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use_prelude!();
use std::sync::Weak;
use ffi_sdk::COrderByParam;
use super::event::CollectionsEvent;
use crate::{
error::DittoError, store::collection::pending_cursor_operation::*, subscription::Subscription,
};
trait_alias! {
/// A closure which is called on each event relating to changes in the known
/// about collections.
///
/// Ditto may call this handler in parallel such as when a second invocation
/// happens before the first invocation has completed. This typically occurs
/// when the closure makes slow, external calls.
pub
trait CollectionsEventHandler =
FnMut(CollectionsEvent) // callable sequentially
+ Send // can be dropped in another thread
+ 'static // cannot dangle
}
/// Use [`ditto.store().collections()`] to query information about Ditto collections themselves.
///
/// They allow chaining of further collections-related functions. You can either call `exec` on the
/// object to get an array of `Collection`s as an immediate return value, or you can establish
/// either a live query or a subscription, which both work over time.
///
/// A live query, established by calling `observe_local`, will notify you every time there's a
/// change in the collections that the device knows about.
///
/// A subscription, established by calling `subscribe`, will act as a signal to other peers that
/// the device connects to that you would like to receive updates from them about the collections
/// that they know about.
///
/// Typically, an app would set up a `subscribe` in some part of the application which is long-lived
/// to ensure the device receives updates from the mesh. These updates will be automatically
/// received and written into the local store. Elsewhere, where you need to use this data, an
/// `observe_local` can be used to notify you of the data, and all subsequent changes to the data.
///
/// [`ditto.store().collections()`]: crate::store::Store::collections
pub struct PendingCollectionsOperation<'order_by> {
pub(super) ditto: Weak<BoxedDitto>,
pub(super) pending_cursor_operation: PendingCursorOperation<'order_by>,
}
impl<'order_by> PendingCollectionsOperation<'order_by> {
pub(crate) fn new(ditto: Weak<BoxedDitto>) -> Self {
#[allow(deprecated)]
let pending_cursor_operation =
PendingCursorOperation::new(ditto.clone(), char_p::new("__collections"), "true", None);
Self {
ditto,
pending_cursor_operation,
}
}
/// Limit the number of documents that get returned when querying a
/// collection for matching documents.
pub fn limit(&mut self, limit: i32) -> &mut Self {
self.pending_cursor_operation.limit(limit);
self
}
/// Offset the resulting set of matching documents. This is useful if you
/// aren’t interested in the first N matching documents for one reason
/// or another. For example, you might already have queried the
/// collection and obtained the first 20 matching documents and so you might
/// want to run the same query as you did previously but ignore the first 20
/// matching documents, and that is where you would use offset.
pub fn offset(&mut self, offset: u32) -> &mut Self {
self.pending_cursor_operation.offset(offset);
self
}
// FIXME: To bring this in line with the other SDKs this should accept a single
// "order_by" expression, which should then be added to the `order_by` vec
/// Sort the documents that match the query provided in the preceding
/// find-like function call.
///
/// Documents that are missing the field to sort by will appear at
/// the beginning of the results when sorting in ascending order.
pub fn sort(&mut self, sort_param: Vec<COrderByParam<'order_by>>) -> &mut Self {
self.pending_cursor_operation.sort(sort_param);
self
}
/// Execute the query generated by the preceding function chaining and
/// return the list of matching documents. This occurs immediately.
pub fn exec(&self) -> Result<Vec<Collection>, DittoError> {
let docs = self.pending_cursor_operation.exec()?;
Ok(PendingCollectionsOperation::collections_from_docs(
docs,
self.ditto.clone(),
))
}
/// Enables you to subscribe to changes that occur on a collection. Having a subscription acts
/// as a signal to others that you are interested in receiving updates when local or remote
/// changes are made to documents that match the query generated by the chain of operations that
/// precedes the call to subscribe. The returned [`Subscription`] object must be kept in scope
/// for as long as you want to keep receiving updates.
pub fn subscribe(&self) -> Subscription {
self.pending_cursor_operation.subscribe()
}
/// Enables you to listen for changes that occur on a collection. This won’t subscribe to
/// receive changes made remotely by others and so it will only fire updates when a local change
/// is made. If you want to receive remotely performed updates as well then also call subscribe
/// with the relevant query. The returned [`LiveQuery`](crate::prelude::Subscription) object
/// must be kept in scope for as long as you want the provided `Handler` to be called when an
/// update occurs.
pub fn observe_local<Handler>(&self, handler: Handler) -> Result<LiveQuery, DittoError>
where
Handler: CollectionsEventHandler,
{
let ditto = self.ditto.clone();
let mut handler = handler;
let handler = move |docs: Vec<BoxedDocument>, event: LiveQueryEvent| {
let colls_ev = PendingCollectionsOperation::collections_event_from_docs_and_event(
docs,
event,
ditto.clone(),
);
handler(colls_ev);
};
self.pending_cursor_operation.observe_local(handler)
}
fn collections_from_docs(docs: Vec<BoxedDocument>, ditto: Weak<BoxedDitto>) -> Vec<Collection> {
docs.iter()
.filter_map(|doc| {
doc.get::<String>("name")
.ok()
.map(|coll_name| Collection::new(ditto.clone(), coll_name))
})
.collect()
}
fn collections_event_from_docs_and_event(
docs: Vec<BoxedDocument>,
event: LiveQueryEvent,
ditto: Weak<BoxedDitto>,
) -> CollectionsEvent {
match event {
#[allow(deprecated)]
LiveQueryEvent::Initial => CollectionsEvent::initial(
PendingCollectionsOperation::collections_from_docs(docs, ditto),
),
#[allow(deprecated)]
LiveQueryEvent::Update {
old_documents,
insertions,
deletions,
updates,
moves,
} => CollectionsEvent::update(
PendingCollectionsOperation::collections_from_docs(docs, ditto.clone()),
PendingCollectionsOperation::collections_from_docs(old_documents, ditto),
insertions,
deletions,
updates,
moves,
),
}
}
}