refactor: extract useAppNavigation hook from App.tsx — reduce god component churn (#194)

Co-authored-by: Test <test@test.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/hooks/useAppNavigation.test.ts

@@ -0,0 +1,134 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { renderHook, act } from '@testing-library/react'
+import { useAppNavigation } from './useAppNavigation'
+import type { VaultEntry } from '../types'
+
+function makeEntry(path: string): VaultEntry {
+  return { path, filename: path.split('/').pop()!, title: path, isA: null, aliases: [] } as VaultEntry
+}
+
+function makeTab(entry: VaultEntry) {
+  return { entry, content: '' }
+}
+
+describe('useAppNavigation', () => {
+  let onSelectNote: ReturnType<typeof vi.fn>
+  let onSwitchTab: ReturnType<typeof vi.fn>
+
+  beforeEach(() => {
+    onSelectNote = vi.fn()
+    onSwitchTab = vi.fn()
+  })
+
+  function renderNav(overrides: {
+    entries?: VaultEntry[]
+    tabs?: Array<{ entry: VaultEntry; content: string }>
+    activeTabPath?: string | null
+  } = {}) {
+    const entries = overrides.entries ?? [makeEntry('/a.md'), makeEntry('/b.md'), makeEntry('/c.md')]
+    const tabs = overrides.tabs ?? []
+    const activeTabPath = overrides.activeTabPath ?? null
+    return renderHook(() =>
+      useAppNavigation({ entries, tabs, activeTabPath, onSelectNote, onSwitchTab }),
+    )
+  }
+
+  // --- entriesByPath ---
+
+  describe('entriesByPath', () => {
+    it('builds a Map from entries for O(1) lookup', () => {
+      const entries = [makeEntry('/a.md'), makeEntry('/b.md')]
+      const { result } = renderNav({ entries })
+      expect(result.current.entriesByPath.get('/a.md')).toBe(entries[0])
+      expect(result.current.entriesByPath.get('/b.md')).toBe(entries[1])
+      expect(result.current.entriesByPath.get('/missing.md')).toBeUndefined()
+    })
+  })
+
+  // --- canGoBack / canGoForward initial state ---
+
+  describe('initial state', () => {
+    it('starts with canGoBack=false and canGoForward=false', () => {
+      const { result } = renderNav()
+      expect(result.current.canGoBack).toBe(false)
+      expect(result.current.canGoForward).toBe(false)
+    })
+  })
+
+  // --- navigation history integration ---
+
+  describe('navigation via activeTabPath changes', () => {
+    it('pushes to history when activeTabPath changes, enabling goBack', () => {
+      const entries = [makeEntry('/a.md'), makeEntry('/b.md')]
+      const tabA = makeTab(entries[0])
+      const tabB = makeTab(entries[1])
+
+      const { result, rerender } = renderHook(
+        ({ activeTabPath, tabs }) =>
+          useAppNavigation({ entries, tabs, activeTabPath, onSelectNote, onSwitchTab }),
+        { initialProps: { activeTabPath: '/a.md' as string | null, tabs: [tabA] } },
+      )
+
+      // Navigate to /b.md
+      rerender({ activeTabPath: '/b.md', tabs: [tabA, tabB] })
+
+      expect(result.current.canGoBack).toBe(true)
+      expect(result.current.canGoForward).toBe(false)
+    })
+
+    it('handleGoBack switches to the tab if it is open', () => {
+      const entries = [makeEntry('/a.md'), makeEntry('/b.md')]
+      const tabA = makeTab(entries[0])
+      const tabB = makeTab(entries[1])
+
+      const { result, rerender } = renderHook(
+        ({ activeTabPath, tabs }) =>
+          useAppNavigation({ entries, tabs, activeTabPath, onSelectNote, onSwitchTab }),
+        { initialProps: { activeTabPath: '/a.md' as string | null, tabs: [tabA, tabB] } },
+      )
+
+      rerender({ activeTabPath: '/b.md', tabs: [tabA, tabB] })
+
+      act(() => { result.current.handleGoBack() })
+
+      expect(onSwitchTab).toHaveBeenCalledWith('/a.md')
+    })
+
+    it('handleGoBack opens entry via onSelectNote if not in tabs', () => {
+      const entries = [makeEntry('/a.md'), makeEntry('/b.md')]
+      const tabB = makeTab(entries[1])
+
+      const { result, rerender } = renderHook(
+        ({ activeTabPath, tabs }) =>
+          useAppNavigation({ entries, tabs, activeTabPath, onSelectNote, onSwitchTab }),
+        { initialProps: { activeTabPath: '/a.md' as string | null, tabs: [tabB] } },
+      )
+
+      rerender({ activeTabPath: '/b.md', tabs: [tabB] })
+
+      act(() => { result.current.handleGoBack() })
+
+      expect(onSelectNote).toHaveBeenCalledWith(entries[0])
+    })
+
+    it('handleGoForward works after going back', () => {
+      const entries = [makeEntry('/a.md'), makeEntry('/b.md')]
+      const tabA = makeTab(entries[0])
+      const tabB = makeTab(entries[1])
+
+      const { result, rerender } = renderHook(
+        ({ activeTabPath, tabs }) =>
+          useAppNavigation({ entries, tabs, activeTabPath, onSelectNote, onSwitchTab }),
+        { initialProps: { activeTabPath: '/a.md' as string | null, tabs: [tabA, tabB] } },
+      )
+
+      rerender({ activeTabPath: '/b.md', tabs: [tabA, tabB] })
+      act(() => { result.current.handleGoBack() })
+
+      expect(result.current.canGoForward).toBe(true)
+      act(() => { result.current.handleGoForward() })
+
+      expect(onSwitchTab).toHaveBeenCalledWith('/b.md')
+    })
+  })
+})