/**
 * This class was created by <Vazkii>. It's distributed as
 * part of the Botania Mod. Get the Source Code in github:
 * https://github.com/Vazkii/Botania
 *
 * Botania is Open Source and distributed under a
 * Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License
 * (http://creativecommons.org/licenses/by-nc-sa/3.0/deed.en_GB)
 *
 * File Created @ [Apr 9, 2014, 11:20:26 PM (GMT)]
 */
package WayofTime.alchemicalWizardry.common.renderer.block;

import org.lwjgl.opengl.ARBFragmentShader;
import org.lwjgl.opengl.ARBShaderObjects;
import org.lwjgl.opengl.ARBVertexShader;
import org.lwjgl.opengl.GL11;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;

public final class ShaderHelper
{

    private static final int VERT = ARBVertexShader.GL_VERTEX_SHADER_ARB;
    private static final int FRAG = ARBFragmentShader.GL_FRAGMENT_SHADER_ARB;

    public static int beam = 0;

    public static void initShaders()
    {
        beam = createProgram(null, "/assets/alchemicalwizardry/shaders/beam.frag");
    }

    public static void useShaderWithProps(int shader, Object... props)
    {
        ARBShaderObjects.glUseProgramObjectARB(shader);

        if (shader != 0 && props.length % 2 == 0)
        {
            int propCount = props.length / 2;
            for (int i = 0; i < propCount; i++)
            {
                String propName = (String) props[i * 2];
                Object propVal = props[i * 2 + 1];

                int uniform = ARBShaderObjects.glGetUniformLocationARB(shader, propName);
                if (propVal instanceof Integer)
                    ARBShaderObjects.glUniform1iARB(uniform, (Integer) propVal);
                if (propVal instanceof Float)
                    ARBShaderObjects.glUniform1fARB(uniform, (Float) propVal);
            }
        }
    }

    public static void useShader(int shader)
    {
        useShaderWithProps(shader);
    }

    public static void releaseShader()
    {
        useShader(0);
    }

    public static boolean useShaders()
    {
        return true;
    }

    // Most of the code taken from the LWJGL wiki
    // http://lwjgl.org/wiki/index.php?title=GLSL_Shaders_with_LWJGL
    private static int createProgram(String vert, String frag)
    {
        int vertId = 0, fragId = 0, program = 0;
        if (vert != null)
            vertId = createShader(vert, VERT);
        if (frag != null)
            fragId = createShader(frag, FRAG);

        program = ARBShaderObjects.glCreateProgramObjectARB();
        if (program == 0)
            return 0;

        if (vert != null)
            ARBShaderObjects.glAttachObjectARB(program, vertId);
        if (frag != null)
            ARBShaderObjects.glAttachObjectARB(program, fragId);

        ARBShaderObjects.glLinkProgramARB(program);
        if (ARBShaderObjects.glGetObjectParameteriARB(program, ARBShaderObjects.GL_OBJECT_LINK_STATUS_ARB) == GL11.GL_FALSE)
        {
            return 0;
        }

        ARBShaderObjects.glValidateProgramARB(program);
        if (ARBShaderObjects.glGetObjectParameteriARB(program, ARBShaderObjects.GL_OBJECT_VALIDATE_STATUS_ARB) == GL11.GL_FALSE)
        {
            return 0;
        }

        return program;
    }

    private static int createShader(String filename, int shaderType)
    {
        int shader = 0;
        try
        {
            shader = ARBShaderObjects.glCreateShaderObjectARB(shaderType);

            if (shader == 0)
                return 0;

            ARBShaderObjects.glShaderSourceARB(shader, readFileAsString(filename));
            ARBShaderObjects.glCompileShaderARB(shader);

            if (ARBShaderObjects.glGetObjectParameteriARB(shader, ARBShaderObjects.GL_OBJECT_COMPILE_STATUS_ARB) == GL11.GL_FALSE)
                throw new RuntimeException("Error creating shader: " + getLogInfo(shader));

            return shader;
        } catch (Exception e)
        {
            ARBShaderObjects.glDeleteObjectARB(shader);
            e.printStackTrace();
            return -1;
        }
    }

    private static String getLogInfo(int obj)
    {
        return ARBShaderObjects.glGetInfoLogARB(obj, ARBShaderObjects.glGetObjectParameteriARB(obj, ARBShaderObjects.GL_OBJECT_INFO_LOG_LENGTH_ARB));
    }

    private static String readFileAsString(String filename) throws Exception
    {
        StringBuilder source = new StringBuilder();
        InputStream in = ShaderHelper.class.getResourceAsStream(filename);
        Exception exception = null;
        BufferedReader reader;

        if (in == null)
            return "";

        try
        {
            reader = new BufferedReader(new InputStreamReader(in, "UTF-8"));

            Exception innerExc = null;
            try
            {
                String line;
                while ((line = reader.readLine()) != null)
                    source.append(line).append('\n');
            } catch (Exception exc)
            {
                exception = exc;
            } finally
            {
                try
                {
                    reader.close();
                } catch (Exception exc)
                {
                    if (innerExc == null)
                        innerExc = exc;
                    else exc.printStackTrace();
                }
            }

            if (innerExc != null)
                throw innerExc;
        } catch (Exception exc)
        {
            exception = exc;
        } finally
        {
            try
            {
                in.close();
            } catch (Exception exc)
            {
                if (exception == null)
                    exception = exc;
                else exc.printStackTrace();
            }

            if (exception != null)
                throw exception;
        }

        return source.toString();
    }
}