1 files changed, 84 insertions, 0 deletions

diff --git a/src/main/java/org/pacien/pandoc/filter/plantuml/Filter.java b/src/main/java/org/pacien/pandoc/filter/plantuml/Filter.java
new file mode 100644
index 0000000..66abc2d
--- /dev/null
+++ b/src/main/java/org/pacien/pandoc/filter/plantuml/Filter.java
@@ -0,0 +1,84 @@
+package org.pacien.pandoc.filter.plantuml;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.ArrayNode;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import com.fasterxml.jackson.databind.node.TextNode;
+import net.sourceforge.plantuml.FileFormat;
+import net.sourceforge.plantuml.FileFormatOption;
+import net.sourceforge.plantuml.SourceStringReader;
+
+import java.io.*;
+import java.util.Iterator;
+import java.util.stream.Collectors;
+
+final public class Filter {
+
+  private static final String BEGIN_TAG = "\\begin{tikzpicture}[yscale=-1]";
+  private static final String LINE_SEP = "\n";
+  private static final String TYPE_KEY = "t";
+  private static final String CONTENT_KEY = "c";
+  private static final String CODE_BLOCK_TYPE = "CodeBlock";
+  private static final String RAW_BLOCK_TYPE = "RawBlock";
+  private static final String PLANTUML_TYPE = "puml";
+  private static final String LATEX_TYPE = "latex";
+  private static final int META_INDEX = 0;
+  private static final int META_PROP_INDEX = 1;
+  private static final int META_PROP_TYPE_INDEX = 0;
+  private static final int CONTENT_INDEX = 1;
+
+  private static String plantumlToLatex(String puml) throws IOException {
+    try (ByteArrayOutputStream s = new ByteArrayOutputStream()) {
+      new SourceStringReader(puml).generateImage(s, new FileFormatOption(FileFormat.LATEX_NO_PREAMBLE));
+      try (BufferedReader r = new BufferedReader(new InputStreamReader(new ByteArrayInputStream(s.toByteArray())))) {
+        return BEGIN_TAG + LINE_SEP + r.lines().filter(l -> !l.equals(BEGIN_TAG)).collect(Collectors.joining(LINE_SEP));
+      }
+    }
+  }
+
+  private static void renderPlantumlNode(ObjectNode n) throws IOException {
+    String puml = n.get(CONTENT_KEY).get(CONTENT_INDEX).asText();
+    String tikz = plantumlToLatex(puml);
+
+    n.set(TYPE_KEY, TextNode.valueOf(RAW_BLOCK_TYPE));
+    ((ArrayNode) n.get(CONTENT_KEY)).removeAll()
+    .add(TextNode.valueOf(LATEX_TYPE))
+    .add(TextNode.valueOf(tikz));
+  }
+
+  private static boolean isPlantumlNode(JsonNode n) {
+    return n.path(TYPE_KEY).asText().equals(CODE_BLOCK_TYPE) &&
+           n.path(CONTENT_KEY).path(META_INDEX).path(META_PROP_INDEX).path(META_PROP_TYPE_INDEX).asText().equals(PLANTUML_TYPE);
+  }
+
+  private static void walk(JsonNode n) throws IOException {
+    if (isPlantumlNode(n))
+      renderPlantumlNode((ObjectNode) n);
+    else if (n.isContainerNode())
+      for (Iterator<JsonNode> i = n.elements(); i.hasNext(); ) walk(i.next());
+  }
+
+  public static void filter(InputStream i, OutputStream o) throws IOException {
+    ObjectMapper m = new ObjectMapper();
+    JsonNode t = m.readTree(i);
+    if (t != null) {
+      walk(t);
+      m.writeValue(o, t);
+    }
+  }
+
+  public static void main(String args[]) {
+    try {
+      filter(System.in, System.out);
+    } catch (IOException e) {
+      e.printStackTrace();
+      System.exit(1);
+    }
+  }
+
+  private Filter() {
+    // static class
+  }
+
+}