using System.Collections.Generic;
using UnityEditor;
using UnityEditor.Rendering;
using UnityEngine;

/// <summary>
/// Custom editor for FullScreenPassRendererFeature class responsible for drawing unavailable by default properties
/// such as custom drop down items and additional properties.
/// </summary>
[CustomEditor(typeof(FullScreenPassRendererFeature))]
public class FullScreenPassRendererFeatureEditor : Editor
{
    private SerializedProperty m_InjectionPointProperty;
    private SerializedProperty m_RequirementsProperty;
    private SerializedProperty m_FetchColorBufferProperty;
    private SerializedProperty m_BindDepthStencilAttachmentProperty;
    private SerializedProperty m_PassMaterialProperty;
    private SerializedProperty m_PassIndexProperty;

    private static readonly GUIContent k_InjectionPointGuiContent = new GUIContent("Injection Point", "Specifies where in the frame this pass will be injected.");
    private static readonly GUIContent k_RequirementsGuiContent = new GUIContent("Requirements", "A mask of URP internal textures that will need to be generated and bound for sampling.\n\nNote that 'Color' here corresponds to '_CameraOpaqueTexture' so most of the time you will want to use the 'Fetch Color Buffer' option instead.");
    private static readonly GUIContent k_FetchColorBufferGuiContent = new GUIContent("Fetch Color Buffer", "Enable this if the assigned material will need to sample the active color target. The active color will be bound to the '_BlitTexture' shader property for sampling. Note that this will introduce an internal color copy pass.");
    private static readonly GUIContent k_BindDepthStencilAttachmentGuiContent = new GUIContent("Bind Depth-Stencil", "Enable this to bind the active camera's depth-stencil attachment to the framebuffer (only use this if depth-stencil ops are used by the assigned material as this could have a performance impact).");
    private static readonly GUIContent k_PassMaterialGuiContent = new GUIContent("Pass Material", "The material used to render the full screen pass.");
    private static readonly GUIContent k_PassGuiContent = new GUIContent("Pass", "The name of the shader pass to use from the assigned material.");

    private void OnEnable()
    {
        m_InjectionPointProperty = serializedObject.FindProperty("injectionPoint");
        m_RequirementsProperty = serializedObject.FindProperty("requirements");
        m_FetchColorBufferProperty = serializedObject.FindProperty("fetchColorBuffer");
        m_BindDepthStencilAttachmentProperty = serializedObject.FindProperty("bindDepthStencilAttachment");
        m_PassMaterialProperty = serializedObject.FindProperty("passMaterial");
        m_PassIndexProperty = serializedObject.FindProperty("passIndex");
    }

    /// <summary>
    /// Implementation for a custom inspector
    /// </summary>
    public override void OnInspectorGUI()
    {
        var currentFeature = target as FullScreenPassRendererFeature;

        if (currentFeature.passMaterial == null || currentFeature.passIndex >= currentFeature.passMaterial.passCount)
            currentFeature.passIndex = 0;

        EditorGUILayout.PropertyField(m_InjectionPointProperty, k_InjectionPointGuiContent);
        EditorGUILayout.PropertyField(m_RequirementsProperty, k_RequirementsGuiContent);
        EditorGUILayout.PropertyField(m_FetchColorBufferProperty, k_FetchColorBufferGuiContent);
        EditorGUILayout.PropertyField(m_BindDepthStencilAttachmentProperty, k_BindDepthStencilAttachmentGuiContent);
        EditorGUILayout.PropertyField(m_PassMaterialProperty, k_PassMaterialGuiContent);

        if (AdvancedProperties.BeginGroup())
        {
            DrawMaterialPassProperty(currentFeature);
        }
        AdvancedProperties.EndGroup();

        serializedObject.ApplyModifiedProperties();
    }

    private void DrawMaterialPassProperty(FullScreenPassRendererFeature feature)
    {
        List<string> selectablePasses;
        bool isMaterialValid = feature.passMaterial != null;
        selectablePasses = isMaterialValid ? GetPassIndexStringEntries(feature) : new List<string>() {"No material"};

        // If material is invalid 0'th index is selected automatically, so it stays on "No material" entry
        // It is invalid index, but FullScreenPassRendererFeature wont execute until material is valid
        m_PassIndexProperty.intValue = EditorGUILayout.Popup(k_PassGuiContent, m_PassIndexProperty.intValue, selectablePasses.ToArray());
    }

    private static List<string> GetPassIndexStringEntries(FullScreenPassRendererFeature component)
    {
        List<string> passIndexEntries = new List<string>();
        for (int i = 0; i < component.passMaterial.passCount; ++i)
        {
            // "Name of a pass (index)" - "PassAlpha (1)"
            string entry = $"{component.passMaterial.GetPassName(i)} ({i})";
            passIndexEntries.Add(entry);
        }

        return passIndexEntries;
    }
}