using System.IO;

namespace Futonizer.Services;

/// <summary>
/// Result of scanning an external subtitle's filename for language and
/// display hints.
/// </summary>
public readonly record struct SubtitleLanguageInfo(string Language, bool Forced, bool HearingImpaired, string TrackName);

/// <summary>
/// Best-effort language/flag detection for external subtitle files, based on
/// common filename tokens (e.g. "Show.S04E06.eng.srt", "Show.S04E06.forced.srt").
/// Never throws — falls back to an "und" (undetermined) language with no
/// track name when nothing recognisable is found.
/// </summary>
public static class SubtitleLanguageHelper
{
    private static readonly Dictionary<string, string> TokenToIso6392 = new(StringComparer.OrdinalIgnoreCase)
    {
        ["en"] = "eng", ["eng"] = "eng", ["english"] = "eng",
        ["ja"] = "jpn", ["jp"] = "jpn", ["jpn"] = "jpn", ["japanese"] = "jpn",
        ["es"] = "spa", ["spa"] = "spa", ["spanish"] = "spa", ["esp"] = "spa",
        ["fr"] = "fre", ["fre"] = "fre", ["fra"] = "fre", ["french"] = "fre",
        ["de"] = "ger", ["ger"] = "ger", ["deu"] = "ger", ["german"] = "ger",
        ["it"] = "ita", ["ita"] = "ita", ["italian"] = "ita",
        ["pt"] = "por", ["por"] = "por", ["portuguese"] = "por", ["ptbr"] = "por",
        ["ru"] = "rus", ["rus"] = "rus", ["russian"] = "rus",
        ["zh"] = "chi", ["chi"] = "chi", ["zho"] = "chi", ["chinese"] = "chi", ["cmn"] = "chi", ["yue"] = "chi",
        ["ko"] = "kor", ["kor"] = "kor", ["korean"] = "kor",
        ["ar"] = "ara", ["ara"] = "ara", ["arabic"] = "ara",
        ["nl"] = "dut", ["dut"] = "dut", ["nld"] = "dut", ["dutch"] = "dut",
        ["sv"] = "swe", ["swe"] = "swe", ["swedish"] = "swe",
        ["no"] = "nor", ["nor"] = "nor", ["norwegian"] = "nor",
        ["da"] = "dan", ["dan"] = "dan", ["danish"] = "dan",
        ["fi"] = "fin", ["fin"] = "fin", ["finnish"] = "fin",
        ["pl"] = "pol", ["pol"] = "pol", ["polish"] = "pol",
        ["tr"] = "tur", ["tur"] = "tur", ["turkish"] = "tur",
        ["vi"] = "vie", ["vie"] = "vie", ["vietnamese"] = "vie",
        ["th"] = "tha", ["tha"] = "tha", ["thai"] = "tha",
        ["id"] = "ind", ["ind"] = "ind", ["indonesian"] = "ind",
        ["he"] = "heb", ["heb"] = "heb", ["hebrew"] = "heb",
        ["hin"] = "hin", ["hindi"] = "hin",
        ["cs"] = "cze", ["cze"] = "cze", ["ces"] = "cze", ["czech"] = "cze",
        ["el"] = "gre", ["gre"] = "gre", ["ell"] = "gre", ["greek"] = "gre",
        ["hu"] = "hun", ["hun"] = "hun", ["hungarian"] = "hun",
        ["ro"] = "rum", ["rum"] = "rum", ["ron"] = "rum", ["romanian"] = "rum",
        ["uk"] = "ukr", ["ukr"] = "ukr", ["ukrainian"] = "ukr",
    };

    private static readonly Dictionary<string, string> Iso6392ToDisplayName = new(StringComparer.OrdinalIgnoreCase)
    {
        ["eng"] = "English", ["jpn"] = "Japanese", ["spa"] = "Spanish", ["fre"] = "French",
        ["ger"] = "German", ["ita"] = "Italian", ["por"] = "Portuguese", ["rus"] = "Russian",
        ["chi"] = "Chinese", ["kor"] = "Korean", ["ara"] = "Arabic", ["dut"] = "Dutch",
        ["swe"] = "Swedish", ["nor"] = "Norwegian", ["dan"] = "Danish", ["fin"] = "Finnish",
        ["pol"] = "Polish", ["tur"] = "Turkish", ["vie"] = "Vietnamese", ["tha"] = "Thai",
        ["ind"] = "Indonesian", ["heb"] = "Hebrew", ["hin"] = "Hindi", ["cze"] = "Czech",
        ["gre"] = "Greek", ["hun"] = "Hungarian", ["rum"] = "Romanian", ["ukr"] = "Ukrainian",
    };

    private static readonly char[] TokenSeparators = { '.', '_', '-', ' ', '(', ')', '[', ']' };

    public static SubtitleLanguageInfo Detect(string fileName)
    {
        string stem = Path.GetFileNameWithoutExtension(fileName);
        var tokens = stem.Split(TokenSeparators, StringSplitOptions.RemoveEmptyEntries);

        string language = "und";
        bool forced = false;
        bool hearingImpaired = false;

        foreach (var token in tokens)
        {
            if (string.Equals(token, "forced", StringComparison.OrdinalIgnoreCase))
            {
                forced = true;
                continue;
            }
            if (string.Equals(token, "sdh", StringComparison.OrdinalIgnoreCase)
                || string.Equals(token, "cc", StringComparison.OrdinalIgnoreCase))
            {
                hearingImpaired = true;
                continue;
            }
            if (language == "und" && TokenToIso6392.TryGetValue(token, out var iso))
                language = iso;
        }

        string trackName = string.Empty;
        if (Iso6392ToDisplayName.TryGetValue(language, out var displayName))
            trackName = displayName;

        if (forced || hearingImpaired)
        {
            var suffixes = new List<string>();
            if (forced) suffixes.Add("Forced");
            if (hearingImpaired) suffixes.Add("SDH");
            string suffix = $" ({string.Join(", ", suffixes)})";
            trackName = string.IsNullOrEmpty(trackName) ? suffix.Trim(' ', '(', ')') : trackName + suffix;
        }

        return new SubtitleLanguageInfo(language, forced, hearingImpaired, trackName);
    }
}