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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package currency
import (
"fmt"
"io"
"sort"
"golang.org/x/text/internal/format"
"golang.org/x/text/internal/language/compact"
)
// Amount is an amount-currency unit pair.
type Amount struct {
amount interface{} // Change to decimal(64|128).
currency Unit
}
// Currency reports the currency unit of this amount.
func (a Amount) Currency() Unit { return a.currency }
// TODO: based on decimal type, but may make sense to customize a bit.
// func (a Amount) Decimal()
// func (a Amount) Int() (int64, error)
// func (a Amount) Fraction() (int64, error)
// func (a Amount) Rat() *big.Rat
// func (a Amount) Float() (float64, error)
// func (a Amount) Scale() uint
// func (a Amount) Precision() uint
// func (a Amount) Sign() int
//
// Add/Sub/Div/Mul/Round.
var space = []byte(" ")
// Format implements fmt.Formatter. It accepts format.State for
// language-specific rendering.
func (a Amount) Format(s fmt.State, verb rune) {
v := formattedValue{
currency: a.currency,
amount: a.amount,
format: defaultFormat,
}
v.Format(s, verb)
}
// formattedValue is currency amount or unit that implements language-sensitive
// formatting.
type formattedValue struct {
currency Unit
amount interface{} // Amount, Unit, or number.
format *options
}
// Format implements fmt.Formatter. It accepts format.State for
// language-specific rendering.
func (v formattedValue) Format(s fmt.State, verb rune) {
var lang compact.ID
if state, ok := s.(format.State); ok {
lang, _ = compact.RegionalID(compact.Tag(state.Language()))
}
// Get the options. Use DefaultFormat if not present.
opt := v.format
if opt == nil {
opt = defaultFormat
}
cur := v.currency
if cur.index == 0 {
cur = opt.currency
}
// TODO: use pattern.
io.WriteString(s, opt.symbol(lang, cur))
if v.amount != nil {
s.Write(space)
// TODO: apply currency-specific rounding
scale, _ := opt.kind.Rounding(cur)
if _, ok := s.Precision(); !ok {
fmt.Fprintf(s, "%.*f", scale, v.amount)
} else {
fmt.Fprint(s, v.amount)
}
}
}
// Formatter decorates a given number, Unit or Amount with formatting options.
type Formatter func(amount interface{}) formattedValue
// func (f Formatter) Options(opts ...Option) Formatter
// TODO: call this a Formatter or FormatFunc?
var dummy = USD.Amount(0)
// adjust creates a new Formatter based on the adjustments of fn on f.
func (f Formatter) adjust(fn func(*options)) Formatter {
var o options = *(f(dummy).format)
fn(&o)
return o.format
}
// Default creates a new Formatter that defaults to currency unit c if a numeric
// value is passed that is not associated with a currency.
func (f Formatter) Default(currency Unit) Formatter {
return f.adjust(func(o *options) { o.currency = currency })
}
// Kind sets the kind of the underlying currency unit.
func (f Formatter) Kind(k Kind) Formatter {
return f.adjust(func(o *options) { o.kind = k })
}
var defaultFormat *options = ISO(dummy).format
var (
// Uses Narrow symbols. Overrides Symbol, if present.
NarrowSymbol Formatter = Formatter(formNarrow)
// Use Symbols instead of ISO codes, when available.
Symbol Formatter = Formatter(formSymbol)
// Use ISO code as symbol.
ISO Formatter = Formatter(formISO)
// TODO:
// // Use full name as symbol.
// Name Formatter
)
// options configures rendering and rounding options for an Amount.
type options struct {
currency Unit
kind Kind
symbol func(compactIndex compact.ID, c Unit) string
}
func (o *options) format(amount interface{}) formattedValue {
v := formattedValue{format: o}
switch x := amount.(type) {
case Amount:
v.amount = x.amount
v.currency = x.currency
case *Amount:
v.amount = x.amount
v.currency = x.currency
case Unit:
v.currency = x
case *Unit:
v.currency = *x
default:
if o.currency.index == 0 {
panic("cannot format number without a currency being set")
}
// TODO: Must be a number.
v.amount = x
v.currency = o.currency
}
return v
}
var (
optISO = options{symbol: lookupISO}
optSymbol = options{symbol: lookupSymbol}
optNarrow = options{symbol: lookupNarrow}
)
// These need to be functions, rather than curried methods, as curried methods
// are evaluated at init time, causing tables to be included unconditionally.
func formISO(x interface{}) formattedValue { return optISO.format(x) }
func formSymbol(x interface{}) formattedValue { return optSymbol.format(x) }
func formNarrow(x interface{}) formattedValue { return optNarrow.format(x) }
func lookupISO(x compact.ID, c Unit) string { return c.String() }
func lookupSymbol(x compact.ID, c Unit) string { return normalSymbol.lookup(x, c) }
func lookupNarrow(x compact.ID, c Unit) string { return narrowSymbol.lookup(x, c) }
type symbolIndex struct {
index []uint16 // position corresponds with compact index of language.
data []curToIndex
}
var (
normalSymbol = symbolIndex{normalLangIndex, normalSymIndex}
narrowSymbol = symbolIndex{narrowLangIndex, narrowSymIndex}
)
func (x *symbolIndex) lookup(lang compact.ID, c Unit) string {
for {
index := x.data[x.index[lang]:x.index[lang+1]]
i := sort.Search(len(index), func(i int) bool {
return index[i].cur >= c.index
})
if i < len(index) && index[i].cur == c.index {
x := index[i].idx
start := x + 1
end := start + uint16(symbols[x])
if start == end {
return c.String()
}
return symbols[start:end]
}
if lang == 0 {
break
}
lang = lang.Parent()
}
return c.String()
}