#!/usr/bin/env python3
"""Validate a complete MTHD archive before including private HD art in a mac bundle."""
import pathlib
import struct
import sys


def verify(path):
    data = pathlib.Path(path).read_bytes()
    if len(data) < 12 or data[:4] != b'MTHD':
        raise ValueError('invalid MTHD header')
    version, count = struct.unpack_from('<II', data, 4)
    if version != 1 or not 0 < count <= 100000:
        raise ValueError('invalid archive version/count')
    index, entries, names = 12, [], set()
    for _ in range(count):
        if index + 2 > len(data): raise ValueError('truncated index')
        size, = struct.unpack_from('<H', data, index)
        index += 2
        if not 0 < size <= 4096 or index + size + 8 > len(data): raise ValueError('invalid entry')
        name = data[index:index+size].decode('latin1')
        index += size
        offset, length = struct.unpack_from('<II', data, index)
        index += 8
        if name in names or not length or offset + length > len(data): raise ValueError('invalid payload range')
        names.add(name)
        entries.append((name, offset, length))
    for name, offset, length in entries:
        image = data[offset:offset+length]
        if offset < index or length < 33 or image[:8] != b'\x89PNG\r\n\x1a\n' or image[12:16] != b'IHDR':
            raise ValueError('invalid PNG: ' + name)
        w, h = struct.unpack_from('>II', image, 16)
        if not 0 < w <= 4096 or not 0 < h <= 4096: raise ValueError('invalid dimensions: ' + name)
    return count


if __name__ == '__main__':
    try:
        print(f'HD UI archive valid: {verify(sys.argv[1])} textures')
    except (ValueError, OSError, IndexError, struct.error) as error:
        sys.exit(str(error))