using System;
using System.Collections;
using UnityEngine;

public class WorldSwitcher : MonoBehaviour {
	[Range(0, 5)]
	[SerializeField] float transitionDuration;
	[SerializeField] AnimationCurve transitionCurve;
	[SerializeField] WorldInfo[] worldInfos;
	[SerializeField] Transform renderQuad;
	[SerializeField] float quadOffset;
	[SerializeField] float tabWidth;
	int lastWorldIndex;
	int currentWorldIndex;
	Coroutine transition;
	RenderTexture renderTexture;
	Material renderMaterial;

	void Awake() {
		if (worldInfos.Length <= 1)
			Debug.LogWarning("WorldSwitcher should have multiple cameras");

		currentWorldIndex = 0;
		lastWorldIndex = 0;

		renderMaterial = renderQuad.GetComponent<Renderer>().material;
		GenerateRenderTexture();

		for (int i = 0; i < worldInfos.Length; i++) {
			WorldInfo worldInfo = worldInfos[i];
			worldInfo.camera.enabled = i == 0;

			Vector3 tabPos = worldInfo.worldTab.position;
			float tabX = worldInfo.side == TabSide.Left ? 0 : ((RectTransform)worldInfo.worldTab.parent).rect.width;
			worldInfo.worldTab.position = new Vector3(tabX, tabPos.y, tabPos.z);
		}
	}

	public void SwitchWorld(int index) {
		if (index == currentWorldIndex)
			return;

		if (index < 0 || index >= worldInfos.Length)
			throw new IndexOutOfRangeException($"{index} is not an available world.");

		lastWorldIndex = currentWorldIndex;
		currentWorldIndex = index;

		Camera currCam = worldInfos[currentWorldIndex].camera; 
		currCam.enabled = true;

		//TODO Block window resize during transition?
		if (Screen.width != renderTexture.width || Screen.height != renderTexture.height)
			GenerateRenderTexture();
		
		currCam.targetTexture = renderTexture;

		renderQuad.localScale = new Vector3(worldInfos[lastWorldIndex].camera.aspect, 1f, 1f);

		Vector3 oldPos = worldInfos[lastWorldIndex].worldTab.position;
		worldInfos[lastWorldIndex].worldTab.position = new Vector3(worldInfos[lastWorldIndex].TabBaseX, oldPos.y, oldPos.z);
		
		transition = StartCoroutine(TransitionCamera());
	}

	void OnGUI() {
		for (int i = 0; i < worldInfos.Length; ++i) {
			if (i == currentWorldIndex)
				continue;
			
			if (GUILayout.Button($"World {i}"))
				SwitchWorld(i);
		}
	}

	IEnumerator TransitionCamera() {
		WorldInfo lastWorld = worldInfos[lastWorldIndex];
		WorldInfo newWorld = worldInfos[currentWorldIndex];

		float startTime = Time.time;
		Transform lastCam = lastWorld.camera.transform;
		Vector3 tabStartPosition = newWorld.worldTab.position;
		float tabParentWidth = newWorld.TabParentWidth;
		

		while (Time.time < startTime + transitionDuration) {
			float t = transitionCurve.Evaluate((Time.time - startTime) / transitionDuration);
			t *= (tabParentWidth + tabWidth) / tabParentWidth;

			renderQuad.position = lastCam.position + Vector3.forward * quadOffset + Vector3.right * (2f * Mathf.Clamp01(t) - 2f);
			//float tabX = newWorld.side == TabSide.Left ? t * (tabParentWidth + tabWidth) : t * -(tabParentWidth + tabWidth) + tabParentWidth;
			newWorld.worldTab.position = new Vector3(tabParentWidth * t, tabStartPosition.y, tabStartPosition.z);

			yield return null;
		}

		newWorld.camera.targetTexture = null;
		lastWorld.camera.enabled = false;
		transition = null;
	}

	void GenerateRenderTexture() {
		renderTexture = new RenderTexture(Screen.width, Screen.height, 32);
		renderMaterial.mainTexture = renderTexture;
	}
}

[Serializable]
struct WorldInfo {
	public Camera camera;
	public RectTransform worldTab;
	public ushort indexFromSide;
	public TabSide side;

	public float TabParentWidth => ((RectTransform)worldTab.parent).rect.width;

	public float TabBaseX => side == TabSide.Left ?
		indexFromSide * 6.25f :
		TabParentWidth - indexFromSide * 6.25f;
}

[Serializable]
enum TabSide { Left, Right }