using UnityEngine;
using System.Collections;

public class Triangles : MonoBehaviour
{



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

    static bool HasMeshes()
    {
        if (meshes != null)
            return false;
        for (int i = 0; i < meshes.Length; i++)
            if (null == meshes[i])
                return false;

        return true;
    }

    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;
    }

    static Mesh[] GetMeshes(int totalWidth, int totalHeight)
    {
        if (HasMeshes() && (currentTris == (totalWidth * totalHeight)))
        {
            return meshes;
        }

        int maxTris = 65000 / 3;
        int totalTris = totalWidth * totalHeight;
        currentTris = totalTris;

        int meshCount = Mathf.CeilToInt((1.0f * totalTris) / (1.0f * maxTris));

        meshes = new Mesh[meshCount];

        int i = 0;
        int index = 0;
        for (i = 0; i < totalTris; i += maxTris)
        {
            int tris = Mathf.FloorToInt(Mathf.Clamp((totalTris - i), 0, maxTris));

            meshes[index] = GetMesh(tris, 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 * 3];
        Vector2[] uvs = new Vector2[triCount * 3];
        Vector2[] uvs2 = new Vector2[triCount * 3];
        int[] tris = new int[triCount * 3];

        for (int i = 0; i < triCount; i++)
        {
            int i3 = i * 3;
            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[i3 + 0] = position;
            verts[i3 + 1] = position;
            verts[i3 + 2] = position;

            uvs[i3 + 0] = new Vector2(0.0f, 0.0f);
            uvs[i3 + 1] = new Vector2(1.0f, 0.0f);
            uvs[i3 + 2] = new Vector2(0.0f, 1.0f);

            uvs2[i3 + 0] = new Vector2(x, y);
            uvs2[i3 + 1] = new Vector2(x, y);
            uvs2[i3 + 2] = new Vector2(x, y);

            tris[i3 + 0] = i3 + 0;
            tris[i3 + 1] = i3 + 1;
            tris[i3 + 2] = i3 + 2;
        }

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

        return mesh;
    }
}