/*
 * Copyright (C) 2019 The Android Open Source Project
 *
 * 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.android.systemui.glwallpaper;

import static android.opengl.GLES20.GL_FLOAT;
import static android.opengl.GLES20.GL_LINEAR;
import static android.opengl.GLES20.GL_TEXTURE0;
import static android.opengl.GLES20.GL_TEXTURE_2D;
import static android.opengl.GLES20.GL_TEXTURE_MAG_FILTER;
import static android.opengl.GLES20.GL_TEXTURE_MIN_FILTER;
import static android.opengl.GLES20.GL_TRIANGLES;
import static android.opengl.GLES20.glActiveTexture;
import static android.opengl.GLES20.glBindTexture;
import static android.opengl.GLES20.glDrawArrays;
import static android.opengl.GLES20.glEnableVertexAttribArray;
import static android.opengl.GLES20.glGenTextures;
import static android.opengl.GLES20.glTexParameteri;
import static android.opengl.GLES20.glUniform1i;
import static android.opengl.GLES20.glVertexAttribPointer;

import android.graphics.Bitmap;
import android.opengl.GLUtils;
import android.util.Log;

import java.io.FileDescriptor;
import java.io.PrintWriter;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;

/**
 * This class takes charge of the geometry data like vertices and texture coordinates.
 * It delivers these data to opengl runtime and triggers draw calls if necessary.
 */
class ImageGLWallpaper {
    private static final String TAG = ImageGLWallpaper.class.getSimpleName();

    private static final String A_POSITION = "aPosition";
    private static final String A_TEXTURE_COORDINATES = "aTextureCoordinates";
    private static final String U_TEXTURE = "uTexture";
    private static final int POSITION_COMPONENT_COUNT = 2;
    private static final int TEXTURE_COMPONENT_COUNT = 2;
    private static final int BYTES_PER_FLOAT = 4;

    // Vertices to define the square with 2 triangles.
    private static final float[] VERTICES = {
            -1.0f,  -1.0f,
            +1.0f,  -1.0f,
            +1.0f,  +1.0f,
            +1.0f,  +1.0f,
            -1.0f,  +1.0f,
            -1.0f,  -1.0f
    };

    // Texture coordinates that maps to vertices.
    private static final float[] TEXTURES = {
            0f, 1f,
            1f, 1f,
            1f, 0f,
            1f, 0f,
            0f, 0f,
            0f, 1f
    };

    private final FloatBuffer mVertexBuffer;
    private final FloatBuffer mTextureBuffer;
    private final ImageGLProgram mProgram;

    private int mAttrPosition;
    private int mAttrTextureCoordinates;
    private int mUniTexture;
    private int mTextureId;

    ImageGLWallpaper(ImageGLProgram program) {
        mProgram = program;

        // Create an float array in opengles runtime (native) and put vertex data.
        mVertexBuffer = ByteBuffer.allocateDirect(VERTICES.length * BYTES_PER_FLOAT)
            .order(ByteOrder.nativeOrder())
            .asFloatBuffer();
        mVertexBuffer.put(VERTICES);
        mVertexBuffer.position(0);

        // Create an float array in opengles runtime (native) and put texture data.
        mTextureBuffer = ByteBuffer.allocateDirect(TEXTURES.length * BYTES_PER_FLOAT)
            .order(ByteOrder.nativeOrder())
            .asFloatBuffer();
        mTextureBuffer.put(TEXTURES);
        mTextureBuffer.position(0);
    }

    void setup(Bitmap bitmap) {
        setupAttributes();
        setupUniforms();
        setupTexture(bitmap);
    }

    private void setupAttributes() {
        mAttrPosition = mProgram.getAttributeHandle(A_POSITION);
        mVertexBuffer.position(0);
        glVertexAttribPointer(mAttrPosition, POSITION_COMPONENT_COUNT, GL_FLOAT,
                false, 0, mVertexBuffer);
        glEnableVertexAttribArray(mAttrPosition);

        mAttrTextureCoordinates = mProgram.getAttributeHandle(A_TEXTURE_COORDINATES);
        mTextureBuffer.position(0);
        glVertexAttribPointer(mAttrTextureCoordinates, TEXTURE_COMPONENT_COUNT, GL_FLOAT,
                false, 0, mTextureBuffer);
        glEnableVertexAttribArray(mAttrTextureCoordinates);
    }

    private void setupUniforms() {
        mUniTexture = mProgram.getUniformHandle(U_TEXTURE);
    }

    void draw() {
        glDrawArrays(GL_TRIANGLES, 0, VERTICES.length / 2);
    }

    private void setupTexture(Bitmap bitmap) {
        final int[] tids = new int[1];

        if (bitmap == null) {
            Log.w(TAG, "setupTexture: invalid bitmap");
            return;
        }

        // Generate one texture object and store the id in tids[0].
        glGenTextures(1, tids, 0);
        if (tids[0] == 0) {
            Log.w(TAG, "setupTexture: glGenTextures() failed");
            return;
        }

        // Bind a named texture to a target.
        glBindTexture(GL_TEXTURE_2D, tids[0]);
        // Load the bitmap data and copy it over into the texture object that is currently bound.
        GLUtils.texImage2D(GL_TEXTURE_2D, 0, bitmap, 0);
        // Use bilinear texture filtering when minification.
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        // Use bilinear texture filtering when magnification.
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

        mTextureId = tids[0];
    }

    void useTexture() {
        // Set the active texture unit to texture unit 0.
        glActiveTexture(GL_TEXTURE0);
        // Bind the texture to this unit.
        glBindTexture(GL_TEXTURE_2D, mTextureId);
        // Let the texture sampler in fragment shader to read form this texture unit.
        glUniform1i(mUniTexture, 0);
    }

    /**
     * Called to dump current state.
     * @param prefix prefix.
     * @param fd fd.
     * @param out out.
     * @param args args.
     */
    public void dump(String prefix, FileDescriptor fd, PrintWriter out, String[] args) {
    }
}