Complete syntax

.gitignore

@@ -20,4 +20,4 @@
 
 # Go workspace file
 go.work
-
+.idea

README.md

@@ -1,3 +1,3 @@
 # beanbot
 
-Bean bot to assist beancount
+Bean bot to assist beancount

go.mod

@@ -0,0 +1,3 @@
+module git.s8k.top/SeraphJACK/beanbot
+
+go 1.21.1

syntax/syntax.go

@@ -0,0 +1,143 @@
+package syntax
+
+import (
+	"errors"
+	"strconv"
+	"time"
+)
+
+var ErrMissingPayee = errors.New("missing payee")
+var ErrUnknownAccount = errors.New("unknown account")
+
+type Config struct {
+	Currencies      []string
+	Accounts        map[string]string
+	DefaultCurrency string
+}
+
+func (c *Config) hasCurrency(cur string) bool {
+	for _, v := range c.Currencies {
+		if v == cur {
+			return true
+		}
+	}
+	return false
+}
+
+func (c *Config) account(abbr string) (string, bool) {
+	if res, ok := c.Accounts[abbr]; ok {
+		return res, true
+	}
+	return "", false
+}
+
+type tokenReader struct {
+	tokens []string
+	cur    int
+}
+
+func (r *tokenReader) HasNext() bool {
+	return r.cur < len(r.tokens)
+}
+
+func (r *tokenReader) Peek() string {
+	return r.tokens[r.cur]
+}
+
+func (r *tokenReader) Next() string {
+	res := r.tokens[r.cur]
+	r.cur++
+	return res
+}
+
+func Parse(tokens []string, cfg *Config) (*Transaction, error) {
+	r := &tokenReader{tokens: tokens}
+	txn := &Transaction{}
+
+	// optional transaction date
+	if r.HasNext() {
+		t, err := time.Parse("2006-01-02", r.Peek())
+		if err == nil {
+			txn.Date = t.Format("2006-01-02")
+			r.Next()
+		} else {
+			// default date: current date
+			txn.Date = time.Now().Format("2006-01-02")
+		}
+	}
+
+	// optional txn mark
+	if r.HasNext() {
+		if r.Peek() == "*" || r.Peek() == "!" {
+			txn.Flag = r.Next()
+		} else {
+			// default flag is * (complete txn)
+			txn.Flag = "*"
+		}
+	}
+
+	// mandatory payee
+	if !r.HasNext() {
+		return nil, ErrMissingPayee
+	}
+	txn.Payee = r.Next()
+
+	p, err := readPosting(r, cfg)
+	if err != nil {
+		// account does not exist, token is optional narration
+		txn.Narration = r.Next()
+	} else {
+		txn.Postings = append(txn.Postings, p)
+	}
+
+	// remaining postings
+	for r.HasNext() {
+		p, err := readPosting(r, cfg)
+		if err != nil {
+			return nil, err
+		}
+		txn.Postings = append(txn.Postings, p)
+	}
+
+	return txn, txn.Validate()
+}
+
+func readPosting(r *tokenReader, cfg *Config) (*Posting, error) {
+	p := &Posting{}
+
+	// mandatory account
+	if !r.HasNext() {
+		return nil, ErrUnknownAccount
+	}
+	account, ok := cfg.account(r.Peek())
+	if !ok {
+		return nil, ErrUnknownAccount
+	}
+	p.Account = account
+	r.Next()
+
+	// optional flag
+	if r.HasNext() && (r.Peek() == "!" || r.Peek() == "*") {
+		p.Flag = r.Next()
+	} else {
+		p.Flag = "*"
+	}
+
+	// optional amount
+	if r.HasNext() {
+		amount, err := strconv.ParseFloat(r.Peek(), 64)
+		if err == nil {
+			p.Amount = amount
+			r.Next()
+		}
+	}
+
+	// optional currency
+	if r.HasNext() && cfg.hasCurrency(r.Peek()) {
+		p.Currency = r.Next()
+	} else {
+		p.Currency = cfg.DefaultCurrency
+	}
+
+	return p, nil
+}

syntax/syntax_test.go

@@ -0,0 +1,34 @@
+package syntax
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+)
+
+var Cfg = &Config{
+	Currencies: []string{"CNY", "USD"},
+	Accounts: map[string]string{
+		"zfb":   "Assets::Digital::Alipay",
+		"wx":    "Assets::Digital::Wechat",
+		"dt":    "Expenses::Travel::Train",
+		"lunch": "Expenses::Food::Lunch",
+	},
+	DefaultCurrency: "CNY",
+}
+
+func TestParse(t *testing.T) {
+	for _, str := range []string{
+		"地铁 dt 3 zfb -1 wx",
+		"午饭 lunch 11.20 wx",
+		"2023-01-01 转账 zfb 100 wx",
+	} {
+		t.Run(str, func(t *testing.T) {
+			txn, err := Parse(strings.Split(str, " "), Cfg)
+			if err != nil {
+				t.Fatalf("%v", err)
+			}
+			fmt.Print(txn.ToBeanLanguageSyntax())
+		})
+	}
+}

syntax/transaction.go

@@ -0,0 +1,70 @@
+package syntax
+
+import (
+	"bytes"
+	_ "embed"
+	"errors"
+	"text/template"
+)
+
+//go:embed transaction.tmpl
+var txnTmpl string
+
+var parsedTmpl *template.Template
+
+func init() {
+	parsedTmpl = template.Must(template.New("bean-language-txn").Parse(txnTmpl))
+}
+
+type Posting struct {
+	Account  string
+	Amount   float64
+	Currency string
+	Flag     string
+}
+
+type Transaction struct {
+	Date      string
+	Payee     string
+	Narration string
+	Flag      string
+	Postings  []*Posting
+}
+
+func (txn *Transaction) Validate() error {
+	// currency: amount
+	sum := map[string]float64{}
+	zeros := map[string]int{}
+	zerop := map[string]*Posting{}
+
+	for _, p := range txn.Postings {
+		sum[p.Currency] += p.Amount
+		if p.Amount == 0 {
+			zeros[p.Currency]++
+			zerop[p.Currency] = p
+		}
+	}
+
+	for cur, s := range sum {
+		if zeros[cur] > 1 {
+			return errors.New("multiple zero amount postings")
+		}
+		if zeros[cur] == 1 {
+			zerop[cur].Amount = -s
+		}
+		if zeros[cur] == 0 && s != 0 {
+			return errors.New("sum of amount is non-zero")
+		}
+	}
+
+	return nil
+}
+
+func (txn *Transaction) ToBeanLanguageSyntax() string {
+	buf := &bytes.Buffer{}
+	err := parsedTmpl.Execute(buf, txn)
+	if err != nil {
+		panic(err)
+	}
+	return buf.String()
+}

syntax/transaction.tmpl

@@ -0,0 +1,3 @@
+{{.Date}} {{.Flag}} "{{.Payee}}"{{if ne .Narration ""}} "{{.Narration}}"{{end}}
+{{range .Postings}}    {{if ne .Flag "*" }}{{.Flag}} {{end}}{{.Account}} {{printf "%.2f" .Amount}} {{.Currency}}
+{{end}}