[templating] Add userExists function

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

docs/content/configuration/actors.md

@@ -523,7 +523,7 @@ Send raw IRC message
 
 ## Send Whisper
 
-Send a whisper (requires a verified bot!)
+Send a whisper
 
 ```yaml
 - type: whisper

docs/content/configuration/templating.md

@@ -467,7 +467,7 @@ Example:
 
 ```
 # Your int this hour: {{ printf "%.0f" (mulf (seededRandom (list "int" .username (now | date "2006-01-02 15") | join ":")) 100) }}%
-< Your int this hour: 88%
+< Your int this hour: 72%
 ```
 
 ### `spotifyCurrentPlaying`
@@ -567,6 +567,19 @@ Example:
 * Weather for Hamburg, DE: Few clouds with a temperature of 22 C (71.6 F). [...]
 ```
 
+### `userExists`
+
+Checks whether the given user exists
+
+Syntax: `userExists <username>`
+
+Example:
+
+```
+# {{ userExists "luziferus" }}
+* true
+```
+
 ### `usernameForID`
 
 Returns the current login name of an user-id

internal/template/twitch/user.go

@@ -14,6 +14,7 @@ func init() {
 		tplTwitchDisplayName,
 		tplTwitchIDForUsername,
 		tplTwitchProfileImage,
+		tplTwitchUserExists,
 		tplTwitchUsernameForID,
 	)
 }
@@ -68,6 +69,25 @@ func tplTwitchProfileImage(args plugins.RegistrationArguments) {
 	})
 }
 
+func tplTwitchUserExists(args plugins.RegistrationArguments) {
+	args.RegisterTemplateFunction("userExists", plugins.GenericTemplateFunctionGetter(func(username string) bool {
+		user, err := args.GetTwitchClient().GetUserInformation(context.Background(), strings.TrimLeft(username, "#@"))
+		if err != nil {
+			// Well, they probably don't exist
+			return false
+		}
+
+		return strings.EqualFold(username, user.Login)
+	}), plugins.TemplateFuncDocumentation{
+		Description: "Checks whether the given user exists",
+		Syntax:      "userExists <username>",
+		Example: &plugins.TemplateFuncDocumentationExample{
+			Template:    `{{ userExists "luziferus" }}`,
+			FakedOutput: "true",
+		},
+	})
+}
+
 func tplTwitchUsernameForID(args plugins.RegistrationArguments) {
 	args.RegisterTemplateFunction("usernameForID", plugins.GenericTemplateFunctionGetter(func(id string) (string, error) {
 		username, err := args.GetTwitchClient().GetUsernameForID(context.Background(), id)