#!/usr/bin/env python3
"""将 dotenv 转成 docker run --env-file 的字面值格式，不打印凭证。"""
import argparse
import os
from pathlib import Path
import re
import tempfile

from dotenv import dotenv_values


def export(source, target):
    source, target = Path(source).resolve(strict=True), Path(target).absolute()
    if source == target.resolve():
        raise ValueError('导出文件不能覆盖原 .env')
    rows = []
    for key, value in dotenv_values(source).items():
        if not re.fullmatch(r'[A-Za-z_][A-Za-z0-9_]*', key):
            raise ValueError('存在 Docker 不支持的环境变量名称')
        if value is None:
            continue
        if any(char in value for char in '\r\n\x00'):
            raise ValueError(f'{key} 含有 Docker env-file 不支持的换行或空字符')
        rows.append(key + '=' + value + '\n')
    target.parent.mkdir(parents=True, exist_ok=True)
    partial = None
    try:
        # 临时文件权限0600；写完后原子替换，保留原 .env，不输出任何配置值。
        with tempfile.NamedTemporaryFile(mode='w', encoding='utf-8', dir=target.parent,
                prefix='.docker-env-', delete=False) as stream:
            partial = Path(stream.name)
            stream.writelines(rows)
        os.replace(partial, target)
    finally:
        if partial is not None:
            partial.unlink(missing_ok=True)
    return len(rows)


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('source', nargs='?', default='.env')
    parser.add_argument('target', nargs='?', default='.env.docker')
    args = parser.parse_args()
    try:
        count = export(args.source, args.target)
    except (OSError, ValueError) as exc:
        parser.exit(1, f'转换失败：{exc}\n')
    print(f'已导出 {count} 个配置项，文件权限0600；未输出配置值。')