"""Application configuration helpers."""

from __future__ import annotations

import os
from pathlib import Path
from typing import Dict

from dotenv import load_dotenv

DEFAULT_IMMICH_URL = "https://photos.4angle.com/"


class ConfigError(RuntimeError):
    """Raised when critical configuration is missing."""


LEGACY_KEY_MAP = {
    "immich": "IMMICH_API_KEY",
    "openai": "OPENAI_API_KEY",
}


def _load_legacy_api_keys(path: Path) -> Dict[str, str]:
    """Parse the legacy ``api_keys`` file if it exists."""

    if not path.exists():
        return {}

    values: Dict[str, str] = {}
    for line in path.read_text().splitlines():
        line = line.strip()
        if not line or line.startswith("#"):
            continue
        if "=" not in line:
            continue
        key, value = [piece.strip() for piece in line.split("=", 1)]
        mapped_key = LEGACY_KEY_MAP.get(key.lower())
        if mapped_key and value:
            values[mapped_key] = value
    return values


def load_settings() -> Dict[str, str]:
    """Load configuration from environment variables and ``api_keys``."""

    load_dotenv()

    settings: Dict[str, str] = {
        "IMMICH_API_URL": os.getenv("IMMICH_API_URL", DEFAULT_IMMICH_URL).rstrip("/"),
        "IMMICH_API_KEY": os.getenv("IMMICH_API_KEY", ""),
        "OPENAI_API_KEY": os.getenv("OPENAI_API_KEY", ""),
        "RECENT_DAYS": int(os.getenv("RECENT_DAYS", "3")),
        "OPENAI_MODEL": os.getenv("OPENAI_MODEL", "gpt-4o-mini"),
        "ALT_TEXT_DB": os.getenv("ALT_TEXT_DB", ""),
        "SECRET_KEY": os.getenv("SECRET_KEY", ""),
    }

    legacy_values = _load_legacy_api_keys(Path("api_keys"))
    for key, value in legacy_values.items():
        if not settings.get(key):
            settings[key] = value

    missing = [
        key for key in ("IMMICH_API_KEY", "OPENAI_API_KEY") if not settings.get(key)
    ]
    if missing:
        raise ConfigError(
            "Missing required configuration values: " + ", ".join(missing)
        )

    return settings