feat: add X parent post article extraction and validation

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");
+});