Use "!" syntax when image URL does not end with file extension

Author: mangstadt

src/main/java/oakbot/command/ReactGiphyCommand.java

@@ -58,22 +58,16 @@ public ChatActions onMessage(ChatCommand chatCommand, IBot bot) {
 				return reply("404 human emotion not found.", chatCommand);
 			}
 
-			/*
-			 * URL must end in a file extension in order for chat to display the
-			 * image.
-			 */
-			if (!imageUrl.endsWith(".gif")) {
-				imageUrl += "&a=.gif";
-			}
-
 			//@formatter:off
 			var condensedMessage = new ChatBuilder()
 				.append("Reaction: ")
 				.link(content, imageUrl)
 				.append(" (powered by ").link("GIPHY", "https://giphy.com").append(")");
 
 			return ChatActions.create(
-				new PostMessage(imageUrl).bypassFilters(true).condensedMessage(condensedMessage)
+				new PostMessage(new ChatBuilder().image(imageUrl))
+					.bypassFilters(true)
+					.condensedMessage(condensedMessage)
 			);
 			//@formatter:on
 		} catch (Exception e) {

src/main/java/oakbot/util/ChatBuilder.java

@@ -57,6 +57,23 @@ public ChatBuilder fixedWidth() {
 		return this;
 	}
 
+	/**
+	 * <p>
+	 * Inserts an image into the message using explicit syntax. Note that images
+	 * and text cannot be mixed.
+	 * </p>
+	 * <p>
+	 * This method must be used if the image URL does not end with the file
+	 * extension of a supported image format (e.g. ".jpg", ".gif"). If the URL
+	 * ends with such as extension, then this syntax is not necessary.
+	 * </p>
+	 * @param url the image URL
+	 * @return this
+	 */
+	public ChatBuilder image(CharSequence url) {
+		return append('!').append(url);
+	}
+
 	/**
 	 * Appends the character sequence for "blockquote". This must go at the
 	 * beginning of the string.