#!/usr/bin/env python3
"""Verify deterministic web generation and the checked-in generated assets."""

from __future__ import annotations

import gzip
import hashlib
import tempfile
from pathlib import Path

from generate_web_assets import generate_assets


PROJECT_DIRECTORY = Path(__file__).resolve().parent.parent
COMPRESSED_PAYLOAD_LIMIT = 1572864


def tree_digest(directory: Path) -> str:
    digest = hashlib.sha256()
    for path in sorted(item for item in directory.rglob("*") if item.is_file()):
        digest.update(path.relative_to(directory).as_posix().encode("utf-8"))
        digest.update(b"\0")
        digest.update(path.read_bytes())
    return digest.hexdigest()


def main() -> int:
    source_directory = PROJECT_DIRECTORY / "web"
    checked_in_directory = PROJECT_DIRECTORY / "data"
    with tempfile.TemporaryDirectory(prefix="maze32-assets-") as temporary:
        temporary_directory = Path(temporary)
        first = temporary_directory / "first"
        second = temporary_directory / "second"
        generate_assets(source_directory, first)
        generate_assets(source_directory, second)

        first_digest = tree_digest(first)
        second_digest = tree_digest(second)
        checked_in_digest = tree_digest(checked_in_directory)
        if first_digest != second_digest:
            raise AssertionError("Repeated web-asset generation produced different output")
        if first_digest != checked_in_digest:
            raise AssertionError("Generated web assets are stale; regenerate the data directory")

        for compressed_path in sorted(path for path in first.rglob("*.gz") if path.is_file()):
            relative_path = compressed_path.relative_to(first)
            source_relative = Path(str(relative_path)[:-3])
            if gzip.decompress(compressed_path.read_bytes()) != (
                source_directory / source_relative
            ).read_bytes():
                raise AssertionError(f"Compressed asset does not reproduce {source_relative}")

        compressed_size = sum(path.stat().st_size for path in first.rglob("*.gz"))
        if compressed_size > COMPRESSED_PAYLOAD_LIMIT:
            raise AssertionError(
                f"Compressed web payload is {compressed_size} bytes and exceeds "
                f"the {COMPRESSED_PAYLOAD_LIMIT}-byte limit"
            )

    print(
        f"web asset reproducibility: PASS ({first_digest}, "
        f"{compressed_size}/{COMPRESSED_PAYLOAD_LIMIT} bytes)"
    )
    return 0


if __name__ == "__main__":
    raise SystemExit(main())