#!/usr/bin/env python3
"""
项目配置读取工具。

读取顺序：
1. 当前进程环境变量
2. 项目根目录下的 .env / .env.local
3. 用户常见 shell 配置文件中的 export 语句
"""

from pathlib import Path
import os


PROJECT_DIR = Path(__file__).resolve().parent
ENV_FILE_NAMES = (".env", ".env.local")
SHELL_RC_FILES = (
    Path("~/.zshrc").expanduser(),
    Path("~/.zprofile").expanduser(),
    Path("~/.zlogin").expanduser(),
    Path("~/.bash_profile").expanduser(),
    Path("~/.bashrc").expanduser(),
    Path("~/.profile").expanduser(),
)


def _parse_assignment(line):
    """解析 KEY=VALUE 或 export KEY=VALUE 形式的配置行。"""
    stripped = line.strip()
    if not stripped or stripped.startswith("#"):
        return None

    if stripped.startswith("export "):
        stripped = stripped[7:].strip()

    if "=" not in stripped:
        return None

    key, value = stripped.split("=", 1)
    key = key.strip()
    value = value.strip()

    if not key or any(ch.isspace() for ch in key):
        return None

    if value[:1] in {"'", '"'} and value[-1:] == value[:1]:
        value = value[1:-1]
    else:
        value = value.split(" #", 1)[0].strip()

    return key, value


def _read_var_from_file(file_path, var_name):
    """从文本配置文件里读取指定变量，后出现的值优先。"""
    try:
        lines = file_path.read_text(encoding="utf-8").splitlines()
    except OSError:
        return ""

    result = ""
    for line in lines:
        parsed = _parse_assignment(line)
        if not parsed:
            continue
        key, value = parsed
        if key == var_name and value:
            result = value
    return result


def _project_env_files(project_dir=None):
    base_dir = Path(project_dir) if project_dir else PROJECT_DIR
    return [base_dir / name for name in ENV_FILE_NAMES]


def load_project_env(project_dir=None):
    """把项目 .env 文件里的变量加载到当前进程环境中。"""
    for file_path in _project_env_files(project_dir):
        if not file_path.exists():
            continue
        try:
            lines = file_path.read_text(encoding="utf-8").splitlines()
        except OSError:
            continue
        for line in lines:
            parsed = _parse_assignment(line)
            if not parsed:
                continue
            key, value = parsed
            if key and value and key not in os.environ:
                os.environ[key] = value


def get_env_value(var_name, default="", project_dir=None):
    """按项目约定顺序读取配置值，并回填到当前进程环境。"""
    value = os.environ.get(var_name, "")
    if value:
        return value

    load_project_env(project_dir)
    value = os.environ.get(var_name, "")
    if value:
        return value

    for file_path in _project_env_files(project_dir):
        value = _read_var_from_file(file_path, var_name)
        if value:
            os.environ[var_name] = value
            return value

    for file_path in SHELL_RC_FILES:
        value = _read_var_from_file(file_path, var_name)
        if value:
            os.environ[var_name] = value
            return value

    return default