freetype/emoji.go

package freetype

import (
	"errors"
	"fmt"
	"strings"
	"unicode/utf8"
)

type Emoji struct {
	Codepoints []rune
	Bytes      int
}

var (
	errNotAnEmoji = errors.New("not an emoji")
)

func inrange(val, min, max rune) bool {
	return val >= min && val < max
}

// https://stackoverflow.com/questions/30757193/find-out-if-character-in-string-is-emoji/39425959
func isEmoji(chr rune) bool {
	switch {
	case inrange(chr, 0x1f600, 0x1f64f), // Emoticons
		inrange(chr, 0x1f300, 0x1f5ff), // Misc Symbols and Pictographs
		inrange(chr, 0x1f680, 0x1f6ff), // Transport and Map
		inrange(chr, 0x1f1e6, 0x1f1ff), // Regional country flags
		inrange(chr, 0x2600, 0x26ff),   // Misc symbols
		inrange(chr, 0x2700, 0x27bf),   // Dingbats
		inrange(chr, 0xfe00, 0xfe0f),   // Variation Selectors
		inrange(chr, 0x1f900, 0x1f9ff), // Supplemental Symbols and Pictographs
		inrange(chr, 127000, 127600),   // Various asian characters
		inrange(chr, 65024, 65039),     // Variation selector
		inrange(chr, 9100, 9300),       // Misc items
		inrange(chr, 8400, 8447):       // Combining Diacritical Marks for Symbols
		return true
	}
	return false
}

func isZWJ(chr rune) bool {
	return chr == 8205
}

func parseEmoji(str string) (Emoji, error) {
	if len(str) < 1 {
		return Emoji{}, errNotAnEmoji
	}

	emoji := Emoji{}

	for _, r := range str {
		// Check if rune is emoji
		if !isEmoji(r) && !isZWJ(r) {
			if len(emoji.Codepoints) < 1 {
				return emoji, errNotAnEmoji
			}
			break
		}

		emoji.Codepoints = append(emoji.Codepoints, r)
		emoji.Bytes += utf8.RuneLen(r)
	}

	return emoji, nil
}

func (e Emoji) String() string {
	codepoints := []string{}
	for _, cp := range e.Codepoints {
		codepoints = append(codepoints, fmt.Sprintf("%U", cp))
	}
	return "Emoji(" + strings.Join(codepoints, ", ") + ")"
}