/**
 * Written in Typescript (v3+).
 *
 * Dependencies:
 *     - rxjs >= 6
 *     - firebase-tools >= 6
 *
 * Have fun!
 *
 */

import { auth } from 'firebase-admin';
import { ReadLine, createInterface } from 'readline';
import { from, Observable, empty } from 'rxjs';
import { catchError, mergeMap, map } from 'rxjs/operators';

export class FirebaseUsers {

    constructor(private auth: auth.Auth, private ignoreFirstLine: boolean) {}

    /**
     * Import all users found inside the CSV stream into Firebase Authentication.
     *
     * Note: Lines that cannot be parsed are skipped. Also users that cannot be imported
     * because they exist already or do not meet other criterias are skipped over as well.
     * Errors are written to the console.
     *
     * @param stream to parse the CSV from
     * @returns string observable delivering user names
     */
    create(stream: NodeJS.ReadableStream): Observable<string> {
        return new Observable<User>(obs => {
            const lineReader = createInterface(stream);
            let isFirstLine = true;
            lineReader.on('line', (line: string) => {
                if (isFirstLine && this.ignoreFirstLine) {
                    isFirstLine = false;
                    return;
                }
                const user = parseUserFromCsvLine(line);
                obs.next(user);
            });
            lineReader.on('close', () => obs.complete());

        }).pipe(
            mergeMap(user => {
                return from(this.auth.createUser(user))
                    .pipe(catchError(err => {
                        console.error(`Cannot create user "${user.email}". ${err.errorInfo.message}`);
                        return empty();
                    }));
            }),
            map(userRecord => userRecord.email),
        );
    }
}

/**
 * Parses either colon or semicolon separated values (4 columns) from a text line.
 * Windows, Linux and OSX line endings do work automatically.
 */
export function parseUserFromCsvLine(line: string): User {
    let lineItems = line.split(';');
    if (lineItems.length < 4) {
        lineItems = line.split(',');
        if (lineItems.length < 4)
            throw new Error('Cannot parse user. No ; line separator found.');
    }
    if (lineItems[2].indexOf(' ') > -1)
        throw new Error('Cannot parse user. User name column 3 must not contain space.');
    return {
        email: `${lineItems[2]}@team-challenge.at`,
        password: lineItems[3]
    };
}

/**
 * The user object that gets parsed from the CSV file and eventually
 * is imported into Firebase Authentication.
 */
export interface User {
    email: string;
    password: string;
}