#include "tankitem.h"

#include <QPainter>
#include <QGraphicsScene>
#include <QDebug>

#include <math.h>

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

class Action
{
public:
    Action(TankItem *item) : m_item(item)
    {
    }

    TankItem *item() const { return m_item; }
    void setItem(TankItem *item) { m_item = item; }

    virtual bool apply(qreal timeDelta) = 0;

private:
    TankItem *m_item;
};

class MoveAction: public Action
{
public:
    MoveAction(TankItem *item, qreal distance)
        : Action(item), m_distance(distance)
    {
        m_reverse = m_distance < 0.0;
    }

    bool apply(qreal timeDelta) 
    {
        qreal dist = timeDelta * item()->speed() * (m_reverse ? -1.0 : 1.0);

        bool done = false;        
        if (qAbs(m_distance) < qAbs(dist)) {            
            done = true;
            dist = m_distance;
        } 
        m_distance -= dist;

        qreal a = item()->direction() * M_PI / 180.0;

        qreal yd = dist * sin(a);
        qreal xd = dist * sin(M_PI / 2.0 - a);

        item()->setPos(item()->pos() + QPointF(xd, yd));
        return !done;
    }

private:
    qreal m_distance;
    bool m_reverse;
};

class TurnAction: public Action
{
public:
    TurnAction(TankItem *item, qreal distance)
        : Action(item), m_distance(distance)
    {
        m_reverse = m_distance < 0.0;
    }

    bool apply(qreal timeDelta) 
    {
        qreal dist = timeDelta * item()->angularSpeed() * (m_reverse ? -1.0 : 1.0);
        bool done = false;        
        if (qAbs(m_distance) < qAbs(dist)) {
            done = true;
            dist = m_distance;
        } 
        m_distance -= dist;

        item()->setDirection(item()->direction() + dist);
        return !done;
    }

private:
    qreal m_distance;
    bool m_reverse;
};

TankItem::TankItem(QObject *parent) 
    : GameItem(parent), m_currentAction(0), m_currentDirection(0.0), m_enabled(true)
{
    connect(this, SIGNAL(cannonFired()), this, SIGNAL(actionCompleted()));
}

void TankItem::idle(qreal elapsed)
{
    if (m_enabled) {
        if (m_currentAction != 0) {
            if (!m_currentAction->apply(elapsed)) {
                setAction(0);
                emit actionCompleted();
            }

            QGraphicsItem *item = 0;
            qreal distance = distanceToObstacle(&item);
            if (TankItem *tankItem = qgraphicsitem_cast<TankItem *>(item))
                emit tankSpotted(tankItem->direction(), distance);        
        }
    }
}

void TankItem::hitByRocket()
{
    emit aboutToBeDestroyed();
    deleteLater();
}

void TankItem::setAction(Action *newAction)
{
    if (m_currentAction != 0) 
        delete m_currentAction;

    m_currentAction = newAction;
}

void TankItem::fireCannon()
{
    emit cannonFired();
}

void TankItem::moveForwards(qreal length)
{
    setAction(new MoveAction(this, length));
}

void TankItem::moveBackwards(qreal length)
{
    setAction(new MoveAction(this, -length));
}

void TankItem::turn(qreal degrees)
{
    setAction(new TurnAction(this, degrees));
}

void TankItem::turnTo(qreal degrees)
{
    setAction(new TurnAction(this, degrees - direction()));
}

void TankItem::stop()
{
    setAction(0);
}

QVariant TankItem::itemChange(QGraphicsItem::GraphicsItemChange change, const QVariant &value)
{
    if (change == ItemPositionChange && scene()) {
        QPointF requestedPosition = value.toPointF();
        QLineF collidedLine;
        QPointF nextPoint = tryMove(requestedPosition, &collidedLine);
        if (nextPoint != requestedPosition)
            emit collision(collidedLine);
        return nextPoint;
    } else {
        return QGraphicsItem::itemChange(change, value);
    }
}


void TankItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
{
    QRectF brect = boundingRect();

    painter->setBrush(m_color);
    painter->setPen(Qt::black);

    // body
    painter->drawRect(brect.adjusted(0.0, 4.0, -2.0, -4.0));

    // cannon
    QRectF cannonBase = brect.adjusted(10.0, 6.0, -12.0, -6.0);
    painter->drawEllipse(cannonBase);

    painter->drawRect(QRectF(QPointF(cannonBase.center().x(), cannonBase.center().y() - 2.0), 
                             QPointF(brect.right(), cannonBase.center().y() + 2.0)));
    
    // left track
    painter->setBrush(QBrush(Qt::black, Qt::VerPattern));
    QRectF leftTrackRect = QRectF(brect.topLeft(), QPointF(brect.right() - 2.0, brect.top() + 4.0));
    painter->fillRect(leftTrackRect, Qt::darkYellow);
    painter->drawRect(leftTrackRect);

    // right track
    QRectF rightTrackRect = QRectF(QPointF(brect.left(), brect.bottom() - 4.0),
                                   QPointF(brect.right() - 2.0, brect.bottom()));
    painter->fillRect(rightTrackRect, Qt::darkYellow);
    painter->drawRect(rightTrackRect);

    if (!m_enabled) {
        painter->setPen(QPen(Qt::red, 5));

        painter->drawEllipse(brect);

        QPainterPath path;
        path.addEllipse(brect);
        painter->setClipPath(path);
        painter->drawLine(brect.topRight(), brect.bottomLeft());
    }
}

QRectF TankItem::boundingRect() const
{
    return QRectF(-20.0, -10.0, 40.0, 20.0);
}

qreal TankItem::direction() const
{
    return m_currentDirection;
}

void TankItem::setDirection(qreal newDirection)
{
    int fullRotations = int(newDirection) / 360;    
    newDirection -= fullRotations * 360.0;

    qreal diff = newDirection - m_currentDirection;
    m_currentDirection = newDirection;
    rotate(diff);
}

qreal TankItem::distanceToObstacle(QGraphicsItem **obstacle) const
{
    qreal dist = sqrt(pow(scene()->sceneRect().width(), 2) + pow(scene()->sceneRect().height(), 2));

    qreal a = m_currentDirection * M_PI / 180.0;

    qreal yd = dist * sin(a);
    qreal xd = dist * sin(M_PI / 2.0 - a);

    QPointF requestedPosition = pos() + QPointF(xd, yd);
    QGraphicsItem *collidedItem = 0;
    QPointF nextPosition = tryMove(requestedPosition, 0, &collidedItem);
    if (collidedItem != 0) {
        if (obstacle != 0)
            *obstacle = collidedItem;        
        
        QPointF d = nextPosition - pos();
        return sqrt(pow(d.x(), 2) + pow(d.y(), 2));
    } else {
        return 0.0;
    }
}

qreal TankItem::distanceToObstacle() const
{
    return distanceToObstacle(0);
}