package com.example.datalibrary.gl.utils;

import android.content.Context;
import android.opengl.GLES20;
import android.util.Log;

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

public class ShaderUtils {
    private static final String TAG = "ShaderUtils";

    public static boolean checkGlError(String label) {
        int error;
        boolean err = true;
        while ((error = GLES20.glGetError()) != GLES20.GL_NO_ERROR) {
            Log.e(TAG, label + ": glError " + error);
            err = false;
        }
        return err;
    }

    public static int createProgram(String vertexSource, String fragmentSource) {
        int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, vertexSource);
        if (vertexShader == 0) {
            return 0;
        }
        int pixelShader = loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentSource);
        if (pixelShader == 0) {
            return 0;
        }
        int program = GLES20.glCreateProgram();
        if (program != 0) {
            GLES20.glAttachShader(program, vertexShader);
            if (!checkGlError("glAttachShader")){
                return 0;
            }
            GLES20.glAttachShader(program, pixelShader);
            if (!checkGlError("glAttachShader")){
                return 0;
            }
            GLES20.glLinkProgram(program);
            int[] linkStatus = new int[1];
            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;
    }


    public static int loadShader(int shaderType, String source) {
        int shader = GLES20.glCreateShader(shaderType);
        if (shader != 0) {
            GLES20.glShaderSource(shader, source);
            GLES20.glCompileShader(shader);
            int[] compiled = new int[1];
            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;
    }

    public static String readRawTextFile(Context context, int resId) {
        InputStream inputStream = context.getResources().openRawResource(resId);
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
            StringBuilder sb = new StringBuilder();
            String line;
            while ((line = reader.readLine()) != null) {
                sb.append(line).append("\n");
            }
            reader.close();
            return sb.toString();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

}