#!/usr/bin/env python3
"""
Quick utility to measure the actual frame rate obtainable from a USB/IP camera.

Usage:
    python test_camera_fps.py --input 0 --frames 300 --width 640 --height 480 --fps 30

It attempts to set the desired resolution/FPS, reads the specified number of
frames, and prints the achieved FPS along with any read failures.
"""

import argparse
import time

import cv2


def parse_args():
    parser = argparse.ArgumentParser(description="Measure camera FPS with OpenCV")
    parser.add_argument("--input", type=str, default="0", help="Camera index or URL")
    parser.add_argument("--frames", type=int, default=200, help="How many frames to capture")
    parser.add_argument("--width", type=int, default=640, help="Requested frame width")
    parser.add_argument("--height", type=int, default=480, help="Requested frame height")
    parser.add_argument("--fps", type=float, default=30.0, help="Requested FPS (hint to driver)")
    parser.add_argument("--backend", type=str, default="", help="Optional OpenCV backend name (e.g., 'dshow')")
    return parser.parse_args()


def open_capture(source, backend):
    if backend:
        backend_map = {
            "dshow": cv2.CAP_DSHOW,
            "msmf": cv2.CAP_MSMF,
            "ffmpeg": cv2.CAP_FFMPEG,
        }
        backend_flag = backend_map.get(backend.lower())
        if backend_flag is None:
            raise ValueError(f"Unsupported backend '{backend}'. Choose from {list(backend_map)}")
        return cv2.VideoCapture(source, backend_flag)
    return cv2.VideoCapture(source)


def main():
    opt = parse_args()
    source = int(opt.input) if opt.input.isdigit() else opt.input
    cap = open_capture(source, opt.backend)

    if not cap.isOpened():
        raise RuntimeError(f"Failed to open camera source: {opt.input}")

    # Try to set desired properties (may be ignored by some drivers)
    cap.set(cv2.CAP_PROP_FRAME_WIDTH, opt.width)
    cap.set(cv2.CAP_PROP_FRAME_HEIGHT, opt.height)
    cap.set(cv2.CAP_PROP_FPS, opt.fps)

    actual_width = cap.get(cv2.CAP_PROP_FRAME_WIDTH)
    actual_height = cap.get(cv2.CAP_PROP_FRAME_HEIGHT)
    actual_fps = cap.get(cv2.CAP_PROP_FPS)

    print(f"Requested: {opt.width}x{opt.height} @{opt.fps:.1f} FPS")
    print(f"Driver reports: {actual_width:.0f}x{actual_height:.0f} @{actual_fps:.1f} FPS")

    total = 0
    failures = 0
    start = time.time()

    while total < opt.frames:
        ok, _ = cap.read()
        if not ok:
            failures += 1
            continue
        total += 1

    elapsed = time.time() - start
    cap.release()

    achieved_fps = total / elapsed if elapsed > 0 else 0.0
    print(f"Captured {total} frames in {elapsed:.2f} s => {achieved_fps:.2f} FPS")
    if failures:
        print(f"Read failures: {failures}")


if __name__ == "__main__":
    main()