cryptomon/internal/web/format.go

package web

import (
	"fmt"
	"strconv"
	"strings"
	"time"
)

var currencySymbols = map[string]string{
	"USD": "$", "GBP": "£", "EUR": "€", "JPY": "¥",
}

func currencySymbol(currency string) string {
	if sym, ok := currencySymbols[currency]; ok {
		return sym
	}
	return currency + " "
}

// money formats an amount in the given currency with thousands separators,
// e.g. money(-1234.5, "GBP") -> "-£1,234.50".
func money(v float64, currency string) string {
	neg := v < 0
	if neg {
		v = -v
	}
	s := strconv.FormatFloat(v, 'f', 2, 64)
	intPart, decPart, _ := strings.Cut(s, ".")
	var out []byte
	n := len(intPart)
	for i := 0; i < n; i++ {
		if i > 0 && (n-i)%3 == 0 {
			out = append(out, ',')
		}
		out = append(out, intPart[i])
	}
	res := currencySymbol(currency) + string(out) + "." + decPart
	if neg {
		res = "-" + res
	}
	return res
}

// amt formats a crypto quantity, trimming trailing zeros.
func amt(v float64) string {
	s := strconv.FormatFloat(v, 'f', 8, 64)
	s = strings.TrimRight(s, "0")
	s = strings.TrimRight(s, ".")
	if s == "" || s == "-" {
		s = "0"
	}
	return s
}

func pctStr(v *float64) string {
	if v == nil {
		return "—"
	}
	sign := ""
	if *v > 0 {
		sign = "+"
	}
	return fmt.Sprintf("%s%.2f%%", sign, *v)
}

func pctClass(v *float64) string {
	if v == nil {
		return "flat"
	}
	return signClass(*v)
}

func signClass(v float64) string {
	if v > 0 {
		return "gain"
	}
	if v < 0 {
		return "loss"
	}
	return "flat"
}

func dateStr(t time.Time) string {
	return t.Format("Jan 2, 2006")
}

// capitalize upper-cases the first letter of an entry type ("withdrawal" -> "Withdrawal").
func capitalize(s string) string {
	if s == "" {
		return s
	}
	return strings.ToUpper(s[:1]) + s[1:]
}

// sortVal renders a float64 or *float64 as a plain number string for a
// data-sort-value attribute, so the client-side table sort compares numbers
// rather than formatted display text ("£1,234.56", "+3.21%", "—").
func sortVal(v interface{}) string {
	switch x := v.(type) {
	case float64:
		return strconv.FormatFloat(x, 'f', -1, 64)
	case *float64:
		if x == nil {
			return ""
		}
		return strconv.FormatFloat(*x, 'f', -1, 64)
	default:
		return fmt.Sprint(v)
	}
}

func holdDuration(t time.Time) string {
	days := int(time.Since(t).Hours() / 24)
	switch {
	case days < 1:
		return "<1 day"
	case days == 1:
		return "1 day"
	case days < 30:
		return fmt.Sprintf("%d days", days)
	case days < 365:
		return fmt.Sprintf("%d mo", days/30)
	default:
		return fmt.Sprintf("%.1f yr", float64(days)/365)
	}
}