import { Level } from 'level';
import { ExporterState, PartialStateUpdate, Status } from './index';
import Config from '../config';

type LevelError = Error | null | undefined;

//@ts-ignore
const errorNotFound = (err: LevelError) => err.code && err.code == 'LEVEL_NOT_FOUND';

class LevelState {
    private _db = new Level('landsbankinn-exporter', { valueEncoding: 'json' });
    private currentTTLHandle: number | undefined = -1;

    constructor() {
        function creator(err: Error | null | undefined) {
            if (err) {
                if (errorNotFound(err)) {
                    console.info('Creating initial empty state');
                    //@ts-ignore
                    this._db.put('state', {});
                }
            }
        }

        const self = this;
        this.prepTTL().then(() => self._db.get('state', {}, creator.bind(self)));
    }

    get current(): Promise<ExporterState> {
        return this._db.get('state') as unknown as Promise<ExporterState>;
    }

    async clear() {
        console.info('Cleared state');
        return await this._db.put('state', { status: Status.NotReady } as any);
    }

    private async clearTTL() {
        if (this.currentTTLHandle) {
            window.clearTimeout(this.currentTTLHandle);
        }
    }

    private async prepTTL() {
        console.info(`Will clear state in ${Config.StateTTL} milliseconds`);
        this.currentTTLHandle = window.setTimeout(async () => await this.clear(), Config.StateTTL);
    }

    async update(stateUpdate: ExporterState | PartialStateUpdate): Promise<ExporterState> {
        this.clearTTL();
        const currentState: ExporterState = await this.current;
        let newState = { ...currentState, ...stateUpdate };
        await this._db.put('state', newState as any);
        this.prepTTL();
        return this.current;
    }
}

export const State: LevelState = new LevelState();