#include "mesh_view.h"
#include <QOpenGLContext>
#include <QOpenGLFunctions_2_1>


MeshView::MeshView(const MyMesh &mesh, QOpenGLShaderProgram &program)
	: buffer(QOpenGLBuffer::VertexBuffer),
	  nverts(mesh.n_faces() * 3),
	  mesh(mesh) {
    QVector<GLfloat> verts(nverts * 6);
	size_t i = 0;
	for (const FaceHandle face : mesh.faces()) {
		for (const VertexHandle vec : mesh.fv_range(face)) {
			verts[6*i + 0] = mesh.point(vec)[0];
			verts[6*i + 1] = mesh.point(vec)[1];
			verts[6*i + 2] = mesh.point(vec)[2];
			verts[6*i + 3] = mesh.color.red();
			verts[6*i + 4] = mesh.color.green();
			verts[6*i + 5] = mesh.color.blue();
			i++;
		}
    }

	vao.create();
	{QOpenGLVertexArrayObject::Binder binder(&vao);
		buffer.create();
		buffer.bind();
		buffer.setUsagePattern(QOpenGLBuffer::StreamDraw);
		buffer.allocate(verts.constData(), nverts * 6 * sizeof (GLfloat));
		program.setAttributeBuffer("pos", GL_FLOAT, 0, 3, 6 * sizeof (GLfloat));
		program.enableAttributeArray("pos");
		program.setAttributeBuffer("col", GL_FLOAT, 3 * sizeof (GLfloat), 3, 6 * sizeof (GLfloat));
		program.enableAttributeArray("col");
	}
}


MeshView::~MeshView() {
	vao.destroy();
	buffer.destroy();
}


void MeshView::paint(QOpenGLShaderProgram &program) {
	QOpenGLContext *ctx = QOpenGLContext::currentContext();
	QOpenGLExtraFunctions *glf = ctx->extraFunctions();

	QOpenGLFunctions_2_1 *glf21 = nullptr;
	glf21 = ctx->versionFunctions<QOpenGLFunctions_2_1>();
	if (!glf21)
		qFatal("Failed to get OpenGL 2.1 functions");

	program.setUniformValue("model", mesh.transform);

	{QOpenGLVertexArrayObject::Binder binder(&vao);
		/* Mesh */
		glf->glEnable(GL_POLYGON_OFFSET_FILL);
		glf->glPolygonOffset(1.0, 2);
		glf->glDrawArrays(GL_TRIANGLES, 0, nverts);
		glf21->glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
		glf->glDisable(GL_POLYGON_OFFSET_FILL);

		/* Wireframe */
		program.setUniformValue("wireframe", 1);
		glf->glDrawArrays(GL_TRIANGLES, 0, nverts);
		glf21->glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
		glf->glLineWidth(2);
		program.setUniformValue("wireframe", 0);
	}
}