feat(mystery): save layer — round-trip, schema versioning, transcript cap

src/engine/save.test.ts

@@ -0,0 +1,87 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { saveState, loadState, clearSave, SAVE_KEY } from './save'
+import type { GameState, TranscriptLine } from './types'
+import { SCHEMA_VERSION, TRANSCRIPT_CAP } from './types'
+
+const baseState = (overrides: Partial<GameState> = {}): GameState => ({
+  schemaVersion: SCHEMA_VERSION,
+  location: 'foyer',
+  inventory: [],
+  roomState: {},
+  flags: {},
+  resolveLevel: 'steady',
+  encounterState: {},
+  lastNoun: null,
+  pendingDisambiguation: null,
+  transcript: [],
+  theme: 'amber',
+  endedWith: null,
+  ...overrides,
+})
+
+describe('save — round trip', () => {
+  let store: Record<string, string>
+
+  beforeEach(() => {
+    store = {}
+    vi.stubGlobal('localStorage', {
+      getItem: (k: string) => (k in store ? store[k]! : null),
+      setItem: (k: string, v: string) => { store[k] = v },
+      removeItem: (k: string) => { delete store[k] },
+    })
+  })
+
+  it('round-trips an identical state', () => {
+    const s = baseState({ location: 'cellar', flags: { gateOpened: true } })
+    saveState(s)
+    expect(loadState()).toEqual(s)
+  })
+
+  it('returns null when nothing is saved', () => {
+    expect(loadState()).toBeNull()
+  })
+
+  it('returns null and clears the slot on schema mismatch', () => {
+    store[SAVE_KEY] = JSON.stringify({ ...baseState(), schemaVersion: SCHEMA_VERSION + 99 })
+    expect(loadState()).toBeNull()
+    expect(store[SAVE_KEY]).toBeUndefined()
+  })
+
+  it('returns null and clears the slot on malformed JSON', () => {
+    store[SAVE_KEY] = 'not-json'
+    expect(loadState()).toBeNull()
+    expect(store[SAVE_KEY]).toBeUndefined()
+  })
+
+  it('truncates transcript to TRANSCRIPT_CAP on save', () => {
+    const long: TranscriptLine[] = Array.from({ length: TRANSCRIPT_CAP + 50 }, (_, i) => ({
+      kind: 'narration',
+      text: `line ${i}`,
+    }))
+    saveState(baseState({ transcript: long }))
+    const loaded = loadState()
+    expect(loaded?.transcript).toHaveLength(TRANSCRIPT_CAP)
+    // Keeps the most recent lines (the tail).
+    expect(loaded?.transcript[0]?.text).toBe(`line ${50}`)
+    expect(loaded?.transcript[TRANSCRIPT_CAP - 1]?.text).toBe(`line ${TRANSCRIPT_CAP + 49}`)
+  })
+})
+
+describe('save — clear', () => {
+  let store: Record<string, string>
+
+  beforeEach(() => {
+    store = { [SAVE_KEY]: JSON.stringify(baseState()) }
+    vi.stubGlobal('localStorage', {
+      getItem: (k: string) => (k in store ? store[k]! : null),
+      setItem: (k: string, v: string) => { store[k] = v },
+      removeItem: (k: string) => { delete store[k] },
+    })
+  })
+
+  it('removes the save slot', () => {
+    clearSave()
+    expect(store[SAVE_KEY]).toBeUndefined()
+    expect(loadState()).toBeNull()
+  })
+})