package visualiser.layout;

import javafx.beans.value.ChangeListener;
import javafx.collections.ListChangeListener;
import javafx.collections.ObservableList;
import javafx.scene.Group;
import javafx.scene.PerspectiveCamera;
import javafx.scene.SubScene;
import javafx.scene.input.PickResult;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Shape3D;
import javafx.scene.transform.Rotate;
import javafx.scene.transform.Translate;

import java.util.HashMap;
import java.util.Map;

/**
 * Control for rendering 3D objects visible through a PerspectiveCamera. Implements Adapter Pattern to
 * interface with camera, and allows clients to add shapes to the scene. All scenes contain sea plane and
 * sky box, whose textures are set with special methods.
 */
public class View3D extends Pane {
    /**
     * Container for group and camera
     */
    private SubScene scene;
    /**
     * Observable list of renderable items
     */
    private ObservableList<Subject3D> items;
    /**
     * Map for selecting Subject3D from Shape3D
     */
    private Map<Shape3D, Subject3D> selectionMap;
    /**
     * Subject tracked by camera
     */
    private Subject3D target;
    /**
     * Rendering container for shapes
     */
    private Group world;
    /**
     * Near limit of view frustum
     */
    private double nearClip;
    /**
     * Far limit of view frustum
     */
    private double farClip;
    /**
     * Camera origin
     */
    private Translate pivot;
    /**
     * Distance of camera from pivot point
     */
    private Translate distance;
    /**
     * Angle along ground between z-axis and camera
     */
    private Rotate yaw;
    /**
     * Angle between ground plane and camera direction
     */
    private Rotate pitch;
    /**
     * Single listener for subject heading changes
     */
    private ChangeListener<? super Number> pivotHeading = (o, prev, curr) -> yaw.setAngle((double)curr);
    /**
     * Single listener for subject position (x) changes
     */
    private ChangeListener<? super Number> pivotX = (o, prev, curr) -> pivot.setX((double)curr);
    /**
     * Single listener for subject position (y) changes
     */
    private ChangeListener<? super Number> pivotY = (o, prev, curr) -> pivot.setY((double)curr);
    /**
     * Single listener for subject position (z) changes
     */
    private ChangeListener<? super Number> pivotZ = (o, prev, curr) -> pivot.setZ((double)curr);
    /**
     * Distance to switch from third person to bird's eye
     */
    private double THIRD_PERSON_LIMIT = 100;

    /**
     * Default constructor for View3D. Sets up Scene and PerspectiveCamera.
     */
    public View3D(boolean fill) {
        this.world = new Group();
        this.selectionMap = new HashMap<>();
        this.target = null;
        this.scene = new SubScene(world, 300, 300);

        scene.widthProperty().bind(this.widthProperty());
        scene.heightProperty().bind(this.heightProperty());
        if (fill) {
            scene.setFill(new Color(0.2, 0.6, 1, 1));
        }
        scene.setCamera(buildCamera());

        this.getChildren().add(scene);
    }

    public View3D(){
        this(true);
    }

    /**
     * Sets up camera view frustum and binds transformations
     * @return perspective camera
     */
    private PerspectiveCamera buildCamera() {
        PerspectiveCamera camera = new PerspectiveCamera(true);

        // Set up view frustum
        nearClip = 0.1;
        farClip = 3000.0;
        camera.setNearClip(nearClip);
        camera.setFarClip(farClip);

        // Set up transformations
        pivot = new Translate();
        distance = new Translate();
        yaw = new Rotate(0, Rotate.Y_AXIS);
        pitch = new Rotate(0, Rotate.X_AXIS);
        camera.getTransforms().addAll(pivot, yaw, pitch, distance);

        return camera;
    }

    /**
     * Provide the list of subjects to be automatically added or removed from the view as the list
     * changes.
     * @param items list managed by client
     */
    public void setItems(ObservableList<Subject3D> items) {
        this.items = items;
        this.items.addListener((ListChangeListener<? super Subject3D>) c -> {
            while(c.next()) {
                if (c.wasRemoved() || c.wasAdded()) {
                    for (Subject3D shape : c.getRemoved()) {
                        world.getChildren().remove(shape.getMesh());
                        selectionMap.remove(shape.getMesh());
                    }
                    for (Subject3D shape : c.getAddedSubList()) {
                        world.getChildren().add(shape.getMesh());
                        selectionMap.put(shape.getMesh(), shape);
                    }
                }
            }
        });
    }

    /**
     * Intercept mouse clicks on subjects in view. The applied listener cannot be removed.
     */
    public void enableTracking() {
        scene.setOnMousePressed(e -> {
            PickResult result = e.getPickResult();
            if(result != null && result.getIntersectedNode() != null && result.getIntersectedNode() instanceof Shape3D) {
                trackSubject(selectionMap.get(result.getIntersectedNode()));
            }
        });
    }

    /**
     * Stop camera from following the last selected subject
     */
    private void untrackSubject() {
        if(target != null) {
            target.getPosition().xProperty().removeListener(pivotX);
            target.getPosition().yProperty().removeListener(pivotY);
            target.getPosition().zProperty().removeListener(pivotZ);
            target.getHeading().angleProperty().removeListener(pivotHeading);
        }
    }

    /**
     * Set camera to follow the selected subject
     * @param subject to track
     */
    private void trackSubject(Subject3D subject) {
        untrackSubject();
        target = subject;

        updatePivot(target.getPosition());
        setYaw(target.getHeading().getAngle());

        target.getPosition().xProperty().addListener(pivotX);
        target.getPosition().yProperty().addListener(pivotY);
        target.getPosition().zProperty().addListener(pivotZ);
        target.getHeading().angleProperty().addListener(pivotHeading);

        this.setDistance(THIRD_PERSON_LIMIT);
        this.setPitch(20);
    }

    public void setNearClip(double nearClip) {
        this.nearClip = nearClip;
    }

    public void setFarClip(double farClip) {
        this.farClip = farClip;
    }

    /**
     * Sets the coordinates of the camera pivot once.
     * @param pivot source of coordinates
     */
    public void updatePivot(Translate pivot) {
        this.pivot.setX(pivot.getX());
        this.pivot.setY(pivot.getY());
        this.pivot.setZ(pivot.getZ());
    }

    /**
     * Set distance of camera from pivot
     * @param distance in units
     */
    public void setDistance(double distance) {
        this.distance.setZ(-distance);
    }

    /**
     * Adds delta to current distance and changes camera mode if applicable.
     * Third person limit specifies the distance at which a third person camera
     * switches to bird's-eye, remaining focused on the same position.
     * @param delta amount to change distance by
     */
    public void updateDistance(double delta) {
        double distance = -this.distance.getZ() + delta;

        if(distance <= 0) {
            this.setDistance(0);
        } else if(distance > THIRD_PERSON_LIMIT) {
            untrackSubject();
            this.setYaw(0);
            this.setPitch(60);
            this.setDistance(distance);
        } else {
            this.setDistance(distance);
        }
    }

    /**
     * Set angle of camera from z-axis along ground
     * @param yaw in degrees
     */
    public void setYaw(double yaw) {
        this.yaw.setAngle(yaw);
    }

    /**
     * Set elevation of camera
     * @param pitch in degrees
     */
    public void setPitch(double pitch) {
        this.pitch.setAngle(-pitch);
    }
}