ryan
f8e74738cc
Motivation: 交易通知等展示场景中，低价资产（如 0.00000059）按保留两位小数的格式渲染会被截断为 0.00，用户无法读取真实价格；需要在不改变存量数值类型和既有模板写法的前提下，保证任意精度价格都能正确展示。 Changes: * 新增价格展示格式化能力：数值不小于 1 时保留两位小数，小于 1 时输出最短精确值 * 新增 Decimal 类型实现自定义格式化，使模板中的浮点值不再坍缩为 0.00 且不产生科学计数法 * 新增模板数据渲染期数值包装能力，不修改原始数据，保证条件判断与既有模板语法兼容 * 补充价格格式化、精度保留及数据不可变性的单元测试
114 lines
2.3 KiB
Go
114 lines
2.3 KiB
Go
package display
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import (
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"fmt"
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"io"
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"math"
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"strconv"
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"strings"
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)
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// FormatPrice renders a price for display. Values >= 1 keep two decimals for
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// readability; smaller values use the shortest exact representation so tiny
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// prices like 0.00000059 are not collapsed to 0.00.
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func FormatPrice(v float64) string {
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if v == 0 {
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return "0.00"
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}
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if math.Abs(v) >= 1 {
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return strconv.FormatFloat(v, 'f', 2, 64)
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}
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return strconv.FormatFloat(v, 'f', -1, 64)
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}
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// Decimal is a float64 that prints without collapsing sub-0.01 values to 0.00
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// and without scientific notation. Templates keep using {{printf "%.2f" .price}}
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// and {{.price}}; wrapping happens at render time so stored data stays numeric.
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type Decimal float64
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func (d Decimal) Format(f fmt.State, verb rune) {
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v := float64(d)
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switch verb {
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case 'f', 'F':
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prec := 6
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if p, ok := f.Precision(); ok {
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prec = p
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}
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s := strconv.FormatFloat(v, byte(verb), prec, 64)
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if v != 0 && isCollapsedZero(s) {
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s = strconv.FormatFloat(v, 'f', -1, 64)
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}
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_, _ = io.WriteString(f, s)
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case 'v', 's':
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_, _ = io.WriteString(f, formatPlain(v))
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default:
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prec := -1
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if p, ok := f.Precision(); ok {
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prec = p
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}
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_, _ = io.WriteString(f, strconv.FormatFloat(v, byte(verb), prec, 64))
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}
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}
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func formatPlain(v float64) string {
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if v == 0 {
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return "0"
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}
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return strconv.FormatFloat(v, 'f', -1, 64)
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}
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func isCollapsedZero(s string) bool {
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t := strings.TrimPrefix(s, "-")
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t = strings.TrimPrefix(t, "+")
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if t == "" {
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return false
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}
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sawZero := false
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for _, r := range t {
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switch r {
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case '0':
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sawZero = true
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case '.':
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default:
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return false
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}
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}
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return sawZero
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}
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// WrapMap copies data and wraps float values so template printing keeps
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// precision. The original map is left unchanged for condition evaluation.
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func WrapMap(data map[string]interface{}) map[string]interface{} {
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if data == nil {
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return nil
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}
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out := make(map[string]interface{}, len(data))
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for k, v := range data {
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out[k] = wrapValue(v)
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}
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return out
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}
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func wrapValue(v any) any {
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switch t := v.(type) {
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case nil:
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return nil
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case float64:
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return Decimal(t)
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case float32:
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return Decimal(t)
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case Decimal:
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return t
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case map[string]interface{}:
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return WrapMap(t)
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case []interface{}:
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out := make([]interface{}, len(t))
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for i, x := range t {
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out[i] = wrapValue(x)
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}
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return out
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default:
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return v
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}
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}
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