using System;
using System.Globalization;

namespace AcDream.Core.Items;

/// <summary>
/// Shared owner for retail <c>GenItemHolder::splitSize</c> and
/// <c>GenItemHolder::maxSplitSize</c>. The toolbar entry/slider edits this state and
/// item-holder operations consume the same value.
/// </summary>
public sealed class StackSplitQuantityState
{
    public uint Value { get; private set; } = 1u;
    public uint Maximum { get; private set; } = 1u;
    public float Ratio => Value / (float)Maximum;

    public event Action? Changed;

    public void Reset(uint stackSize, uint? initialValue = null)
    {
        uint maximum = Math.Max(stackSize, 1u);
        Set(initialValue ?? maximum, maximum);
    }

    public void SetFromText(string? text)
    {
        // Retail uses wcstoul, whose invalid/empty result is zero, then clamps to one.
        uint parsed = uint.TryParse(text, NumberStyles.None, CultureInfo.InvariantCulture, out uint value)
            ? value
            : 0u;
        SetValue(parsed);
    }

    /// <summary>
    /// Ports <c>gmToolbarUI::ListenToElementMessage @ 0x004BEFE0</c> and
    /// <c>UIElement_Scrollbar::SetScrollbarPosition @ 0x00470EC0</c>. The scrollbar
    /// first truncates its normalized position to an integer in [0,1000], then the
    /// toolbar converts it to <c>1 + floor(position * max / 1000)</c> and clamps.
    /// </summary>
    public void SetFromSliderRatio(float ratio)
    {
        float clamped = Math.Clamp(ratio, 0f, 1f);
        uint positionMillis = (uint)MathF.Truncate(clamped * 1000f);
        ulong scaled = (ulong)positionMillis * Maximum;
        uint value = 1u + (uint)(scaled / 1000u);
        SetValue(value);
    }

    public void SetValue(uint value) => Set(value, Maximum);

    /// <summary>
    /// Ports <c>ItemHolder::GetObjectSplitSize @ 0x00586F00</c>: only the
    /// currently selected object consumes <c>GenItemHolder::splitSize</c>.
    /// Every other object operation uses that object's full stack size.
    /// </summary>
    public uint GetObjectSplitSize(uint objectId, uint selectedObjectId, uint objectStackSize)
    {
        if (objectId == selectedObjectId)
            return Value;
        return Math.Max(objectStackSize, 1u);
    }

    private void Set(uint value, uint maximum)
    {
        maximum = Math.Max(maximum, 1u);
        value = Math.Clamp(value, 1u, maximum);
        if (Value == value && Maximum == maximum)
            return;

        Value = value;
        Maximum = maximum;
        Changed?.Invoke();
    }
}