Commits on Dec 30, 2021

1. ✨ Add presence support …

   This change adds support for the `transformPresence()` method that
   [`sharedb` uses][1].
   
   We add support for both `text0` and `json0`.
   
   `text0`
   -------
   
   The `text0` implementation leans on the existing
   [`transformPosition`][2], and takes its form and tests from
   [`rich-text`][3].
   
   Its shape takes the form:
   
   ```js
   {
     index: 3,
     length: 5,
   }
   ```
   
   Where:
   
    - `index` is the cursor position
    - `length` is the selection length (`0` for a collapsed selection)
   
   `json0`
   -------
   
   The `json0` implementation has limited functionality because of the
   limitations of the `json0` type itself: we handle list moves `lm`, but
   cannot infer any information when moving objects around the tree,
   because the `oi` and `od` operations are destructive.
   
   However, it will attempt to transform embedded subtypes that support
   presence.
   
   Its shape takes the form:
   
   ```js
   {
     p: ['key', 123],
     v: {},
   }
   ```
   
   Where:
   
    - `p` is the path to the client's position within the document
    - `v` is the presence value
   
   The presence value `v` can take any arbitrary value (in simple cases it
   may even be omitted entirely).
   
   The exception to this is when using subtypes, where `v` should take the
   presence shape defined by the subtype. For example, when using `text0`:
   
   ```js
   {
     p: ['key'],
     v: {index: 5, length: 0},
   }
   ```
   
   [1]: share/sharedb#322
   [2]: https://github.com/ottypes/json0/blob/90a3ae26364c4fa3b19b6df34dad46707a704421/lib/text0.js#L147
   [3]: ottypes/rich-text#32

   

   alecgibson committed Dec 30, 2021
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