/*
 * Copyright 2014 Google Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.hoperun.cordova.vuforia.utils;

import android.opengl.GLES20;
import android.opengl.GLES30;
import android.opengl.Matrix;
import android.util.Log;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.ShortBuffer;

/**
 * Some OpenGL utility functions.
 */
public class GlUtil {

    public static final String TAG = "GlUtil";

    /** Identity matrix for general use.  Don't modify or life will get weird. */
    public static final float[] IDENTITY_MATRIX;

    static {
        IDENTITY_MATRIX = new float[16];
        Matrix.setIdentityM(IDENTITY_MATRIX, 0);
    }

    private static final int SIZEOF_FLOAT = 4;
    private static final int SIZEOF_SHORT = 2;

    /**
     * Creates a new program from the supplied vertex and fragment shaders.
     *
     * @return A handle to the program, or 0 on failure.
     */
    public static int createProgram(String vertexSource, String fragmentSource) {

        int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, vertexSource);
        if (vertexShader == 0) {
            return 0;
        }

        int fragmentShader = loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentSource);
        if (fragmentShader == 0) {
            return 0;
        }

        // 创建一个空的OpenGL ES Program
        int program = GLES20.glCreateProgram();
        if (program == 0) {
            Log.e(TAG, "Could not create program");
        }

        // 将vertex shader添加到program
        GLES20.glAttachShader(program, vertexShader);

        // 将fragment shader添加到program
        GLES20.glAttachShader(program, fragmentShader);

        // 创建可执行的 OpenGL ES program
        GLES20.glLinkProgram(program);

        int[] linkStatus = new int[1];

        // Check the link status
        GLES20.glGetProgramiv(program, GLES20.GL_LINK_STATUS, linkStatus, 0);
        if (linkStatus[0] != GLES20.GL_TRUE) {
            Log.e(TAG, "Could not link program: ");
            Log.e(TAG, GLES20.glGetProgramInfoLog(program));
            GLES20.glDeleteProgram(program);
            program = 0;
        }

        return program;

    }

    /**
     * Compiles the provided shader source.
     *
     * @return A handle to the shader, or 0 on failure.
     */
    public static int loadShader(int shaderType, String shaderCode) {

        // 创建一个vertex shader类型(GLES20.GL_VERTEX_SHADER)
        // 或fragment shader类型(GLES20.GL_FRAGMENT_SHADER)
        int shader = GLES20.glCreateShader(shaderType);

        // 将源码添加到shader并编译之
        GLES20.glShaderSource(shader, shaderCode);
        GLES20.glCompileShader(shader);

        int[] compiled = new int[1];

        // Check the compile status
        GLES20.glGetShaderiv(shader, GLES20.GL_COMPILE_STATUS, compiled, 0);
        if (compiled[0] == 0) {
            Log.e(TAG, "Could not compile shader " + shaderType + ":");
            Log.e(TAG, " " + GLES20.glGetShaderInfoLog(shader));
            GLES20.glDeleteShader(shader);
            shader = 0;
        }

        return shader;

    }

    /**
     * Checks to see if a GLES error has been raised.
     */
    public static void checkGlError(String op) {

        int error = GLES20.glGetError();
        if (error != GLES20.GL_NO_ERROR) {
            String msg = op + ": glError 0x" + Integer.toHexString(error);
            Log.e(TAG, msg);
            throw new RuntimeException(msg);
        }

    }

    /**
     * Checks to see if the location we obtained is valid.  GLES returns -1 if a label
     * could not be found, but does not set the GL error.
     * <p>
     * Throws a RuntimeException if the location is invalid.
     */
    public static void checkLocation(int location, String label) {

        if (location < 0) {
            throw new RuntimeException("Unable to locate '" + label + "' in program");
        }

    }

    /**
     * Creates a texture from raw data.
     *
     * @param data Image data, in a "direct" ByteBuffer.
     * @param width Texture width, in pixels (not bytes).
     * @param height Texture height, in pixels.
     * @param format Image data format (use constant appropriate for glTexImage2D(), e.g. GL_RGBA).
     * @return Handle to texture.
     */
    public static int createImageTexture(ByteBuffer data, int width, int height, int format) {

        int[] textureHandles = new int[1];
        int textureHandle;

        GLES20.glGenTextures(1, textureHandles, 0);
        textureHandle = textureHandles[0];

        GlUtil.checkGlError("glGenTextures");

        // Bind the texture handle to the 2D texture target.
        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureHandle);

        // Configure min/mag filtering, i.e. what scaling method do we use if what we're rendering
        // is smaller or larger than the source image.
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_LINEAR);
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR);

        GlUtil.checkGlError("loadImageTexture");

        // Load the data from the buffer into the texture handle.
        GLES20.glTexImage2D(GLES20.GL_TEXTURE_2D, /*level*/ 0, format, width, height, /*border*/ 0, format, GLES20.GL_UNSIGNED_BYTE, data);

        GlUtil.checkGlError("loadImageTexture");

        return textureHandle;

    }

    /**
     * Allocates a direct float buffer, and populates it with the float array data.
     */
    public static FloatBuffer createFloatBuffer(float[] coords) {

        // Allocate a direct ByteBuffer, using 4 bytes per float, and copy coords into it.
        ByteBuffer bb = ByteBuffer.allocateDirect(coords.length * SIZEOF_FLOAT);
        bb.order(ByteOrder.nativeOrder());
        FloatBuffer fb = bb.asFloatBuffer();
        fb.put(coords);
        fb.position(0);

        return fb;

    }

    /**
     * Allocates a direct float buffer, and populates it with the float array data.
     */
    public static ShortBuffer createShortBuffer(short[] order) {

        // Allocate a direct ByteBuffer, using 2 bytes per float, and copy coords into it.
        ByteBuffer bb = ByteBuffer.allocateDirect(order.length * SIZEOF_SHORT);
        bb.order(ByteOrder.nativeOrder());
        ShortBuffer fb = bb.asShortBuffer();
        fb.put(order);
        fb.position(0);

        return fb;

    }

    /**
     * Writes GL version info to the log.
     */
    public static void logVersionInfo() {

        Log.i(TAG, "vendor  : " + GLES20.glGetString(GLES20.GL_VENDOR));
        Log.i(TAG, "renderer: " + GLES20.glGetString(GLES20.GL_RENDERER));
        Log.i(TAG, "version : " + GLES20.glGetString(GLES20.GL_VERSION));

        if (false) {
            int[] values = new int[1];
            GLES30.glGetIntegerv(GLES30.GL_MAJOR_VERSION, values, 0);

            int majorVersion = values[0];
            GLES30.glGetIntegerv(GLES30.GL_MINOR_VERSION, values, 0);

            int minorVersion = values[0];
            if (GLES30.glGetError() == GLES30.GL_NO_ERROR) {
                Log.i(TAG, "iversion: " + majorVersion + "." + minorVersion);
            }
        }

    }

}