using DatReaderWriter.DBObjs;
using DatReaderWriter.Types;

namespace AcDream.App.Net;

/// <summary>
/// Exact unsigned formula used by retail <c>SkillFormula::Calculate @
/// 0x00591960</c>. DAT reader fields are signed storage views, so their bits
/// are deliberately reinterpreted as retail's unsigned W/X/Y/Z words.
/// </summary>
internal static class RetailSkillFormula
{
    public static bool TryCalculate(
        SkillFormula formula,
        uint attribute1,
        uint attribute2,
        out uint result)
    {
        ArgumentNullException.ThrowIfNull(formula);

        uint divisor = unchecked((uint)formula.Divisor);
        if (divisor == 0u)
        {
            result = 0u;
            return false;
        }

        uint x = unchecked((uint)formula.Attribute1Multiplier);
        uint y = unchecked((uint)formula.Attribute2Multiplier);
        uint w = unchecked((uint)formula.AdditiveBonus);
        uint numerator = unchecked(x * attribute1 + y * attribute2 + w);
        result = (uint)Math.Floor((double)numerator / divisor + 0.5d);
        return true;
    }
}

/// <summary>
/// Named live-session resolver for the attribute contribution to one skill.
/// Table lookup and missing-property policy stay separate from retail math.
/// </summary>
internal sealed class LiveSkillCreditResolver(SkillTable? skillTable)
{
    public uint Resolve(
        uint skillId,
        IReadOnlyDictionary<uint, uint> attributeCurrents)
    {
        ArgumentNullException.ThrowIfNull(attributeCurrents);

        if (skillTable?.Skills is null
            || !skillTable.Skills.TryGetValue(
                (DatReaderWriter.Enums.SkillId)skillId,
                out var skillBase))
        {
            return 0u;
        }

        SkillFormula formula = skillBase.Formula;
        attributeCurrents.TryGetValue(
            (uint)formula.Attribute1,
            out uint attribute1);
        attributeCurrents.TryGetValue(
            (uint)formula.Attribute2,
            out uint attribute2);
        return RetailSkillFormula.TryCalculate(
            formula,
            attribute1,
            attribute2,
            out uint result)
            ? result
            : 0u;
    }
}