"""
DermIQ API Server
FastAPI backend — port binds instantly, engine loads in background thread
"""

import sys
import os
import logging
import threading
from contextlib import asynccontextmanager
from pathlib import Path

from fastapi import FastAPI, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from fastapi.staticfiles import StaticFiles
from fastapi.responses import FileResponse, JSONResponse
from pydantic import BaseModel, Field, field_validator

sys.path.insert(0, str(Path(__file__).parent))
from rag_engine import DermIQEngine

logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s | %(levelname)s | %(message)s",
)
logger = logging.getLogger("dermiq-api")

# ── Singleton engine ──────────────────────────────────────────────────────────
engine = DermIQEngine()


def _init_engine_background():
    """
    Runs in a daemon thread so uvicorn binds the port immediately.
    Queries return 503 until this finishes — frontend shows Initializing status.
    """
    logger.info("Background thread: starting engine initialization...")
    try:
        engine.initialize(force_rebuild=False)
        logger.info("Background thread: engine ready")
    except Exception as exc:
        logger.error(f"Background thread: engine init failed — {exc}", exc_info=True)


# ── Lifespan ──────────────────────────────────────────────────────────────────
@asynccontextmanager
async def lifespan(app: FastAPI):
    logger.info("DermIQ server starting — launching engine in background thread")
    t = threading.Thread(target=_init_engine_background, daemon=True)
    t.start()
    yield
    logger.info("DermIQ server shutting down")


# ── App ───────────────────────────────────────────────────────────────────────
app = FastAPI(
    title="DermIQ — Skin Disease RAG API",
    description="RAG API for skin disease classification. LangGraph + Cohere + FAISS.",
    version="1.0.0",
    lifespan=lifespan,
)

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# ── Frontend ──────────────────────────────────────────────────────────────────
frontend_path = Path(__file__).parent / "frontend"
if frontend_path.exists():
    app.mount("/static", StaticFiles(directory=str(frontend_path)), name="static")
    logger.info(f"Frontend mounted from: {frontend_path}")


# ── Pydantic models ───────────────────────────────────────────────────────────
class QueryRequest(BaseModel):
    question: str = Field(..., min_length=3, max_length=1000)

    @field_validator("question")
    @classmethod
    def sanitize_question(cls, v: str) -> str:
        return v.strip()


class QueryResponse(BaseModel):
    question: str
    answer: str
    sources: list[str]
    confidence: str
    processing_time: float
    docs_retrieved: int
    status: str = "success"


class RebuildRequest(BaseModel):
    confirm: bool = Field(..., description="Must be true to trigger rebuild")


# ── Routes ────────────────────────────────────────────────────────────────────
@app.get("/", include_in_schema=False)
async def serve_frontend():
    index_file = frontend_path / "index.html"
    if index_file.exists():
        return FileResponse(str(index_file))
    return JSONResponse({
        "message": "DermIQ API is running",
        "status": "ready" if engine.is_ready else "initializing",
        "docs": "/docs",
        "health": "/health",
    })


@app.get("/health", tags=["System"])
async def health_check():
    stats = engine.get_stats()
    return {
        "status": "healthy" if engine.is_ready else "initializing",
        "service": "DermIQ RAG API",
        "version": "1.0.0",
        "engine": stats,
    }


@app.post("/api/query", response_model=QueryResponse, tags=["RAG"])
async def run_query(request: QueryRequest):
    if not engine.is_ready:
        raise HTTPException(
            status_code=503,
            detail="Engine is still initializing — please wait ~2 minutes and retry.",
        )
    try:
        result = engine.query(request.question)
        return QueryResponse(**result)
    except ValueError as exc:
        raise HTTPException(status_code=400, detail=str(exc))
    except RuntimeError as exc:
        raise HTTPException(status_code=503, detail=str(exc))
    except Exception as exc:
        logger.error(f"Query error: {exc}", exc_info=True)
        raise HTTPException(status_code=500, detail="Internal error. Please retry.")


@app.post("/api/rebuild-index", tags=["Admin"])
async def rebuild_vector_index(request: RebuildRequest):
    if not request.confirm:
        raise HTTPException(status_code=400, detail="Set confirm: true to proceed.")
    try:
        engine.build_vectorstore(force_rebuild=True)
        return {"status": "success", "stats": engine.get_stats()}
    except Exception as exc:
        raise HTTPException(status_code=500, detail=str(exc))


@app.get("/api/stats", tags=["System"])
async def get_engine_stats():
    return engine.get_stats()


# ── Entry point ───────────────────────────────────────────────────────────────
if __name__ == "__main__":
    import uvicorn
    port = int(os.environ.get("PORT", 7860))
    uvicorn.run(
        "server:app",
        host="0.0.0.0",
        port=port,
        reload=False,
        log_level="info",
    )