ButtonAttribute

// Based on : http://baba-s.hatenablog.com/entry/2014/07/30/152826


using System;
using System.Linq;
using System.Reflection;
using UnityEngine;

#if UNITY_EDITOR
using UnityEditor;
#endif


/// <summary> Example of use : [ButtonAttribute ("MethodName", "ButtonNameInInspector", "TooltipInInspector", true, true, "param1", 10, "param3")] </summary>
[AttributeUsage(AttributeTargets.Field, Inherited = true, AllowMultiple = true)]
public sealed class ButtonAttribute : PropertyAttribute
{
    public string Function { get; private set; }
    public string ButtonName { get; private set; }
    public object[] Parameters { get; private set; }

    public bool OnlyInPlayMode { get; private set; }
    public string Tooltip { get; private set; }

    public bool DisplayVariable { get; private set; }

    /// <summary> WARNING : not working with overloaded functions </summary>
    public ButtonAttribute(string function, string name, string tooltip, bool onlyInPlayMode, bool displayVariable, params object[] parameters)
    {
        Function = function;
        ButtonName = name;

        OnlyInPlayMode = onlyInPlayMode;
        Tooltip = tooltip;

        DisplayVariable = displayVariable;

        Parameters = parameters;
    }
}

#if UNITY_EDITOR
[CustomPropertyDrawer(typeof(ButtonAttribute))]
public sealed class ButtonDrawer : PropertyDrawer
{
    private ButtonAttribute typedAttribute;
    public ButtonAttribute TypedAttribute
    {
        get
        {
            if (typedAttribute == null) typedAttribute = attribute as ButtonAttribute;
            return typedAttribute;
        }
    }

    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
    {
        if (TypedAttribute.DisplayVariable)
        {
            EditorGUI.PropertyField(position, property, label, true);
            position.y += EditorGUI.GetPropertyHeight(property, label, true);
            position.y += 2; // add little space above helpbox
        }

        string tooltip = TypedAttribute.Tooltip;
        if (TypedAttribute.OnlyInPlayMode && !Application.isPlaying)
        {
            EditorGUI.BeginDisabledGroup(true);
            if (string.IsNullOrEmpty(tooltip)) tooltip = "Button only available in play mode";
            else tooltip = TypedAttribute.Tooltip + " (button only available in play mode)";
        }

        position.height = EditorGUI.GetPropertyHeight(property, label, true);
        if (GUI.Button(position, new GUIContent(TypedAttribute.ButtonName, tooltip)))
        {
            var objectReferenceValue = property.serializedObject.targetObject;
            var type = objectReferenceValue.GetType();
            var bindingAttr = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic;

            try
            {
                var method = type.GetMethod(TypedAttribute.Function, bindingAttr);
                method.Invoke(objectReferenceValue, TypedAttribute.Parameters);
            }
            catch (AmbiguousMatchException)
            {
                var format = @"{0}.{1} : AmbiguousMatchException. Unable to determine which overloaded function is called for {0}.{1}. Please delete overloading function";
                var message = string.Format(format, type.Name, TypedAttribute.Function);

                Debug.LogError(message, objectReferenceValue);
            }
            catch (ArgumentException)
            {
                var parameters = string.Join(", ", TypedAttribute.Parameters.Select(c => c.ToString()).ToArray());
                var format = @"{0}.{1} : ArgumentException. You can't pass argument {2} to the function {0}.{1}. Please verify the types of the arguments";
                var message = string.Format(format, type.Name, TypedAttribute.Function, parameters);

                Debug.LogError(message, objectReferenceValue);
            }
            catch (NullReferenceException)
            {
                var format = @"{0}.{1} : NullReferenceException. Undefined function. Please verify if function is defined in {0}.{1}";
                var message = string.Format(format, type.Name, TypedAttribute.Function);

                Debug.LogError(message, objectReferenceValue);
            }
            catch (TargetParameterCountException)
            {
                var parameters = string.Join(", ", TypedAttribute.Parameters.Select(c => c.ToString()).ToArray());
                var format = @"{0}.{1} : TargetParameterCountException. You can't pass argument {2} to the function {0}.{1}. Please verify the number of the parameters given to the function ";
                var message = string.Format(format, type.Name, TypedAttribute.Function, parameters);

                Debug.LogError(message, objectReferenceValue);
            }
        }

        if (TypedAttribute.OnlyInPlayMode && !Application.isPlaying) EditorGUI.EndDisabledGroup();
    }

    public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
    {
        if (TypedAttribute.DisplayVariable) return EditorGUI.GetPropertyHeight(property, label, true) + GetButtonHeight();
        else return GetButtonHeight();
    }

    public float GetButtonHeight()
    {
        GUIContent content = new GUIContent(TypedAttribute.ButtonName);

        GUIStyle style = GUI.skin.box;
        style.alignment = TextAnchor.MiddleCenter;

        // Compute how large the button needs to be.        
        Vector2 size = style.CalcSize(content);
        return size.y;
    }
}
#endif