package main

import (
    "fmt"

    "golang.org/x/text/language"
    "golang.org/x/text/message"
    "golang.org/x/text/number"
)

func main() {
    ts := []language.Tag{
        language.MustParse("en-GB"),
        language.MustParse("en-GB-u-nu-fullwide"),
        language.MustParse("ar"),
        language.MustParse("ar-u-nu-latn"),
        language.MustParse("ta"),
        language.MustParse("ta-u-nu-taml"),
        language.MustParse("ta-u-nu-tamldec"),
    }

    for _, t := range ts {
        fmt.Printf("%s\n", t.String())

        r, _ := t.Region()
        fmt.Printf("%s, %s\n", r.String(), r.ISO3())

        s, _ := t.Script()
        fmt.Printf("%s\n", s.String())

        message.NewPrinter(t).Println(number.Decimal(123456789))

        // PROPOSED:
        // n, _ := number.SystemFromTag(t)
        // fmt.Printf("%s\n", n.String())

        fmt.Println("---")
    }


    // Expected Outputs:
    // en-GB
    // GB, GBR
    // Latn
    // 123,456,789
    // latn
    // ---
    // en-GB-u-nu-fullwide
    // GB, GBR
    // Latn
    // １２３,４５６,７８９
    // fullwide
    // ---
    // ar
    // EG, EGY
    // Arab
    // ١٢٣٬٤٥٦٬٧٨٩
    // arab
    // ---
    // ar-u-nu-latn
    // EG, EGY
    // Arab
    // 123,456,789
    // latn
    // ---
    // ta
    // IN, IND
    // Taml
    // 12,34,56,789
    // latn
    // ---
    // ta
    // IN, IND
    // Taml
    // 12,34,56,789 // taml is not a decimal format, so ignore this line
    // taml
    // ---
    // ta-u-nu-tamldec
    // IN, IND
    // Taml
    // ௧௨,௩௪,௫௬,௭௮௯
    // tamldec
    // ---
}

// System holds information about a numbering system
type System struct {
    info number.Info // from /x/text/internal/number
}

// SystemFromTag returns a Numbering System for the given language tag.  If it
// was not explicitly given (e.g. "en-u-nu-mathbold"), it will infer a most
// likely candidate. This is subject to change.
func SystemFromTag(t language.Tag) System, Confidence {
    // TODO select a Confidence
    return number.info.InfoFromTag(t), confidence
}

// String returns the BCP 47 U Extension representation for the Number System Identifier.
func (s System) String() string {
    ....
}