feat(task-013): add draft assembly API, immutable versioning, and editor preview

apps/frontend/src/features/article-draft/model.ts

@@ -0,0 +1,170 @@
+import type { DraftFaqItem, DraftSummary } from "@pipeline/shared";
+
+export type DraftPreviewBlock =
+  | { type: "heading"; level: number; text: string }
+  | { type: "paragraph"; text: string; links: DraftPreviewLink[] }
+  | { type: "table"; headers: string[]; rows: string[][] }
+  | { type: "image"; alt: string; src: string }
+  | { type: "faq"; items: DraftFaqItem[] };
+
+export type DraftPreviewLink = {
+  label: string;
+  href: string;
+};
+
+export type DraftVersionComparison = {
+  leftVersion: number;
+  rightVersion: number;
+  titleChanged: boolean;
+  metaTitleChanged: boolean;
+  metaDescriptionChanged: boolean;
+  bodyChanged: boolean;
+  changedLineCount: number;
+};
+
+export function selectDraftById(
+  drafts: readonly DraftSummary[],
+  draftId: string | null,
+): DraftSummary | null {
+  if (!draftId) {
+    return drafts[0] ?? null;
+  }
+  return drafts.find((draft) => draft.id === draftId) ?? null;
+}
+
+export function compareDraftVersions(
+  left: DraftSummary,
+  right: DraftSummary,
+): DraftVersionComparison {
+  const leftBodyMarkdown = left.body_markdown ?? "";
+  const rightBodyMarkdown = right.body_markdown ?? "";
+  const leftLines = normalizedLines(leftBodyMarkdown);
+  const rightLines = normalizedLines(rightBodyMarkdown);
+  return {
+    leftVersion: left.version,
+    rightVersion: right.version,
+    titleChanged: left.title !== right.title,
+    metaTitleChanged: (left.meta_title ?? "") !== (right.meta_title ?? ""),
+    metaDescriptionChanged:
+      (left.meta_description ?? "") !== (right.meta_description ?? ""),
+    bodyChanged: leftBodyMarkdown !== rightBodyMarkdown,
+    changedLineCount: changedLineCount(leftLines, rightLines),
+  };
+}
+
+export function parseDraftPreview(
+  markdown: string,
+  faqItems: readonly DraftFaqItem[],
+): DraftPreviewBlock[] {
+  const lines = markdown.split(/\r?\n/);
+  const blocks: DraftPreviewBlock[] = [];
+  let index = 0;
+
+  while (index < lines.length) {
+    const line = lines[index].trim();
+    if (!line) {
+      index += 1;
+      continue;
+    }
+
+    if (line.startsWith("#")) {
+      const match = line.match(/^(#{1,6})\s+(.+)$/);
+      if (match) {
+        blocks.push({
+          type: "heading",
+          level: match[1].length,
+          text: match[2].trim(),
+        });
+        index += 1;
+        continue;
+      }
+    }
+
+    if (line.startsWith("![") && line.includes("](") && line.endsWith(")")) {
+      const match = line.match(/^!\[([^\]]*)\]\(([^)]+)\)$/);
+      if (match) {
+        blocks.push({
+          type: "image",
+          alt: match[1],
+          src: match[2],
+        });
+        index += 1;
+        continue;
+      }
+    }
+
+    if (line.startsWith("|") && index + 1 < lines.length && lines[index + 1].includes("|")) {
+      const tableLines: string[] = [];
+      while (index < lines.length && lines[index].trim().startsWith("|")) {
+        tableLines.push(lines[index].trim());
+        index += 1;
+      }
+      if (tableLines.length >= 2) {
+        const headers = parseTableRow(tableLines[0]);
+        const rows = tableLines.slice(2).map(parseTableRow);
+        blocks.push({
+          type: "table",
+          headers,
+          rows,
+        });
+      }
+      continue;
+    }
+
+    const paragraphLines: string[] = [];
+    while (index < lines.length && lines[index].trim()) {
+      paragraphLines.push(lines[index].trim());
+      index += 1;
+    }
+    const paragraphText = paragraphLines.join(" ");
+    blocks.push({
+      type: "paragraph",
+      text: paragraphText,
+      links: extractLinks(paragraphText),
+    });
+  }
+
+  if (faqItems.length > 0) {
+    blocks.push({
+      type: "faq",
+      items: [...faqItems],
+    });
+  }
+  return blocks;
+}
+
+function normalizedLines(value: string): string[] {
+  return value
+    .split(/\r?\n/)
+    .map((line) => line.trim())
+    .filter(Boolean);
+}
+
+function changedLineCount(left: string[], right: string[]): number {
+  const limit = Math.max(left.length, right.length);
+  let changes = 0;
+  for (let index = 0; index < limit; index += 1) {
+    if ((left[index] ?? "") !== (right[index] ?? "")) {
+      changes += 1;
+    }
+  }
+  return changes;
+}
+
+function parseTableRow(row: string): string[] {
+  return row
+    .slice(1, row.endsWith("|") ? -1 : row.length)
+    .split("|")
+    .map((cell) => cell.trim());
+}
+
+function extractLinks(text: string): DraftPreviewLink[] {
+  const links: DraftPreviewLink[] = [];
+  const pattern = /\[([^\]]+)\]\(([^)]+)\)/g;
+  let match: RegExpExecArray | null = pattern.exec(text);
+  while (match) {
+    links.push({ label: match[1], href: match[2] });
+    match = pattern.exec(text);
+  }
+  return links;
+}