Matthias Blankertz
7327549eea
To simplify the playlist handling, enforce that the indices are always formatted to the same length (5, which allows for 100000 entries, that should be enough). Then make the position stored in the Playlist object be a simple integer instead of a database key. This simplifies the code, and will make implementing shuffle much easier. Signed-off-by: Matthias Blankertz <matthias@blankertz.org>
55 lines
2.4 KiB
Markdown
55 lines
2.4 KiB
Markdown
# Developer notes
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## How to setup python environment for mypy and pytest
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```bash
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cd software
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python -m venv test-venv
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. test-venv/bin/activate
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pip install -r tests/requirements.txt
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pip install -U micropython-rp2-pico_w-stubs --target typings
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```
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## 'database' schema for btree db
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### Playlist storage
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The playlist data is stored in the btree database in a hierarchical schema. The hierarchy levels are
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separated by the '/' character. Currently, the schema is as follows: The top level for a playlist
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is the 'tag' id encoded as a hexadecimal string. Beneath this, the 'playlist' key contains the
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elements in the playlist. The keys used for the playlist entries must be decimal integers,
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left-padded with zeros so their length is 5 (e.g. format `{:05}`).
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#### Playlist modes
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The 'playlistshuffle' key located under the 'tag' key can be 'no' or 'yes' and specifies whether the
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playlist is in shuffle mode. Should this key be absent the default value is 'no'.
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The 'playlistpersist' key located under the 'tag' key can be 'no', 'track' or 'offset'. Should this
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key be absent the default value is 'track'.
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* When it is 'no', the playlist position is not saved when playback stops. If shuffle mode is
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active, the shuffle random seed is also not saved.
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* When it is 'track', the currently playing track is saved when playback stops. If shuffle mode is
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active, the shuffle random seed is also saved. Should playback reach the last track (in shuffle
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mode: the last track in the permutated order), the saved position is reset and playback is
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stopped. The next time the playlist is started it will start from the first track and with a new
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shuffle seed if applicable.
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* When it is 'offset', the operation is basically the same as in 'track' mode. The difference is
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that the offset in the currently playing track is also saved and playback will resume at that
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position.
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The 'playlistpos' key located under the 'tag' key stores the key of the current playlist
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entry. The 'playlistshuffleseed' key stores the random seed used to shuffle the playlist.
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The 'playlistposoffset' key stores the offset in the current playlist entry.
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#### Example
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For example, a playlist with two entries 'a.mp3' and 'b.mp3' for a tag with the id '00aa11bb22'
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would be stored in the following key/value pairs in the btree db:
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* 00aa11bb22/playlist/00000: a.mp3
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* 00aa11bb22/playlist/00001: b.mp3
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* 00aa11bb22/playlistpos: 00000
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