feat: /xr command for currency exchange rates

bot.go

@@ -4,10 +4,14 @@ import (
 	"fmt"
 	"html"
 	"math"
+	"regexp"
+	"strconv"
 	"strings"
 	"text/tabwriter"
 	"time"
 
+	"git.gensokyo.cafe/kkyy/mycurrencynet"
+	"github.com/dustin/go-humanize"
 	"github.com/go-errors/errors"
 	"github.com/samber/lo"
 	tele "gopkg.in/telebot.v3"
@@ -49,6 +53,7 @@ func initBot() (*tele.Bot, error) {
 	b.Handle("/me", handleUserInfoCmd)
 	b.Handle("/chat", handleChatInfoCmd)
 	b.Handle("/year_progress", handleYearProgressCmd)
+	b.Handle("/xr", handleExchangeRateCmd)
 
 	b.Handle(tele.OnText, handleGeneralMessage)
 	b.Handle(tele.OnSticker, handleGeneralMessage)
@@ -292,3 +297,159 @@ func handleDigCmd(c tele.Context) error {
 	}
 	return c.Reply(strings.Join(replyText, ""), &tele.SendOptions{ParseMode: tele.ModeHTML}, tele.Silent)
 }
+
+func handleExchangeRateCmd(c tele.Context) error {
+	msg := c.Message()
+	if msg == nil {
+		return nil
+	}
+
+	if msg.Payload == "" {
+		return c.Reply("Usage: `/xr <currency> [<currency> ...] [to] <currency>`",
+			&tele.SendOptions{ParseMode: tele.ModeMarkdown},
+			tele.Silent,
+		)
+	}
+
+	from, to, err := parseXrRequest(msg.Payload)
+	if err != nil {
+		return c.Reply(err.Error(), tele.Silent)
+	}
+	codes := append([]string{to.Code}, lo.Map(from, func(i xrCurrency, _ int) string { return i.Code })...)
+	currencies, err := exchangeRates.Get(codes...)
+	if err != nil {
+		return c.Reply(err.Error(), tele.Silent)
+	}
+	toCur := currencies[0]
+
+	// format reply
+	var replyLines []string
+	for i, fromItem := range from {
+		fromCur := currencies[i+1]
+		replyLines = append(replyLines, fmtXrPair(fromCur, toCur, fromItem.Amount))
+	}
+
+	return c.Reply(strings.Join(replyLines, "\n"), &tele.SendOptions{ParseMode: tele.ModeMarkdown}, tele.Silent)
+}
+
+type xrCurrency struct {
+	Code   string
+	Amount float64
+}
+
+func parseXrRequest(input string) (from []xrCurrency, to xrCurrency, err error) {
+	args := strings.Fields(input)
+
+	var tmpTo *xrCurrency = nil
+	fillFrom := true
+
+	c := xrCurrency{Amount: -1}
+	for _, arg := range args {
+		arg = strings.ToUpper(arg)
+
+		switch {
+		case arg == "TO":
+			fillFrom = false
+			continue
+
+		case fillFrom:
+			num, sym, tErr := parseXrToken(arg)
+			if tErr != nil {
+				err = tErr
+				return
+			}
+			if num != -1 {
+				if c.Amount != -1 {
+					err = errors.New("invalid input")
+					return
+				}
+				c.Amount = num
+			}
+			if c.Amount == -1 {
+				c.Amount = 1
+			}
+
+			if sym != "" {
+				c.Code = sym
+				from = append(from, c)
+				c = xrCurrency{Amount: -1}
+			}
+
+		case !fillFrom:
+			if tmpTo != nil {
+				err = errors.New("invalid input")
+				return
+			}
+			tmpTo = &xrCurrency{Code: arg}
+
+		default:
+			err = errors.New("invalid input")
+			return
+		}
+	}
+
+	if len(from) < 1 || len(from) > 10 {
+		err = errors.New("invalid input")
+		return
+	}
+
+	if fillFrom {
+		if len(from) < 2 {
+			err = errors.New("invalid input")
+			return
+		}
+		tmpTo = &from[len(from)-1]
+		from = from[:len(from)-1]
+	}
+
+	if tmpTo == nil {
+		err = errors.New("invalid input")
+		return
+	}
+	to = *tmpTo
+
+	return
+}
+
+var xrTokenRe = regexp.MustCompile(`^([0-9.]+)?([A-Z]{3,})?$`)
+
+func parseXrToken(token string) (num float64, sym string, err error) {
+	num = -1
+	matches := xrTokenRe.FindStringSubmatch(token)
+	if len(matches) != 3 {
+		err = errors.New("invalid input")
+		return
+	}
+
+	if matches[1] != "" {
+		num, err = strconv.ParseFloat(matches[1], 64)
+		if err != nil {
+			return
+		}
+		if num <= 0 {
+			err = errors.New("invalid input: amount must be positive")
+			return
+		}
+	}
+
+	sym = matches[2]
+	if num == 0 && sym == "" {
+		err = errors.New("invalid input")
+	}
+	return
+}
+
+func fmtXrPair(from, to *mycurrencynet.Currency, amount float64) string {
+	rate := from.To(to) * amount
+	fromInfo := fmt.Sprintf("%s (%s)", from.Name, from.Code)
+	toInfo := fmt.Sprintf("%s (%s)", to.Name, to.Code)
+
+	return fmt.Sprintf("*%s* %s\n= *%s* %s\n", fmtXrFloat(amount), fromInfo, fmtXrFloat(rate), toInfo)
+}
+
+func fmtXrFloat(num float64) string {
+	if num < 100 {
+		return fmt.Sprintf("%.4g", num)
+	}
+	return humanize.CommafWithDigits(num, 2)
+}

main.go

@@ -4,7 +4,9 @@ import (
 	"os"
 	"os/signal"
 	"syscall"
+	"time"
 
+	"git.gensokyo.cafe/kkyy/mycurrencynet"
 	"go.uber.org/zap"
 	tele "gopkg.in/telebot.v3"
 
@@ -22,6 +24,25 @@ func initLogger() {
 	logger = l.Sugar()
 }
 
+var exchangeRates = mycurrencynet.New()
+
+func initExchangeRates() {
+	if err := exchangeRates.Update(); err != nil {
+		logger.Panicw("Failed to update exchange rates", "err", err)
+	}
+	logger.Info("Exchange rates updated")
+
+	go exchangeRates.UpdateEvery(
+		time.Hour,
+		func(err error) {
+			logger.Errorw("Failed to update exchange rates", "err", err)
+		},
+		func() {
+			logger.Info("Exchange rates updated")
+		},
+	)
+}
+
 func runBot() {
 	logger.Info("Bot initializing...")
 	bot, err := initBot()
@@ -37,6 +58,7 @@ func runBot() {
 			{Text: "traffic", Description: "Show traffic usage."},
 			{Text: "dig", Description: "Diggy diggy dig."},
 			{Text: "year_progress", Description: "Time doesn't wait."},
+			{Text: "xr", Description: "Currency exchange rates"},
 		}); err != nil {
 			logger.Fatalw("Failed to announce commands", "err", err)
 		}
@@ -45,6 +67,8 @@ func runBot() {
 	botFinCh := utils.WaitFor(bot.Start)
 	logger.Infow("Bot started", "username", bot.Me.Username)
 
+	go initExchangeRates()
+
 	// listen for shutdown signal
 	sigCh := make(chan os.Signal, 1)
 	signal.Notify(sigCh, os.Interrupt, syscall.SIGTERM)