test: define housekeeping migration inventory

src/features/housekeeping/migration/discover-legacy-pages.ts

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+import { readdirSync } from "node:fs";
+import { join, relative } from "node:path";
+import type { LegacyPage, LegacySurface } from "./types";
+
+const pageFileName = "page.tsx";
+
+function toLegacyPath(
+	surface: LegacySurface,
+	segments: readonly string[],
+): string {
+	const routeSegments = segments
+		.filter((segment) => !(segment.startsWith("(") && segment.endsWith(")")))
+		.map((segment) =>
+			segment.replace(/^\[\.\.\.(.+)\]$/, ":$1*").replace(/^\[(.+)\]$/, ":$1"),
+		);
+
+	return `/${[surface, ...routeSegments].join("/")}`;
+}
+
+function discoverSurface(
+	rootDir: string,
+	surface: LegacySurface,
+): LegacyPage[] {
+	const surfaceDirectory = join(rootDir, "src", "app", surface);
+	const pages: LegacyPage[] = [];
+
+	function walk(directory: string): void {
+		for (const entry of readdirSync(directory, { withFileTypes: true })) {
+			const entryPath = join(directory, entry.name);
+
+			if (entry.isDirectory()) {
+				walk(entryPath);
+				continue;
+			}
+
+			if (!entry.isFile() || entry.name !== pageFileName) continue;
+
+			const sourceFile = relative(rootDir, entryPath).replaceAll("\\", "/");
+			const routeSegments = relative(surfaceDirectory, directory)
+				.split(/[/\\]/)
+				.filter(Boolean);
+			pages.push({
+				surface,
+				legacyPath: toLegacyPath(surface, routeSegments),
+				sourceFile,
+			});
+		}
+	}
+
+	walk(surfaceDirectory);
+	return pages;
+}
+
+export function discoverLegacyPages(rootDir = process.cwd()): LegacyPage[] {
+	return (["admin", "mod"] as const)
+		.flatMap((surface) => discoverSurface(rootDir, surface))
+		.sort((a, b) =>
+			`${a.surface}:${a.legacyPath}:${a.sourceFile}`.localeCompare(
+				`${b.surface}:${b.legacyPath}:${b.sourceFile}`,
+			),
+		);
+}
+
+export function ownedLegacyPages(
+	prefixes: readonly string[],
+	pages: readonly LegacyPage[] = discoverLegacyPages(),
+): LegacyPage[] {
+	return pages.filter((page) =>
+		prefixes.some(
+			(prefix) =>
+				page.legacyPath === prefix || page.legacyPath.startsWith(`${prefix}/`),
+		),
+	);
+}