#!/usr/bin/env python3
"""
Embeds every file of an asset folder as a C byte array.

Usage: generate-assets.py <asset-folder> <output-folder>

Writes generated_assets.h and generated_assets.c. A file "fonts/AdwaitaSans.ttf" becomes the symbols
asset_fonts_AdwaitaSans_ttf (the bytes) and asset_fonts_AdwaitaSans_ttf_size (the byte count).
The size is also available as the constant asset_fonts_AdwaitaSans_ttf_SIZE for use in constant initializers.
Text files get an extra terminating 0 byte that is not part of the size, so they can be used as C strings.
Output files are only rewritten when their content changes, to avoid needless recompiles.
"""
import os
import re
import sys

TEXT_EXTENSIONS = {".pem", ".csv", ".html", ".json", ".codepoints", ".i18n", ".txt"}


def symbol_name(relative_path: str) -> str:
    return "asset_" + re.sub(r"[^A-Za-z0-9]", "_", relative_path)


def write_if_changed(path: str, content: str):
    if os.path.exists(path):
        with open(path, "r", encoding="utf-8", newline="") as file:
            if file.read() == content:
                return
    with open(path, "w", encoding="utf-8", newline="") as file:
        file.write(content)


def main():
    if len(sys.argv) != 3:
        print(f"Usage: {sys.argv[0]} <asset-folder> <output-folder>")
        sys.exit(1)
    asset_folder = os.path.abspath(sys.argv[1])
    output_folder = os.path.abspath(sys.argv[2])
    os.makedirs(output_folder, exist_ok=True)

    relative_paths = []
    for directory, _, file_names in os.walk(asset_folder):
        for file_name in file_names:
            relative_paths.append(os.path.relpath(os.path.join(directory, file_name), asset_folder).replace(os.sep, "/"))
    relative_paths.sort()

    header = [
        "// Generated by Buildscripts/generate-assets.py. Do not edit.",
        "#pragma once",
        "",
        "#include <stddef.h>",
        "#include <stdint.h>",
        "",
        "#ifdef __cplusplus",
        'extern "C" {',
        "#endif",
        "",
    ]
    source = [
        "// Generated by Buildscripts/generate-assets.py. Do not edit.",
        '#include "generated_assets.h"',
        "",
    ]
    for relative_path in relative_paths:
        with open(os.path.join(asset_folder, relative_path), "rb") as file:
            data = file.read()
        symbol = symbol_name(relative_path)
        size = len(data)
        if os.path.splitext(relative_path)[1].lower() in TEXT_EXTENSIONS:
            data += b"\0"
        header.append(f"// {relative_path}")
        header.append(f"extern const uint8_t {symbol}[];")
        header.append(f"extern const size_t {symbol}_size;")
        header.append(f"#define {symbol}_SIZE {size}")
        source.append(f"// {relative_path}")
        source.append(f"const uint8_t {symbol}[] = {{")
        for offset in range(0, len(data), 24):
            source.append("    " + ", ".join(f"0x{byte:02x}" for byte in data[offset:offset + 24]) + ",")
        if len(data) == 0:
            source.append("    0")
        source.append("};")
        source.append(f"const size_t {symbol}_size = {size};")
        source.append("")
    header += ["", "#ifdef __cplusplus", "}", "#endif", ""]

    write_if_changed(os.path.join(output_folder, "generated_assets.h"), "\n".join(header))
    write_if_changed(os.path.join(output_folder, "generated_assets.c"), "\n".join(source))


if __name__ == "__main__":
    main()