Add displayName template function

Signed-off-by: Knut Ahlers <knut@ahlers.me>

functions_twitch.go

@@ -5,6 +5,15 @@ import (
 )
 
 func init() {
+	tplFuncs.Register("displayName", genericTemplateFunctionGetter(func(username string, v ...string) (string, error) {
+		displayName, err := twitch.GetDisplayNameForUser(strings.TrimLeft(username, "#"))
+		if err != nil && len(v) > 0 {
+			return v[0], nil
+		}
+
+		return displayName, err
+	}))
+
 	tplFuncs.Register("recentGame", genericTemplateFunctionGetter(func(username string, v ...string) (string, error) {
 		game, _, err := twitch.GetRecentStreamInfo(strings.TrimLeft(username, "#"))
 		if err != nil && len(v) > 0 {

twitch.go

@@ -48,6 +48,43 @@ func (t twitchClient) getAuthorizedUsername() (string, error) {
 	return payload.Data[0].Login, nil
 }
 
+func (t twitchClient) GetDisplayNameForUser(username string) (string, error) {
+	cacheKey := []string{"displayNameForUsername", username}
+	if d := t.apiCache.Get(cacheKey); d != nil {
+		return d.(string), nil
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), twitchRequestTimeout)
+	defer cancel()
+
+	var payload struct {
+		Data []struct {
+			ID          string `json:"id"`
+			DisplayName string `json:"display_name"`
+			Login       string `json:"login"`
+		} `json:"data"`
+	}
+
+	if err := t.request(
+		ctx,
+		http.MethodGet,
+		fmt.Sprintf("https://api.twitch.tv/helix/users?login=%s", username),
+		nil,
+		&payload,
+	); err != nil {
+		return "", errors.Wrap(err, "request channel info")
+	}
+
+	if l := len(payload.Data); l != 1 {
+		return "", errors.Errorf("unexpected number of users returned: %d", l)
+	}
+
+	// The DisplayName for an username will not change (often), cache for a decent time
+	t.apiCache.Set(cacheKey, time.Hour, payload.Data[0].DisplayName)
+
+	return payload.Data[0].DisplayName, nil
+}
+
 func (t twitchClient) GetFollowDate(from, to string) (time.Time, error) {
 	cacheKey := []string{"followDate", from, to}
 	if d := t.apiCache.Get(cacheKey); d != nil {

wiki/Home.md

@@ -106,6 +106,7 @@ Additionally there are some functions available in the templates:
 - `arg <idx>` - Takes the message sent to the channel, splits by space and returns the Nth element
 - `channelCounter <counter name>` - Wraps the counter name into a channel specific counter name including the channel name
 - `counterValue <counter name>` - Returns the current value of the counter which identifier was supplied
+- `displayName <username> [fallback]` - Returns the display name the specified user set for themselves
 - `fixUsername <username>` - Ensures the username no longer contains the `@` or `#` prefix
 - `followDate <from> <to>` - Looks up when `from` followed `to`
 - `group <idx>` - Gets matching group specified by index from `match_message` regular expression