# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Commands

```bash
npm start          # Run the Electron app in development
npm run build      # Build macOS app bundle (no DMG, arm64 + x64)
npm run dist       # Build and package as DMG for distribution
./setup.sh         # First-time setup: npm install + npm start
```

There are no tests or linting configured.

## Architecture

This is a macOS Electron desktop app for batch-renaming and moving photo files. It follows strict Electron security practices: `contextIsolation: true`, `nodeIntegration: false`.

**Process boundary:** All filesystem access lives exclusively in `src/main/` (main process). The renderer never touches `fs` directly.

### File structure

```
src/
├── main/
│   ├── index.js          # Main process entry point; creates BrowserWindow, calls registerAll()
│   └── ipc/
│       ├── index.js      # registerAll(mainWindow) — delegates to folder and files modules
│       ├── folder.js     # select-folder, list-directories, get/set-last-folder,
│       │                 # get/set-preview-on, get-home-dir, reveal-folder
│       └── files.js      # list-images, read-image, rename-files,
│                         # check-files-exist, move-files
├── preload/
│   └── index.js          # Bridges IPC to window.api via contextBridge (isolated context)
└── renderer/
    ├── index.html        # App shell; dark theme, CSS variables in :root, modal HTML
    ├── style.css         # All CSS
    ├── state.js          # Shared mutable state: files[], currentFolder, selectedIdxs, sortMode
    ├── renderer.js       # Entry point: init, loadFolder, sortFiles, keyboard shortcuts, startup
    ├── ui.js             # showLoading, hideLoading, setStatus, showToast
    ├── grid.js           # renderGrid, createCard, card UI update functions, showEmptyGrid
    ├── rename.js         # doRename + rename-conflict modal
    ├── move.js           # handleFolderDrop + move modals + _doMoveFiles
    └── handlers/
        ├── drag-drop.js      # Card reorder (single/multi) + drag-to-folder in sidebar
        ├── file-explorer.js  # Sidebar directory tree (lazy-load, expand/collapse)
        ├── selection.js      # Rubber-band, Shift-click, Cmd+click, resetAnchor
        ├── pinch-zoom.js     # Ctrl+scroll to resize thumbnails (CSS --thumb-size, 150–400px)
        └── image-preview.js  # Hover preview overlay with circular loading indicator
```

### IPC surface

Defined in `src/main/ipc/`, bridged via `src/preload/index.js` as `window.api`:

| Channel | Direction | Description |
|---|---|---|
| `select-folder` | invoke | Opens native folder picker, returns path or null |
| `list-images` | invoke | Reads directory, returns `{name, path, mtime}[]` filtered to image extensions, sorted by filename |
| `read-image` | invoke | Reads file, returns base64 data URL for display |
| `rename-files({folderPath, files, prefix, digits})` | invoke | Two-phase rename: temp names (crypto.randomUUID) first, then final names |
| `check-files-exist(folderPath, names[])` | invoke | Returns subset of names that already exist in folderPath |
| `move-files({targetFolder, files[]})` | invoke | Moves files; each file may have optional `newName`; handles cross-device (EXDEV) |
| `list-directories(folderPath)` | invoke | Returns `{name, path, hasChildren}[]` subdirs, or `null` on access error |
| `get-home-dir` | invoke | Returns `os.homedir()` |
| `get-last-folder` / `set-last-folder` | invoke | Persists last opened folder in userData config.json |
| `get-preview-on` / `set-preview-on` | invoke | Persists hover preview toggle state in userData config.json |
| `reveal-folder` | invoke | Opens folder in Finder via `shell.openPath` |
| `fullscreen-change` | push (main→renderer) | Sent on `enter-full-screen` / `leave-full-screen` window events |

### Renderer (`src/renderer/`)

Uses ES module imports (`type="module"`). No framework.

**Dependency direction** (no cycles):
```
renderer.js → rename.js, move.js → grid.js → handlers/*
                                 ↘         ↗
                                   ui.js
```

**State** (`src/renderer/state.js`):
- `files[]` — ordered array of `{name, path, mtime}`; order determines rename sequence
- `selectedIdxs` — `Set<number>` of selected card indices
- `currentFolder` — active directory path
- `sortMode` — `'name'` | `'date'` | `null`

**Keyboard shortcuts:**
- `O` — 폴더 열기
- `S` — 이름 변경 실행
- `A` — 전체 선택

**Card selection** (`selection.js`):
- Click — 단독 선택 (재클릭 시 해제)
- Shift+Click — 범위 선택
- Cmd+Click — 개별 토글
- Rubber-band drag — 영역 선택 (rAF throttle 적용)
- `resetAnchor()` — 그리드 재렌더 시 Shift 기준점 초기화 (grid.js에서 호출)

**Drag-and-drop** (`drag-drop.js`):
- 그리드 내: 카드 순서 재배치 (single/multi)
- 사이드바 폴더로: 선택된 파일들을 해당 폴더로 이동
  - 파일명 충돌 시 rename-and-move 모달 표시
  - 드래그 중 `.tree-row.drop-target` 클래스로 대상 폴더 하이라이트

**Rename** (`rename.js`):
- 선택된 파일만 이름 변경 (선택 없으면 전체)
- 변경될 이름이 미선택 파일과 충돌하면 충돌 목록 모달 표시

**Move** (`move.js`):
- 충돌 없으면 즉시 이동
- 충돌 있으면 prefix + digits 입력 모달 → 새 이름으로 이동
- 새 이름도 충돌이면 에러 모달

**Thumbnail loading:** `IntersectionObserver` with `rootMargin: '400px 0px'` — lazy load as cards enter viewport. `entry.target.isConnected` 체크로 폴더 전환 중 스탈 카드 방지. Drag reorder remaps card elements via `card.dataset.filepath` to avoid re-fetching.

**Hover preview** (`image-preview.js`): 1초 지연 후 전체 크기 팝업. 썸네일 캐시 우선 사용. 상태는 config.json에 영속.

**Sidebar tree** (`file-explorer.js`): Lazy-load 자식 폴더. 접근 불가 폴더는 `null` 반환 → "접근 불가" 표시. 행 클릭 시 항상 펼침, 화살표 클릭 시 토글.

**Styling:** CSS는 `src/renderer/style.css`에 집중. Dark theme, CSS variables in `:root`. macOS traffic-light은 `header`의 `-webkit-app-region: drag`.

**Build output:** `electron-builder` targets DMG for arm64 and x64. The app icon must be at `assets/icon.icns`.

**Config persistence:** `app.getPath('userData')/config.json`에 `lastFolder`, `previewOn` 저장.