GameJamMenuTemplateFix

using UnityEngine;
using System.Collections;
using UnityEngine.Audio;
using UnityEngine.SceneManagement;
using UnityEngine.UI;


public class StartOptions : MonoBehaviour {


    public MenuSettings menuSettingsData;
    public int sceneToStart = 1;                                        //Index number in build settings of scene to load if changeScenes is true
    public bool changeScenes;                                           //If true, load a new scene when Start is pressed, if false, fade out UI and continue in single scene
    public bool changeMusicOnStart;                                     //Choose whether to continue playing menu music or start a new music clip
    public CanvasGroup fadeOutImageCanvasGroup;                         //Canvas group used to fade alpha of image which fades in before changing scenes
    public Image fadeImage;                                             //Reference to image used to fade out before changing scenes

    [HideInInspector] public bool inMainMenu = true;                    //If true, pause button disabled in main menu (Cancel in input manager, default escape key)
    [HideInInspector] public AnimationClip fadeAlphaAnimationClip;      //Animation clip fading out UI elements alpha


    private PlayMusic playMusic;                                        //Reference to PlayMusic script
    private float fastFadeIn = .01f;                                    //Very short fade time (10 milliseconds) to start playing music immediately without a click/glitch
    private ShowPanels showPanels;                                      //Reference to ShowPanels script on UI GameObject, to show and hide panels
    private CanvasGroup menuCanvasGroup;


    void Awake()
    {
        //Get a reference to ShowPanels attached to UI object
        showPanels = GetComponent<ShowPanels> ();

        //Get a reference to PlayMusic attached to UI object
        playMusic = GetComponent<PlayMusic> ();

        //Get a reference to the CanvasGroup attached to the main menu so that we can fade it's alpha
        menuCanvasGroup = GetComponent<CanvasGroup>();

        fadeImage.color = menuSettingsData.sceneChangeFadeColor;
    }


    public void StartButtonClicked()
    {
        //If changeMusicOnStart is true, fade out volume of music group of AudioMixer by calling FadeDown function of PlayMusic
        //To change fade time, change length of animation "FadeToColor"
        if (menuSettingsData.musicLoopToChangeTo != null)
        {
            playMusic.FadeDown(menuSettingsData.menuFadeTime);
        }

        //If changeScenes is true, start fading and change scenes halfway through animation when screen is blocked by FadeImage
        if (menuSettingsData.nextSceneIndex != 0)
        {
            //Use invoke to delay calling of LoadDelayed by half the length of fadeColorAnimationClip
            Invoke ("LoadDelayed", menuSettingsData.menuFadeTime);

            StartCoroutine(FadeCanvasGroupAlpha(0f, 1f, fadeOutImageCanvasGroup));

        }

        //If changeScenes is false, call StartGameInScene
        else
        {
            //Call the StartGameInScene function to start game without loading a new scene.
            StartGameInScene();
        }

    }

    void OnEnable()
    {
        SceneManager.sceneLoaded += SceneWasLoaded;
    }

    void OnDisable()
    {
        SceneManager.sceneLoaded -= SceneWasLoaded;
    }

    //Once the level has loaded, check if we want to call PlayLevelMusic
    void SceneWasLoaded(Scene scene, LoadSceneMode mode)
    {
        //if changeMusicOnStart is true, call the PlayLevelMusic function of playMusic
        if (menuSettingsData.musicLoopToChangeTo != null)
        {
            playMusic.PlayLevelMusic ();
        }
    }


    public void LoadDelayed()
    {
        //Pause button now works if escape is pressed since we are no longer in Main menu.
        inMainMenu = false;

        //Hide the main menu UI element
        showPanels.HideMenu ();

        //Load the selected scene, by scene index number in build settings
        SceneManager.LoadScene (sceneToStart);
    }

    public void HideDelayed()
    {
        //Hide the main menu UI element after fading out menu for start game in scene
        showPanels.HideMenu();
    }

    public void StartGameInScene()
    {
        //Pause button now works if escape is pressed since we are no longer in Main menu.
        inMainMenu = false;

        //If there is a second music clip in MenuSettings, fade out volume of music group of AudioMixer by calling FadeDown function of PlayMusic
        if (menuSettingsData.musicLoopToChangeTo != null)
        {
            //Wait until game has started, then play new music
            Invoke ("PlayNewMusic", menuSettingsData.menuFadeTime);
        }

        StartCoroutine(FadeCanvasGroupAlpha(1f,0f, menuCanvasGroup));
    }

    public IEnumerator FadeCanvasGroupAlpha(float startAlpha, float endAlpha, CanvasGroup canvasGroupToFadeAlpha)
    {

        float elapsedTime = 0f;
        float totalDuration = menuSettingsData.menuFadeTime;

        while (elapsedTime < totalDuration)
        {
            elapsedTime += Time.deltaTime;
            float currentAlpha = Mathf.Lerp(startAlpha, endAlpha, elapsedTime / totalDuration);
            canvasGroupToFadeAlpha.alpha = currentAlpha;
            yield return null;
        }

        HideDelayed();

        elapsedTime = 0f;
        while (elapsedTime < totalDuration)
        {
            elapsedTime += Time.deltaTime;
            float currentAlpha = Mathf.Lerp(endAlpha, startAlpha, elapsedTime / totalDuration);
            canvasGroupToFadeAlpha.alpha = currentAlpha;
            yield return null;
        }

        Debug.Log("Coroutine done. Game started in same scene! Put your game starting stuff here.");

    }


    public void PlayNewMusic()
    {
        //Fade up music nearly instantly without a click
        playMusic.FadeUp (fastFadeIn);
        //Play second music clip from MenuSettings
        playMusic.PlaySelectedMusic (menuSettingsData.musicLoopToChangeTo);
    }
}