import re
from pathlib import Path

from linkki_poster.models import Language, LanguageAssets, ScanResult


KNOWN_IMAGE_EXTENSIONS = {
    "jpg",
    "jpeg",
    "png",
    "webp",
    "gif",
}

GLOBAL_IMAGE_PREFIXES = ["Kuva"]

LANGUAGE_TEXT_CANDIDATES: dict[Language, list[str]] = {
    Language.FI: ["Suomi.md"],
    Language.SV: ["Svenska.md"],
    Language.EN: ["English.md"],
}

LANGUAGE_IMAGE_PREFIXES: dict[Language, list[str]] = {
    Language.FI: ["Suomi"],
    Language.SV: ["Svenska"],
    Language.EN: ["English"],
}


def scan_directory(directory: Path) -> ScanResult:
    files = sorted((entry for entry in directory.iterdir() if entry.is_file()), key=lambda path: path.name.lower())
    casefold_name_index = _build_casefold_name_index(files)

    global_images = select_first_matching_image_family(files, GLOBAL_IMAGE_PREFIXES)

    language_assets: list[LanguageAssets] = []
    for language in (Language.FI, Language.SV, Language.EN):
        text_file = select_first_matching_text_file(casefold_name_index, LANGUAGE_TEXT_CANDIDATES[language])
        if text_file is None:
            continue

        text_raw = text_file.read_text(encoding="utf-8")
        if text_raw.strip() == "":
            continue

        language_images = select_first_matching_image_family(files, LANGUAGE_IMAGE_PREFIXES[language])
        language_assets.append(
            LanguageAssets(
                language=language,
                text_file=text_file,
                text_raw=text_raw,
                images=language_images,
            )
        )

    return ScanResult(global_images=global_images, languages=language_assets)


def select_first_matching_text_file(casefold_name_index: dict[str, Path], candidate_names: list[str]) -> Path | None:
    for candidate_name in candidate_names:
        match = casefold_name_index.get(candidate_name.lower())
        if match is not None:
            return match
    return None


def select_first_matching_image_family(files: list[Path], prefixes: list[str]) -> list[Path]:
    for prefix in prefixes:
        matches = collect_image_matches_for_prefix(files, prefix)
        if matches:
            return [match[0] for match in sorted(matches, key=image_sort_key)]
    return []


def collect_image_matches_for_prefix(files: list[Path], prefix: str) -> list[tuple[Path, str, str]]:
    pattern = re.compile(rf"^{re.escape(prefix)}(\d*)\.([^.]+)$", re.IGNORECASE)
    matches: list[tuple[Path, str, str]] = []
    for file_path in files:
        match = pattern.match(file_path.name)
        if match is None:
            continue

        extension = match.group(2).lower()
        if extension not in KNOWN_IMAGE_EXTENSIONS:
            continue

        numeric_suffix = match.group(1)
        matches.append((file_path, numeric_suffix, extension))
    return matches


def image_sort_key(match_item: tuple[Path, str, str]) -> tuple[int, int, str, str]:
    file_path, numeric_suffix, extension = match_item
    has_numeric_suffix = numeric_suffix != ""
    numeric_value = int(numeric_suffix) if has_numeric_suffix else -1
    return (
        1 if has_numeric_suffix else 0,
        numeric_value,
        extension.lower(),
        file_path.name.lower(),
    )


def _build_casefold_name_index(files: list[Path]) -> dict[str, Path]:
    index: dict[str, Path] = {}
    for file_path in files:
        lowered = file_path.name.lower()
        if lowered not in index:
            index[lowered] = file_path
    return index