// ----------------------------------------------------------------------------
// Simple sample to prove that Assimp is absolutely easy to use with OpenGL.
// It takes a file name as command line parameter, loads it using standard
// settings and displays it.
//
// If you intend to _use_ this code sample in your app, do yourself a favour 
// and replace immediate mode calls with VBOs ...
//
// The vc8 solution links against assimp-release-dll_win32 - be sure to
// have this configuration built.
// ----------------------------------------------------------------------------

#include "GL/glut.h"

// assimp include files. These three are usually needed.
#include "assimp.h"
#include "aiPostProcess.h"
#include "aiScene.h"

// the global Assimp scene object
const struct aiScene* scene = NULL;
struct aiVector3D scene_min,scene_max;

// current rotation angle
static float angle = 0.f;

#define aisgl_min(x,y) (x<y?x:y)
#define aisgl_max(x,y) (y>x?y:x)

// ----------------------------------------------------------------------------
void reshape(int width, int height)
{
	const double aspectRatio = (float) width / height, fieldOfView = 45.0;

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(fieldOfView, aspectRatio,
		1.0, 1000.0);  /* Znear and Zfar */
	glViewport(0, 0, width, height);
}

// ----------------------------------------------------------------------------
void get_bounding_box_for_node (const struct aiNode* nd, 
	struct aiVector3D* min, 
	struct aiVector3D* max, 
	struct aiMatrix4x4* trafo
){
	struct aiMatrix4x4 prev;
	unsigned int n = 0, t;

	aiMultiplyMatrix4(trafo,&nd->mTransformation);

	for (; n < nd->mNumMeshes; ++n) {
		const struct aiMesh* mesh = scene->mMeshes[nd->mMeshes[n]];
		for (t = 0; t < mesh->mNumVertices; ++t) {

			struct aiVector3D tmp = mesh->mVertices[t];
			aiTransformVecByMatrix4(&tmp,trafo);

			min->x = aisgl_min(min->x,tmp.x);
			min->y = aisgl_min(min->y,tmp.y);
			min->z = aisgl_min(min->z,tmp.z);

			max->x = aisgl_max(max->x,tmp.x);
			max->y = aisgl_max(max->y,tmp.y);
			max->z = aisgl_max(max->z,tmp.z);
		}
	}

	prev = nd->mTransformation;
	for (n = 0; n < nd->mNumChildren; ++n) {
		get_bounding_box_for_node(nd->mChildren[n],min,max,trafo);
	}
	*trafo = prev;
}

// ----------------------------------------------------------------------------
void get_bounding_box (struct aiVector3D* min, struct aiVector3D* max)
{
	struct aiMatrix4x4 trafo;
	aiIdentityMatrix4(&trafo);

	min->x = min->y = min->z =  1e10f;
	max->x = max->y = max->z = -1e10f;
	get_bounding_box_for_node(scene->mRootNode,min,max,&trafo);
}

// ----------------------------------------------------------------------------
void recursive_render (const struct aiNode* nd)
{
	unsigned int n = 0, t;
	struct aiMatrix4x4 m = nd->mTransformation;

	// update transform
	aiTransposeMatrix4(&m);
	glMultMatrixf((float*)&m);

	// draw all meshes assigned to this node
	for (; n < nd->mNumMeshes; ++n) {
		const struct aiMesh* mesh = scene->mMeshes[nd->mMeshes[n]];

		glBegin(GL_TRIANGLES);

		for (t = 0; t < mesh->mNumFaces; ++t) {
			const struct aiFace* face = &mesh->mFaces[t];

			glColor3f(1.f,0.f,0.f);
			glVertex3fv(&mesh->mVertices[face->mIndices[0]].x);
			glVertex3fv(&mesh->mVertices[face->mIndices[1]].x);
			glVertex3fv(&mesh->mVertices[face->mIndices[2]].x);
		}

		glEnd();
	}

	// draw all children
	for (n = 0; n < nd->mNumChildren; ++n) {
		recursive_render(nd->mChildren[n]);
	}
}

// ----------------------------------------------------------------------------
void do_motion (void)
{
	static GLint prev_time = 0;

	int time = glutGet(GLUT_ELAPSED_TIME);
	angle += (time-prev_time)*0.01;
	prev_time = time;

	glutPostRedisplay ();
}

// ----------------------------------------------------------------------------
void display(void)
{
	float tmp;
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	gluLookAt(0.f,0.f,3.f,0.f,0.f,-5.f,0.f,1.f,0.f);

	// scale the whole asset to fit into our view frustum 
	tmp = scene_max.x-scene_min.x;
	tmp = aisgl_max(scene_max.y-scene_min.y,tmp);
	tmp = aisgl_max(scene_max.z-scene_min.z,tmp);

	tmp = 1.f/(tmp);
	glScalef(tmp,tmp,tmp);

	// fixme: center around origin
	
	// rotate it around the y axis
	glRotatef(angle,0.f,1.f,0.f);

	// now begin at the root node of the imported data and traverse
	// the scenegraph by multipliying subsequent local transforms
	// together on GL's matrix stack.
	recursive_render(scene->mRootNode);
	glutSwapBuffers();

	do_motion();
}

// ----------------------------------------------------------------------------
int loadasset (const char* path)
{
	// we are taking one of the postprocessing presets to avoid
	// writing 20 single postprocessing flags here.
	scene = aiImportFile(path,aiProcessPreset_TargetRealtime_Quality);

	if (scene) {

		get_bounding_box(&scene_min,&scene_max);
		return 0;
	}
	return 1;
}

// ----------------------------------------------------------------------------
int main(int argc, char **argv)
{
	struct aiLogStream stream;
	glutInitWindowSize(900,600);
	glutInitWindowPosition(100,100);
	glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
	glutInit(&argc, argv);

	glutCreateWindow("Assimp - Very simple OpenGL sample");
	glutDisplayFunc(display);
	glutReshapeFunc(reshape);

	// get a handle to the predefined STDOUT log stream and attach
	// it to the logging system. It will be active for all further
	// calls to aiImportFile(Ex) and aiApplyPostProcessing.
	stream = aiGetPredefinedLogStream(aiDefaultLogStream_STDOUT,NULL);
	aiAttachLogStream(&stream);

	// ... exactly the same, but this stream will now write the
	// log file to assimp_log.txt
	stream = aiGetPredefinedLogStream(aiDefaultLogStream_FILE,"assimp_log.txt");
	aiAttachLogStream(&stream);

	if( 0 != loadasset( argc >= 2 ? argv[1] : "../../test/models/X/dwarf.x")) {
		if( argc != 1 || 0 != loadasset( "../../../../test/models/X/dwarf.x")) { 
			return -1;
		}
	}

	glPolygonMode(GL_FRONT,GL_LINE);
	glPolygonMode(GL_BACK,GL_LINE);
	glClearColor(0.1f,0.1f,0.1f,1.f);

	glutGet(GLUT_ELAPSED_TIME);
	glutMainLoop();

	// cleanup - calling 'aiReleaseImport' is important, as the library 
	// keeps internal resources until the scene is freed again. Not 
	// doing so can cause severe resource leaking.
	aiReleaseImport(scene);

	// We added a log stream to the library, it's our job to disable it
	// again. This will definitely release the last resources allocated
	// by Assimp.
	aiDetachAllLogStreams();
	return 0;
}