#include "glview.h"

#include <QMatrix4x4>
#include <QMouseEvent>
#include <QVector3D>
#include <QWheelEvent>
#include <QtMath>

GlView::GlView(QWidget *parent)
    : QOpenGLWidget(parent)
    , m_yawDeg(-30.0f)
    , m_pitchDeg(25.0f)
    , m_distance(4.0f)
    , m_minDistance(0.5f)
    , m_maxDistance(2000.0f)
    , m_center(0.0f, 0.0f, 0.0f)
    , m_radius(1.0f)
    , m_panX(0.0f)
    , m_panY(0.0f)
    , m_surfaceVisible(true)
{
}

void GlView::setData(const QVector<core::Point3f> &points, const QVector<core::Triangle> &triangles)
{
    m_points = points;
    m_triangles = triangles;

    if (!m_points.isEmpty()) {
        QVector3D bmin(m_points[0].x, m_points[0].y, m_points[0].z);
        QVector3D bmax = bmin;
        for (const core::Point3f &p : m_points) {
            bmin.setX(qMin(bmin.x(), p.x));
            bmin.setY(qMin(bmin.y(), p.y));
            bmin.setZ(qMin(bmin.z(), p.z));
            bmax.setX(qMax(bmax.x(), p.x));
            bmax.setY(qMax(bmax.y(), p.y));
            bmax.setZ(qMax(bmax.z(), p.z));
        }

        m_center = (bmin + bmax) * 0.5f;
        m_radius = qMax(1e-3f, (bmax - bmin).length() * 0.5f);
        m_distance = qMax(2.5f * m_radius, 1.0f);
        m_minDistance = qMax(0.05f * m_radius, 0.01f);
        m_maxDistance = qMax(100.0f * m_radius, m_distance * 2.0f);
        m_panX = 0.0f;
        m_panY = 0.0f;
    }

    update();
}

void GlView::setSurfaceVisible(const bool visible)
{
    if (m_surfaceVisible == visible) {
        return;
    }
    m_surfaceVisible = visible;
    update();
}

void GlView::initializeGL()
{
    initializeOpenGLFunctions();
    glEnable(GL_DEPTH_TEST);
    glDisable(GL_CULL_FACE);

    m_program.addShaderFromSourceCode(QOpenGLShader::Vertex,
                                      "attribute vec3 aPos;\n"
                                      "uniform mat4 uMvp;\n"
                                      "void main() {\n"
                                      "  gl_Position = uMvp * vec4(aPos, 1.0);\n"
                                      "}\n");
    m_program.addShaderFromSourceCode(QOpenGLShader::Fragment,
                                      "uniform vec3 uColor;\n"
                                      "void main() {\n"
                                      "  gl_FragColor = vec4(uColor, 1.0);\n"
                                      "}\n");
    m_program.link();
}

void GlView::resizeGL(int w, int h)
{
    glViewport(0, 0, w, h);
}

void GlView::paintGL()
{
    glClearColor(0.08f, 0.09f, 0.11f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    if (m_points.isEmpty()) {
        return;
    }

    QVector<float> vertices;
    vertices.reserve(m_points.size() * 3);
    for (const core::Point3f &p : m_points) {
        vertices.push_back(p.x - m_center.x());
        vertices.push_back(p.y - m_center.y());
        vertices.push_back(p.z - m_center.z());
    }

    QVector<GLuint> indices;
    indices.reserve(m_triangles.size() * 3);
    QVector<GLuint> edgeIndices;
    edgeIndices.reserve(m_triangles.size() * 6);
    for (const core::Triangle &t : m_triangles) {
        indices.push_back(static_cast<GLuint>(t.i0));
        indices.push_back(static_cast<GLuint>(t.i1));
        indices.push_back(static_cast<GLuint>(t.i2));

        edgeIndices.push_back(static_cast<GLuint>(t.i0));
        edgeIndices.push_back(static_cast<GLuint>(t.i1));
        edgeIndices.push_back(static_cast<GLuint>(t.i1));
        edgeIndices.push_back(static_cast<GLuint>(t.i2));
        edgeIndices.push_back(static_cast<GLuint>(t.i2));
        edgeIndices.push_back(static_cast<GLuint>(t.i0));
    }

    QMatrix4x4 projection;
    projection.perspective(45.0f,
                           static_cast<float>(width()) / qMax(1, height()),
                           qMax(0.001f, m_distance * 0.001f),
                           qMax(m_distance + 4.0f * m_radius, m_distance * 2.0f));

    QMatrix4x4 view;
    view.translate(m_panX, m_panY, -m_distance);
    view.rotate(m_pitchDeg, 1.0f, 0.0f, 0.0f);
    view.rotate(m_yawDeg, 0.0f, 1.0f, 0.0f);

    const QMatrix4x4 mvp = projection * view;

    m_program.bind();
    m_program.setUniformValue("uMvp", mvp);
    m_program.enableAttributeArray("aPos");
    m_program.setAttributeArray("aPos", GL_FLOAT, vertices.constData(), 3);

    if (m_surfaceVisible) {
        glEnable(GL_POLYGON_OFFSET_FILL);
        glPolygonOffset(1.0f, 1.0f);
        m_program.setUniformValue("uColor", QVector3D(0.20f, 0.72f, 0.95f));
        if (!indices.isEmpty()) {
            glDrawElements(GL_TRIANGLES, indices.size(), GL_UNSIGNED_INT, indices.constData());
        }
        glDisable(GL_POLYGON_OFFSET_FILL);

        glLineWidth(2.2f);
        m_program.setUniformValue("uColor", QVector3D(1.0f, 0.2f, 0.08f));
        if (!edgeIndices.isEmpty()) {
            glDrawElements(GL_LINES, edgeIndices.size(), GL_UNSIGNED_INT, edgeIndices.constData());
        }
    }

    glPointSize(4.0f);
    m_program.setUniformValue("uColor", QVector3D(1.0f, 0.85f, 0.2f));
    glDrawArrays(GL_POINTS, 0, m_points.size());

    m_program.disableAttributeArray("aPos");
    m_program.release();
}

void GlView::mousePressEvent(QMouseEvent *event)
{
    m_lastMousePos = event->pos();
}

void GlView::mouseMoveEvent(QMouseEvent *event)
{
    const QPoint delta = event->pos() - m_lastMousePos;
    m_lastMousePos = event->pos();

    if (event->buttons() & Qt::LeftButton) {
        m_yawDeg += static_cast<float>(delta.x()) * 0.5f;
        m_pitchDeg += static_cast<float>(delta.y()) * 0.5f;
        m_pitchDeg = qBound(-89.0f, m_pitchDeg, 89.0f);
        update();
    } else if (event->buttons() & (Qt::RightButton | Qt::MiddleButton)) {
        const float panScale = qMax(0.0005f * m_distance, 0.0005f);
        m_panX += static_cast<float>(delta.x()) * panScale;
        m_panY -= static_cast<float>(delta.y()) * panScale;
        update();
    }
}

void GlView::wheelEvent(QWheelEvent *event)
{
    const float step = static_cast<float>(event->angleDelta().y()) / 120.0f;
    const float zoomFactor = qPow(1.15f, step);
    m_distance /= zoomFactor;
    m_distance = qBound(m_minDistance, m_distance, m_maxDistance);
    update();
}