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

public class StartOptions : MonoBehaviour
{
    public GameObject BackGround;
    public Sprite ImageIntro;

    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

    [HideInInspector]
    public bool inMainMenu = true;                  //If true, pause button disabled in main menu (Cancel in input manager, default escape key)

    [HideInInspector]
    public Animator animColorFade;                  //Reference to animator which will fade to and from black when starting game.

    [HideInInspector]
    public Animator animMenuAlpha;                  //Reference to animator that will fade out alpha of MenuPanel canvas group

    public AnimationClip fadeColorAnimationClip;        //Animation clip fading to color (black default) when changing scenes

    [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 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>();
    }

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

        showPanels.HideMenu();

        BackGround.GetComponent<Image>().sprite = ImageIntro;

        StartCoroutine(Next());
    }

    private IEnumerator Next()
    {
        yield return new WaitForSeconds(7f);

        //If changeScenes is true, start fading and change scenes halfway through animation when screen is blocked by FadeImage
        if (changeScenes)
        {
            //Use invoke to delay calling of LoadDelayed by half the length of fadeColorAnimationClip
            Invoke("LoadDelayed", fadeColorAnimationClip.length * .5f);

            //Set the trigger of Animator animColorFade to start transition to the FadeToOpaque state.
            animColorFade.SetTrigger("fade");
        }

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

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

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

    //Once the level has loaded, check if we want to call PlayLevelMusic
    private void SceneWasLoaded(Scene scene, LoadSceneMode mode)
    {
        //if changeMusicOnStart is true, call the PlayLevelMusic function of playMusic
        if (changeMusicOnStart)
        {
            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();
        BackGround.SetActive(false);

        //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 changeMusicOnStart is true, fade out volume of music group of AudioMixer by calling FadeDown function of PlayMusic, using length of fadeColorAnimationClip as time.
        //To change fade time, change length of animation "FadeToColor"
        if (changeMusicOnStart)
        {
            //Wait until game has started, then play new music
            Invoke("PlayNewMusic", fadeAlphaAnimationClip.length);
        }
        //Set trigger for animator to start animation fading out Menu UI
        animMenuAlpha.SetTrigger("fade");
        Invoke("HideDelayed", fadeAlphaAnimationClip.length);
        Debug.Log("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 music clip assigned to mainMusic in PlayMusic script
        playMusic.PlaySelectedMusic(1);
    }
}