"""
Main FastAPI application for Unsloth UI Backend
"""
import os
import secrets
import shutil
from contextlib import asynccontextmanager

from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware
from fastapi.staticfiles import StaticFiles
from fastapi.responses import FileResponse, HTMLResponse, Response
from pathlib import Path
from datetime import datetime

# Import routers
from routes import (
    auth_router,
    data_recipe_router,
    datasets_router,
    export_router,
    inference_router,
    models_router,
    training_router,
)
from auth import storage
from utils.hardware import detect_hardware, get_device, DeviceType
import utils.hardware.hardware as _hw_module

from utils.cache_cleanup import clear_unsloth_compiled_cache


@asynccontextmanager
async def lifespan(app: FastAPI):
    """Startup: detect hardware, print setup token if needed. Shutdown: clean up compiled cache."""
    # Clean up any stale compiled cache from previous runs
    clear_unsloth_compiled_cache()

    # Remove stale .venv_overlay from previous versions — no longer used.
    # Version switching now uses .venv_t5/ (pre-installed by setup.sh).
    overlay_dir = Path(__file__).resolve().parent.parent.parent / ".venv_overlay"
    if overlay_dir.is_dir():
        shutil.rmtree(overlay_dir, ignore_errors=True)

    # Detect hardware first — sets DEVICE global used everywhere
    detect_hardware()

    # Disable flex attention on Blackwell+ GPUs (sm_120 and above)
    if get_device() == DeviceType.CUDA:
        import torch
        props = torch.cuda.get_device_properties(0)
        sm_version = props.major * 10 + props.minor
        if sm_version >= 120:
            os.environ["UNSLOTH_ENABLE_FLEX_ATTENTION"] = "0"
            import logging
            logging.getLogger(__name__).info(
                f"GPU sm_{sm_version} detected — setting UNSLOTH_FLEX_ATTENTION=0"
            )

    if not storage.is_initialized():
        setup_token = secrets.token_urlsafe(32)
        storage.save_setup_token(setup_token)
        print("\n" + "=" * 60)
        print("FIRST-TIME SETUP REQUIRED")
        print("Use this one-time setup token to create your admin account:\n")
        print(f"    {setup_token}\n")
        print("This token can only be used once.")
        print("=" * 60 + "\n")
    yield
    # Cleanup
    _hw_module.DEVICE = None
    clear_unsloth_compiled_cache()


# Create FastAPI app
app = FastAPI(
    title="Unsloth UI Backend",
    version="1.0.0",
    description="Backend API for Unsloth UI - Training and Model Management",
    lifespan=lifespan,
)

# CORS middleware
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],  # In production, specify allowed origins
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# ============ Register API Routes ============

# Register routers
app.include_router(auth_router, prefix="/api/auth", tags=["auth"])
app.include_router(training_router, prefix="/api/train", tags=["training"])
app.include_router(models_router, prefix="/api/models", tags=["models"])
app.include_router(inference_router, prefix="/api/inference", tags=["inference"])

# OpenAI-compatible endpoints: mount the same inference router at /v1
# so external tools (Open WebUI, SillyTavern, etc.) can use the
# standard /v1/chat/completions path.
app.include_router(inference_router, prefix="/v1", tags=["openai-compat"])
app.include_router(datasets_router, prefix="/api/datasets", tags=["datasets"])
app.include_router(data_recipe_router, prefix="/api/data-recipe", tags=["data-recipe"])
app.include_router(export_router, prefix="/api/export", tags=["export"])


# ============ Health and System Endpoints ============

@app.get("/api/health")
async def health_check():
    """Health check endpoint"""
    return {
        "status": "healthy",
        "timestamp": datetime.now().isoformat(),
        "service": "Unsloth UI Backend"
    }


@app.get("/api/system")
async def get_system_info():
    """Get system information"""
    import platform
    import psutil
    from utils.hardware import get_device, get_gpu_memory_info, DeviceType

    # GPU Info — uses the hardware module (works on CUDA, MPS, CPU)
    mem_info = get_gpu_memory_info()
    gpu_info = {"available": mem_info.get("available", False), "devices": []}

    if mem_info.get("available"):
        gpu_info["devices"].append({
            "index": mem_info.get("device", 0),
            "name": mem_info.get("device_name", "Unknown"),
            "memory_total_gb": round(mem_info.get("total_gb", 0), 2),
        })

    # CPU & Memory
    memory = psutil.virtual_memory()

    return {
        "platform": platform.platform(),
        "python_version": platform.python_version(),
        "device_backend": get_device().value,
        "cpu_count": psutil.cpu_count(),
        "memory": {
            "total_gb": round(memory.total / 1e9, 2),
            "available_gb": round(memory.available / 1e9, 2),
            "percent_used": memory.percent,
        },
        "gpu": gpu_info,
    }


@app.get("/api/system/hardware")
async def get_hardware_info():
    """Return GPU name, total VRAM, and key ML package versions."""
    from utils.hardware import get_gpu_summary, get_package_versions

    return {
        "gpu": get_gpu_summary(),
        "versions": get_package_versions(),
    }


# ============ Serve Frontend (Optional) ============

def setup_frontend(app: FastAPI, build_path: Path):
    """Mount frontend static files (optional)"""
    if not build_path.exists():
        return False

    # Mount assets
    assets_dir = build_path / "assets"
    if assets_dir.exists():
        app.mount("/assets", StaticFiles(directory=assets_dir), name="assets")

    @app.get("/")
    async def serve_root():
        content = (build_path / "index.html").read_bytes()
        return Response(
            content=content,
            media_type="text/html",
            headers={"Cache-Control": "no-cache, no-store, must-revalidate"},
        )

    @app.get("/{full_path:path}")
    async def serve_frontend(full_path: str):
        if full_path.startswith("api"):
            return {"error": "API endpoint not found"}

        file_path = (build_path / full_path).resolve()

        # Block path traversal — ensure resolved path stays inside build_path
        if not str(file_path).startswith(str(build_path.resolve())):
            return Response(status_code=403)

        if file_path.is_file():
            return FileResponse(file_path)

        # Serve index.html as bytes — avoids Content-Length mismatch
        content = (build_path / "index.html").read_bytes()
        return Response(
            content=content,
            media_type="text/html",
            headers={"Cache-Control": "no-cache, no-store, must-revalidate"},
        )

    return True