import {EventEmitter, Injectable} from '@angular/core';
import {BehaviorSubject, combineLatest} from "rxjs";
import {PermissionsService} from "../components/permissions/permissions.service";

@Injectable({
    providedIn: 'root'
})
export class PhysicsService {
    private motionTimestamp;

    requireCalibration = new EventEmitter();
    calibrate = new BehaviorSubject<number>(Infinity);

    info = new BehaviorSubject(null);
    motion = new BehaviorSubject<DeviceMotionEvent>(null);
    orientation = new BehaviorSubject<DeviceOrientationEvent>(null);
    position = new BehaviorSubject<Position>(null);
    speed = new BehaviorSubject(null);

    constructor(permissionsService: PermissionsService) {
        permissionsService.requestPermission('geolocation', 'gps_fixed', 'Can we use your location?').then(granted => {
            if(granted) {
                // Gather physical data
                window.addEventListener('deviceorientation', orientation => this.orientation.next(orientation));
                window.addEventListener('devicemotion', motion => this.motion.next(motion));
                navigator.geolocation.watchPosition(position => this.position.next(position));

                // Calculate speed from motion events
                this.motion.subscribe(event => {
                    if (!this.motionTimestamp) return this.motionTimestamp = new Date().getTime();

                    let currentTime = new Date().getTime();
                    let {speedX, speedY, speedZ} = this.speed.value || {speedX: 0, speedY: 0, speedZ: 0};
                    this.speed.next({
                        speedX: speedX + event.acceleration.x / 1000 * ((currentTime - this.motionTimestamp) / 1000) / 3600,
                        speedY: speedY + event.acceleration.y / 1000 * ((currentTime - this.motionTimestamp) / 1000) / 3600,
                        speedZ: speedZ + event.acceleration.z / 1000 * ((currentTime - this.motionTimestamp) / 1000) / 3600
                    });
                    this.motionTimestamp = currentTime;
                });

                // Combine data into one nice package
                combineLatest(this.position, this.orientation, this.calibrate, this.speed).subscribe(data => {
                    if(!data[0]) return;

                    let info = {
                        accuracy: data[0].coords.accuracy,
                        altitude: data[0].coords.altitude,
                        altitudeAccuracy: data[0].coords.altitudeAccuracy,
                        heading: data[0].coords.heading,
                        latitude: data[0].coords.latitude,
                        longitude: data[0].coords.longitude,
                        speed: data[0].coords.speed
                    };

                    if(info.heading == null && data[1]) {
                        if(!data[1].absolute && data[2] == Infinity) {
                            this.calibrate.next(0);
                            this.requireCalibration.emit();
                        }

                        info.heading = -data[1].alpha + (data[2] == Infinity ? 0 : data[2]);
                        if(info.heading < 0) info.heading += 360;
                        if(info.heading >= 360) info.heading -= 360;
                    }
                    if(info.speed == null && !!data[3]) info.speed = Math.sqrt(data[3].x**2 + data[3].y**2 + data[3].z**2);

                    this.info.next(info);
                })
            }
        });
    }
}