1 files changed, 57 insertions, 0 deletions
diff --git a/doc-tool/src/dotty/tools/dottydoc/model/comment/MarkdownShortener.scala b/doc-tool/src/dotty/tools/dottydoc/model/comment/MarkdownShortener.scala
new file mode 100644
index 000000000..841232e52
--- /dev/null
+++ b/doc-tool/src/dotty/tools/dottydoc/model/comment/MarkdownShortener.scala
@@ -0,0 +1,57 @@
+package dotty.tools
+package dottydoc
+package model
+package comment
+
+/** The `MarkdownShortener` takes a node and *mutates* it and all children so
+  * that the displayed length of the generated HTML doesn't exceeed `maxLen`.
+  * This number defaults to 150 characters.
+  *
+  * @note calling `shorten` **will** mutate the Markdown AST node.
+  */
+class MarkdownShortener {
+  import com.vladsch.flexmark.ast._
+
+  def shorten(node: Node, maxLen: Int = 150): Node = {
+    var len = 0
+
+    def count(node: Node, length: => Int, shortenOrUnlink: Int => Unit) = {
+      val remaining = math.max(maxLen - len, 0)
+      if (remaining == 0) node.unlink()
+      else {
+        if (length <= remaining) len += length
+        else {
+          shortenOrUnlink(remaining)
+          len = maxLen
+        }
+      }
+    }
+
+    val nodeVisitor = new NodeVisitor(
+      new VisitHandler(classOf[Text], new Visitor[Text] {
+        override def visit(node: Text) = count(
+          node,
+          node.getChars.length,
+          remaining => node.setChars(
+            node.getChars.subSequence(0, remaining).trimEnd.append("...")
+          )
+        )
+      }),
+      new VisitHandler(classOf[Code], new Visitor[Code] {
+        override def visit(node: Code) = count(
+          node,
+          node.getText.length,
+          remaining => node.setText(
+            node.getText.subSequence(0, remaining).trimEnd.append("...")
+          )
+        )
+      }),
+      new VisitHandler(classOf[Image], new Visitor[Image] {
+        override def visit(node: Image) = count(node, maxLen, _ => node.unlink())
+      })
+    )
+
+    nodeVisitor.visit(node)
+    node
+  }
+}