mt940-mbank-ts/src/index.ts

import {
	addLineNumbers,
	chunks,
	fillWithEmpty,
	removeRepeatingSpace,
} from "./utils";

class Account {
	constructor(
		public number: string,
		public initial_balance: number,
		public closing_balance: number,
		public currency: string
	) {}
}

class Transaction {
	constructor(
		public acc_date: Date,
		public op_date: Date,
		public description: string,
		public title: string,
		public person: string,
		public account_number: string,
		public amount: number,
		public balance_after: number
	) {}

	public static counter = (function* () {
		let c = 1;
		while (true) {
			yield c.toString().padStart(11, "0");
			c++;
		}
	})();

	formatTitle() {
		return addLineNumbers(
			fillWithEmpty(chunks(this.title.trim(), 27), 9),
			20
		).join("\n");
	}

	formatPerson() {
		return addLineNumbers(
			fillWithEmpty(
				chunks(removeRepeatingSpace(this.person).trim(), 27),
				2
			).slice(0, 2),
			32
		).join("\n");
	}

	toMT940() {
		const prefixes = { incoming: "150", outcoming: "169" };
		const prefix = this.amount > 0 ? prefixes.incoming : prefixes.outcoming;
		return `:61:${mtDate(this.acc_date)}${mtDate(this.op_date).slice(
			2
		)}C${mtAmount(this.amount)}S${prefix}${Transaction.counter.next().value}
:86:${prefix}
:86:${prefix}~00B${prefix}${this.description.slice(0, 23)}
${this.formatTitle()}
~29${this.account_number}
~30${this.account_number.slice(2, 10)}
~31${this.account_number.slice(10)}
${this.formatPerson()}
~34${prefix}
~38PL${this.account_number}
~62
~63`;
	}
}

class Range {
	constructor(public date_start: Date, public date_end: Date) {}
}

abstract class CSVParser {
	abstract read_csv(content_utf8: string): {
		account: Account;
		range: Range;
		transactions: Transaction[];
	};
}

class mBankParser extends CSVParser {
	read_csv(content_utf8: string): {
		account: Account;
		range: Range;
		transactions: Transaction[];
	} {
		const lines = content_utf8.split("\r\n").map((line) => line.split(";"));
		let last = 0;
		while (!lines[last][0].startsWith("Niniejszy dokument sporządzono")) {
			last++;
		}
		const account = new Account(
			lines[20][0],
			this.parseAmount(lines[35][1]),
			this.parseAmount(lines[last - 2][7]),
			lines[18][0]
		);
		const range = new Range(
			this.parseDate(lines[14][0]),
			this.parseDate(lines[14][1])
		);
		const transactions = [];
		for (let i = 38; i <= last - 5; i++) {
			const line = lines[i];
			if (line.length != 9) {
				throw new Error(
					"Wrong amount of columns! maybe a semicolon got stuck in a transaction description?"
				);
			}
			const date_acc = new Date(line[0]);
			const date_op = new Date(line[1]);
			const [description, title, person, account_number] = line
				.slice(2)
				.map(this.trimString);
			const [amount, balance_after] = line
				.slice(6)
				.map((s) => this.parseAmount(s));
			transactions.push(
				new Transaction(
					date_acc,
					date_op,
					description,
					title,
					person,
					account_number,
					amount,
					balance_after
				)
			);
		}
		return { account, range, transactions };
	}

	parseAmount(s: string): number {
		return parseFloat(s.replace(/[^0-9,-]/g, "").replace(",", "."));
	}

	parseDate(s: string): Date {
		const [day, month, year] = s.split(".").map((s) => parseInt(s));
		const d = new Date();
		d.setHours(0);
		d.setMinutes(0);
		d.setSeconds(0);
		d.setMilliseconds(0);
		d.setDate(day);
		d.setMonth(month - 1);
		d.setFullYear(year);
		return d;
	}

	trimString(s: string): string {
		//removes redundant quotes at the beginning or end of the transaction
		return s.replaceAll(/(^["']|["']$)/g, "");
	}
}

function mtDate(d: Date) {
	return `${d.getFullYear() - 2000}${(d.getMonth() + 1)
		.toString()
		.padStart(2, "0")}${d.getDate().toString().padStart(2, "0")}`;
}

function mtAmount(n: number) {
	return Math.abs(n).toString().replace(".", ",");
}

export function convert(csv_utf8: string): { output: string; range: Range } {
	const result = new mBankParser().read_csv(csv_utf8);
	const { account, transactions, range } = result;
	const string = `:20:MT940
:25:/PL${account.number.replaceAll(/[^0-9]/g, "")}
:28C:${mtDate(range.date_start)}
:60F:D${mtDate(range.date_start)}${account.currency}${mtAmount(
		account.initial_balance
	)}
${transactions.map((t) => t.toMT940()).join("\n")}
:62F:D${mtDate(range.date_end)}${account.currency}${mtAmount(
		account.closing_balance
	)}`;
	return { output: string, range };
}