/**************************************************************************/
/*  OvrConfigChooser.java                                                 */
/**************************************************************************/
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/*                             GODOT ENGINE                               */
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/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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package org.godotengine.godot.xr.ovr;

import org.godotengine.godot.gl.GLSurfaceView;

import android.opengl.EGLExt;

import javax.microedition.khronos.egl.EGL10;
import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.egl.EGLDisplay;

/**
 * EGL config chooser for the Oculus Mobile VR SDK.
 */
public class OvrConfigChooser implements GLSurfaceView.EGLConfigChooser {
	private static final int[] CONFIG_ATTRIBS = {
		EGL10.EGL_RED_SIZE, 8,
		EGL10.EGL_GREEN_SIZE, 8,
		EGL10.EGL_BLUE_SIZE, 8,
		EGL10.EGL_ALPHA_SIZE, 8, // Need alpha for the multi-pass timewarp compositor
		EGL10.EGL_DEPTH_SIZE, 0,
		EGL10.EGL_STENCIL_SIZE, 0,
		EGL10.EGL_SAMPLES, 0,
		EGL10.EGL_NONE
	};

	@Override
	public EGLConfig chooseConfig(EGL10 egl, EGLDisplay display) {
		// Do NOT use eglChooseConfig, because the Android EGL code pushes in
		// multisample flags in eglChooseConfig if the user has selected the "force 4x
		// MSAA" option in settings, and that is completely wasted for our warp
		// target.
		int[] numConfig = new int[1];
		if (!egl.eglGetConfigs(display, null, 0, numConfig)) {
			throw new IllegalArgumentException("eglGetConfigs failed.");
		}

		int configsCount = numConfig[0];
		if (configsCount <= 0) {
			throw new IllegalArgumentException("No configs match configSpec");
		}

		EGLConfig[] configs = new EGLConfig[configsCount];
		if (!egl.eglGetConfigs(display, configs, configsCount, numConfig)) {
			throw new IllegalArgumentException("eglGetConfigs #2 failed.");
		}

		int[] value = new int[1];
		for (EGLConfig config : configs) {
			egl.eglGetConfigAttrib(display, config, EGL10.EGL_RENDERABLE_TYPE, value);
			if ((value[0] & EGLExt.EGL_OPENGL_ES3_BIT_KHR) != EGLExt.EGL_OPENGL_ES3_BIT_KHR) {
				continue;
			}

			// The pbuffer config also needs to be compatible with normal window rendering
			// so it can share textures with the window context.
			egl.eglGetConfigAttrib(display, config, EGL10.EGL_SURFACE_TYPE, value);
			if ((value[0] & (EGL10.EGL_WINDOW_BIT | EGL10.EGL_PBUFFER_BIT)) != (EGL10.EGL_WINDOW_BIT | EGL10.EGL_PBUFFER_BIT)) {
				continue;
			}

			// Check each attribute in CONFIG_ATTRIBS (which are the attributes we care about)
			// and ensure the value in config matches.
			int attribIndex = 0;
			while (CONFIG_ATTRIBS[attribIndex] != EGL10.EGL_NONE) {
				egl.eglGetConfigAttrib(display, config, CONFIG_ATTRIBS[attribIndex], value);
				if (value[0] != CONFIG_ATTRIBS[attribIndex + 1]) {
					// Attribute key's value does not match the configs value.
					// Start checking next config.
					break;
				}

				// Step by two because CONFIG_ATTRIBS is in key/value pairs.
				attribIndex += 2;
			}

			if (CONFIG_ATTRIBS[attribIndex] == EGL10.EGL_NONE) {
				// All relevant attributes match, set the config and stop checking the rest.
				return config;
			}
		}
		return null;
	}
}
