#!/usr/bin/env python3
"""
Camera Snapshot Server

Simple FastAPI server that serves snapshots from a USB camera.
Features:
- API key authentication
- HTTPS support
- Thread-safe camera access
- Auto-reconnect on camera failure
"""

import os
import cv2
import threading
import secrets
from typing import Optional
from dotenv import load_dotenv
from fastapi import FastAPI, Security, HTTPException, Response
from fastapi.security import APIKeyHeader
from fastapi.responses import JSONResponse

# Load environment variables
load_dotenv()

# Configuration
API_KEY = os.getenv("API_KEY")
CAMERA_INDEX = int(os.getenv("CAMERA_INDEX", "0"))
CAMERA_WIDTH = int(os.getenv("CAMERA_WIDTH", "1920"))
CAMERA_HEIGHT = int(os.getenv("CAMERA_HEIGHT", "1080"))
JPEG_QUALITY = int(os.getenv("JPEG_QUALITY", "85"))

if not API_KEY:
    raise ValueError("API_KEY not set in .env file. Generate one with: python3 -c 'import secrets; print(secrets.token_urlsafe(32))'")

# FastAPI app
app = FastAPI(
    title="Camera Snapshot Server",
    description="Serves snapshots from USB camera with API key authentication",
    version="1.0.0"
)

# API Key authentication
api_key_header = APIKeyHeader(name="X-API-Key", auto_error=False)


class CameraManager:
    """Thread-safe camera manager with auto-reconnect"""

    def __init__(self, camera_index: int = 0, width: int = 1920, height: int = 1080):
        self.camera_index = camera_index
        self.width = width
        self.height = height
        self.camera: Optional[cv2.VideoCapture] = None
        self.lock = threading.Lock()

    def _open_camera(self) -> bool:
        """Open camera connection"""
        try:
            self.camera = cv2.VideoCapture(self.camera_index)
            if not self.camera.isOpened():
                return False

            # Set camera resolution
            self.camera.set(cv2.CAP_PROP_FRAME_WIDTH, self.width)
            self.camera.set(cv2.CAP_PROP_FRAME_HEIGHT, self.height)

            # Set camera properties for better performance
            self.camera.set(cv2.CAP_PROP_BUFFERSIZE, 1)  # Reduce buffer to get latest frame

            # Log actual resolution (camera may not support requested resolution)
            actual_width = int(self.camera.get(cv2.CAP_PROP_FRAME_WIDTH))
            actual_height = int(self.camera.get(cv2.CAP_PROP_FRAME_HEIGHT))
            print(f"Camera resolution: {actual_width}x{actual_height} (requested: {self.width}x{self.height})")

            return True
        except Exception as e:
            print(f"Error opening camera: {e}")
            return False

    def get_snapshot(self) -> Optional[bytes]:
        """
        Capture a snapshot from the camera.

        Returns:
            JPEG-encoded image bytes, or None if failed
        """
        with self.lock:
            # Open camera if not initialized or closed
            if self.camera is None or not self.camera.isOpened():
                if not self._open_camera():
                    return None

            # Flush buffer to get latest frame
            # Read and discard several frames to clear old buffered frames
            for _ in range(5):
                self.camera.grab()

            # Capture the latest frame
            ret, frame = self.camera.read()

            # Retry on failure
            if not ret:
                print("Failed to capture frame, attempting reconnect...")
                self.release()
                if not self._open_camera():
                    return None
                # Flush buffer again after reconnect
                for _ in range(5):
                    self.camera.grab()
                ret, frame = self.camera.read()

                if not ret:
                    return None

            # Encode as JPEG
            try:
                ret, buffer = cv2.imencode(
                    '.jpg',
                    frame,
                    [cv2.IMWRITE_JPEG_QUALITY, JPEG_QUALITY]
                )
                if not ret:
                    return None

                return buffer.tobytes()
            except Exception as e:
                print(f"Error encoding image: {e}")
                return None

    def release(self):
        """Release camera resources"""
        if self.camera is not None:
            self.camera.release()
            self.camera = None

    def __del__(self):
        """Cleanup on deletion"""
        self.release()


# Global camera manager
camera_manager = CameraManager(CAMERA_INDEX, CAMERA_WIDTH, CAMERA_HEIGHT)


def verify_api_key(api_key: str = Security(api_key_header)) -> str:
    """Verify API key from header"""
    if api_key is None or api_key != API_KEY:
        raise HTTPException(
            status_code=403,
            detail="Invalid or missing API key"
        )
    return api_key


@app.get("/")
def root():
    """Root endpoint with API info"""
    return {
        "service": "Camera Snapshot Server",
        "version": "1.0.0",
        "endpoints": {
            "/snapshot": "GET - Returns JPEG snapshot (requires X-API-Key header)",
            "/health": "GET - Health check (no auth required)"
        }
    }


@app.get("/health")
def health():
    """Health check endpoint"""
    return {"status": "ok"}


@app.get("/snapshot")
def get_snapshot(api_key: str = Security(verify_api_key)):
    """
    Get a snapshot from the USB camera.

    Requires X-API-Key header for authentication.

    Returns:
        JPEG image
    """
    snapshot = camera_manager.get_snapshot()

    if snapshot is None:
        raise HTTPException(
            status_code=503,
            detail="Failed to capture snapshot. Check camera connection."
        )

    return Response(
        content=snapshot,
        media_type="image/jpeg",
        headers={
            "Cache-Control": "no-cache, no-store, must-revalidate",
            "Pragma": "no-cache",
            "Expires": "0"
        }
    )


@app.on_event("shutdown")
def shutdown_event():
    """Cleanup on shutdown"""
    camera_manager.release()


if __name__ == "__main__":
    import uvicorn

    # For development only - use uvicorn command for production
    uvicorn.run(
        "main:app",
        host="0.0.0.0",
        port=8443,
        ssl_keyfile="ssl/key.pem",
        ssl_certfile="ssl/cert.pem"
    )