"""
Nexus-Core Inference API (Fixed)
Fast and efficient chess engine with proper error handling
"""

from fastapi import FastAPI, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from pydantic import BaseModel, Field
import time
import logging
import os
from typing import Optional

from engine import NexusCoreEngine

logging.basicConfig(
    level=logging.INFO,
    format='%(asctime)s - %(levelname)s - %(message)s'
)
logger = logging.getLogger(__name__)

app = FastAPI(
    title="Nexus-Core Inference API",
    description="Fast chess engine (13M params)",
    version="2.0.0"
)

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

engine = None


class MoveRequest(BaseModel):
    fen: str
    depth: Optional[int] = Field(4, ge=1, le=6)
    time_limit: Optional[int] = Field(3000, ge=1000, le=10000)


class MoveResponse(BaseModel):
    best_move: str
    evaluation: float
    depth_searched: int
    nodes_evaluated: int
    time_taken: int


class HealthResponse(BaseModel):
    status: str
    model_loaded: bool
    version: str
    model_path: Optional[str] = None


@app.on_event("startup")
async def startup_event():
    global engine
    logger.info("🚀 Starting Nexus-Core API...")
    
    # Check model file
    model_path = "/app/models/nexus_core.onnx"
    
    # Debug: List files in models directory
    if os.path.exists("/app/models"):
        logger.info(f"📂 Files in /app/models/:")
        for f in os.listdir("/app/models"):
            full_path = os.path.join("/app/models", f)
            size = os.path.getsize(full_path) / (1024*1024)
            logger.info(f"   - {f} ({size:.2f} MB)")
    else:
        logger.error("❌ /app/models/ directory does not exist!")
        raise FileNotFoundError("/app/models/ not found")
    
    # Check if model exists
    if not os.path.exists(model_path):
        logger.error(f"❌ Model not found at {model_path}")
        logger.error("Available files:", os.listdir("/app/models") if os.path.exists("/app/models") else "No models dir")
        raise FileNotFoundError(f"Model file not found: {model_path}")
    
    logger.info(f"✅ Model found: {model_path} ({os.path.getsize(model_path)/(1024*1024):.2f} MB)")
    
    try:
        engine = NexusCoreEngine(
            model_path=model_path,
            num_threads=2
        )
        logger.info("✅ Nexus-Core engine loaded successfully")
    except Exception as e:
        logger.error(f"❌ Failed to load engine: {e}", exc_info=True)
        raise


@app.get("/health", response_model=HealthResponse)
async def health_check():
    return {
        "status": "healthy" if engine else "unhealthy",
        "model_loaded": engine is not None,
        "version": "2.0.0",
        "model_path": "/app/models/nexus_core.onnx" if engine else None
    }


@app.post("/get-move", response_model=MoveResponse)
async def get_move(request: MoveRequest):
    if not engine:
        raise HTTPException(503, "Engine not loaded")
    
    if not engine.validate_fen(request.fen):
        raise HTTPException(400, "Invalid FEN")
    
    start = time.time()
    
    try:
        result = engine.get_best_move(
            request.fen,
            request.depth,
            request.time_limit
        )
        
        logger.info(
            f"Move: {result['best_move']} | "
            f"Eval: {result['evaluation']:+.2f} | "
            f"Depth: {result['depth_searched']} | "
            f"Nodes: {result['nodes_evaluated']} | "
            f"Time: {result['time_taken']}ms"
        )
        
        return MoveResponse(**result)
    
    except Exception as e:
        logger.error(f"Error during search: {e}", exc_info=True)
        raise HTTPException(500, str(e))


@app.get("/")
async def root():
    return {
        "name": "Nexus-Core API",
        "version": "2.0.0",
        "model": "13M parameters",
        "speed": "Ultra-fast (0.5-1s per move)",
        "status": "healthy" if engine else "loading",
        "endpoints": {
            "POST /get-move": "Get best move",
            "GET /health": "Health check",
            "GET /docs": "API documentation"
        }
    }


if __name__ == "__main__":
    import uvicorn
    uvicorn.run(app, host="0.0.0.0", port=7860, log_level="info")