import gettext
import logging
import os
from pathlib import Path


LOG = logging.getLogger("frigate-camera-control-bridge")
TRANSLATION_DOMAIN = "frigate_camera_control_bridge"
DEFAULT_LANGUAGE = "en"
DEFAULT_LOCALE_DIR = Path(__file__).resolve().parents[1] / "locale"
LOCALE_DIR = Path(os.environ.get("LOCALE_DIR", DEFAULT_LOCALE_DIR))

_TRANSLATIONS = {}
_AVAILABLE_LANGUAGES = None


def parse_po_language_name(path):
    # gettext compiled catalogs do not expose a friendly language name, so the
    # editable .po file may carry an optional Language-Name header for the GUI.
    try:
        text = path.read_text(encoding="utf-8")
    except OSError:
        return None
    for line in text.splitlines():
        if line.startswith('"Language-Name:'):
            return line.split(":", 1)[1].strip().strip("\\n\"")
    return None


def available_languages():
    # Discover languages dynamically from locale/*/LC_MESSAGES/*.mo. Adding a
    # language should not require a code change; ship a new .po/.mo pair instead.
    global _AVAILABLE_LANGUAGES
    if _AVAILABLE_LANGUAGES is not None:
        return _AVAILABLE_LANGUAGES

    languages = {DEFAULT_LANGUAGE: DEFAULT_LANGUAGE.upper()}
    if LOCALE_DIR.exists():
        for item in sorted(LOCALE_DIR.iterdir()):
            if not item.is_dir():
                continue
            code = item.name
            catalog = item / "LC_MESSAGES" / f"{TRANSLATION_DOMAIN}.mo"
            if catalog.exists():
                languages[code] = (
                    parse_po_language_name(item / "LC_MESSAGES" / f"{TRANSLATION_DOMAIN}.po")
                    or code.upper()
                )
    _AVAILABLE_LANGUAGES = languages
    return languages


def normalize_language(value):
    if not value:
        return DEFAULT_LANGUAGE
    base = str(value).lower().replace("_", "-").split("-", 1)[0]
    return base if base in available_languages() else DEFAULT_LANGUAGE


def translation_for(lang):
    # fallback=True makes English msgids work even if a translation file is
    # missing, which is useful while developing a new language catalog.
    lang = normalize_language(lang)
    if lang not in _TRANSLATIONS:
        _TRANSLATIONS[lang] = gettext.translation(
            TRANSLATION_DOMAIN,
            localedir=str(LOCALE_DIR),
            languages=[lang],
            fallback=True,
        )
    return _TRANSLATIONS[lang]


def text_for(lang, msgid, **kwargs):
    text = translation_for(lang).gettext(msgid)
    if kwargs:
        try:
            return text.format(**kwargs)
        except KeyError as exc:
            LOG.warning("missing translation placeholder %s for %s", exc, msgid)
    return text