/*
 * Copyright (C) 2007 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.
 */

#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <sched.h>
#include <sys/resource.h>

#include <EGL/egl.h>
#include <GLES2/gl2.h>
#include <GLES2/gl2ext.h>

#include <utils/Timers.h>

#include <ui/FramebufferNativeWindow.h>
#include <ui/EGLUtils.h>

using namespace android;

static void printGLString(const char *name, GLenum s) {
    // fprintf(stderr, "printGLString %s, %d\n", name, s);
    const char *v = (const char *) glGetString(s);
    // int error = glGetError();
    // fprintf(stderr, "glGetError() = %d, result of glGetString = %x\n", error,
    //        (unsigned int) v);
    // if ((v < (const char*) 0) || (v > (const char*) 0x10000))
    //    fprintf(stderr, "GL %s = %s\n", name, v);
    // else
    //    fprintf(stderr, "GL %s = (null) 0x%08x\n", name, (unsigned int) v);
    fprintf(stderr, "GL %s = %s\n", name, v);
}

static void checkEglError(const char* op, EGLBoolean returnVal = EGL_TRUE) {
    if (returnVal != EGL_TRUE) {
        fprintf(stderr, "%s() returned %d\n", op, returnVal);
    }

    for (EGLint error = eglGetError(); error != EGL_SUCCESS; error
            = eglGetError()) {
        fprintf(stderr, "after %s() eglError %s (0x%x)\n", op, EGLUtils::strerror(error),
                error);
    }
}

static void checkGlError(const char* op) {
    for (GLint error = glGetError(); error; error
            = glGetError()) {
        fprintf(stderr, "after %s() glError (0x%x)\n", op, error);
    }
}

static const char gVertexShader[] = "attribute vec4 vPosition;\n"
    "void main() {\n"
    "  gl_Position = vPosition;\n"
    "}\n";

static const char gFragmentShader[] = "precision mediump float;\n"
    "void main() {\n"
    "  gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);\n"
    "}\n";

GLuint loadShader(GLenum shaderType, const char* pSource) {
    GLuint shader = glCreateShader(shaderType);
    if (shader) {
        glShaderSource(shader, 1, &pSource, NULL);
        glCompileShader(shader);
        GLint compiled = 0;
        glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
        if (!compiled) {
            GLint infoLen = 0;
            glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLen);
            if (infoLen) {
                char* buf = (char*) malloc(infoLen);
                if (buf) {
                    glGetShaderInfoLog(shader, infoLen, NULL, buf);
                    fprintf(stderr, "Could not compile shader %d:\n%s\n",
                            shaderType, buf);
                    free(buf);
                }
                glDeleteShader(shader);
                shader = 0;
            }
        }
    }
    return shader;
}

GLuint createProgram(const char* pVertexSource, const char* pFragmentSource) {
    GLuint vertexShader = loadShader(GL_VERTEX_SHADER, pVertexSource);
    if (!vertexShader) {
        return 0;
    }

    GLuint pixelShader = loadShader(GL_FRAGMENT_SHADER, pFragmentSource);
    if (!pixelShader) {
        return 0;
    }

    GLuint program = glCreateProgram();
    if (program) {
        glAttachShader(program, vertexShader);
        checkGlError("glAttachShader");
        glAttachShader(program, pixelShader);
        checkGlError("glAttachShader");
        glLinkProgram(program);
        GLint linkStatus = GL_FALSE;
        glGetProgramiv(program, GL_LINK_STATUS, &linkStatus);
        if (linkStatus != GL_TRUE) {
            GLint bufLength = 0;
            glGetProgramiv(program, GL_INFO_LOG_LENGTH, &bufLength);
            if (bufLength) {
                char* buf = (char*) malloc(bufLength);
                if (buf) {
                    glGetProgramInfoLog(program, bufLength, NULL, buf);
                    fprintf(stderr, "Could not link program:\n%s\n", buf);
                    free(buf);
                }
            }
            glDeleteProgram(program);
            program = 0;
        }
    }
    return program;
}

GLuint gProgram;
GLuint gvPositionHandle;

bool setupGraphics(int w, int h) {
    gProgram = createProgram(gVertexShader, gFragmentShader);
    if (!gProgram) {
        return false;
    }
    gvPositionHandle = glGetAttribLocation(gProgram, "vPosition");
    checkGlError("glGetAttribLocation");
    fprintf(stderr, "glGetAttribLocation(\"vPosition\") = %d\n",
            gvPositionHandle);

    glViewport(0, 0, w, h);
    checkGlError("glViewport");
    return true;
}

const GLfloat gTriangleVertices[] = { 0.0f, 0.5f, -0.5f, -0.5f,
        0.5f, -0.5f };

void renderFrame() {
    glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
    checkGlError("glClearColor");
    glClear( GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
    checkGlError("glClear");

    glUseProgram(gProgram);
    checkGlError("glUseProgram");

    glVertexAttribPointer(gvPositionHandle, 2, GL_FLOAT, GL_FALSE, 0, gTriangleVertices);
    checkGlError("glVertexAttribPointer");
    glEnableVertexAttribArray(gvPositionHandle);
    checkGlError("glEnableVertexAttribArray");
    glDrawArrays(GL_TRIANGLES, 0, 3);
    checkGlError("glDrawArrays");
}

#if 0

void PrintEGLConfig(EGLDisplay dpy, EGLConfig config) {
	int attrib[] = {EGL_RED_SIZE, EGL_GREEN_SIZE, EGL_BLUE_SIZE, EGL_ALPHA_SIZE,
			EGL_DEPTH_SIZE, EGL_SURFACE_TYPE, EGL_RENDERABLE_TYPE
	};
	for(size_t i = 0; i < sizeof(attrib)/sizeof(attrib[0]); i++) {
        int value = 0;
        int a = attrib[i];
        if (eglGetConfigAttrib(dpy, config, a, &value)) {
            printf(" 0x%04x: %d", a, value);
        }
	}
	printf("\n");
}

#endif

int main(int argc, char** argv) {
    EGLBoolean returnValue;
    EGLConfig myConfig = {0};

    EGLint context_attribs[] = { EGL_CONTEXT_CLIENT_VERSION, 2, EGL_NONE };
    EGLint s_configAttribs[] = {
            EGL_SURFACE_TYPE, EGL_PBUFFER_BIT|EGL_WINDOW_BIT,
            EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
            EGL_NONE };
    EGLint majorVersion;
    EGLint minorVersion;
    EGLContext context;
    EGLSurface surface;
    EGLint w, h;

    EGLDisplay dpy;

    checkEglError("<init>");
    dpy = eglGetDisplay(EGL_DEFAULT_DISPLAY);
    checkEglError("eglGetDisplay");
    if (dpy == EGL_NO_DISPLAY) {
        printf("eglGetDisplay returned EGL_NO_DISPLAY.\n");
        return 0;
    }

    returnValue = eglInitialize(dpy, &majorVersion, &minorVersion);
    checkEglError("eglInitialize", returnValue);
    fprintf(stderr, "EGL version %d.%d\n", majorVersion, minorVersion);
    if (returnValue != EGL_TRUE) {
        printf("eglInitialize failed\n");
        return 0;
    }

    EGLNativeWindowType window = android_createDisplaySurface();
    returnValue = EGLUtils::selectConfigForNativeWindow(dpy, s_configAttribs, window, &myConfig);
    if (returnValue) {
    	printf("EGLUtils::selectConfigForNativeWindow() returned %d", returnValue);
    	return 0;
    }

    surface = eglCreateWindowSurface(dpy, myConfig, window, NULL);
    checkEglError("eglCreateWindowSurface");
    if (surface == EGL_NO_SURFACE) {
        printf("gelCreateWindowSurface failed.\n");
        return 0;
    }

    context = eglCreateContext(dpy, myConfig, EGL_NO_CONTEXT, context_attribs);
    checkEglError("eglCreateContext");
    if (context == EGL_NO_CONTEXT) {
        printf("eglCreateContext failed\n");
        return 0;
    }
    returnValue = eglMakeCurrent(dpy, surface, surface, context);
    checkEglError("eglMakeCurrent", returnValue);
    if (returnValue != EGL_TRUE) {
        return 0;
    }
    eglQuerySurface(dpy, surface, EGL_WIDTH, &w);
    checkEglError("eglQuerySurface");
    eglQuerySurface(dpy, surface, EGL_HEIGHT, &h);
    checkEglError("eglQuerySurface");
    GLint dim = w < h ? w : h;

    fprintf(stderr, "Window dimensions: %d x %d\n", w, h);

    printGLString("Version", GL_VERSION);
    printGLString("Vendor", GL_VENDOR);
    printGLString("Renderer", GL_RENDERER);
    printGLString("Extensions", GL_EXTENSIONS);

    if(!setupGraphics(w, h)) {
        fprintf(stderr, "Could not set up graphics.\n");
        return 0;
    }

    for (;;) {
        renderFrame();
        eglSwapBuffers(dpy, surface);
        checkEglError("eglSwapBuffers");
    }

    return 0;
}