feat: add X parent post article extraction and validation

src/lib/article.js

@@ -0,0 +1,37 @@
+"use strict";
+
+function normalizeWhitespace(text) {
+  return text.replace(/\s+/g, " ").trim();
+}
+
+function extractArticleFromParent(parentPost) {
+  if (!parentPost || typeof parentPost !== "object") {
+    return { ok: false, error: "parent_post_missing" };
+  }
+
+  const article = parentPost.article;
+  if (!article || typeof article.body !== "string") {
+    return { ok: false, error: "not_article" };
+  }
+
+  const rawBody = normalizeWhitespace(article.body);
+  if (!rawBody) {
+    return { ok: false, error: "empty_article" };
+  }
+
+  return {
+    ok: true,
+    article: {
+      xArticleId: article.id || null,
+      parentPostId: parentPost.id,
+      authorId: parentPost.authorId || null,
+      title: article.title || "Untitled",
+      content: rawBody,
+      charCount: rawBody.length,
+    },
+  };
+}
+
+module.exports = {
+  extractArticleFromParent,
+};

test/article.test.js

@@ -0,0 +1,40 @@
+"use strict";
+
+const test = require("node:test");
+const assert = require("node:assert/strict");
+const { extractArticleFromParent } = require("../src/lib/article");
+
+test("returns not_article when parent has no article payload", () => {
+  const result = extractArticleFromParent({ id: "p1", text: "hello" });
+  assert.equal(result.ok, false);
+  assert.equal(result.error, "not_article");
+});
+
+test("extracts article body and char count", () => {
+  const result = extractArticleFromParent({
+    id: "p1",
+    authorId: "author-1",
+    article: {
+      id: "art-1",
+      title: "My Article",
+      body: "  Hello   world\n\nfrom X article. ",
+    },
+  });
+
+  assert.equal(result.ok, true);
+  assert.equal(result.article.title, "My Article");
+  assert.equal(result.article.content, "Hello world from X article.");
+  assert.equal(result.article.charCount, "Hello world from X article.".length);
+});
+
+test("returns empty_article when body is blank", () => {
+  const result = extractArticleFromParent({
+    id: "p1",
+    article: {
+      body: "   \n\n\t",
+    },
+  });
+
+  assert.equal(result.ok, false);
+  assert.equal(result.error, "empty_article");
+});