/*
* Copyright (C) 2010 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 <malloc.h>

#define LOGI(...) ((void)__android_log_print(ANDROID_LOG_INFO, "AndroidProject1.NativeActivity", __VA_ARGS__))
#define LOGW(...) ((void)__android_log_print(ANDROID_LOG_WARN, "AndroidProject1.NativeActivity", __VA_ARGS__))

/**
* Our saved state data.
*/
struct saved_state {
     float angle;
     int32_t x;
     int32_t y;
};

/**
* Shared state for our app.
*/
struct engine {
     struct android_app* app;

     ASensorManager* sensorManager;
     const ASensor* accelerometerSensor;
     ASensorEventQueue* sensorEventQueue;

     int animating;
     EGLDisplay display;
     EGLSurface surface;
     EGLContext context;
     int32_t width;
     int32_t height;
     struct saved_state state;
};

/**
* Initialize an EGL context for the current display.
*/
static int engine_init_display(struct engine* engine) {
     // initialize OpenGL ES and EGL

     /*
     * Here specify the attributes of the desired configuration.
     * Below, we select an EGLConfig with at least 8 bits per color
     * component compatible with on-screen windows
     */
     const EGLint attribs[] = {
          EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
          EGL_BLUE_SIZE, 8,
          EGL_GREEN_SIZE, 8,
          EGL_RED_SIZE, 8,
          EGL_NONE
     };
     EGLint w, h, format;
     EGLint numConfigs;
     EGLConfig config;
     EGLSurface surface;
     EGLContext context;

     EGLDisplay display = eglGetDisplay(EGL_DEFAULT_DISPLAY);

     eglInitialize(display, 0, 0);

     /* Here, the application chooses the configuration it desires. In this
     * sample, we have a very simplified selection process, where we pick
     * the first EGLConfig that matches our criteria */
     eglChooseConfig(display, attribs, &config, 1, &numConfigs);

     /* EGL_NATIVE_VISUAL_ID is an attribute of the EGLConfig that is
     * guaranteed to be accepted by ANativeWindow_setBuffersGeometry().
     * As soon as we picked a EGLConfig, we can safely reconfigure the
     * ANativeWindow buffers to match, using EGL_NATIVE_VISUAL_ID. */
     eglGetConfigAttrib(display, config, EGL_NATIVE_VISUAL_ID, &format);

     ANativeWindow_setBuffersGeometry(engine->app->window, 0, 0, format);

     surface = eglCreateWindowSurface(display, config, engine->app->window, NULL);
     context = eglCreateContext(display, config, NULL, NULL);

     if (eglMakeCurrent(display, surface, surface, context) == EGL_FALSE) {
          LOGW("Unable to eglMakeCurrent");
          return -1;
     }

     eglQuerySurface(display, surface, EGL_WIDTH, &w);
     eglQuerySurface(display, surface, EGL_HEIGHT, &h);

     engine->display = display;
     engine->context = context;
     engine->surface = surface;
     engine->width = w;
     engine->height = h;
     engine->state.angle = 0;

     // Initialize GL state.
     glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_FASTEST);
     glEnable(GL_CULL_FACE);
     glShadeModel(GL_SMOOTH);
     glDisable(GL_DEPTH_TEST);

     return 0;
}

/**
* Just the current frame in the display.
*/
static void engine_draw_frame(struct engine* engine) {
     if (engine->display == NULL) {
          // No display.
          return;
     }

     // Just fill the screen with a color.
     glClearColor(((float)engine->state.x) / engine->width, engine->state.angle,
          ((float)engine->state.y) / engine->height, 1);
     glClear(GL_COLOR_BUFFER_BIT);

     eglSwapBuffers(engine->display, engine->surface);
}

/**
* Tear down the EGL context currently associated with the display.
*/
static void engine_term_display(struct engine* engine) {
     if (engine->display != EGL_NO_DISPLAY) {
          eglMakeCurrent(engine->display, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
          if (engine->context != EGL_NO_CONTEXT) {
               eglDestroyContext(engine->display, engine->context);
          }
          if (engine->surface != EGL_NO_SURFACE) {
               eglDestroySurface(engine->display, engine->surface);
          }
          eglTerminate(engine->display);
     }
     engine->animating = 0;
     engine->display = EGL_NO_DISPLAY;
     engine->context = EGL_NO_CONTEXT;
     engine->surface = EGL_NO_SURFACE;
}

/**
* Process the next input event.
*/
static int32_t engine_handle_input(struct android_app* app, AInputEvent* event) {
     struct engine* engine = (struct engine*)app->userData;
     if (AInputEvent_getType(event) == AINPUT_EVENT_TYPE_MOTION) {
          engine->state.x = AMotionEvent_getX(event, 0);
          engine->state.y = AMotionEvent_getY(event, 0);
          return 1;
     }
     return 0;
}

/**
* Process the next main command.
*/
static void engine_handle_cmd(struct android_app* app, int32_t cmd) {
     struct engine* engine = (struct engine*)app->userData;
     switch (cmd) {
     case APP_CMD_SAVE_STATE:
          // The system has asked us to save our current state. Do so.
          engine->app->savedState = malloc(sizeof(struct saved_state));
          *((struct saved_state*)engine->app->savedState) = engine->state;
          engine->app->savedStateSize = sizeof(struct saved_state);
          break;
     case APP_CMD_INIT_WINDOW:
          // The window is being shown, get it ready.
          if (engine->app->window != NULL) {
               engine_init_display(engine);
               engine_draw_frame(engine);
          }
          break;
     case APP_CMD_TERM_WINDOW:
          // The window is being hidden or closed, clean it up.
          engine_term_display(engine);
          break;
     case APP_CMD_GAINED_FOCUS:
          // When our app gains focus, we start monitoring the accelerometer.
          if (engine->accelerometerSensor != NULL) {
               ASensorEventQueue_enableSensor(engine->sensorEventQueue,
                    engine->accelerometerSensor);
               // We'd like to get 60 events per second (in microseconds).
               ASensorEventQueue_setEventRate(engine->sensorEventQueue,
                    engine->accelerometerSensor, (1000L / 60) * 1000);
          }
          break;
     case APP_CMD_LOST_FOCUS:
          // When our app loses focus, we stop monitoring the accelerometer.
          // This is to avoid consuming battery while not being used.
          if (engine->accelerometerSensor != NULL) {
               ASensorEventQueue_disableSensor(engine->sensorEventQueue,
                    engine->accelerometerSensor);
          }
          // Also stop animating.
          engine->animating = 0;
          engine_draw_frame(engine);
          break;
     }
}

/**
* This is the main entry point of a native application that is using
* android_native_app_glue. It runs in its own thread, with its own
* event loop for receiving input events and doing other things.
*/
void android_main(struct android_app* state) {
     struct engine engine;

     memset(&engine, 0, sizeof(engine));
     state->userData = &engine;
     state->onAppCmd = engine_handle_cmd;
     state->onInputEvent = engine_handle_input;
     engine.app = state;

     // Prepare to monitor accelerometer
     engine.sensorManager = ASensorManager_getInstance();
     engine.accelerometerSensor = ASensorManager_getDefaultSensor(engine.sensorManager,
          ASENSOR_TYPE_ACCELEROMETER);
     engine.sensorEventQueue = ASensorManager_createEventQueue(engine.sensorManager,
          state->looper, LOOPER_ID_USER, NULL, NULL);

     if (state->savedState != NULL) {
          // We are starting with a previous saved state; restore from it.
          engine.state = *(struct saved_state*)state->savedState;
     }

     engine.animating = 1;

     // loop waiting for stuff to do.

     while (1) {
          // Read all pending events.
          int ident;
          int events;
          struct android_poll_source* source;

          // If not animating, we will block forever waiting for events.
          // If animating, we loop until all events are read, then continue
          // to draw the next frame of animation.
          while ((ident = ALooper_pollAll(engine.animating ? 0 : -1, NULL, &events,
               (void**)&source)) >= 0) {

               // Process this event.
               if (source != NULL) {
                    source->process(state, source);
               }

               // If a sensor has data, process it now.
               if (ident == LOOPER_ID_USER) {
                    if (engine.accelerometerSensor != NULL) {
                         ASensorEvent event;
                         while (ASensorEventQueue_getEvents(engine.sensorEventQueue,
                              &event, 1) > 0) {
                              LOGI("accelerometer: x=%f y=%f z=%f",
                                   event.acceleration.x, event.acceleration.y,
                                   event.acceleration.z);
                         }
                    }
               }

               // Check if we are exiting.
               if (state->destroyRequested != 0) {
                    engine_term_display(&engine);
                    return;
               }
          }

          if (engine.animating) {
               // Done with events; draw next animation frame.
               engine.state.angle += .01f;
               if (engine.state.angle > 1) {
                    engine.state.angle = 0;
               }

               // Drawing is throttled to the screen update rate, so there
               // is no need to do timing here.
               engine_draw_frame(&engine);
          }
     }
}