package com.baidu.facelibrary.gl;

import android.opengl.GLES20;

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

public class Shape {

    public Shape() {
        initializeBuffers();
        initializeProgram();
    }

    private float vertices[] = {
            -1f, -1f,
            1f, -1f,
            -1f, 1f,
            1f, 1f,
    };
    private float textureVertices[] = {
            0f, 1f,
            1f, 1f,
            0f, 0f,
            1f, 0f
    };

    private final String vertexShaderCode =
            "attribute vec4 aPosition;" +
                    "attribute vec2 aTexPosition;" +
                    "varying vec2 vTexPosition;" +
                    "void main() {" +
                    "  gl_Position = aPosition;" +
                    "  vTexPosition = aTexPosition;" +
                    "}";

    private final String fragmentShaderCode =
            "precision mediump float;" +
                    "uniform sampler2D uTexture;" +
                    "varying vec2 vTexPosition;" +
                    "void main() {" +
                    "  gl_FragColor = texture2D(uTexture, vTexPosition);" +
                    "}";
    private FloatBuffer verticesBuffer;
    private FloatBuffer textureBuffer;
    private int vertexShader;
    private int fragmentShader;
    private int program;


    private void initializeBuffers() {
        ByteBuffer buff = ByteBuffer.allocateDirect(vertices.length * 4);
        buff.order(ByteOrder.nativeOrder());
        verticesBuffer = buff.asFloatBuffer();
        verticesBuffer.put(vertices);
        verticesBuffer.position(0);

        buff = ByteBuffer.allocateDirect(textureVertices.length * 4);
        buff.order(ByteOrder.nativeOrder());
        textureBuffer = buff.asFloatBuffer();
        textureBuffer.put(textureVertices);
        textureBuffer.position(0);
    }

    private void initializeProgram() {
        vertexShader = GLES20.glCreateShader(GLES20.GL_VERTEX_SHADER);
        GLES20.glShaderSource(vertexShader, vertexShaderCode);
        GLES20.glCompileShader(vertexShader);

        fragmentShader = GLES20.glCreateShader(GLES20.GL_FRAGMENT_SHADER);
        GLES20.glShaderSource(fragmentShader, fragmentShaderCode);
        GLES20.glCompileShader(fragmentShader);

        program = GLES20.glCreateProgram();
        GLES20.glAttachShader(program, vertexShader);
        GLES20.glAttachShader(program, fragmentShader);

        GLES20.glLinkProgram(program);
    }

    public void draw(int texture) {
        GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);
        GLES20.glUseProgram(program);
        GLES20.glDisable(GLES20.GL_BLEND);

        int positionHandle = GLES20.glGetAttribLocation(program, "aPosition");
        int textureHandle = GLES20.glGetUniformLocation(program, "uTexture");
        int texturePositionHandle = GLES20.glGetAttribLocation(program, "aTexPosition");

        GLES20.glVertexAttribPointer(texturePositionHandle, 2, GLES20.GL_FLOAT, false, 0, textureBuffer);
        GLES20.glEnableVertexAttribArray(texturePositionHandle);

        GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texture);
        GLES20.glUniform1i(textureHandle, 0);

        GLES20.glVertexAttribPointer(positionHandle, 2, GLES20.GL_FLOAT, false, 0, verticesBuffer);
        GLES20.glEnableVertexAttribArray(positionHandle);

        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
        GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);


    }
}