53 lines
1.8 KiB
Markdown
53 lines
1.8 KiB
Markdown
### Matrix state resolution in rust!
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```rust
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/// StateMap is just a wrapper/deserialize target for a PDU.
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struct StateEvent {
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content: serde_json::Value,
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room_id: RoomId,
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event_id: EventId,
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// ... and so on
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}
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/// A mapping of event type and state_key to some value `T`, usually an `EventId`.
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pub type StateMap<T> = BTreeMap<(EventType, String), T>;
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/// A mapping of `EventId` to `T`, usually a `StateEvent`.
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pub type EventMap<T> = BTreeMap<EventId, T>;
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struct StateResolution {
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// For now the StateResolution struct is empty. If "caching `event_map` between `resolve` calls
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// ends up being more efficient it may have an `event_map` field.
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}
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impl StateResolution {
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/// The point of this all, resolve the possibly conflicting sets of events.
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pub fn resolve(
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&self,
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room_id: &RoomId,
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room_version: &RoomVersionId,
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state_sets: &[StateMap<EventId>],
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event_map: Option<EventMap<StateEvent>>,
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store: &dyn StateStore,
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) -> Result<ResolutionResult>;
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}
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// The tricky part, making a good abstraction...
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trait StateStore {
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/// Return a single event based on the EventId.
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fn get_event(&self, event_id: &EventId) -> Result<StateEvent, String>;
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// There are 3 methods that have default implementations `get_events`, `auth_event_ids` and
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// `auth_chain_diff`. Each could be overridden if the user has an optimization with their database of
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// choice.
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}
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```
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The `StateStore` trait is an abstraction around what ever database your server (or maybe even client) uses to store __P__[]()ersistant __D__[]()ata __U__[]()nits.
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We use `ruma`s types when deserializing any PDU or it's contents which helps avoid a lot of type checking logic [synapse](https://github.com/matrix-org/synapse) must do while authenticating event chains.
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