#include "mesh_viewer.h"

#include <tgmath.h>
#include <algorithm>


const GLchar *vertex_shader_source = R"glsl(
attribute vec3 pos;
attribute vec3 col;

varying vec3 frag_col;

uniform mat4 proj;
uniform mat4 view;
uniform mat4 model;

void main() {
	gl_Position = proj * view * model * vec4(pos, 1.0);
	frag_col = col;
}
)glsl";

const GLchar *fragment_shader_source = R"glsl(
varying vec3 frag_col;

uniform vec3 wf_col;
uniform bool wireframe;
uniform float alpha;

void main() {
	if (!wireframe)
		// gl_FragColor = vec4(wf_col, alpha);
		gl_FragColor = vec4(.5, .5, .5, 1);
	else
		gl_FragColor = vec4(frag_col, alpha);
}
)glsl";


MeshViewer::MeshViewer(QWidget *parent) : QOpenGLWidget(parent) {
	setMouseTracking(true);
	setFocus();
}


QSize MeshViewer::sizeHint() const {
	return QSize(640, 480);
}


void GLAPIENTRY
opengl_debug_cb(GLenum source,
				GLenum type,
				GLuint id,
				GLenum severity,
				GLsizei length,
				const GLchar* message,
				const void* userParam) {
	(void) source;
	(void) type;
	(void) id;
	(void) severity;
	(void) length;
	(void) userParam;
	qDebug() << "OpenGL debug output:" << message;
}


void MeshViewer::initializeGL() {
	// initializeOpenGLFunctions();

	qDebug("OpenGL version %d.%d",
		   	context()->format().majorVersion(),
			context()->format().minorVersion());

	glEnable(GL_DEBUG_OUTPUT);
	glDebugMessageCallback(opengl_debug_cb, 0);

	/* Compile the vertex shader. */
	GLuint vertex_shader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertex_shader, 1, &vertex_shader_source, NULL);
	glCompileShader(vertex_shader);
	GLint status;
	glGetShaderiv(vertex_shader, GL_COMPILE_STATUS, &status);
	if (status != GL_TRUE) {
		char log[1024];
		glGetShaderInfoLog(vertex_shader, sizeof log, NULL, log);
		fprintf(stderr, "Failed to compile the vertex shader: %s\n", log);
		exit(1);
	}

	/* Compile the fragment shader. */
	GLuint fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragment_shader, 1, &fragment_shader_source, NULL);
	glCompileShader(fragment_shader);
	glGetShaderiv(fragment_shader, GL_COMPILE_STATUS, &status);
	if (status != GL_TRUE) {
		char log[1024];
		glGetShaderInfoLog(fragment_shader, sizeof log, NULL, log);
		fprintf(stderr, "Failed to compile the fragment shader: %s\n", log);
		exit(1);
	}

	/* Link the shader program. */
	GLuint shader_program = glCreateProgram();
	glAttachShader(shader_program, vertex_shader);
	glAttachShader(shader_program, fragment_shader);
	glBindFragDataLocation(shader_program, 0, "out_color");
	glLinkProgram(shader_program);
	glGetProgramiv(shader_program, GL_LINK_STATUS, &status);
	if (status != GL_TRUE) {
		char log[1024];
		glGetProgramInfoLog(shader_program, sizeof log, NULL, log);
		fprintf(stderr, "Failed to link the shader program: %s\n", log);
		exit(1);
	}

	/* Use it. */
	glUseProgram(shader_program);

	/* Get the position attribute. */
	pos_attr = glGetAttribLocation(shader_program, "pos");
	col_attr = glGetAttribLocation(shader_program, "col");

	proj_attr = glGetUniformLocation(shader_program, "proj");
	view_attr = glGetUniformLocation(shader_program, "view");
	model_attr = glGetUniformLocation(shader_program, "model");
	wf_col_attr = glGetUniformLocation(shader_program, "wf_col");
	wireframe_attr = glGetUniformLocation(shader_program, "wireframe");
	alpha_attr = glGetUniformLocation(shader_program, "alpha");

	glUniform1f(alpha_attr, 1);
	glUniform3f(wf_col_attr, WIREFRAME_COLOR);

	glClearColor(1, 1, 1, 0);

	glEnable(GL_DEPTH_TEST);
	glEnable(GL_MULTISAMPLE);

	qDebug("Mesh viewer initialized");
	emit initialized();
}


void MeshViewer::resizeGL(int w, int h) {
	QMatrix4x4 projection;
	projection.perspective(FOV, (float) w/h, .01, 100);
	glUniformMatrix4fv(proj_attr, 1, GL_FALSE, projection.data());
}


void MeshViewer::paintGL() {
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	QMatrix4x4 trans;
	trans.translate(0, 0, -cam_dist);
	QMatrix4x4 view = trans * rot;
	glUniformMatrix4fv(view_attr, 1, GL_FALSE, view.data());
	for (const MeshView m : meshes) {
		m.paint(context(), model_attr, wireframe_attr);
	}
}


void MeshViewer::addMesh(const MyMesh &mesh) {
	makeCurrent();
	meshes.emplace_back(context()->extraFunctions(), mesh,
						pos_attr, col_attr);
	doneCurrent();
	update();
}


void MeshViewer::removeMesh(const MyMesh &mesh) {
	makeCurrent();
	meshes.remove_if([&](const MeshView &mv) {
		return &mv.mesh == &mesh;
	});
	doneCurrent();
	update();
}


void MeshViewer::mousePressEvent(QMouseEvent *e) {
	if (e->button() == Qt::LeftButton) {
		mouse_pos = e->pos();
	}
}


void MeshViewer::mouseReleaseEvent(QMouseEvent *e) {
	(void) e;
	rot_start = rot;
}


void MeshViewer::mouseMoveEvent(QMouseEvent *e) {
	if (e->buttons() & Qt::LeftButton) {
		QPoint delta = e->pos() - mouse_pos;
		rot = rot_start;
		rot.rotate(delta.x() / 5., 0, 1, 0);
		rot.rotate(delta.y() / 5., QVector3D(1, 0, 0) * rot);
		update();
	}
}


void MeshViewer::wheelEvent(QWheelEvent *e) {
	cam_dist -= e->angleDelta().y() / 1000. * cam_dist;
	update();
}