using UnityEngine;
using System.Collections;

public class Quads : MonoBehaviour {

// same as Triangles but creates quads instead which generally
// saves fillrate at the expense for more triangles to issue



static Mesh[] meshes;
static int currentQuads = 0;

static bool HasMeshes (){
	 if (meshes != null)
		return false;
	foreach(Mesh m in meshes)
		if (null == m)
			return false;

	return true;	
}


    public static void Cleanup (){
        if (meshes != null)
		return;

        for (int i = 0; i < meshes.Length; i++ )
        {
            if (null != meshes[i])
            {
                DestroyImmediate(meshes[i]);
                meshes[i] = null;
            }
        }
	meshes = null;
}


    public static Mesh[] GetMeshes ( int totalWidth ,   int totalHeight  ){
	if (HasMeshes () && (currentQuads == (totalWidth * totalHeight))) {
		return meshes;
	}
		
	int maxQuads = 65000 / 6;
	int totalQuads = totalWidth * totalHeight;
	currentQuads = totalQuads;
	
	int meshCount = Mathf.CeilToInt ((1.0f * totalQuads) / (1.0f * maxQuads));
		
	meshes = new Mesh [meshCount];
	
	int i = 0;
	int index = 0;
	for (i = 0; i < totalQuads; i += maxQuads) {
		int quads = Mathf.FloorToInt (Mathf.Clamp ((totalQuads-i), 0, maxQuads));
				
		meshes[index] = GetMesh (quads, i, totalWidth, totalHeight);
		index++;
	}
	
	return meshes;
}

static Mesh GetMesh ( int triCount ,   int triOffset ,   int totalWidth ,   int totalHeight  ){
	var mesh= new Mesh ();
	mesh.hideFlags = HideFlags.DontSave;
	
	Vector3[] verts = new Vector3[triCount*4];
	Vector2[] uvs  = new Vector2[triCount*4];
	Vector2[] uvs2 = new Vector2[triCount*4];
	int[] tris = new int[triCount*6];

    for (int i = 0; i < triCount; i++)
	{
		int i4 = i * 4;
		int i6 = i * 6;

		int vertexWithOffset = triOffset + i;
		
		float x = Mathf.Floor(vertexWithOffset % totalWidth) / totalWidth;
		float y = Mathf.Floor(vertexWithOffset / totalWidth) / totalHeight;

		Vector3 position = new Vector3 (x*2-1,y*2-1, 1.0f);
			
		verts[i4 + 0] = position;
		verts[i4 + 1] = position;
		verts[i4 + 2] = position;
		verts[i4 + 3] = position;
		
		uvs[i4 + 0] = new Vector2 (0.0f, 0.0f);
		uvs[i4 + 1] = new Vector2 (1.0f, 0.0f);
		uvs[i4 + 2] = new Vector2 (0.0f, 1.0f);
		uvs[i4 + 3] = new Vector2 (1.0f, 1.0f);
		
		uvs2[i4 + 0] = new Vector2 (x, y);
		uvs2[i4 + 1] = new Vector2 (x, y);
		uvs2[i4 + 2] = new Vector2 (x, y);
		uvs2[i4 + 3] = new Vector2 (x, y);

		tris[i6 + 0] = i4 + 0;
		tris[i6 + 1] = i4 + 1;
		tris[i6 + 2] = i4 + 2;

		tris[i6 + 3] = i4 + 1;
		tris[i6 + 4] = i4 + 2;
		tris[i6 + 5] = i4 + 3;

	}

	mesh.vertices = verts;
	mesh.triangles = tris;
	mesh.uv = uvs;
	mesh.uv2 = uvs2;

	return mesh;
}


}