#ifndef TOOLSELECTOR_H
#define TOOLSELECTOR_H


#include "Tool.h"
#include "../MapView2D.h"

#include "../../model/MapModelElement.h"
#include "../../model/MapModel.h"


/**
 * this tool allows:
 * - selecting elements within the 2D view (focus/unfocus)
 * - selecting and moving nodes of elements inheriting from HasMoveableNodes
 *
 */
class ToolSelector : public Tool {

	Q_OBJECT

private:

	/** the currently focused MapElement (if any) */
	MapModelElement* focused = nullptr;

	/** whether the mouse-button is currently pressed */
	bool mouseIsDown = false;

public:

	virtual ~ToolSelector() {;}


	const std::string getName() const override {
		return "Selection";
	}

	void becomesActive() override {
		showHelp();
	}

	/** needed eg. when the focused element gets invalid (switching visible layers) */
	void layerChange(MapView2D* m) override {
		(void) m;
		setFocused(m, nullptr);
	}

private:

	void processUnfocus(MapView2D* m, MapModelElement* elem) {

		MV2DElement* me = elem->getMV2D();
		if (!me) {return;}

		// elements has selectedable nodes? unselect them
		if (dynamic_cast<HasMoveableNodes*>(me)) {
			dynamic_cast<HasMoveableNodes*>(me)->onNodeUnselect(m);
		}

		// let the element itself process the unfocus
		me->unfocus();

	}

	void processPress(MapView2D* m, const Point2 p, MapModelElement* elem) {

		MV2DElement* me = elem->getMV2D();
		if (!me) {return;}

		// let the element itself process all events
		me->mousePressed(m, p);

	}

	void processMove(MapView2D* m, const Point2 p, MapModelElement* elem) {

		MV2DElement* me = elem->getMV2D();
		if (!me) {return;}

		// elements has selectedable nodes? try to process them
		if (dynamic_cast<HasMoveableNodes*>(me)) {
			if (moveNode(m, p, dynamic_cast<HasMoveableNodes*>(me))) {return;}
		}

		// otherwise: let the element itself process all events
		me->mouseMove(m, p);

	}

	void processRelease(MapView2D* m, const Point2 p, MapModelElement* elem) {

		MV2DElement* me = elem->getMV2D();
		if (!me) {return;}

		// element has selectedable nodes? try to process them
		if (dynamic_cast<HasMoveableNodes*>(me)) {
			if (selectNode(m, p, dynamic_cast<HasMoveableNodes*>(me))) {return;}
		}

		// otherwise: let the element itself process all events
		me->mouseReleased(m, p);

	}



private:

	/** the given element has selectable nodes. try to select the one near to the mouse. true if successful */
	bool selectNode(MapView2D* v, Point2 p, HasMoveableNodes* elem) {

		// select a new point on mouse-release (more robust than on mouse-press)

		// find the node nearest to p
		auto comp = [&] (const MoveableNode& n1, const MoveableNode& n2) {return n1.pos.getDistance(p) < n2.pos.getDistance(p);};
		auto lst = elem->getMoveableNodes();
		auto it = std::min_element(lst.begin(), lst.end(), comp);

		// is the nearest point below the threshold?
		const float t = v->getScaler().sm(CFG::SEL_THRESHOLD_SIZE_PX);
		const float d = it->pos.getDistance(p);
		if (d < t) {
			elem->onNodeSelect(v, it->userIdx);
			return true;
		} else {
			elem->onNodeSelect(v, -1);
			return false;
		}

	}

	/** move the currently selected node. true if successful */
	bool moveNode(MapView2D* v, Point2 p, HasMoveableNodes* elem) {

		// no node selected? -> done
		if (elem->getSelectedNode() == -1) {return false;}

		// snap the node
		const Point2 pSnapped = v->getScaler().snap(p);

		// move
		elem->onNodeMove(v, elem->getSelectedNode(), pSnapped);
		return true;

	}



private:

	void showHelp() {
		if (focused)	{emit onHelpTextChange("select one of the element's nodes");}
		if (!focused)	{emit onHelpTextChange("select an element by clicking on it");}
	}

	/**
	 * @brief change the currently focused element. throws an event.
	 * @param el the to-be-focused element or null
	 * @return true if the focused element has changed. false otherwise
	 */
	bool setFocused(MapView2D* v, MapModelElement* el) {

		// whether the focus has changed or not
		const bool focusChanged = (focused != el);

		if (focusChanged) {

			// unfocus the old one (if any)
			if (focused) {processUnfocus(v, focused);}

			// set the currently focused object (if any)
			focused = el;

			// focus the new one (if any)
			if (focused) {focused->getMV2D()->focus();}

			// update the help-text
			showHelp();

			emit onMapElementSelected(el);

		}

		// done
		return focusChanged;

	}



private:

	virtual bool mousePressEvent(MapView2D* m, QMouseEvent* e) override {

		if (e->button() != Qt::MouseButton::LeftButton) {return false;}

		mouseIsDown = true;

		const Scaler& s = m->getScaler();
		const Point2 p2(s.xsm(e->x()), s.ysm(e->y()));

		const float g = m->getScaler().sm(15);					// increase each BBox by 15 px (needed mainly for hor/ver lines)

		// get all elements with bounding-box matchings
		std::vector<MapModelElement*> possible;
		for (MapModelElement* el : m->getModel()->getSelectedLayerElements()) {
			if (!el->getMV2D()) {continue;}
			BBox2 bbox = el->getMV2D()->getBoundingBox();		// elements 2D bbox
			bbox.grow(Point2(g, g));							// grow a little (needed for straight lines)
			if (bbox.contains(p2)) {possible.push_back(el);}	// intersection?
		}

		// among those, find the best-matching one (smallest distance to an intersection)
		auto lambda = [&] (const MapModelElement* el1, const MapModelElement* el2) {return el1->getMV2D()->getMinDistanceXY(p2) < el2->getMV2D()->getMinDistanceXY(p2);};
		auto it = std::min_element(possible.begin(), possible.end(), lambda);
		MapModelElement* el = (it == possible.end()) ? (nullptr) : (*it);



		// focus changed? -> unfocus the old one (if any)
		if (setFocused(m, el)) {

			;

		} else {

			// focus kept. provide the currently focused element with events
			if (focused) {
				processPress(m, p2, focused);
			}

		}

		return true;

	}

	virtual bool mouseMoveEvent(MapView2D* m, QMouseEvent* e) override {

		const Scaler& s = m->getScaler();
		Point2 p2(s.xsm(e->x()), s.ysm(e->y()));

		// mouse pressed?
		if (mouseIsDown) {

			// provide the focused element with the mouse event?
			if (focused) {processMove(m, p2, focused);}

		}

		return false;

	}

	virtual bool mouseReleaseEvent(MapView2D* m, QMouseEvent* e) override {

		const Scaler& s = m->getScaler();
		Point2 p2(s.xsm(e->x()), s.ysm(e->y()));

		// provide the focused element with the mouse event?
		if (focused) {processRelease(m, p2, focused);}

		mouseIsDown = false;

		return false;

	}

	virtual bool keyPressEvent(MapView2D* m, QKeyEvent* e) override {

		(void) m;

		if (focused) {

			// pass it to the element which may consume this event
			if (focused->getMV2D()->keyPressEvent(m, e)) {return false;}

			// not consumed -> additional options

			// ESCAPE -> unfocus
			if (e->key() == Qt::Key_Escape) {setFocused(m, nullptr);}

			// DELETE -> delete
			if (e->key() == Qt::Key_Delete) {
				focused->deleteMe();
				setFocused(m, nullptr);
				return true;
			}

		}

		return false;

	}

signals:

	/** map element was selected */
	void onMapElementSelected(MapModelElement* el);

};

#endif // TOOLSELECTOR_H