/*----------------------------------------------------------------
// 多 RawImage + 多 Decoder、同时只播一路时：共用一份 UI 材质，仅当前激活 Decoder 写贴图与参数。
//----------------------------------------------------------------*/

using UnityEngine;

/// <summary>
/// 与多个 <see cref="LeviathanVideoDecoder"/> 配合：全组共用<strong>一个</strong> <see cref="Material"/> 实例，
/// 任意时刻只有 <see cref="ActivateDecoder"/> 指定的那一路会把它赋到自己的 RawImage 并更新 Y/U/V。
/// 要求：各解码器的 <see cref="LeviathanVideoDecoderBase.AlphaType"/> 与控制器上配置的 Shared Alpha Type 一致（同一套 Shader）。
/// </summary>
public class LeviathanVideoSharedMaterialController : MonoBehaviour
{
    private static Shader FindShaderForAlphaType(LeviathanVideoDecoderBase.PlayAlphaType alphaType)
    {
        string name = alphaType switch
        {
            LeviathanVideoDecoderBase.PlayAlphaType.RightSide => "LeviathanVideo/YUV420P_Alpha_Right",
            LeviathanVideoDecoderBase.PlayAlphaType.BottomSide => "LeviathanVideo/YUV420P_Alpha_Bottom",
            LeviathanVideoDecoderBase.PlayAlphaType.ChromaKey => "LeviathanVideo/YUV420P_ChromaKey",
            _ => "LeviathanVideo/YUV420P",
        };
        return Shader.Find(name);
    }

    [SerializeField]
    [Tooltip("共用材质使用的 Alpha/Shader 类型，须与各 Decoder 的 Alpha Type 一致")]
    private LeviathanVideoDecoderBase.PlayAlphaType _sharedAlphaType = LeviathanVideoDecoderBase.PlayAlphaType.ChromaKey;

    [SerializeField]
    [Tooltip("可选：用工程里的材质做模板 Instantiate；为空则按 Shared Alpha Type 从 Shader 创建")]
    private Material _materialTemplate;

    private Material _sharedMaterial;
    private LeviathanVideoDecoder _activeDecoder;

    /// <summary>当前独占共用材质的解码器；无则为 null。</summary>
    public LeviathanVideoDecoder ActiveDecoder => _activeDecoder;

    /// <summary>共用材质实例（只读，勿在外部 Dispose）。</summary>
    public Material SharedMaterial
    {
        get
        {
            EnsureSharedMaterial();
            return _sharedMaterial;
        }
    }

    private void EnsureSharedMaterial()
    {
        if (_sharedMaterial != null)
            return;

        if (_materialTemplate != null)
        {
            _sharedMaterial = new Material(_materialTemplate);
            return;
        }

        var sh = FindShaderForAlphaType(_sharedAlphaType);
        if (sh == null)
        {
            LeviathanLogConfig.LogError(nameof(LeviathanVideoSharedMaterialController),
                $"无法创建共用材质：Shader 未找到（AlphaType={_sharedAlphaType}）");
            return;
        }

        _sharedMaterial = new Material(sh);
    }

    /// <summary>
    /// 将共用材质交给指定解码器；可选停止上一路。
    /// </summary>
    /// <param name="decoder">若为 null，则仅解绑当前路并清空激活项</param>
    /// <param name="stopPreviousDecoder">为 true 时对上一路调用 <see cref="LeviathanVideoDecoderBase.Stop"/></param>
    public void ActivateDecoder(LeviathanVideoDecoder decoder, bool stopPreviousDecoder = true)
    {
        EnsureSharedMaterial();
        if (_sharedMaterial == null)
            return;

        if (_activeDecoder == decoder)
        {
            if (decoder != null)
                decoder.RefreshSharedMaterialDisplay();
            return;
        }

        if (_activeDecoder != null)
        {
            if (stopPreviousDecoder)
                _activeDecoder.Stop();
            _activeDecoder.UnbindSharedMaterialController();
            _activeDecoder = null;
        }

        if (decoder == null)
            return;

        if (decoder.AlphaType != _sharedAlphaType)
        {
            LeviathanLogConfig.LogError(nameof(LeviathanVideoSharedMaterialController),
                $"ActivateDecoder: 解码器 AlphaType={decoder.AlphaType} 与控制器 {_sharedAlphaType} 不一致，拒绝绑定。请统一 Inspector 中的 Alpha Type。");
            return;
        }

        _activeDecoder = decoder;
        _activeDecoder.BindToSharedMaterialController(this, _sharedMaterial);
        _activeDecoder.RefreshSharedMaterialDisplay();
    }

    /// <summary>解绑当前解码器并停止播放（共用材质仍保留在控制器上）。</summary>
    public void DeactivateCurrent(bool stopDecoder = true)
    {
        if (_activeDecoder == null)
            return;
        if (stopDecoder)
            _activeDecoder.Stop();
        _activeDecoder.UnbindSharedMaterialController();
        _activeDecoder = null;
    }

    private void OnDestroy()
    {
        if (_activeDecoder != null)
        {
            _activeDecoder.UnbindSharedMaterialController();
            _activeDecoder = null;
        }

        if (_sharedMaterial != null)
        {
            Destroy(_sharedMaterial);
            _sharedMaterial = null;
        }
    }

    /// <summary>
    /// 解码器销毁或主动 <see cref="LeviathanVideoDecoder.UnbindSharedMaterialController"/> 时调用，清除激活引用。
    /// </summary>
    public void NotifyDecoderReleased(LeviathanVideoDecoder decoder)
    {
        if (_activeDecoder == decoder)
            _activeDecoder = null;
    }
}