import sys
import os


def read_ppm(filename):
    with open(filename, "rb") as f:
        header = f.readline()
        if header != b"P6\n":
            raise ValueError(f"Not a P6 PPM file: {filename}")

        while True:
            line = f.readline()
            if not line.startswith(b"#"):
                break

        dims = line.split()
        width, height = int(dims[0]), int(dims[1])

        line = f.readline()
        maxval = int(line.strip())

        data = f.read()
        return width, height, data


def compare_ppm(file1, file2, threshold):
    w1, h1, d1 = read_ppm(file1)
    w2, h2, d2 = read_ppm(file2)

    if w1 != w2 or h1 != h2:
        print(f"ERROR: Size mismatch - {file1}: {w1}x{h1}, {file2}: {w2}x{h2}")
        return False

    total_pixels = w1 * h1
    diff_count = 0

    for i in range(len(d1)):
        diff = abs(d1[i] - d2[i])
        if diff > threshold:
            diff_count += 1

    diff_percent = (diff_count / (total_pixels * 3)) * 100

    print(f"Image 1: {file1} ({w1}x{h1})")
    print(f"Image 2: {file2} ({w2}x{h2})")
    print(f"Threshold: {threshold}")
    print(f"Different pixels: {diff_count} / {total_pixels * 3} ({diff_percent:.2f}%)")

    if diff_percent <= 1.0:
        print("PASS: Images match!")
        return True
    else:
        print("FAIL: Images differ!")
        return False


if __name__ == "__main__":
    if len(sys.argv) != 4:
        print("Usage: python compare_ppm.py <file1.ppm> <file2.ppm> <threshold>")
        sys.exit(1)

    file1 = sys.argv[1]
    file2 = sys.argv[2]
    threshold = int(sys.argv[3])

    if not os.path.exists(file1):
        print(f"ERROR: File not found: {file1}")
        sys.exit(1)

    if not os.path.exists(file2):
        print(f"ERROR: File not found: {file2}")
        sys.exit(1)

    result = compare_ppm(file1, file2, threshold)
    sys.exit(0 if result else 1)