import { inject, Injectable } from '@angular/core';
import { BehaviorSubject, Observable, switchMap } from 'rxjs';
import { HttpClient } from '@angular/common/http';
import { tap } from 'rxjs/operators';
import { HeadersConfiguration, mapEach, RequiredParam, Validate } from '../utils';

@Injectable()
export abstract class StatsService<E, I = E> {
    protected abstract readonly _primaryKey: string;
    protected abstract readonly _entityClass: new (entityInterface: I, ...args: unknown[]) => E;
    protected abstract readonly _defaultModelPath: string;

    readonly #http = inject(HttpClient);
    readonly #map = new Map<string, BehaviorSubject<E>>();

    @Validate()
    getFor(@RequiredParam() ids: string[]): Observable<E[]> {
        const request = this.#http.post<I[]>(`/${encodeURI(this._defaultModelPath)}`, ids, {
            headers: HeadersConfiguration.getHeaders(),
            observe: 'body',
        });

        return request.pipe(
            mapEach(entity => new this._entityClass(entity)),
            tap(entities => entities.forEach(entity => this.set(entity))),
        );
    }

    get(key: string): E {
        return this._getBehaviourSubject(key).value;
    }

    set(stats: E): void {
        if (!this.#map.has(this._pluckPrimaryKey(stats))) {
            this.#map.set(this._pluckPrimaryKey(stats), new BehaviorSubject<E>(stats));
            return;
        }

        const old = this.get(this._pluckPrimaryKey(stats));
        if (JSON.stringify(old) !== JSON.stringify(stats)) {
            this._getBehaviourSubject(this._pluckPrimaryKey(stats)).next(stats);
        }
    }

    watch$(key: string): Observable<E> {
        const subject = this.#map.get(key);
        if (!subject) {
            return this.getFor([key]).pipe(switchMap(() => this._getBehaviourSubject(key).asObservable()));
        }

        return subject.asObservable();
    }

    private _pluckPrimaryKey(stats: E): string {
        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
        // @ts-ignore
        return stats[this._primaryKey] as string;
    }

    private _getBehaviourSubject(key: string): BehaviorSubject<E> {
        const subject = this.#map.get(key);
        if (!subject) {
            throw new Error(`No stats for key ${key}`);
        }

        return subject;
    }
}