refactor: decompose backend services and routes for maintainability

backend/src/db/path-utils.ts

@@ -0,0 +1,48 @@
+import { accessSync, constants, existsSync, mkdirSync } from "node:fs";
+import { resolve } from "node:path";
+
+/**
+ * Get the data directory path.
+ *
+ * Resolution order:
+ * 1. DATA_DIR env var (set by docker-compose for containers)
+ * 2. Monorepo detection: if ../docker-compose.yml exists, we're in backend/
+ *    subdirectory -> use ../data (project root's data folder)
+ * 3. Fallback: resolve(cwd, "data") (running from project root or standalone)
+ */
+export function getDataDir(cwd: string = process.cwd()): string {
+	if (process.env.DATA_DIR) return resolve(process.env.DATA_DIR);
+
+	if (existsSync(resolve(cwd, "..", "docker-compose.yml"))) {
+		return resolve(cwd, "..", "data");
+	}
+
+	return resolve(cwd, "data");
+}
+
+/** Build the database URL from a path */
+export function buildDbUrl(dbPath: string): string {
+	return `file:${dbPath}`;
+}
+
+/** Get data directory and database path */
+export function getDbPaths(cwd: string = process.cwd()): { dataDir: string; dbPath: string; url: string } {
+	const dataDir = getDataDir(cwd);
+	const dbPath = resolve(dataDir, "medassist-ng.db");
+	const url = buildDbUrl(dbPath);
+	return { dataDir, dbPath, url };
+}
+
+/** Ensure data directory exists and is writable */
+export function ensureDataDirectory(dataDir: string): { success: boolean; error?: string } {
+	try {
+		if (!existsSync(dataDir)) {
+			mkdirSync(dataDir, { recursive: true });
+		}
+
+		accessSync(dataDir, constants.W_OK);
+		return { success: true };
+	} catch (err: unknown) {
+		return { success: false, error: (err as Error).message };
+	}
+}