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

public class MenuAdditions
{
    [MenuItem("Assets/Generate Animation")]
    static public void CreateAnimation()
    {
        string[] selected = Selection.assetGUIDs;

        //Get Frame Sprites
        List<Sprite> frames = new List<Sprite>();
        string containingFolder = null;
        string folderName = null;
        for (int i = 0; i < selected.Length; i++)
        {
            string path = AssetDatabase.GUIDToAssetPath(selected[i]);
            string[] slice = path.Split('/');
            if (string.IsNullOrEmpty(containingFolder))
            {
                containingFolder = path.Remove(path.LastIndexOf('/'));
                folderName = slice[slice.Length - 2];
            }
            Sprite loaded = AssetDatabase.LoadAssetAtPath<Sprite>(path);
            frames.Add(loaded);
        }

        //basic alphanumeric sort
        frames.Sort((s1, s2) => string.Compare(s1.name, s2.name, System.StringComparison.Ordinal));

        //generate clip
        AnimationClip clip = new AnimationClip();

        clip.frameRate = 12f;
        clip.wrapMode = WrapMode.Loop;

        EditorCurveBinding spriteBinding = new EditorCurveBinding();
        spriteBinding.type = typeof(SpriteRenderer);
        spriteBinding.path = "MainSprite";
        spriteBinding.propertyName = "m_Sprite";

        ObjectReferenceKeyframe[] spriteKeyFrames = new ObjectReferenceKeyframe[frames.Count];
        for (int i = 0; i < frames.Count; i++)
        {
            spriteKeyFrames[i] = new ObjectReferenceKeyframe();
            spriteKeyFrames[i].time = (float)i / clip.frameRate;
            spriteKeyFrames[i].value = frames[i];
        }

        AnimationClipSettings settings = new AnimationClipSettings();
        settings.loopTime = true;

        AnimationUtility.SetAnimationClipSettings(clip, settings);
        AnimationUtility.SetObjectReferenceCurve(clip, spriteBinding, spriteKeyFrames);
        AssetDatabase.CreateAsset(clip, containingFolder + "/" + folderName + ".anim");

        AssetDatabase.SaveAssets();
        AssetDatabase.Refresh();
    }
}