feat: polish issue thread markdown and references

ui/src/lib/remark-soft-breaks.ts

@@ -0,0 +1,63 @@
+type MarkdownNode = {
+  type?: unknown;
+  value?: unknown;
+  children?: unknown;
+};
+
+type MarkdownTextNode = {
+  type: "text";
+  value: string;
+};
+
+type MarkdownBreakNode = {
+  type: "break";
+};
+
+type MarkdownParentNode = {
+  children: MarkdownTreeNode[];
+};
+
+type MarkdownTreeNode = MarkdownTextNode | MarkdownBreakNode | (MarkdownNode & { children?: MarkdownTreeNode[] });
+
+function isParentNode(value: unknown): value is MarkdownParentNode {
+  return typeof value === "object" && value !== null && Array.isArray((value as MarkdownNode).children);
+}
+
+function buildSoftBreakReplacement(value: string): Array<MarkdownTextNode | MarkdownBreakNode> {
+  const parts = value.split("\n");
+  const replacement: Array<MarkdownTextNode | MarkdownBreakNode> = [];
+
+  for (let index = 0; index < parts.length; index += 1) {
+    const part = parts[index];
+    if (part.length > 0) {
+      replacement.push({ type: "text", value: part });
+    }
+    if (index < parts.length - 1) {
+      replacement.push({ type: "break" });
+    }
+  }
+
+  return replacement.length > 0 ? replacement : [{ type: "text", value: "" }];
+}
+
+function transformNode(node: MarkdownTreeNode) {
+  if (!isParentNode(node)) return;
+
+  for (let index = 0; index < node.children.length; index += 1) {
+    const child = node.children[index];
+    if (child?.type === "text" && typeof child.value === "string" && child.value.includes("\n")) {
+      const replacement = buildSoftBreakReplacement(child.value);
+      node.children.splice(index, 1, ...replacement);
+      index += replacement.length - 1;
+      continue;
+    }
+
+    transformNode(child);
+  }
+}
+
+export function remarkSoftBreaks() {
+  return (tree: MarkdownTreeNode) => {
+    transformNode(tree);
+  };
+}