"""Helpers for loading Hermes .env files consistently across entrypoints."""

from __future__ import annotations

import os
from pathlib import Path

from dotenv import load_dotenv


def _load_dotenv_with_fallback(path: Path, *, override: bool) -> None:
    try:
        load_dotenv(dotenv_path=path, override=override, encoding="utf-8")
    except UnicodeDecodeError:
        load_dotenv(dotenv_path=path, override=override, encoding="latin-1")


def _sanitize_env_file_if_needed(path: Path) -> None:
    """Pre-sanitize a .env file before python-dotenv reads it.

    python-dotenv does not handle corrupted lines where multiple
    KEY=VALUE pairs are concatenated on a single line (missing newline).
    This produces mangled values — e.g. a bot token duplicated 8×
    (see #8908).

    We delegate to ``hermes_cli.config._sanitize_env_lines`` which
    already knows all valid Hermes env-var names and can split
    concatenated lines correctly.
    """
    if not path.exists():
        return
    try:
        from hermes_cli.config import _sanitize_env_lines
    except ImportError:
        return  # early bootstrap — config module not available yet

    read_kw = {"encoding": "utf-8", "errors": "replace"}
    try:
        with open(path, **read_kw) as f:
            original = f.readlines()
        sanitized = _sanitize_env_lines(original)
        if sanitized != original:
            import tempfile
            fd, tmp = tempfile.mkstemp(
                dir=str(path.parent), suffix=".tmp", prefix=".env_"
            )
            try:
                with os.fdopen(fd, "w", encoding="utf-8") as f:
                    f.writelines(sanitized)
                    f.flush()
                    os.fsync(f.fileno())
                os.replace(tmp, path)
            except BaseException:
                try:
                    os.unlink(tmp)
                except OSError:
                    pass
                raise
    except Exception:
        pass  # best-effort — don't block gateway startup


def load_hermes_dotenv(
    *,
    hermes_home: str | os.PathLike | None = None,
    project_env: str | os.PathLike | None = None,
) -> list[Path]:
    """Load Hermes environment files with user config taking precedence.

    Behavior:
    - `~/.hermes/.env` overrides stale shell-exported values when present.
    - project `.env` acts as a dev fallback and only fills missing values when
      the user env exists.
    - if no user env exists, the project `.env` also overrides stale shell vars.
    """
    loaded: list[Path] = []

    home_path = Path(hermes_home or os.getenv("HERMES_HOME", Path.home() / ".hermes"))
    user_env = home_path / ".env"
    project_env_path = Path(project_env) if project_env else None

    # Fix corrupted .env files before python-dotenv parses them (#8908).
    if user_env.exists():
        _sanitize_env_file_if_needed(user_env)

    if user_env.exists():
        _load_dotenv_with_fallback(user_env, override=True)
        loaded.append(user_env)

    if project_env_path and project_env_path.exists():
        _load_dotenv_with_fallback(project_env_path, override=not loaded)
        loaded.append(project_env_path)

    return loaded
