Adding Tex Inline support for the issue #386

application/src/main/java/org/togetherjava/tjbot/commands/mathcommands/TeXCommand.java

@@ -21,6 +21,8 @@
 import java.io.IOException;
 import java.util.List;
 import java.util.Objects;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 /**
  * Implementation of a tex command which takes a string and renders an image corresponding to the
@@ -34,6 +36,11 @@
 public class TeXCommand extends SlashCommandAdapter {
 
     private static final String LATEX_OPTION = "latex";
+    // Matches regions between two dollars, like '$foo$'.
+    private static final String MATH_REGION = "(\\$[^$]+\\$)";
+    private static final String TEXT_REGION = "([^$]+)";
+    private static final Pattern INLINE_LATEX_REPLACEMENT =
+            Pattern.compile(MATH_REGION + "|" + TEXT_REGION);
     private static final String RENDERING_ERROR = "There was an error generating the image";
     private static final float DEFAULT_IMAGE_SIZE = 40F;
     private static final Color BACKGROUND_COLOR = Color.decode("#36393F");
@@ -44,8 +51,7 @@ public class TeXCommand extends SlashCommandAdapter {
      * Creates a new Instance.
      */
     public TeXCommand() {
-        super("tex",
-                "This command accepts a latex expression and generates an image corresponding to it.",
+        super("tex", "Renders LaTeX, also supports inline $-regions like 'see this $frac[x}{2}$'.",
                 SlashCommandVisibility.GUILD);
         getData().addOption(OptionType.STRING, LATEX_OPTION,
                 "The latex which is rendered as an image", true);
@@ -56,42 +62,102 @@ public void onSlashCommand(@NotNull final SlashCommandEvent event) {
         String latex = Objects.requireNonNull(event.getOption(LATEX_OPTION)).getAsString();
         String userID = (Objects.requireNonNull(event.getMember()).getId());
         TeXFormula formula;
+
         try {
+            if (latex.contains("$")) {
+                latex = convertInlineLatexToFull(latex);
+            }
             formula = new TeXFormula(latex);
         } catch (ParseException e) {
             event.reply("That is an invalid latex: " + e.getMessage()).setEphemeral(true).queue();
             return;
         }
+
         event.deferReply().queue();
-        Image image = formula.createBufferedImage(TeXConstants.STYLE_DISPLAY, DEFAULT_IMAGE_SIZE,
-                FOREGROUND_COLOR, BACKGROUND_COLOR);
-        if (image.getWidth(null) == -1 || image.getHeight(null) == -1) {
-            event.getHook().setEphemeral(true).editOriginal(RENDERING_ERROR).queue();
-            logger.warn(
-                    "Unable to render latex, image does not have an accessible width or height. Formula was {}",
-                    latex);
-            return;
-        }
-        BufferedImage renderedTextImage = new BufferedImage(image.getWidth(null),
-                image.getHeight(null), BufferedImage.TYPE_4BYTE_ABGR);
-        renderedTextImage.getGraphics().drawImage(image, 0, 0, null);
-        ByteArrayOutputStream renderedTextImageStream = new ByteArrayOutputStream();
 
         try {
-            ImageIO.write(renderedTextImage, "png", renderedTextImageStream);
+            Image image = renderImage(formula);
+            sendImage(event, userID, image);
         } catch (IOException e) {
-            event.getHook().setEphemeral(true).editOriginal(RENDERING_ERROR).queue();
+            event.getHook().editOriginal(RENDERING_ERROR).queue();
             logger.warn(
                     "Unable to render latex, could not convert the image into an attachable form. Formula was {}",
                     latex, e);
-            return;
+
+        } catch (IllegalStateException e) {
+            event.getHook().editOriginal(RENDERING_ERROR).queue();
+
+            logger.warn(
+                    "Unable to render latex, image does not have an accessible width or height. Formula was {}",
+                    latex, e);
+        }
+    }
+
+    private @NotNull Image renderImage(@NotNull TeXFormula formula) {
+        Image image = formula.createBufferedImage(TeXConstants.STYLE_DISPLAY, DEFAULT_IMAGE_SIZE,
+                FOREGROUND_COLOR, BACKGROUND_COLOR);
+
+        if (image.getWidth(null) == -1 || image.getHeight(null) == -1) {
+            throw new IllegalStateException("Image has no height or width");
         }
+        return image;
+    }
+
+    private void sendImage(@NotNull SlashCommandEvent event, @NotNull String userID,
+            @NotNull Image image) throws IOException {
+
+        ByteArrayOutputStream renderedTextImageStream = getRenderedTextImageStream(image);
         event.getHook()
             .editOriginal(renderedTextImageStream.toByteArray(), "tex.png")
             .setActionRow(Button.of(ButtonStyle.DANGER, generateComponentId(userID), "Delete"))
             .queue();
     }
 
+    @NotNull
+    private ByteArrayOutputStream getRenderedTextImageStream(@NotNull Image image)
+            throws IOException {
+
+        BufferedImage renderedTextImage = new BufferedImage(image.getWidth(null),
+                image.getHeight(null), BufferedImage.TYPE_4BYTE_ABGR);
+
+        renderedTextImage.getGraphics().drawImage(image, 0, 0, null);
+        ByteArrayOutputStream renderedTextImageStream = new ByteArrayOutputStream();
+
+        ImageIO.write(renderedTextImage, "png", renderedTextImageStream);
+
+        return renderedTextImageStream;
+    }
+
+    /**
+     * Converts inline latex like: {@code hello $\frac{x}{2}$ world} to full latex
+     * {@code \text{hello}\frac{x}{2}\text{ world}}.
+     */
+    @NotNull
+    private String convertInlineLatexToFull(@NotNull String latex) {
+        if (isInvalidInlineFormat(latex)) {
+            throw new ParseException(
+                    "The amount of $-symbols must be divisible by two. Did you forget to close an expression? ");
+        }
+
+        Matcher matcher = INLINE_LATEX_REPLACEMENT.matcher(latex);
+        StringBuilder sb = new StringBuilder();
+
+        while (matcher.find()) {
+            boolean isInsideMathRegion = matcher.group(1) != null;
+            if (isInsideMathRegion) {
+                sb.append(matcher.group(1).replace("$", ""));
+            } else {
+                sb.append("\\text{").append(matcher.group(2)).append("}");
+            }
+        }
+
+        return sb.toString();
+    }
+
+    private boolean isInvalidInlineFormat(String latex) {
+        return latex.chars().filter(ch -> ch == '$').count() % 2 == 1;
+    }
+
     @Override
     public void onButtonClick(@NotNull final ButtonClickEvent event,
             @NotNull final List<String> args) {