using DatReaderWriter;
using DatReaderWriter.DBObjs;

namespace AcDream.App.UI.Layout;

/// <summary>
/// Resolves retail <c>StringInfo</c> values through local.dat string tables.
/// The caller owns synchronization around <see cref="DatCollection"/> reads.
/// </summary>
/// <remarks>
/// Retail reference: <c>StringInfo::GetString</c> and
/// <c>compute_str_hash @ 0x00413110</c>. A StringInfo's token selects one
/// localized string variant; ordinary UI labels use token zero.
/// </remarks>
public sealed class DatStringResolver
{
    private readonly DatCollection _dats;
    private readonly Dictionary<uint, StringTable?> _tables = new();

    public DatStringResolver(DatCollection dats)
        => _dats = dats ?? throw new ArgumentNullException(nameof(dats));

    public string? Resolve(UiStringInfoValue info)
        => Resolve(info.TableId, info.StringId, info.Token);

    public string? Resolve(uint tableId, uint stringId, int token = 0)
    {
        if (tableId == 0u || stringId == 0u)
            return null;

        if (!_tables.TryGetValue(tableId, out StringTable? table))
        {
            table = _dats.Get<StringTable>(tableId);
            _tables[tableId] = table;
        }

        if (table is null
            || !table.Strings.TryGetValue(stringId, out var entry)
            || entry.Strings.Count == 0)
            return null;

        int index = token >= 0 && token < entry.Strings.Count ? token : 0;
        return entry.Strings[index].Value;
    }

    /// <summary>Returns every literal token for one retail StringInfo entry.</summary>
    public string[]? ResolveAll(uint tableId, uint stringId)
    {
        if (tableId == 0u || stringId == 0u)
            return null;
        if (!_tables.TryGetValue(tableId, out StringTable? table))
        {
            table = _dats.Get<StringTable>(tableId);
            _tables[tableId] = table;
        }
        return table is not null
            && table.Strings.TryGetValue(stringId, out var entry)
            && entry.Strings.Count != 0
                ? entry.Strings.Select(value => value.Value).ToArray()
                : null;
    }

    /// <summary>
    /// Exact retail ELF-style string hash used for StringInfo keys.
    /// Ported line-for-line from <c>compute_str_hash @ 0x00413110</c>.
    /// </summary>
    public static uint ComputeHash(string value)
    {
        ArgumentNullException.ThrowIfNull(value);

        uint result = 0u;
        foreach (char c in value)
        {
            result = unchecked((result << 4) + (byte)c);
            uint high = result & 0xF0000000u;
            if (high != 0u)
                result = ((high >> 24) ^ result) & 0x0FFFFFFFu;
        }

        return result == uint.MaxValue ? uint.MaxValue - 1u : result;
    }
}