sjansen/messageformat

package compiler

import (
    "fmt"
    "strconv"
    "strings"

    "golang.org/x/text/feature/plural"
    "golang.org/x/text/language"

    "github.com/sjansen/messageformat/ast"
)

type numberSign struct {
    ArgID  string
    Offset int
}

type pluralArg struct {
    ArgID    string
    Ordinal  bool
    Offset   int
    Messages map[string]*Message
}

func (n *numberSign) format(b *strings.Builder, lang language.Tag, arguments map[string]interface{}) error {
    value, ok := arguments[n.ArgID]
    if !ok {
        return fmt.Errorf("missing arg: %q", n.ArgID)
    }
    i, ok := value.(int)
    if !ok {
        return fmt.Errorf("expected int got: %T", value)
    }
    b.WriteString(strconv.Itoa(i - n.Offset))
    return nil
}

func newPluralArg(lang language.Tag, p *ast.PluralArg) (*pluralArg, error) {
    if _, ok := p.Messages["other"]; !ok {
        return nil, fmt.Errorf(`missing required plural category: "other"`)
    }
    n := &numberSign{
        ArgID:  p.ArgID,
        Offset: p.Offset,
    }
    messages := make(map[string]*Message, len(p.Messages))
    for k, v := range p.Messages {
        msg, err := compile(lang, v, n)
        if err != nil {
            return nil, err
        }
        messages[k] = msg
    }
    return &pluralArg{
        ArgID:    p.ArgID,
        Ordinal:  p.Ordinal,
        Offset:   p.Offset,
        Messages: messages,
    }, nil
}

func (p *pluralArg) format(b *strings.Builder, lang language.Tag, arguments map[string]interface{}) error {
    value, ok := arguments[p.ArgID]
    if !ok {
        return fmt.Errorf("missing arg: %q", p.ArgID)
    }

    n, ok := value.(int)
    if !ok {
        return fmt.Errorf("expected int got: %T", value)
    }

    category := fmt.Sprintf("=%d", n)
    if msg, ok := p.Messages[category]; ok {
        return msg.format(b, lang, arguments)
    }

    var form plural.Form
    if p.Ordinal {
        form = plural.Ordinal.MatchPlural(lang, n, 0, 0, 0, 0)
    } else {
        form = plural.Cardinal.MatchPlural(lang, n, 0, 0, 0, 0)
    }

    category = "other"
    switch form {
    case plural.Zero:
        category = "zero"
    case plural.One:
        category = "one"
    case plural.Two:
        category = "two"
    case plural.Few:
        category = "few"
    case plural.Many:
        category = "many"
    }

    if msg, ok := p.Messages[category]; ok {
        return msg.format(b, lang, arguments)
    }

    msg := p.Messages["other"]
    return msg.format(b, lang, arguments)
}