Token pair/symbol parsing

pairs.go

package main

import (
	"fmt"
	"strings"
)

type TokenPair struct {
	InToken  string
	OutToken string
}

type SymbolAndSideInfo struct {
	Symbol string
	Side   string
}

var pairs = map[TokenPair]SymbolAndSideInfo{
	{"USD", "ETH"}: {"ETH-USD", "buy"},
	{"ETH", "USD"}: {"ETH-USD", "sell"},
}

var ErrInvalidPair = fmt.Errorf("invalid pair")

// GetSymbolAndSide returns the trading symbol and side for given inToken and outToken.
func GetSymbolAndSide(inToken, outToken string) (string, string, error) {
	// Upper case the tokens
	normalizedInToken := strings.ToUpper(inToken)
	normalizedOutToken := strings.ToUpper(outToken)

	// Lookup the pair
	info, exists := pairs[TokenPair{InToken: normalizedInToken, OutToken: normalizedOutToken}]
	if !exists {
		return "", "", ErrInvalidPair
	}

	return info.Symbol, info.Side, nil
}

func main() {

	symbol, side, err := GetSymbolAndSide("usd", "eth")
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}

	fmt.Printf("Symbol: %s, Side: %s\n", symbol, side)
}

pairs_improved.go

package main

import (
	"fmt"
	"strings"
)

type Symbol string

var symbolsMap = map[string]Symbol{
	"ETH-USD": "ETH-USD",
}

type Side string

const (
	BUY  Side = "buy"
	SELL Side = "sell"
)

type TokenPair struct {
	InToken  string
	OutToken string
}

type SymbolAndSideInfo struct {
	Symbol Symbol
	Side   Side
}

var pairs = map[TokenPair]SymbolAndSideInfo{
	{"USD", "ETH"}: {symbolsMap["ETH-USD"], "buy"},
	{"ETH", "USD"}: {symbolsMap["ETH-USD"], "sell"},
}

var ErrInvalidPair = fmt.Errorf("invalid pair")

// GetSymbolAndSide returns the trading symbol and side for given inToken and outToken.
func GetSymbolAndSide(inToken, outToken string) (Symbol, Side, error) {
	// Upper case the tokens
	normalizedInToken := strings.ToUpper(inToken)
	normalizedOutToken := strings.ToUpper(outToken)

	// Lookup the pair
	info, exists := pairs[TokenPair{InToken: normalizedInToken, OutToken: normalizedOutToken}]
	if !exists {
		return "", "", ErrInvalidPair
	}

	return info.Symbol, info.Side, nil
}

func main() {

	symbol, side, err := GetSymbolAndSide("usd", "eth")
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}

	fmt.Printf("Symbol: %s, Side: %s\n", symbol, side)
}