using ADOFAIRenderer.Core;
using HarmonyLib;
using UnityEngine;

namespace ADOFAIRenderer.Patch.Game;

/// <summary>
/// Makes the game's bloom compute its blur size as if the frame were 720 pixels high
/// ("High-Resolution Bloom Correction" option).
/// <para>
/// Patched member: <c>VideoBloom.OnRenderImage(RenderTexture source, RenderTexture destination)</c>. The game scales the
/// frame down to a bloom buffer 198 pixels high (<c>scale = 198 / source.height</c>) and sets the blur radius in bloom
/// buffer pixels to <c>KernelSize * MediumKernelScale * scale</c> (and <c>KernelSize * LargeKernelScale * scale</c>).
/// <c>BloomBlit</c> turns the radius into the number of 5-tap blur passes and the blend amount of the last pass.
/// </para>
/// <para>
/// While the render is active (<see cref="RenderManager.IsActive"/>) and <c>AdvancedConfig.HighResBloomCorrection</c> is
/// enabled, the prefix multiplies <c>KernelSize</c> by <c>source.height / 720</c> for the duration of the call, so the
/// radius equals <c>KernelSize * MediumKernelScale * 198 / 720</c> and the blur passes on the bloom buffer are the same
/// as in a 720p frame. The finalizer restores the original <c>KernelSize</c>. The bloom buffer size and the downscale
/// from the source frame keep the game's behavior.
/// </para>
/// </summary>
[HarmonyPatch(typeof(VideoBloom))]
public class VideoBloomPatch
{
    /// <summary>Frame height in pixels the blur size is computed for.</summary>
    private const float ReferenceHeight = 720f;

    /// <summary>Prefix of <c>VideoBloom.OnRenderImage</c>.</summary>
    /// <param name="__instance">The bloom component on the game camera.</param>
    /// <param name="source">The camera frame; its height selects the multiplier.</param>
    /// <param name="__state">Original <c>KernelSize</c>, or null when it was not changed.</param>
    [HarmonyPrefix]
    [HarmonyPatch("OnRenderImage")]
    // ReSharper disable InconsistentNaming
    public static void ScaleKernelSize(VideoBloom __instance, RenderTexture source, out float? __state)
    // ReSharper restore InconsistentNaming
    {
        __state = null;
        if (!source || !RenderManager.IsActive || !RenderManager.Instance.Configuration.AdvancedConfig.HighResBloomCorrection)
            return;

        __state = __instance.KernelSize;
        __instance.KernelSize *= source.height / ReferenceHeight;
    }

    /// <summary>Finalizer of <c>VideoBloom.OnRenderImage</c>: restores <c>KernelSize</c> when the prefix changed it.</summary>
    /// <param name="__instance">The bloom component on the game camera.</param>
    /// <param name="__state">Original <c>KernelSize</c> stored by the prefix, or null.</param>
    [HarmonyFinalizer]
    [HarmonyPatch("OnRenderImage")]
    // ReSharper disable InconsistentNaming
    public static void RestoreKernelSize(VideoBloom __instance, float? __state)
    // ReSharper restore InconsistentNaming
    {
        if (__state.HasValue) __instance.KernelSize = __state.Value;
    }
}