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docs/by-claude-opus/development.md

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+# Development Guide
+
+## Development Environment
+
+### Required Tools
+
+| Tool | Version | Purpose |
+|------|---------|---------|
+| Python | 3.13+ | Runtime |
+| uv | Latest | Dependency management |
+| Docker | Latest | Container builds |
+| Git | Any | Version control |
+| Make | Any | Build automation |
+
+### Initial Setup
+
+```bash
+# 1. Clone the repository
+git clone <repo-url>
+cd fuj-management
+
+# 2. Install dependencies (creates .venv automatically)
+uv sync
+
+# 3. Activate the virtual environment
+source .venv/bin/activate
+
+# 4. Set up credentials
+mkdir -p .secret
+# Copy your Google service account JSON here:
+cp ~/Downloads/fuj-management-bot-credentials.json .secret/
+
+# 5. (Optional) Set Fio API token
+export FIO_API_TOKEN=your_token_here
+```
+
+### IDE Configuration
+
+The `.vscode/` directory contains workspace settings. If using VS Code, the Python interpreter should automatically detect the `.venv` directory.
+
+**PYTHONPATH note**: When running scripts from the project root, the Makefile sets `PYTHONPATH=scripts:$PYTHONPATH`. If your IDE doesn't do this, you may see import errors in `match_payments.py` and other scripts that import sibling modules.
+
+## Project Dependencies
+
+Defined in `pyproject.toml`:
+
+| Dependency | Version | Purpose |
+|------------|---------|---------|
+| `flask` | ≥3.1.3 | Web framework |
+| `google-api-python-client` | ≥2.162.0 | Google Sheets API |
+| `google-auth-httplib2` | ≥0.2.0 | Google auth transport |
+| `google-auth-oauthlib` | ≥1.2.1 | OAuth2 support |
+| `qrcode[pil]` | ≥8.0 | QR code generation (with PIL/Pillow backend) |
+
+The project uses `uv` with `package = false` in `[tool.uv]`, meaning it's not an installable package — dependencies are synced directly to the virtual environment.
+
+## Coding Conventions
+
+### Python Style
+
+- No linter or formatter is configured — the codebase uses a pragmatic, readable style
+- Type hints are used for function signatures but not exhaustively
+- Docstrings follow Google-style format on key functions
+- Scripts use `if __name__ == "__main__": main()` pattern
+
+### Import Pattern
+
+Scripts in the `scripts/` directory import from each other as top-level modules:
+
+```python
+# In match_payments.py:
+from attendance import get_members_with_fees
+from czech_utils import normalize, parse_month_references
+from sync_fio_to_sheets import get_sheets_service, DEFAULT_SPREADSHEET_ID
+```
+
+This works because `scripts/` is added to `sys.path` at runtime (by `app.py` on startup, by Makefile via `PYTHONPATH`, or by scripts adding their own directory to `sys.path`).
+
+### Template Style
+
+- All CSS is inline (no external stylesheets)
+- No CSS preprocessors or frameworks
+- No JavaScript frameworks — plain DOM manipulation
+- Terminal-inspired aesthetic: monospace fonts, green-on-black, dashed borders
+
+### Commit Conventions
+
+The project uses [Conventional Commits](https://www.conventionalcommits.org/):
+```
+feat: add keyboard navigation to member popup
+fix: correct diacritic-insensitive search filter
+chore: update dependencies
+```
+
+AI commits include a co-author trailer:
+```
+Co-authored-by: Antigravity <antigravity@google.com>
+```
+
+## Architecture Decisions
+
+### Why No Database?
+
+Google Sheets serves as the database because:
+1. Club members can view and correct data without special tools
+2. No database server to manage or back up
+3. Built-in version history and collaborative editing
+4. Good enough for ~40 members and ~hundreds of transactions
+
+### Why No Template Inheritance?
+
+Each HTML template is self-contained. While this means CSS duplication, it keeps each page fully independent and easy to understand. For a 3-page app, the duplication cost is minimal.
+
+### Why Flask Development Server in Production?
+
+The Docker container runs Flask's built-in server (`python3 app.py`) rather than gunicorn or waitress. This is intentional — the dashboard is an internal tool accessed by one person at a time. The simplicity outweighs the performance cost.
+
+### Why Scrape HTML When There's an API?
+
+The Fio transparent page scraping exists as a **zero-configuration fallback**. Not everyone has an API token, and the transparent page is always publicly accessible. The API is preferred when available (richer data, stable IDs).
+
+## Common Development Tasks
+
+### Adding a New Web Route
+
+1. Add the route function in `app.py`:
+```python
+@app.route("/new-page")
+def new_page():
+    # Fetch data
+    record_step("fetch_data")
+    # Process
+    record_step("process_data")
+    return render_template("new_page.html", ...)
+```
+
+2. Create `templates/new_page.html` (copy structure from `fees.html`)
+
+3. Add a link in the nav bar across all templates:
+```html
+<a href="/new-page">[New Page]</a>
+```
+
+4. Add a test in `tests/test_app.py`
+
+### Adding a New Script
+
+1. Create `scripts/new_script.py`
+2. Add a Makefile target:
+```makefile
+new-target: $(PYTHON)
+    $(PYTHON) scripts/new_script.py
+```
+3. Update `make help` output
+4. Add the `.PHONY` declaration
+
+### Modifying Fee Rules
+
+Fee rules are defined as constants in `scripts/attendance.py`:
+```python
+FEE_FULL = 750    # 2+ practices
+FEE_SINGLE = 200  # 1 practice
+```
+
+The calculation logic is in `calculate_fee()`:
+```python
+def calculate_fee(attendance_count: int) -> int:
+    if attendance_count == 0: return 0
+    if attendance_count == 1: return FEE_SINGLE
+    return FEE_FULL
+```
+
+### Adding a New Czech Month Form
+
+If you encounter a Czech month declension not yet supported, add it to `CZECH_MONTHS` in `scripts/czech_utils.py`:
+
+```python
+CZECH_MONTHS = {
+    "leden": 1, "ledna": 1, "lednu": 1,
+    "lednem": 1,  # New instrumental case
+    ...
+}
+```
+
+## Project History
+
+The project evolved through distinct phases:
+
+1. **Design phase** — Initial brainstorming captured in `docs/project-notes.md`
+2. **CLI tools** — `calculate_fees.py` and `match_payments.py` for command-line workflows
+3. **Bank integration** — `fio_utils.py` for transparent page scraping, later API support
+4. **Google Sheets sync** — `sync_fio_to_sheets.py` + `infer_payments.py` for the ledger pipeline
+5. **Web dashboard** — `app.py` with the `/fees`, `/reconcile`, and `/payments` pages
+6. **Interactive features** — Modal popups, QR payments, keyboard navigation, search filter
+7. **Fee exceptions** — Manual override system via the `exceptions` sheet tab
+8. **CI/CD** — Gitea Actions for Docker builds and Kubernetes deployment
+
+## Troubleshooting
+
+### "No data." on the web dashboard
+
+The attendance Google Sheet couldn't be fetched, or it returned empty data. Check:
+- Internet connectivity
+- The sheet ID in `attendance.py` is still valid
+- The sheet's public sharing settings haven't changed
+
+### Slow page loads
+
+Each page fetches data from Google Sheets on every request (no caching). Typical load times are 1-3 seconds. If significantly slower:
+- Check the performance breakdown (click the render time in the footer)
+- Google Sheets API rate limiting may be the cause
+
+### Import errors in scripts
+
+Ensure `PYTHONPATH` includes the `scripts/` directory:
+```bash
+export PYTHONPATH=scripts:$PYTHONPATH
+```
+
+Or use the Makefile, which sets this automatically.
+
+### "Could not fetch exceptions" warning
+
+The `exceptions` tab doesn't exist in the Payments Google Sheet. This is non-fatal — reconciliation proceeds without fee overrides.
+
+---
+
+*Development guide generated from comprehensive code analysis on 2026-03-03.*