using System.Text.RegularExpressions;

namespace PlotLine.Services;

public static class StoryIntelligenceEntityTextNormaliser
{
    private static readonly Regex Whitespace = new(@"\s+", RegexOptions.Compiled);
    private static readonly Regex TitleFullStops = new(@"\b(Mr|Mrs|Ms|Miss|Dr|Prof|Rev|Revd)\.", RegexOptions.IgnoreCase | RegexOptions.Compiled);
    private static readonly Regex NonKeyCharacters = new(@"[^\p{L}\p{N}']+", RegexOptions.Compiled);

    public static string Clean(string? value)
        => Whitespace.Replace((value ?? string.Empty).Replace('’', '\''), " ").Trim();

    public static string CleanName(string? value)
        => Clean(value).Trim(' ', '.', ',', ';', ':', '!', '?', '"', '\'');

    public static string StripLeadingArticle(string value)
    {
        var clean = Clean(value);
        return clean.StartsWith("the ", StringComparison.OrdinalIgnoreCase)
            ? clean[4..]
            : clean.StartsWith("a ", StringComparison.OrdinalIgnoreCase)
                ? clean[2..]
                : clean.StartsWith("an ", StringComparison.OrdinalIgnoreCase)
                    ? clean[3..]
                    : clean;
    }

    public static string SafeKey(string? value)
    {
        var clean = TitleFullStops.Replace(Clean(value), "$1");
        clean = NonKeyCharacters.Replace(clean, " ");
        clean = Whitespace.Replace(clean, " ").Trim().ToLowerInvariant();
        return clean;
    }

    public static string SingulariseSafeFinalWord(string value, IReadOnlySet<string> singularisableWords)
    {
        var words = SafeKey(value).Split(' ', StringSplitOptions.RemoveEmptyEntries).ToList();
        if (words.Count == 0)
        {
            return string.Empty;
        }

        var last = words[^1];
        if (last.EndsWith("ies", StringComparison.OrdinalIgnoreCase))
        {
            var singular = $"{last[..^3]}y";
            if (singularisableWords.Contains(singular))
            {
                words[^1] = singular;
            }
        }
        else if (last.EndsWith('s') && last.Length > 3)
        {
            var singular = last[..^1];
            if (singularisableWords.Contains(singular))
            {
                words[^1] = singular;
            }
        }

        return string.Join(' ', words);
    }
}