import {
    merge as observableMerge,
    empty as observableEmpty,
    combineLatest as observableCombineLatest,
    Observable,
    Subject,
    Subscription,
} from "rxjs";

import {
    distinctUntilChanged,
    withLatestFrom,
    switchMap,
    auditTime,
    first,
    map,
} from "rxjs/operators";

import { ILatLon } from "../API";
import {
    ILatLonAlt,
    Transform,
} from "../Geo";
import {
    IEdgeStatus,
    Node,
} from "../Graph";
import { RenderCamera } from "../Render";
import { EventEmitter } from "../Utils";
import {
    Container,
    IUnprojection,
    IViewerMouseEvent,
    Navigator,
    Projection,
    Viewer,
} from "../Viewer";
import SubscriptionHolder from "../utils/SubscriptionHolder";

export class Observer {
    private _started: boolean;

    private _navigable$: Subject<boolean>;

    private _bearingSubscription: Subscription;
    private _currentNodeSubscription: Subscription;
    private _fovSubscription: Subscription;
    private _moveSubscription: Subscription;
    private _positionSubscription: Subscription;
    private _povSubscription: Subscription;
    private _sequenceEdgesSubscription: Subscription;
    private _spatialEdgesSubscription: Subscription;
    private _viewerMouseEventSubscription: Subscription;

    private _subscriptions: SubscriptionHolder = new SubscriptionHolder();

    private _container: Container;
    private _eventEmitter: EventEmitter;
    private _navigator: Navigator;
    private _projection: Projection;

    constructor(eventEmitter: EventEmitter, navigator: Navigator, container: Container) {
        this._container = container;
        this._eventEmitter = eventEmitter;
        this._navigator = navigator;
        this._projection = new Projection();

        this._started = false;

        this._navigable$ = new Subject<boolean>();

        const subs = this._subscriptions;

        // navigable and loading should always emit, also when cover is activated.
        subs.push(this._navigable$
            .subscribe(
                (navigable: boolean): void => {
                    this._eventEmitter.fire(Viewer.navigablechanged, navigable);
                }));

        subs.push(this._navigator.loadingService.loading$
            .subscribe(
                (loading: boolean): void => {
                    this._eventEmitter.fire(Viewer.loadingchanged, loading);
                }));
    }

    public get started(): boolean {
        return this._started;
    }

    public get navigable$(): Subject<boolean> {
        return this._navigable$;
    }

    public get projection(): Projection {
        return this._projection;
    }

    public dispose(): void {
        this.stopEmit();
        this._subscriptions.unsubscribe();
    }

    public project$(latLon: ILatLon): Observable<number[]> {
        return observableCombineLatest(
            this._container.renderService.renderCamera$,
            this._navigator.stateService.currentNode$,
            this._navigator.stateService.reference$).pipe(
                first(),
                map(
                    ([render, node, reference]: [RenderCamera, Node, ILatLonAlt]): number[] => {
                        if (this._projection.distanceBetweenLatLons(latLon, node.latLon) > 1000) {
                            return null;
                        }

                        const canvasPoint: number[] = this._projection.latLonToCanvas(
                            latLon,
                            this._container.container,
                            render,
                            reference);

                        return !!canvasPoint ?
                            [Math.round(canvasPoint[0]), Math.round(canvasPoint[1])] :
                            null;
                    }));
    }

    public projectBasic$(basicPoint: number[]): Observable<number[]> {
        return observableCombineLatest(
            this._container.renderService.renderCamera$,
            this._navigator.stateService.currentTransform$).pipe(
                first(),
                map(
                    ([render, transform]: [RenderCamera, Transform]): number[] => {
                        const canvasPoint: number[] = this._projection.basicToCanvas(
                            basicPoint,
                            this._container.container,
                            render,
                            transform);

                        return !!canvasPoint ?
                            [Math.round(canvasPoint[0]), Math.round(canvasPoint[1])] :
                            null;
                    }));
    }

    public startEmit(): void {
        if (this._started) {
            return;
        }

        this._started = true;

        this._currentNodeSubscription = this._navigator.stateService.currentNodeExternal$
            .subscribe((node: Node): void => {
                this._eventEmitter.fire(Viewer.nodechanged, node);
            });

        this._sequenceEdgesSubscription = this._navigator.stateService.currentNodeExternal$.pipe(
            switchMap(
                (node: Node): Observable<IEdgeStatus> => {
                    return node.sequenceEdges$;
                }))
            .subscribe(
                (status: IEdgeStatus): void => {
                    this._eventEmitter.fire(Viewer.sequenceedgeschanged, status);
                });

        this._spatialEdgesSubscription = this._navigator.stateService.currentNodeExternal$.pipe(
            switchMap(
                (node: Node): Observable<IEdgeStatus> => {
                    return node.spatialEdges$;
                }))
            .subscribe(
                (status: IEdgeStatus): void => {
                    this._eventEmitter.fire(Viewer.spatialedgeschanged, status);
                });

        this._moveSubscription = observableCombineLatest(
            this._navigator.stateService.inMotion$,
            this._container.mouseService.active$,
            this._container.touchService.active$).pipe(
                map(
                    (values: boolean[]): boolean => {
                        return values[0] || values[1] || values[2];
                    }),
                distinctUntilChanged())
            .subscribe(
                (started: boolean) => {
                    if (started) {
                        this._eventEmitter.fire(Viewer.movestart, null);
                    } else {
                        this._eventEmitter.fire(Viewer.moveend, null);
                    }
                });

        this._bearingSubscription = this._container.renderService.bearing$.pipe(
            auditTime(100),
            distinctUntilChanged(
                (b1: number, b2: number): boolean => {
                    return Math.abs(b2 - b1) < 1;
                }))
            .subscribe(
                (bearing): void => {
                    this._eventEmitter.fire(Viewer.bearingchanged, bearing);
                });

        const mouseMove$: Observable<MouseEvent> = this._container.mouseService.active$.pipe(
            switchMap(
                (active: boolean): Observable<MouseEvent> => {
                    return active ?
                        observableEmpty() :
                        this._container.mouseService.mouseMove$;
                }));

        this._viewerMouseEventSubscription = observableMerge(
            this._mapMouseEvent$(Viewer.click, this._container.mouseService.staticClick$),
            this._mapMouseEvent$(Viewer.contextmenu, this._container.mouseService.contextMenu$),
            this._mapMouseEvent$(Viewer.dblclick, this._container.mouseService.dblClick$),
            this._mapMouseEvent$(Viewer.mousedown, this._container.mouseService.mouseDown$),
            this._mapMouseEvent$(Viewer.mousemove, mouseMove$),
            this._mapMouseEvent$(Viewer.mouseout, this._container.mouseService.mouseOut$),
            this._mapMouseEvent$(Viewer.mouseover, this._container.mouseService.mouseOver$),
            this._mapMouseEvent$(Viewer.mouseup, this._container.mouseService.mouseUp$)).pipe(
                withLatestFrom(
                    this._container.renderService.renderCamera$,
                    this._navigator.stateService.reference$,
                    this._navigator.stateService.currentTransform$),
                map(
                    ([[type, event], render, reference, transform]:
                        [[string, MouseEvent], RenderCamera, ILatLonAlt, Transform]): IViewerMouseEvent => {
                        const unprojection: IUnprojection =
                            this._projection.eventToUnprojection(
                                event,
                                this._container.container,
                                render,
                                reference,
                                transform);

                        return {
                            basicPoint: unprojection.basicPoint,
                            latLon: unprojection.latLon,
                            originalEvent: event,
                            pixelPoint: unprojection.pixelPoint,
                            target: <Viewer>this._eventEmitter,
                            type: type,
                        };
                    }))
            .subscribe(
                (event: IViewerMouseEvent): void => {
                    this._eventEmitter.fire(event.type, event);
                });

        this._positionSubscription = this._container.renderService.renderCamera$.pipe(
            distinctUntilChanged(
                ([x1, y1], [x2, y2]): boolean => {
                    return this._closeTo(x1, x2, 1e-2) &&
                        this._closeTo(y1, y2, 1e-2);
                },
                (rc: RenderCamera): number[] => {
                    return rc.camera.position.toArray();
                }))
            .subscribe(
                (): void => {
                    this._eventEmitter.fire(
                        Viewer.positionchanged,
                        {
                            target: this._eventEmitter,
                            type: Viewer.positionchanged,
                        });
                });

        this._povSubscription = this._container.renderService.renderCamera$.pipe(
            distinctUntilChanged(
                ([phi1, theta1], [phi2, theta2]): boolean => {
                    return this._closeTo(phi1, phi2, 1e-3) &&
                        this._closeTo(theta1, theta2, 1e-3);
                },
                (rc: RenderCamera): [number, number] => {
                    return [rc.rotation.phi, rc.rotation.theta];
                }))
            .subscribe(
                (): void => {
                    this._eventEmitter.fire(
                        Viewer.povchanged,
                        {
                            target: this._eventEmitter,
                            type: Viewer.povchanged,
                        });
                });

        this._fovSubscription = this._container.renderService.renderCamera$.pipe(
            distinctUntilChanged(
                (fov1, fov2): boolean => {
                    return this._closeTo(fov1, fov2, 1e-2);
                },
                (rc: RenderCamera): number => {
                    return rc.perspective.fov;
                }))
            .subscribe(
                (): void => {
                    this._eventEmitter.fire(
                        Viewer.fovchanged,
                        {
                            target: this._eventEmitter,
                            type: Viewer.fovchanged,
                        });
                });
    }

    public stopEmit(): void {
        if (!this.started) {
            return;
        }

        this._started = false;

        this._bearingSubscription.unsubscribe();
        this._currentNodeSubscription.unsubscribe();
        this._fovSubscription.unsubscribe();
        this._moveSubscription.unsubscribe();
        this._positionSubscription.unsubscribe();
        this._povSubscription.unsubscribe();
        this._sequenceEdgesSubscription.unsubscribe();
        this._spatialEdgesSubscription.unsubscribe();
        this._viewerMouseEventSubscription.unsubscribe();

        this._bearingSubscription = null;
        this._currentNodeSubscription = null;
        this._fovSubscription = null;
        this._moveSubscription = null;
        this._positionSubscription = null;
        this._povSubscription = null;
        this._sequenceEdgesSubscription = null;
        this._spatialEdgesSubscription = null;
        this._viewerMouseEventSubscription = null;
    }

    public unproject$(canvasPoint: number[]): Observable<ILatLon> {
        return observableCombineLatest(
            this._container.renderService.renderCamera$,
            this._navigator.stateService.reference$,
            this._navigator.stateService.currentTransform$).pipe(
                first(),
                map(
                    ([render, reference, transform]: [RenderCamera, ILatLonAlt, Transform]): ILatLon => {
                        const unprojection: IUnprojection =
                            this._projection.canvasToUnprojection(
                                canvasPoint,
                                this._container.container,
                                render,
                                reference,
                                transform);

                        return unprojection.latLon;
                    }));
    }

    public unprojectBasic$(canvasPoint: number[]): Observable<number[]> {
        return observableCombineLatest(
            this._container.renderService.renderCamera$,
            this._navigator.stateService.currentTransform$).pipe(
                first(),
                map(
                    ([render, transform]: [RenderCamera, Transform]): number[] => {
                        return this._projection.canvasToBasic(
                            canvasPoint,
                            this._container.container,
                            render,
                            transform);
                    }));
    }

    private _closeTo(v1: number, v2: number, absoluteTolerance: number): boolean {
        return Math.abs(v1 - v2) <= absoluteTolerance;
    }

    private _mapMouseEvent$(type: string, mouseEvent$: Observable<MouseEvent>): Observable<[string, MouseEvent]> {
        return mouseEvent$.pipe(map(
            (event: MouseEvent): [string, MouseEvent] => {
                return [type, event];
            }));
    }
}

export default Observer;