1 files changed, 186 insertions, 0 deletions
diff --git a/modules/emoji/emoji.go b/modules/emoji/emoji.go
new file mode 100644
index 00000000..3d4ef859
--- /dev/null
+++ b/modules/emoji/emoji.go
@@ -0,0 +1,186 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Copyright 2015 Kenneth Shaw
+// SPDX-License-Identifier: MIT
+
+package emoji
+
+import (
+	"io"
+	"sort"
+	"strings"
+	"sync"
+)
+
+// Gemoji is a set of emoji data.
+type Gemoji []Emoji
+
+// Emoji represents a single emoji and associated data.
+type Emoji struct {
+	Emoji          string
+	Description    string
+	Aliases        []string
+	UnicodeVersion string
+	SkinTones      bool
+}
+
+var (
+	// codeMap provides a map of the emoji unicode code to its emoji data.
+	codeMap map[string]int
+
+	// aliasMap provides a map of the alias to its emoji data.
+	aliasMap map[string]int
+
+	// emptyReplacer is the string replacer for emoji codes.
+	emptyReplacer *strings.Replacer
+
+	// codeReplacer is the string replacer for emoji codes.
+	codeReplacer *strings.Replacer
+
+	// aliasReplacer is the string replacer for emoji aliases.
+	aliasReplacer *strings.Replacer
+
+	once sync.Once
+)
+
+func loadMap() {
+	once.Do(func() {
+		// initialize
+		codeMap = make(map[string]int, len(GemojiData))
+		aliasMap = make(map[string]int, len(GemojiData))
+
+		// process emoji codes and aliases
+		codePairs := make([]string, 0)
+		emptyPairs := make([]string, 0)
+		aliasPairs := make([]string, 0)
+
+		// sort from largest to small so we match combined emoji first
+		sort.Slice(GemojiData, func(i, j int) bool {
+			return len(GemojiData[i].Emoji) > len(GemojiData[j].Emoji)
+		})
+
+		for i, e := range GemojiData {
+			if e.Emoji == "" || len(e.Aliases) == 0 {
+				continue
+			}
+
+			// setup codes
+			codeMap[e.Emoji] = i
+			codePairs = append(codePairs, e.Emoji, ":"+e.Aliases[0]+":")
+			emptyPairs = append(emptyPairs, e.Emoji, e.Emoji)
+
+			// setup aliases
+			for _, a := range e.Aliases {
+				if a == "" {
+					continue
+				}
+
+				aliasMap[a] = i
+				aliasPairs = append(aliasPairs, ":"+a+":", e.Emoji)
+			}
+		}
+
+		// create replacers
+		emptyReplacer = strings.NewReplacer(emptyPairs...)
+		codeReplacer = strings.NewReplacer(codePairs...)
+		aliasReplacer = strings.NewReplacer(aliasPairs...)
+	})
+}
+
+// FromCode retrieves the emoji data based on the provided unicode code (ie,
+// "\u2618" will return the Gemoji data for "shamrock").
+func FromCode(code string) *Emoji {
+	loadMap()
+	i, ok := codeMap[code]
+	if !ok {
+		return nil
+	}
+
+	return &GemojiData[i]
+}
+
+// FromAlias retrieves the emoji data based on the provided alias in the form
+// "alias" or ":alias:" (ie, "shamrock" or ":shamrock:" will return the Gemoji
+// data for "shamrock").
+func FromAlias(alias string) *Emoji {
+	loadMap()
+	if strings.HasPrefix(alias, ":") && strings.HasSuffix(alias, ":") {
+		alias = alias[1 : len(alias)-1]
+	}
+
+	i, ok := aliasMap[alias]
+	if !ok {
+		return nil
+	}
+
+	return &GemojiData[i]
+}
+
+// ReplaceCodes replaces all emoji codes with the first corresponding emoji
+// alias (in the form of ":alias:") (ie, "\u2618" will be converted to
+// ":shamrock:").
+func ReplaceCodes(s string) string {
+	loadMap()
+	return codeReplacer.Replace(s)
+}
+
+// ReplaceAliases replaces all aliases of the form ":alias:" with its
+// corresponding unicode value.
+func ReplaceAliases(s string) string {
+	loadMap()
+	return aliasReplacer.Replace(s)
+}
+
+type rememberSecondWriteWriter struct {
+	pos        int
+	idx        int
+	end        int
+	writecount int
+}
+
+func (n *rememberSecondWriteWriter) Write(p []byte) (int, error) {
+	n.writecount++
+	if n.writecount == 2 {
+		n.idx = n.pos
+		n.end = n.pos + len(p)
+		n.pos += len(p)
+		return len(p), io.EOF
+	}
+	n.pos += len(p)
+	return len(p), nil
+}
+
+func (n *rememberSecondWriteWriter) WriteString(s string) (int, error) {
+	n.writecount++
+	if n.writecount == 2 {
+		n.idx = n.pos
+		n.end = n.pos + len(s)
+		n.pos += len(s)
+		return len(s), io.EOF
+	}
+	n.pos += len(s)
+	return len(s), nil
+}
+
+// FindEmojiSubmatchIndex returns index pair of longest emoji in a string
+func FindEmojiSubmatchIndex(s string) []int {
+	loadMap()
+	secondWriteWriter := rememberSecondWriteWriter{}
+
+	// A faster and clean implementation would copy the trie tree formation in strings.NewReplacer but
+	// we can be lazy here.
+	//
+	// The implementation of strings.Replacer.WriteString is such that the first index of the emoji
+	// submatch is simply the second thing that is written to WriteString in the writer.
+	//
+	// Therefore we can simply take the index of the second write as our first emoji
+	//
+	// FIXME: just copy the trie implementation from strings.NewReplacer
+	_, _ = emptyReplacer.WriteString(&secondWriteWriter, s)
+
+	// if we wrote less than twice then we never "replaced"
+	if secondWriteWriter.writecount < 2 {
+		return nil
+	}
+
+	return []int{secondWriteWriter.idx, secondWriteWriter.end}
+}