ledger-ts：基于 TypeScript 的开源记账 DSL

项目开源地址为 https://github.com/hamsterbase/ledger-ts/blob/main/src/example/beancount.ts

使用之前推荐先学习一下 beancount 语法。

在日常使用 beancount 记账时，我遇到了一些困扰。这些问题激发了我自行创造 DSL 的想法。简而言之，我的目标是开发一种更高级的记账语言，而将 beancount 当作底层的“汇编语言”。

我选择基于 TypeScript 开发，通过一些工具函数来实现账单的记录。在 typescript 代码里定义所有的货币、账户和交易记录。借助这种方法，无需自己开发编译器。可以充分利用 Visual Studio Code 强大的代码补全功能，而且还可以在 TypeScript 的类型系统中进行进阶操作和验证。

此外，对于一些常见的账目模式，可以开发工具函数来进一步简化和自动化账单的处理

这个是原始的 beancount 账单

1970-10-01 commodity USD

1970-10-01 commodity CNY

1970-01-01 open Assets:CN:Cash CNY

1970-01-01 open Assets:Cash USD

1970-01-01 open Assets:UTrade:Account:AAPL USD

1970-01-01 open Assets:UTrade:Account:EWJ USD

1970-01-01 open Expenses:Food:Groceries USD

1970-01-01 open Expenses:Food:Alcool USD

1970-01-01 * "Distribution of cash expenses"
  Assets:Cash -300 USD
  Expenses:Food:Alcool 300 USD

1970-01-01 * "CN to usd"
  Assets:CN:Cash -700 CNY @@ 100 USD
  Assets:Cash 100 USD

这个是我发明的 DSL

import { EAccountType, Ledger, utils } from "../index.js";

// 声明货币
const { USD, CNY } = utils.createCurrencies({ defaultDate: "1970-10-01" }, [
  "USD",
  "CNY",
] as const);

// 声明 Assets 账户
const Assets = utils.buildAccountHierarchy(USD, EAccountType.Assets, {
  CN: {
    Cash: utils.createAccountNodeConfig({ open: "1970-01-01", currency: CNY }),
  },
  Cash: utils.createAccountNodeConfig({ open: "1970-01-01" }),
  UTrade: {
    Account: {
      AAPL: utils.createAccountNodeConfig({ open: "1970-01-01" }),
      EWJ: utils.createAccountNodeConfig({ open: "1970-01-01" }),
    },
  },
});

// 声明消费 Expenses 账户
const Expenses = utils.buildAccountHierarchy(USD, EAccountType.Expenses, {
  Food: {
    Groceries: utils.createAccountNodeConfig({ open: "1970-01-01" }),
    Alcool: utils.createAccountNodeConfig({ open: "1970-01-01" }),
  },
});

const ledger = new Ledger(
  [
    ...utils.flattenAccountHierarchy(Assets),
    ...utils.flattenAccountHierarchy(Expenses),
  ],
  [USD, CNY]
);

const { tr } = utils.transactionBuilder(ledger);

// 记录账单
tr(
  "1970-01-01",
  "Distribution of cash expenses",
  Assets.Cash.posting(-300),
  Expenses.Food.Alcool.posting(300)
);

tr(
  "1970-01-01",
  "CN to usd",
  Assets.CN.Cash.posting(-700).asCost(100, USD),
  Assets.Cash.posting(100)
);

console.log(utils.beanCount.serializationLedger(ledger));

基于 typescript ，可以很方便的编写复杂逻辑。

比如 ledger 就内置了 prepaid 分帐这个函数，可以很方便的将年付的订阅服务，均摊到每一个月。

  ledger.transaction(
    ...prepaid({
      date: "2021-01-03",
      start: "2021-01-01",
      from: assets.CN.Bank.Card.USTC,
      to: expenses.XGP,
      amount: -100,
      prepaid: assets.Prepaid,
      parts: 12,
      payee: "xgp",
      narration: "xgp prepaid",
    })
  );

2021-01-03 * "xgp" "xgp prepaid"
  Assets:CN:Bank:Card:USTC -100 CNY
  Assets:Prepaid 100 CNY

2021-01-01 * "xgp" "xgp prepaid"
  remain: 11
  Assets:Prepaid -8.33 CNY
  Expenses:XGP 8.33 CNY

2021-02-01 * "xgp" "xgp prepaid"
  remain: 10
  Assets:Prepaid -8.33 CNY
  Expenses:XGP 8.33 CNY

2021-03-01 * "xgp" "xgp prepaid"
  remain: 9
  Assets:Prepaid -8.33 CNY
  Expenses:XGP 8.33 CNY

2021-04-01 * "xgp" "xgp prepaid"
  remain: 8
  Assets:Prepaid -8.33 CNY
  Expenses:XGP 8.33 CNY

2021-05-01 * "xgp" "xgp prepaid"
  remain: 7
  Assets:Prepaid -8.33 CNY
  Expenses:XGP 8.33 CNY

2021-06-01 * "xgp" "xgp prepaid"
  remain: 6
  Assets:Prepaid -8.33 CNY
  Expenses:XGP 8.33 CNY

2021-07-01 * "xgp" "xgp prepaid"
  remain: 5
  Assets:Prepaid -8.33 CNY
  Expenses:XGP 8.33 CNY

2021-08-01 * "xgp" "xgp prepaid"
  remain: 4
  Assets:Prepaid -8.33 CNY
  Expenses:XGP 8.33 CNY

2021-09-01 * "xgp" "xgp prepaid"
  remain: 3
  Assets:Prepaid -8.33 CNY
  Expenses:XGP 8.33 CNY

2021-10-01 * "xgp" "xgp prepaid"
  remain: 2
  Assets:Prepaid -8.33 CNY
  Expenses:XGP 8.33 CNY

2021-11-01 * "xgp" "xgp prepaid"
  remain: 1
  Assets:Prepaid -8.33 CNY
  Expenses:XGP 8.33 CNY

2021-12-01 * "xgp" "xgp prepaid"
  remain: 0
  Assets:Prepaid -8.37 CNY
  Expenses:XGP 8.37 CNY