# CLAUDE.md

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

Additional guidance is provided in @AGENTS.md

## Project Overview

Nibasa Viewer is a lightweight, pure HTML+CSS gallery viewer designed for compatibility with older browsers. It uses Django as a backend framework but serves images directly from the filesystem rather than using database models.

**Key Design Principles:**
- Filesystem-first architecture (no image/folder models in database)
- No JavaScript or modern frontend frameworks
- Broad browser compatibility (uses HTML tables, not flexbox/grid)
- Dark theme optimized for image viewing
- Lazy thumbnail generation with on-disk caching

## Development Commands

```bash
# Install dependencies
pip install -r requirements.txt

# Run development server
python manage.py runserver

# Create user for gallery access (required)
python manage.py shell
>>> from django.contrib.auth.models import User
>>> user = User.objects.create_user('<USERNAME>', '<EMAIL>', '<PASSWORD>')
>>> user.save()
>>> exit()

# Pre-generate all thumbnails (optional, done on-demand otherwise)
python manage.py makethumbnails

# Django admin commands
python manage.py migrate
python manage.py createsuperuser
python manage.py collectstatic
```

## Architecture

### Single App Structure

The project has one Django app: **`viewer`**. All gallery functionality is consolidated here:
- `views.py` - Gallery directory browsing and image viewing (viewer/views.py:65-189)
- `utils.py` - Thumbnail generation helpers
- `templates/` - Pure HTML templates (no JavaScript)
- `static/` - CSS styling and navigation icons
 - `views.py` - Thin delegating entry points that route to `viewer/directory.py` and `viewer/image.py` (see `gallery_view` in `viewer/views.py`).
 - `directory.py` - Directory browsing, search, and list rendering helpers.
 - `image.py` - Single-image rendering and metadata helpers.
 - `common.py` - Shared helpers: URL/query builders, sorting, breadcrumbs, thumbnail utilities.
 - `utils.py` - Thumbnail generation helpers.
 - `templates/` - HTML templates (minimal JS via Bootstrap where needed).
 - `static/` - CSS styling and navigation icons

### Gallery Data Flow

**Filesystem as Data Source:**
- Images served from `GALLERY_ROOT` path (configured in `.env`)
- Thumbnails cached in `THUMBNAILS_ROOT` path
- No database models for images or directories
- Directory structure navigated using Python's `pathlib`

**Static File Routing:**
- `/imgs/` → Original images from `GALLERY_ROOT`
- `/thumbs/` → Cached thumbnails from `THUMBNAILS_ROOT`
- `/static/` → CSS and navigation icons

### Authentication

Uses Django's built-in `django.contrib.auth` system:
- All gallery views protected with `@login_required` decorator
- Users manually created via Django shell (no signup form)
- Database only stores user accounts (SQLite)
- Login/logout redirects configured in NibasaViewer/settings.py:108-110

### View Logic

**`gallery_view()` function** (viewer/views.py:65-189) handles both:

1. **Directory browsing** when path points to folder:
    - Lists subdirectories and images
    - Supports search with recursive directory scanning (`viewer/directory.py:do_recursive_search`)
    - Does not use server-side pagination; the gallery returns full image lists and templates render them in a grid
    - Converts image lists to structured context used by templates

2. **Image viewing** when path points to file:
    - Displays single image with prev/next navigation
    - Finds sibling images in same directory
    - Links to full-resolution image

The image view logic now lives in `viewer/image.py` and exposes additional context keys used by templates and tests (see `viewer/test.py`): `prev_url`, `next_url`, `prev_thumb`, `next_thumb`, `back_url`, `back_thumb`, `home_url`, `home_thumb`, and `image_meta` (filename/width/height/filesize/created/modified).

### Thumbnail Generation

**Lazy generation approach** (viewer/utils.py):
- Thumbnails created on-demand when viewing gallery
 - 128×128 pixel size (`THUMB_SIZE`) and cached under `THUMBNAILS_ROOT`
- Uses Pillow for image processing
- Fast extension-based image detection (no MIME-type I/O)

**Batch pre-generation:**
- `python manage.py makethumbnails` command available
- Useful for initial setup or after adding many images

### Performance Optimizations

**Extension-based image filtering** (viewer/utils.py:17-27):
- Uses `is_image_file()` helper that checks file extensions instead of reading file contents
- Supported extensions defined in `IMAGE_EXTENSIONS` constant
- Eliminates ~99% of I/O operations when listing directories
- Significantly faster than MIME-type detection for large directories

## Configuration

### Required Environment Variables

Create `.env` (not in git):

```env
GALLERY_ROOT=/path/to/your/images
THUMBNAILS_ROOT=/path/to/thumbnail/cache
```

`settings.py` loads `.env` with `python-dotenv` and parses both values as `pathlib.Path`. Each variable is optional and resolves to `None` when unset or empty.

### Pagination Constants

Defined in viewer/views.py:23-25:
- `CELLS_PER_ROW = 7` - Image grid columns
- `ROWS_PER_PAGE = 4` - Image grid rows
- `IMAGES_PER_PAGE = 28` - Total images per page

## Production Deployment

Systemd service files included for Gunicorn deployment:
- `nibasaviewer.service` - Service configuration
- `nibasaviewer.socket` - Socket activation

Default production location: `/var/lib/NibasaViewer`

## Dependencies

- **Django 4.2.3** - Web framework
- **Pillow 10.0.0** - Image processing (thumbnails)
- **python-dotenv 1.1.1** - Loads local `.env` configuration
- **gunicorn 21.2.0** - WSGI server (production)

## Code Patterns

**Template rendering:**
- All views use `render(request, template, context)`
- Context includes pagination data, image paths, and navigation state

**Path handling:**
- Use `pathlib.Path` for all filesystem operations
- Convert to relative paths for URLs: `image.relative_to(settings.GALLERY_ROOT)`
- Gallery URLs follow pattern: `/gallery/{relative_path}`

**Image filtering:**
- Use `is_image_file(path)` from `viewer.utils` to validate image files
- Fast extension-based detection (checks `IMAGE_EXTENSIONS` set)
- Supports common formats: JPEG, PNG, GIF, WebP, BMP, TIFF, SVG
- Accepts both `pathlib.Path` and string paths

### Recent changes notes

- The image view was refactored to match the gallery layout and styling; `viewer/templates/image_view.html` now uses the shared `viewer/static/css/styles.css` file and Bootstrap/Font Awesome includes like `gallery_view.html`.
- `_render_image` in `viewer/views.py` now exposes additional context keys used by the template and tests: `prev_url`, `next_url`, `prev_thumb`, `next_thumb`, `back_url`, `back_thumb`, `home_url`, `home_thumb`, and `image_meta` (dictionary with `filename`, `width`, `height`, `filesize`, `created`, `modified`). Agents modifying image-view behavior should update tests in `viewer/test.py` as well.
- The top-bar sort button for the image view was replaced by an Info button (`fa-circle-info`) which shows a dropdown containing image metadata. The dropdown is vertically scrollable for long content.
- The main displayed image now uses the same drop shadow and rounded corners as thumbnails (styles added to `viewer/static/css/styles.css`).