[presto] add AGENTS.md

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Claudio Ortolina
2026-05-06 08:54:18 +01:00
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# Presto App Guidance
This directory contains MicroPython apps for the Pimoroni Presto. The main app is
`records_on_the_day.py`, deployed to the device as `main.py`.
## Context To Read First
- Read `README.md` before changing setup, deployment, user-facing behavior, or API response assumptions.
- Read `records_on_the_day.py` before changing layout, touch handling, networking, display sleep, or performance-sensitive code.
- The root project conventions still apply, but most Phoenix/Elixir conventions are not relevant inside `presto/`.
## Deployment And Verification
- The project task deploys the records app:
```bash
mise run presto
```
- Manual deployment copies `records_on_the_day.py` to the device as `main.py`:
```bash
mpremote fs cp records_on_the_day.py :main.py
mpremote fs cp secrets.py :secrets.py
mpremote reset
```
- Before finishing Python edits, run a syntax-only check that does not leave `__pycache__` behind:
```bash
python3 -c "import py_compile; py_compile.compile('records_on_the_day.py', cfile='/tmp/records_on_the_day.pyc', doraise=True)"
```
- Do not claim device behavior is verified unless it was tested on the physical Presto.
## Hardware And Runtime Constraints
- Target stock Pimoroni Presto firmware: MicroPython, PicoGraphics, touch driver, `urequests`, `ntptime`, and usually `jpegdec`.
- Presto hardware is RP2350B, but stock firmware should be treated as a single Python runtime. Do not assume `_thread` or user-accessible multicore support.
- Keep memory pressure low. Avoid large in-memory image buffers, aggressive caching of large responses, and repeated `gc.collect()` in hot render paths.
- Network calls are blocking. Avoid doing HTTP requests during drag scrolling or repeated redraw loops.
## Records App Behavior
- Boot should land on today's records, not the month calendar.
- The Back button returns from day view to month view.
- Month and day headers should share the same header geometry: height, button dimensions, side margins, and centered title/date positioning.
- Day rows show cover art, title, artists, and a dim metadata line of `format | year`.
- `release_date` is displayed as year only.
- Text shown with bitmap fonts should pass through `display_text()` to replace unsupported punctuation such as smart dashes and quotes. Do not strip diacritics; the font can render them.
## Image Handling
- Prefer `micro_cover_url`, then `mini_cover_url`, then `thumb_url`.
- Keep `THUMB_SIZE` aligned with the micro image size when possible.
- Cache downloaded thumbnail bytes on the record dict as `_thumb_data`.
- Keep the placeholder-while-dragging behavior. Decoding JPEGs during drag was too slow on device, even with micro covers.
- Repaint real covers after the finger is released.
- Do not call `gc.collect()` per row draw. Collect after record preparation, after API fetches, or at other non-hot-path points.
- JPEG is the practical default on stock firmware. PNG generally has worse memory characteristics, and raw/RGB565 should only be attempted after confirming a stable on-device blit API.
## Scroll Performance
- The scroll hot path must not measure text, join artist lists, sanitize strings, calculate full content height, or fetch images.
- After fetching records, call the preparation path that caches:
- `_display_title`
- `_display_artists`
- `_display_meta`
- `_thumb_url`
- `_row_height`
- total `_content_height`
- Preload only `micro_cover_url` thumbnails before the first day-view draw. Do not eagerly fetch larger fallback images.
- Drag scrolling should remain pixel-based, but redraws should be throttled by both time and pixel delta (`DRAG_REDRAW_MS`, `DRAG_REDRAW_PX`).
- Preserve any pending drag delta on touch release and redraw once with real covers if the view moved.
## Layout Details
- Use named constants for pixel geometry instead of scattered literals.
- For record rows, keep cover top and bottom spacing visually symmetric:
- `ROW_PAD_Y` is the padding above and below the cover.
- `ROW_SEPARATOR_H` is the separator line height after the bottom padding.
- If row spacing looks wrong on device, reason in terms of inclusive pixel drawing: a separator drawn inside the padding visually consumes that padding.
## Display Sleep
- The display sleeps by setting the backlight to `0.0`; the app and WiFi stay running.
- The first touch after sleep should wake the backlight and be consumed so it does not also activate a control.
- On wake, check WiFi and reconnect only if it dropped.
## API Contract
The records endpoint is:
```text
GET https://music-library.claudio-ortolina.org/api/v1/collection/on_this_day?date=YYYY-MM-DD
Authorization: Bearer <API_TOKEN>
```
Expected record fields used by the app:
- `title`
- `artists`
- `format`
- `release_date`
- `micro_cover_url`
- `mini_cover_url`
- `thumb_url`
When adding or changing API assumptions, update `README.md`.