Add guarded dev restart handling

Co-Authored-By: Paperclip <noreply@paperclip.ing>

server/src/dev-server-status.ts

@@ -0,0 +1,103 @@
+import { existsSync, readFileSync } from "node:fs";
+
+export type PersistedDevServerStatus = {
+  dirty: boolean;
+  lastChangedAt: string | null;
+  changedPathCount: number;
+  changedPathsSample: string[];
+  pendingMigrations: string[];
+  lastRestartAt: string | null;
+};
+
+export type DevServerHealthStatus = {
+  enabled: true;
+  restartRequired: boolean;
+  reason: "backend_changes" | "pending_migrations" | "backend_changes_and_pending_migrations" | null;
+  lastChangedAt: string | null;
+  changedPathCount: number;
+  changedPathsSample: string[];
+  pendingMigrations: string[];
+  autoRestartEnabled: boolean;
+  activeRunCount: number;
+  waitingForIdle: boolean;
+  lastRestartAt: string | null;
+};
+
+function normalizeStringArray(value: unknown): string[] {
+  if (!Array.isArray(value)) return [];
+  return value
+    .filter((entry): entry is string => typeof entry === "string")
+    .map((entry) => entry.trim())
+    .filter((entry) => entry.length > 0);
+}
+
+function normalizeTimestamp(value: unknown): string | null {
+  if (typeof value !== "string") return null;
+  const trimmed = value.trim();
+  return trimmed.length > 0 ? trimmed : null;
+}
+
+export function readPersistedDevServerStatus(
+  env: NodeJS.ProcessEnv = process.env,
+): PersistedDevServerStatus | null {
+  const filePath = env.PAPERCLIP_DEV_SERVER_STATUS_FILE?.trim();
+  if (!filePath || !existsSync(filePath)) return null;
+
+  try {
+    const raw = JSON.parse(readFileSync(filePath, "utf8")) as Record<string, unknown>;
+    const changedPathsSample = normalizeStringArray(raw.changedPathsSample).slice(0, 5);
+    const pendingMigrations = normalizeStringArray(raw.pendingMigrations);
+    const changedPathCountRaw = raw.changedPathCount;
+    const changedPathCount =
+      typeof changedPathCountRaw === "number" && Number.isFinite(changedPathCountRaw)
+        ? Math.max(0, Math.trunc(changedPathCountRaw))
+        : changedPathsSample.length;
+    const dirtyRaw = raw.dirty;
+    const dirty =
+      typeof dirtyRaw === "boolean"
+        ? dirtyRaw
+        : changedPathCount > 0 || pendingMigrations.length > 0;
+
+    return {
+      dirty,
+      lastChangedAt: normalizeTimestamp(raw.lastChangedAt),
+      changedPathCount,
+      changedPathsSample,
+      pendingMigrations,
+      lastRestartAt: normalizeTimestamp(raw.lastRestartAt),
+    };
+  } catch {
+    return null;
+  }
+}
+
+export function toDevServerHealthStatus(
+  persisted: PersistedDevServerStatus,
+  opts: { autoRestartEnabled: boolean; activeRunCount: number },
+): DevServerHealthStatus {
+  const hasPathChanges = persisted.changedPathCount > 0;
+  const hasPendingMigrations = persisted.pendingMigrations.length > 0;
+  const reason =
+    hasPathChanges && hasPendingMigrations
+      ? "backend_changes_and_pending_migrations"
+      : hasPendingMigrations
+        ? "pending_migrations"
+        : hasPathChanges
+          ? "backend_changes"
+          : null;
+  const restartRequired = persisted.dirty || reason !== null;
+
+  return {
+    enabled: true,
+    restartRequired,
+    reason,
+    lastChangedAt: persisted.lastChangedAt,
+    changedPathCount: persisted.changedPathCount,
+    changedPathsSample: persisted.changedPathsSample,
+    pendingMigrations: persisted.pendingMigrations,
+    autoRestartEnabled: opts.autoRestartEnabled,
+    activeRunCount: opts.activeRunCount,
+    waitingForIdle: restartRequired && opts.autoRestartEnabled && opts.activeRunCount > 0,
+    lastRestartAt: persisted.lastRestartAt,
+  };
+}