/************************************************************************************
Copyright : Copyright (c) Facebook Technologies, LLC and its affiliates. All rights reserved.

Your use of this SDK or tool is subject to the Oculus SDK License Agreement, available at
https://developer.oculus.com/licenses/oculussdk/

Unless required by applicable law or agreed to in writing, the Utilities SDK distributed
under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
ANY KIND, either express or implied. See the License for the specific language governing
permissions and limitations under the License.
************************************************************************************/

using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;

using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEngine.UI;

public class OVRSceneLoader : MonoBehaviour
{
	public const string externalStoragePath = "/sdcard/Android/data";
	public const string sceneLoadDataName = "SceneLoadData.txt";
	public const string resourceBundleName = "asset_resources";

	public float sceneCheckIntervalSeconds = 1f;
	public float logCloseTime = 5.0f;

	public Canvas mainCanvas;
	public Text logTextBox;

	private AsyncOperation loadSceneOperation;
	private string formattedLogText;

	private float closeLogTimer;
	private bool closeLogDialogue;

	private bool canvasPosUpdated;

	private struct SceneInfo
	{
		public List<string> scenes;
		public long version;

		public SceneInfo(List<string> sceneList, long currentSceneEpochVersion)
		{
			scenes = sceneList;
			version = currentSceneEpochVersion;
		}
	}

	private string scenePath = "";
	private string sceneLoadDataPath = "";
	private List<AssetBundle> loadedAssetBundles = new List<AssetBundle>();
	private SceneInfo currentSceneInfo;

	private void Awake()
	{
		// Make it presist across scene to continue checking for changes
		DontDestroyOnLoad(this.gameObject);
	}

	void Start()
	{
		string applicationPath = Path.Combine(externalStoragePath, Application.identifier);
		scenePath = Path.Combine(applicationPath, "cache/scenes");
		sceneLoadDataPath = Path.Combine(scenePath, sceneLoadDataName);

		closeLogDialogue = false;
		StartCoroutine(DelayCanvasPosUpdate());

		currentSceneInfo = GetSceneInfo();
		// Check valid scene info has been fetched, and load the scenes
		if (currentSceneInfo.version != 0 && !string.IsNullOrEmpty(currentSceneInfo.scenes[0]))
		{
			LoadScene(currentSceneInfo);
		}
	}

	private void LoadScene(SceneInfo sceneInfo)
	{
		AssetBundle mainSceneBundle = null;
		Debug.Log("[OVRSceneLoader] Loading main scene: " + sceneInfo.scenes[0] + " with version " + sceneInfo.version.ToString());

		logTextBox.text += "Target Scene: " + sceneInfo.scenes[0] + "\n";
		logTextBox.text += "Version: " + sceneInfo.version.ToString() + "\n";

		// Load main scene and dependent additive scenes (if any)
		Debug.Log("[OVRSceneLoader] Loading scene bundle files.");
		// Fetch all files under scene cache path, excluding unnecessary files such as scene metadata file
		string[] bundles = Directory.GetFiles(scenePath, "*_*");
		logTextBox.text += "Loading " + bundles.Length + " bundle(s) . . . ";
		string mainSceneBundleFileName = "scene_" + sceneInfo.scenes[0].ToLower();
		try
		{
			foreach (string b in bundles)
			{
				var assetBundle = AssetBundle.LoadFromFile(b);
				if (assetBundle != null)
				{
					Debug.Log("[OVRSceneLoader] Loading file bundle: " + assetBundle.name == null ? "null" : assetBundle.name);
					loadedAssetBundles.Add(assetBundle);
				}
				else
				{
					Debug.LogError("[OVRSceneLoader] Loading file bundle failed");
				}

				if (assetBundle.name == mainSceneBundleFileName)
				{
					mainSceneBundle = assetBundle;
				}

				if (assetBundle.name == resourceBundleName)
				{
					OVRResources.SetResourceBundle(assetBundle);
				}
			}
		}
		catch(Exception e)
		{
			logTextBox.text += "<color=red>" + e.Message + "</color>";
			return;
		}
		logTextBox.text += "<color=green>DONE\n</color>";

		if (mainSceneBundle != null)
		{
			logTextBox.text += "Loading Scene: {0:P0}\n";
			formattedLogText = logTextBox.text;
			string[] scenePaths = mainSceneBundle.GetAllScenePaths();
			string sceneName = Path.GetFileNameWithoutExtension(scenePaths[0]);
			
			loadSceneOperation = SceneManager.LoadSceneAsync(sceneName);
			loadSceneOperation.completed += LoadSceneOperation_completed;
		}
		else
		{
			logTextBox.text += "<color=red>Failed to get main scene bundle.\n</color>";
		}
	}

	private void LoadSceneOperation_completed(AsyncOperation obj)
	{
		StartCoroutine(onCheckSceneCoroutine());
		StartCoroutine(DelayCanvasPosUpdate());

		closeLogTimer = 0;
		closeLogDialogue = true;

		logTextBox.text += "Log closing in {0} seconds.\n";
		formattedLogText = logTextBox.text;
	}

	public void Update()
	{
		// Display scene load percentage
		if (loadSceneOperation != null)
		{
			if (!loadSceneOperation.isDone)
			{
				logTextBox.text = string.Format(formattedLogText, loadSceneOperation.progress + 0.1f);
				if (loadSceneOperation.progress >= 0.9f)
				{
					logTextBox.text = formattedLogText.Replace("{0:P0}", "<color=green>DONE</color>");
					logTextBox.text += "Transitioning to new scene.\nLoad times will vary depending on scene complexity.\n";
					
				}
			}
		}

		UpdateCanvasPosition();

		// Wait a certain time before closing the log dialogue after the scene has transitioned
		if (closeLogDialogue)
		{
			if (closeLogTimer < logCloseTime)
			{
				closeLogTimer += Time.deltaTime;
				logTextBox.text = string.Format(formattedLogText, (int)(logCloseTime - closeLogTimer));
			}
			else
			{
				mainCanvas.gameObject.SetActive(false);
				closeLogDialogue = false;
			}
		}
	}

	private void UpdateCanvasPosition()
	{
		// Update canvas camera reference and position if the main camera has changed
		if (mainCanvas.worldCamera != Camera.main)
		{
			mainCanvas.worldCamera = Camera.main;
			if (Camera.main != null)
			{
				Vector3 newPosition = Camera.main.transform.position + Camera.main.transform.forward * 0.3f;
				gameObject.transform.position = newPosition;
				gameObject.transform.rotation = Camera.main.transform.rotation;
			}
		}
	}

	private SceneInfo GetSceneInfo()
	{
		SceneInfo sceneInfo = new SceneInfo();
		try
		{
			StreamReader reader = new StreamReader(sceneLoadDataPath);
			sceneInfo.version = System.Convert.ToInt64(reader.ReadLine());
			List<string> sceneList = new List<string>();
			while (!reader.EndOfStream)
			{
				sceneList.Add(reader.ReadLine());
			}
			sceneInfo.scenes = sceneList;
		}
		catch
		{
			logTextBox.text += "<color=red>Failed to get scene info data.\n</color>";
		}
		return sceneInfo;
	}

	// Update canvas position after a slight delay to get accurate headset position after scene transitions
	IEnumerator DelayCanvasPosUpdate()
	{
		yield return new WaitForSeconds(0.1f);
		UpdateCanvasPosition();
	}

	IEnumerator onCheckSceneCoroutine()
	{
		SceneInfo newSceneInfo;
		while (true)
		{
			newSceneInfo = GetSceneInfo();
			if (newSceneInfo.version != currentSceneInfo.version)
			{
				Debug.Log("[OVRSceneLoader] Scene change detected.");

				// Unload all asset bundles
				foreach (var b in loadedAssetBundles)
				{
					if (b != null)
					{
						b.Unload(true);
					}
				}
				loadedAssetBundles.Clear();

				// Unload all scenes in the hierarchy including main scene and 
				// its dependent additive scenes.
				int activeScenes = SceneManager.sceneCount;
				for (int i = 0; i < activeScenes; i++)
				{
					SceneManager.UnloadSceneAsync(SceneManager.GetSceneAt(i));
				}
				DestroyAllGameObjects();
				SceneManager.LoadSceneAsync("OVRTransitionScene");
				break;
			}
			yield return new WaitForSeconds(sceneCheckIntervalSeconds);
		}
	}

	void DestroyAllGameObjects()
	{
		foreach (GameObject go in Resources.FindObjectsOfTypeAll(typeof(GameObject)) as GameObject[])
		{
			Destroy(go);
		}
	}
}