamp: float = Field(..., description="Unix timestamp")


class StatsResponse(BaseModel):
    """
    Response model for statistics endpoint.

    Attributes:
        collection_info: Qdrant collection information
        pipeline_config: Query engine pipeline configuration
        documents_indexed: Number of indexed documents
        timestamp: Stats timestamp
    """
    collection_info: dict = Field(..., description="Collection information")
    pipeline_config: dict = Field(..., description="Pipeline configuration")
    documents_indexed: int = Field(..., description="Number of indexed documents")
    timestamp: float = Field(..., description="Unix timestamp")


class ErrorResponse(BaseModel):
    """
    Error response model.

    Attributes:
        error: Error message
        detail: Optional detailed error information
        timestamp: Error timestamp
    """
    error: str = Field(..., description="Error message")
    detail: Optional[str] = Field(default=None, description="Error details")
    timestamp: float = Field(..., description="Unix timestamp")


# ============================================================================
# Global State
# ============================================================================

class AppState:
    """Application state container."""

    def __init__(self):
        self.settings: Optional[Settings] = None
        self.llm_client: Optional[LLMClient] = None
        self.embedding_client: Optional[SentenceTransformerClient] = None
        self.qdrant_manager: Optional[QdrantStoreManager] = None
        self.retriever: Optional[HybridRetriever] = None
        self.reranker: Optional[CrossEncoderReranker] = None
        self.query_engine: Optional[EyeWikiQueryEngine] = None
        self.initialized: bool = False
        self.initialization_error: Optional[str] = None


app_state = AppState()


# ============================================================================
# Lifecycle Management
# ============================================================================

@asynccontextmanager
async def lifespan(app: FastAPI):
    """
    Application lifespan manager.

    Handles startup and shutdown events.
    """
    # Startup
    logger.info("Starting EyeWiki RAG API...")

    try:
        # Load settings
        logger.info("Loading settings...")
        app_state.settings = Settings()

        # Initialize LLM client based on provider
        logger.info(f"Initializing LLM client (provider: {app_state.settings.llm_provider.value})...")
        if app_state.settings.llm_provider == LLMProvider.OPENAI:
            app_state.llm_client = OpenAIClient(
                api_key=app_state.settings.openai_api_key,
                base_url=app_state.settings.openai_base_url,
                model=app_state.settings.openai_model,
            )
        else:
            app_state.llm_client = OllamaClient(
                base_url=app_state.settings.ollama_base_url,
                embedding_model=None,  # We use SentenceTransformerClient for embeddings
                llm_model=app_state.settings.llm_model,
                timeout=app_state.settings.ollama_timeout,
            )

        # Initialize embedding client (sentence-transformers for stable embeddings)
        logger.info("Initializing embedding client...")
        app_state.embedding_client = SentenceTransformerClient(
            model_name=app_state.settings.embedding_model,
        )
        logger.info(f"Embedding model loaded: {app_state.settings.embedding_model}")

        # Initialize Qdrant manager
        logger.info("Initializing Qdrant manager...")
        app_state.qdrant_manager = QdrantStoreManager(
            collection_name=app_state.settings.qdrant_collection_name,
            path=app_state.settings.qdrant_path,
            url=app_state.settings.qdrant_url,
            api_key=app_state.settings.qdrant_api_key,
            embedding_dim=app_state.embedding_client.embedding_dim,
        )

        # Verify collection exists
        collection_info = app_state.qdrant_manager.get_collection_info()
        if not collection_info:
            raise RuntimeError(
                f"Qdrant collection '{app_state.settings.qdrant_collection_name}' not found. "
                "Please run 'python scripts/build_index.py --index-vectors' first."
            )

        logger.info(
            f"Qdrant collection loaded: {collection_info['vectors_count']} vectors"
        )

        # Initialize retriever
        logger.info("Initializing retriever...")
        app_state.retriever = HybridRetriever(
            qdrant_manager=app_state.qdrant_manager,
            embedding_client=app_state.embedding_client,
        )

        # Initialize reranker
        logger.info("Initializing reranker...")
        app_state.reranker = CrossEncoderReranker(
            model_name=app_state.settings.reranker_model,
        )

        # Load prompt files
        project_root = Path(__file__).parent.parent.parent
        prompts_dir = project_root / "prompts"

        system_prompt_path = prompts_dir / "system_prompt.txt"
        query_prompt_path = prompts_dir / "query_prompt.txt"
        disclaimer_path = prompts_dir / "medical_disclaimer.txt"

        # Verify prompts exist
        if not system_prompt_path.exists():
            logger.warning(f"System prompt not found: {system_prompt_path}")
            system_prompt_path = None

        if not query_prompt_path.exists():
            logger.warning(f"Query prompt not found: {query_prompt_path}")
            query_prompt_path = None

        if not disclaimer_path.exists():
            logger.warning(f"Disclaimer not found: {disclaimer_path}")
            disclaimer_path = None

        # Initialize query engine
        logger.info("Initializing query engine...")
        app_state.query_engine = EyeWikiQueryEngine(
            retriever=app_state.retriever,
            reranker=app_state.reranker,
            llm_client=app_state.llm_client,
            system_prompt_path=system_prompt_path,
            query_prompt_path=query_prompt_path,
            disclaimer_path=disclaimer_path,
            max_context_tokens=app_state.settings.max_context_tokens,
            retrieval_k=20,
            rerank_k=5,
        )

        app_state.initialized = True
        logger.info("EyeWiki RAG API started successfully")
        logger.info("Gradio UI available at /ui")

    except Exception as e:
        error_msg = f"Failed to initialize application: {e}"
        logger.error(error_msg, exc_info=True)
        app_state.initialization_error = error_msg
        # Don't raise - allow app to start but endpoints will return errors

    yield

    # Shutdown
    logger.info("Shutting down EyeWiki RAG API...")

    # Cleanup Qdrant client
    if app_state.qdrant_manager:
        try:
            app_state.qdrant_manager.close()
            logger.info("Qdrant client closed")
        except Exception as e:
            logger.error(f"Error closing Qdrant client: {e}")


# ============================================================================
# FastAPI App
# ============================================================================

app = FastAPI(
    title="EyeWiki RAG API",
    description="Retrieval-Augmented Generation API for EyeWiki medical knowledge base",
    version="1.0.0",
    lifespan=lifespan,
)


# ============================================================================
# Middleware
# ============================================================================

# CORS middleware for local development
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],  # Configure appropriately for production
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)


@app.middleware("http")
async def log_requests(request: Request, call_next):
    """
    Request logging middleware.

    Logs all incoming requests with timing information.
    """
    start_time = time.time()

    # Log request
    logger.info(
        f"Request: {request.method} {request.url.path} "
        f"from {request.client.host if request.client else 'unknown'}"
    )

    # Process request
    response = await call_next(request)

    # Log response
    duration = time.time() - start_time
    logger.info(
        f"Response: {response.status_code} "
        f"in {duration:.3f}s"
    )

    return response


# ============================================================================
# Helper Functions
# ============================================================================

def check_initialization():
    """
    Check if application is initialized.

    Raises:
        HTTPException: If app not initialized
    """
    if not app_state.initialized:
        error_detail = app_state.initialization_error or "Application not initialized"
        raise HTTPException(
            status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
            detail=error_detail
        )


# ============================================================================
# Endpoints
# ============================================================================

@app.get("/")
async def root():
    """
    Root endpoint.

    Returns:
        Welcome message with API information
    """
    return {
        "name": "EyeWiki RAG API",
        "version": "1.0.0",
        "description": "Retrieval-Augmented Generation API for EyeWiki medical knowledge base",
        "endpoints": {
            "health": "GET /health",
            "query": "POST /query",
            "stream": "POST /query/stream",
            "stats": "GET /stats",
            "docs": "GET /docs",
        }
    }


@app.get("/health", response_model=HealthResponse)
async def health_check():
    """
    Health check endpoint.

    Checks status of:
    - Ollama service
    - Qdrant service
    - Query engine initialization

    Returns:
        HealthResponse with service statuses
    """
    timestamp = time.time()

    # Check LLM provider
    llm_status = {"status": "unknown", "detail": None}
    if app_state.llm_client:
        provider = app_state.settings.llm_provider.value if app_state.settings else "unknown"
        llm_status["provider"] = provider
        try:
            if isinstance(app_state.llm_client, OllamaClient):
                health_ok = app_state.llm_client.check_health()
                llm_status["status"] = "healthy" if health_ok else "unhealthy"
                llm_status["model"] = app_state.llm_client.llm_model
            else:
                # For OpenAI-compatible clients, assume healthy if initialized
                llm_status["status"] = "healthy"
                llm_status["model"] = app_state.llm_client.llm_model
        except Exception as e:
            llm_status = {"status": "unhealthy", "detail": str(e), "provider": provider}
    else:
        llm_status = {"status": "not_initialized", "detail": "Client not created"}

    # Check Qdrant
    qdrant_status = {"status": "unknown", "detail": None}
    if app_state.qdrant_manager:
        try:
            info = app_state.qdrant_manager.get_collection_info()
            if info:
                qdrant_status = {
                    "status": "healthy",
                    "collection": info["name"],
                    "vectors_count": info["vectors_count"],
                }
            else:
                qdrant_status = {
                    "status": "unhealthy",
                    "detail": "Collection not found"
                }
        except Exception as e:
            qdrant_status = {"status": "unhealthy", "detail": str(e)}
    else:
        qdrant_status = {"status": "not_initialized", "detail": "Manager not created"}

    # Check query engine
    query_engine_status = {
        "status": "initialized" if app_state.initialized else "not_initialized",
        "error": app_state.initialization_error,
    }

    # Overall status
    overall_status = "healthy"
    if not app_state.initialized:
        overall_status = "unhealthy"
    elif llm_status["status"] != "healthy" or qdrant_status["status"] != "healthy":
        overall_status = "degraded"

    return HealthResponse(
        status=overall_status,
        llm=llm_status,
        qdrant=qdrant_status,
        query_engine=query_engine_status,
        timestamp=timestamp,
    )


@app.post("/query", response_model=QueryResponse)
async def query(request: QueryRequest):
    """
    Main query endpoint.

    Processes a question using the full RAG pipeline:
    1. Retrieval (hybrid search)
    2. Reranking (cross-encoder)
    3. Context assembly
    4. LLM generation

    Args:
        request: QueryRequest with question and options

    Returns:
        QueryResponse with answer, sources, and disclaimer

    Raises:
        HTTPException: If service unavailable or query fails
    """
    check_initialization()

    try:
        logger.info(f"Processing query: '{request.question}'")

        response = app_state.query_engine.query(
            question=request.question,
            include_sources=request.include_sources,
            filters=request.filters,
        )

        logger.info(
            f"Query complete: {len(response.sources)} sources, "
            f"confidence: {response.confidence:.2f}"
        )

        return response

    except Exception as e:
        logger.error(f"Error processing query: {e}", exc_info=True)
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Error processing query: {str(e)}"
        )


@app.post("/query/stream")
async def stream_query(request: StreamQueryRequest):
    """
    Streaming query endpoint.

    Returns answer as Server-Sent Events (SSE) for real-time streaming.

    Args:
        request: StreamQueryRequest with question and options

    Returns:
        StreamingResponse with SSE

    Raises:
        HTTPException: If service unavailable or query fails
    """
    check_initialization()

    async def generate():
        """Generate SSE stream."""
        try:
            logger.info(f"Processing streaming query: '{request.question}'")

            # Stream answer chunks
            for chunk in app_state.query_engine.stream_query(
                question=request.question,
                filters=request.filters,
            ):
                # SSE format: data: <content>\n\n
                yield f"data: {chunk}\n\n"

            logger.info("Streaming query complete")

        except Exception as e:
            logger.error(f"Error in streaming query: {e}", exc_info=True)
            yield f"data: [ERROR] {str(e)}\n\n"

    return StreamingResponse(
        generate(),
        media_type="text/event-stream",
        headers={
            "Cache-Control": "no-cache",
            "Connection": "keep-alive",
        }
    )


@app.get("/stats", response_model=StatsResponse)
async def get_stats():
    """
    Get index and pipeline statistics.

    Returns:
        StatsResponse with collection info and pipeline config

    Raises:
        HTTPException: If service unavailable or stats retrieval fails
    """
    check_initialization()

    try:
        # Get collection info
        collection_info = app_state.qdrant_manager.get_collection_info()
        if not collection_info:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Collection not found"
            )

        # Get pipeline config
        pipeline_config = app_state.query_engine.get_pipeline_info()

        return StatsResponse(
            collection_info=collection_info,
            pipeline_config=pipeline_config,
            documents_indexed=collection_info.get("vectors_count", 0),
            timestamp=time.time(),
        )

    except HTTPException:
        raise
    except Exception as e:
        logger.error(f"Error retrieving stats: {e}", exc_info=True)
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Error retrieving stats: {str(e)}"
        )


# ============================================================================
# Error Handlers
# ============================================================================

@app.exception_handler(HTTPException)
async def http_exception_handler(request: Request, exc: HTTPException):
    """
    Handle HTTP exceptions.

    Returns:
        JSON error response with proper status code
    """
    return {
        "error": exc.detail,
        "status_code": exc.status_code,
        "timestamp": time.time(),
    }


@app.exception_handler(Exception)
async def general_exception_handler(request: Request, exc: Exception):
    """
    Handle general exceptions.

    Returns:
        JSON error response with 500 status
    """
    logger.error(f"Unhandled exception: {exc}", exc_info=True)

    return {
        "error": "Internal server error",
        "detail": str(exc),
        "status_code": status.HTTP_500_INTERNAL_SERVER_ERROR,
        "timestamp": time.time(),
    }


# ============================================================================
# Mount Gradio UI
# ============================================================================

# Create and mount Gradio interface
# Gradio will access query_engine through app_state once initialized
gradio_interface = create_gradio_interface(
    query_engine_getter=lambda: app_state.query_engine
)
app = gr.mount_gradio_app(app, gradio_interface, path="/ui")
logger.info("Gradio UI mounted at /ui")