Move some variables out of model (#17909)

* Move some variables out of model

There were some stuff that's not necessary to be in model
and can just remain unexported variables.

```release-note
NONE
```

* Add license

```release-note
NONE
```

model/at_mentions.go

@@ -1,47 +0,0 @@
-// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
-// See LICENSE.txt for license information.
-
-package model
-
-import (
-	"regexp"
-	"strings"
-)
-
-var atMentionRegexp = regexp.MustCompile(`\B@[[:alnum:]][[:alnum:]\.\-_:]*`)
-
-const usernameSpecialChars = ".-_"
-
-// PossibleAtMentions returns all substrings in message that look like valid @
-// mentions.
-func PossibleAtMentions(message string) []string {
-	var names []string
-
-	if !strings.Contains(message, "@") {
-		return names
-	}
-
-	alreadyMentioned := make(map[string]bool)
-	for _, match := range atMentionRegexp.FindAllString(message, -1) {
-		name := NormalizeUsername(match[1:])
-		if !alreadyMentioned[name] && IsValidUsernameAllowRemote(name) {
-			names = append(names, name)
-			alreadyMentioned[name] = true
-		}
-	}
-
-	return names
-}
-
-// TrimUsernameSpecialChar tries to remove the last character from word if it
-// is a special character for usernames (dot, dash or underscore). If not, it
-// returns the same string.
-func TrimUsernameSpecialChar(word string) (string, bool) {
-	len := len(word)
-
-	if len > 0 && strings.LastIndexAny(word, usernameSpecialChars) == (len-1) {
-		return word[:len-1], true
-	}
-
-	return word, false
-}

model/at_mentions_test.go

@@ -1,84 +0,0 @@
-// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
-// See LICENSE.txt for license information.
-
-package model
-
-import (
-	"testing"
-
-	"github.com/stretchr/testify/require"
-)
-
-func TestPossibleAtMentions(t *testing.T) {
-	fixture := []struct {
-		message  string
-		expected []string
-	}{
-		{
-			"",
-			[]string{},
-		},
-		{
-			"@user",
-			[]string{"user"},
-		},
-		{
-			"@user-with_special.chars @multiple.-_chars",
-			[]string{"user-with_special.chars", "multiple.-_chars"},
-		},
-		{
-			"@repeated @user @repeated",
-			[]string{"repeated", "user"},
-		},
-		{
-			"@user1 @user2 @user3",
-			[]string{"user1", "user2", "user3"},
-		},
-		{
-			"@李",
-			[]string{},
-		},
-		{
-			"@withfinaldot. @withfinaldash- @withfinalunderscore_",
-			[]string{
-				"withfinaldot.",
-				"withfinaldash-",
-				"withfinalunderscore_",
-			},
-		},
-	}
-
-	for _, data := range fixture {
-		actual := PossibleAtMentions(data.message)
-		require.ElementsMatch(t, actual, data.expected)
-	}
-}
-
-func TestTrimUsernameSpecialChar(t *testing.T) {
-	fixture := []struct {
-		word           string
-		expectedString string
-		expectedBool   bool
-	}{
-		{"user...", "user..", true},
-		{"user..", "user.", true},
-		{"user.", "user", true},
-		{"user--", "user-", true},
-		{"user-", "user", true},
-		{"user_.-", "user_.", true},
-		{"user_.", "user_", true},
-		{"user_", "user", true},
-		{"user", "user", false},
-		{"user.with-inner_chars", "user.with.inner.chars", false},
-	}
-
-	for _, data := range fixture {
-		actualString, actualBool := TrimUsernameSpecialChar(data.word)
-		require.Equal(t, actualBool, data.expectedBool)
-		if actualBool {
-			require.Equal(t, actualString, data.expectedString)
-		} else {
-			require.Equal(t, actualString, data.word)
-		}
-	}
-}

model/emoji.go

@@ -18,8 +18,6 @@ const (
 
 var EmojiPattern = regexp.MustCompile(`:[a-zA-Z0-9_+-]+:`)
 
-var ReverseSystemEmojisMap = makeReverseEmojiMap()
-
 type Emoji struct {
 	Id        string `json:"id"`
 	CreateAt  int64  `json:"create_at"`
@@ -51,8 +49,10 @@ func makeReverseEmojiMap() map[string][]string {
 	return reverseEmojiMap
 }
 
+var reverseSystemEmojisMap = makeReverseEmojiMap()
+
 func GetEmojiNameFromUnicode(unicode string) (emojiName string, count int) {
-	if emojiNames, found := ReverseSystemEmojisMap[unicode]; found {
+	if emojiNames, found := reverseSystemEmojisMap[unicode]; found {
 		return emojiNames[0], len(emojiNames)
 	}
 

model/post.go

@@ -69,8 +69,6 @@ const (
 	PostPropsGroupHighlightDisabled   = "disable_group_highlight"
 )
 
-var AtMentionPattern = regexp.MustCompile(`\B@`)
-
 type Post struct {
 	Id         string `json:"id"`
 	CreateAt   int64  `json:"create_at"`