# Overview – what the app does

There is a **Hilfe** menu with "Nach Update suchen" (self-update via `git`, see
[setup.md](setup.md#updating)) and "Version…".

The app is a single window: a **DRK-red header bar**, two tabs, and a
**colour-coded status bar** at the bottom (grey = neutral, green = success,
orange = warning, red = error; transient messages fade back to neutral after
~8 s). The window title shows the total entry count, and the window remembers
its size and position between sessions (`data/window.json`). The UI font is
enlarged for readability (`UI_FONT_SIZE`).

## Tab 1 – "Neuer Eintrag" (new entry)

Workflow: build up a **queue** of entries, let them geocode in the background,
then save the whole batch at once.

1. **Entry form** – date (a **calendar picker**, `ttkbootstrap.DateEntry`,
   pre-filled with today; typed input is accepted in `JJJJ-MM-TT` or
   `TT.MM.JJJJ` and **validated** – an invalid date is rejected with a dialog),
   city (autocomplete combobox), postal code (optional). Pressing `Return` in any
   field, or the **+ Hinzufügen** button, adds the row to the queue.
   The PLZ field only accepts digits.
2. **Queue table** – shows date, city, PLZ, and a live coordinate column that
   updates from `⏳ wird gesucht…` to either `lat / lon` or `⚠ nicht gefunden`
   as the background geocoder works through the queue.
   - Select a row and press <kbd>Delete</kbd>, use the **"Auswahl entfernen"**
     button, or click the `✕` cell.
   - Right-click a row for *Entfernen* / *Koordinaten erneut suchen*.
3. **Action bar**
   - **Alle speichern** – appends every queued row to `orte.csv`. If any row
     looks like a duplicate (same date + city + PLZ), a **modal** lists them and
     asks whether to save anyway.
   - **Warteschlange leeren** – discards the queue (asks for confirmation).
   - **Karte öffnen** – regenerates `karte.html` and opens it in the browser.

## Tab 2 – "Einträge verwalten" (manage entries)

A table view of everything in `orte.csv`.

- **Columns:** Datum, Ort, PLZ, and **Karte** – a status column showing `✓` when
  the row has coordinates or a red `fehlt` when it doesn't (the whole row is red
  too). The raw lat/lon numbers live in the edit dialog, not this table.
- **Search box** – live filter across date, city, and PLZ (substring match).
- **Sortable columns** – click a header to sort; clicking again reverses. The
  active column shows a ▲/▼ arrow. Default sort is by date, newest first.
  Sorting by **Karte** groups the rows without coordinates together.
- **"Nur ohne Koordinaten"** toggle – filters to entries that have no
  coordinates yet. The hint line always shows the total count, plus how many are
  missing coordinates.
- **Edit** – double-click a row (or *Bearbeiten*) opens a modal dialog to change
  date (calendar picker, validated) / city / PLZ. Two ways to fix coordinates:
  a "Koordinaten automatisch neu suchen" toggle re-runs geocoding after saving,
  or the **Breitengrad / Längengrad** fields let you type them in by hand
  (both empty = no map marker).
- **Right-click → Koordinaten suchen** – runs geocoding for that one row
  (handy for rows that failed the first time).
- **Delete** – *Löschen* removes the selected row(s) after a confirmation
  dialog. This is **irreversible**, but a timestamped copy of the file is
  written to `data/backups/` before every change (see
  [data-model.md](data-model.md#backups)).
- **Karte öffnen** – same as on Tab 1.

## The map (`karte.html`)

Generated by `generate_map()`:

- Base layer: **Esri "World Light Gray"** (`MAP_TILES` + a labels overlay) – a
  light, muted basemap that needs no API key and no `Referer`. Initial view
  centred on `[49.0, 9.0]`, zoom 8; auto-fits to the markers when there is more
  than one.
- One **`CircleMarker`** per unique `(city, lat, lon)` group. Radius scales
  linearly with the visit count for that location
  (`5 + count / max_count * 20` px), colour is DRK red (`#CC0000`).
- Popup shows the city and the visit count; tooltip shows the city.
- Rows with missing/blank coordinates are silently excluded.
- If there are no usable coordinates at all, a dialog says so (and the status
  bar shows a warning).

> The generated HTML pulls Leaflet, jQuery and Bootstrap from CDNs, and the map
> tiles from `server.arcgisonline.com`, so the map needs an internet connection
> to render even though the data is local. To change the look, edit `MAP_TILES` /
> `MAP_TILES_LABELS` near the top of `app.py` — the comment there lists other
> no-key Esri layers (Street, Topo). `tile.openstreetmap.org` was tried first
> but its tile-usage policy **403s** pages opened from `file://` (no `Referer`);
> `CartoDB positron` needs an API key.

## Geocoding behaviour

`geocode_city(city, postal_code)` tries a series of queries in order and returns
the first hit:

1. `"<PLZ> <city>, Germany"` (only if a PLZ was given)
2. `"<city>, Baden-Württemberg, Germany"`
3. `"<city>, Hessen, Germany"`
4. `"<city>, Germany"`

The regional bias is the `GEOCODE_REGIONS` constant (`Baden-Württemberg`,
`Hessen`) near the top of `app.py`. Results are rounded to five decimal places.
Nominatim's usage policy (max 1 req/s, identifying `user_agent`) is respected by
a manual `time.sleep(1)` in the worker loop.

If the geocoding service is unreachable (no internet), entries still save –
without coordinates – and after a few consecutive failures a one-time dialog
explains that the coordinates can be added later via *Bearbeiten*. The worker
thread logs failures to `data/app.log` and keeps running.