"""Load project-local environment variables from ``.env``."""

from __future__ import annotations

import os
from pathlib import Path

from chess_tutor.paths import project_root


def _parse_dotenv_line(line: str) -> tuple[str, str] | None:
    stripped = line.strip()
    if not stripped or stripped.startswith("#"):
        return None
    if stripped.startswith("export "):
        stripped = stripped[len("export ") :].strip()
    if "=" not in stripped:
        return None
    key, _, value = stripped.partition("=")
    key = key.strip()
    if not key:
        return None
    value = value.strip()
    if len(value) >= 2 and value[0] == value[-1] and value[0] in ("'", '"'):
        value = value[1:-1]
    return key, value


def load_project_dotenv(
    path: Path | str | None = None,
    *,
    override: bool = False,
) -> bool:
    """
    Load ``KEY=VALUE`` pairs from the repo ``.env`` into ``os.environ``.

    Returns ``True`` when the file exists and was read. Existing environment
    variables are left unchanged unless ``override=True``.
    """
    env_path = Path(path) if path is not None else project_root() / ".env"
    if not env_path.is_file():
        return False

    for raw_line in env_path.read_text(encoding="utf-8").splitlines():
        parsed = _parse_dotenv_line(raw_line)
        if parsed is None:
            continue
        key, value = parsed
        if not override and key in os.environ:
            continue
        os.environ[key] = value
    return True