using UnityEngine;
using System.Collections;

[ExecuteInEditMode]
[AddComponentMenu("Image Effects/Blur (island)")]
public class BlurEffectIsland : MonoBehaviour
{
    /// Blur iterations - larger number means more blur.
    public int iterations = 3;

    /// Blur spread for each iteration. Lower values
    /// give better looking blur, but require more iterations to
    /// get large blurs. Value is usually between 0.5 and 1.0.
    public float blurSpread = 0.6f;

    // --------------------------------------------------------
    // The blur iteration shader.
    // Basically it just takes 4 texture samples and averages them.
    // By applying it repeatedly and spreading out sample locations
    // we get a Gaussian blur approximation.

    private static string blurMatString =
@"Shader ""BlurConeTap"" {
	SubShader {
		Pass {
			ZTest Always Cull Off ZWrite Off Fog { Mode Off }
			SetTexture [__RenderTex] {constantColor (0,0,0,0.25) combine texture * constant alpha}
			SetTexture [__RenderTex] {constantColor (0,0,0,0.25) combine texture * constant + previous}
			SetTexture [__RenderTex] {constantColor (0,0,0,0.25) combine texture * constant + previous}
			SetTexture [__RenderTex] {constantColor (0,0,0,0.25) combine texture * constant + previous}
		}
	}
	Fallback off
}";

    static Material m_Material = null;
    protected static Material material
    {
        get
        {
            if (m_Material == null)
            {
                m_Material = new Material(blurMatString);
                m_Material.hideFlags = HideFlags.HideAndDontSave;
                m_Material.shader.hideFlags = HideFlags.HideAndDontSave;
            }
            return m_Material;
        }
    }

    protected void OnDisable()
    {
        if (m_Material)
        {
            DestroyImmediate(m_Material.shader);
            DestroyImmediate(m_Material);
        }
    }

    // --------------------------------------------------------

    public bool IsSupported()
    {
        // Disable if we don't support image effects
        if (!SystemInfo.supportsImageEffects)
            return false;
        // Disable if the shader can't run on the users graphics card
        if (!material.shader.isSupported)
            return false;

        return true;
    }

    protected void Start()
    {
        if (!IsSupported())
            enabled = false;
    }

    // Performs one blur iteration.
    public void FourTapCone(RenderTexture source, RenderTexture dest, int iteration)
    {
        RenderTexture.active = dest;
        source.SetGlobalShaderProperty("__RenderTex");

        float offsetX = (.5F + iteration * blurSpread) / (float)source.width;
        float offsetY = (.5F + iteration * blurSpread) / (float)source.height;
        GL.PushMatrix();
        GL.LoadOrtho();

        for (int i = 0; i < material.passCount; i++)
        {
            material.SetPass(i);
            Render4TapQuad(dest, offsetX, offsetY);
        }
        GL.PopMatrix();
    }

    // Downsamples the texture to a quarter resolution.
    private void DownSample4x(RenderTexture source, RenderTexture dest)
    {
        RenderTexture.active = dest;
        source.SetGlobalShaderProperty("__RenderTex");

        float offsetX = 1.0f / (float)source.width;
        float offsetY = 1.0f / (float)source.height;

        GL.PushMatrix();
        GL.LoadOrtho();
        for (int i = 0; i < material.passCount; i++)
        {
            material.SetPass(i);
            Render4TapQuad(dest, offsetX, offsetY);
        }
        GL.PopMatrix();
    }

    // Called by the camera to apply the image effect
    void OnRenderImage(RenderTexture source, RenderTexture destination)
    {
        RenderTexture buffer = RenderTexture.GetTemporary(source.width / 4, source.height / 4, 0);
        RenderTexture buffer2 = RenderTexture.GetTemporary(source.width / 4, source.height / 4, 0);

        // Copy source to the 4x4 smaller texture.
        DownSample4x(source, buffer);

        // Blur the small texture
        bool oddEven = true;
        for (int i = 0; i < iterations; i++)
        {
            if (oddEven)
                FourTapCone(buffer, buffer2, i);
            else
                FourTapCone(buffer2, buffer, i);
            oddEven = !oddEven;
        }
        if (oddEven)
            ImageEffects.Blit(buffer, destination);
        else
            ImageEffects.Blit(buffer2, destination);

        RenderTexture.ReleaseTemporary(buffer);
        RenderTexture.ReleaseTemporary(buffer2);
    }

    private static void Render4TapQuad(RenderTexture dest, float offsetX, float offsetY)
    {
        GL.Begin(GL.QUADS);

        // Direct3D needs interesting texel offsets!		
        Vector2 off = Vector2.zero;
        if (dest != null)
            off = dest.GetTexelOffset() * 0.75f;

        Set4TexCoords(off.x, off.y, offsetX, offsetY);
        GL.Vertex3(0, 0, .1f);

        Set4TexCoords(1.0f + off.x, off.y, offsetX, offsetY);
        GL.Vertex3(1, 0, .1f);

        Set4TexCoords(1.0f + off.x, 1.0f + off.y, offsetX, offsetY);
        GL.Vertex3(1, 1, .1f);

        Set4TexCoords(off.x, 1.0f + off.y, offsetX, offsetY);
        GL.Vertex3(0, 1, .1f);

        GL.End();
    }

    private static void Set4TexCoords(float x, float y, float offsetX, float offsetY)
    {
        GL.MultiTexCoord2(0, x - offsetX, y - offsetY);
        GL.MultiTexCoord2(1, x + offsetX, y - offsetY);
        GL.MultiTexCoord2(2, x + offsetX, y + offsetY);
        GL.MultiTexCoord2(3, x - offsetX, y + offsetY);
    }
}