84 lines
3.5 KiB
JavaScript
84 lines
3.5 KiB
JavaScript
import {directionalConcat, directionalAppend} from "./common.js";
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import Direction from "../Direction.js";
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import EventEntry from "../entries/EventEntry.js";
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import FragmentBoundaryEntry from "../entries/FragmentBoundaryEntry.js";
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export default class TimelineReader {
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constructor({roomId, storage, fragmentIdComparer}) {
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this._roomId = roomId;
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this._storage = storage;
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this._fragmentIdComparer = fragmentIdComparer;
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}
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_openTxn() {
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return this._storage.readTxn([
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this._storage.storeNames.timelineEvents,
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this._storage.storeNames.timelineFragments,
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]);
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}
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async readFrom(eventKey, direction, amount) {
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const txn = await this._openTxn();
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return this._readFrom(eventKey, direction, amount, txn);
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}
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async _readFrom(eventKey, direction, amount, txn) {
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let entries = [];
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const timelineStore = txn.timelineEvents;
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const fragmentStore = txn.timelineFragments;
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while (entries.length < amount && eventKey) {
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let eventsWithinFragment;
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if (direction.isForward) {
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eventsWithinFragment = await timelineStore.eventsAfter(this._roomId, eventKey, amount);
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} else {
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eventsWithinFragment = await timelineStore.eventsBefore(this._roomId, eventKey, amount);
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}
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const eventEntries = eventsWithinFragment.map(e => new EventEntry(e, this._fragmentIdComparer));
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entries = directionalConcat(entries, eventEntries, direction);
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// prepend or append eventsWithinFragment to entries, and wrap them in EventEntry
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if (entries.length < amount) {
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const fragment = await fragmentStore.get(this._roomId, eventKey.fragmentId);
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// this._fragmentIdComparer.addFragment(fragment);
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let fragmentEntry = new FragmentBoundaryEntry(fragment, direction.isBackward, this._fragmentIdComparer);
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// append or prepend fragmentEntry, reuse func from GapWriter?
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directionalAppend(entries, fragmentEntry, direction);
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// don't count it in amount perhaps? or do?
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if (fragmentEntry.hasLinkedFragment) {
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const nextFragment = await fragmentStore.get(this._roomId, fragmentEntry.linkedFragmentId);
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this._fragmentIdComparer.add(nextFragment);
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const nextFragmentEntry = new FragmentBoundaryEntry(nextFragment, direction.isForward, this._fragmentIdComparer);
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directionalAppend(entries, nextFragmentEntry, direction);
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eventKey = nextFragmentEntry.asEventKey();
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} else {
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eventKey = null;
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}
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}
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}
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return entries;
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}
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async readFromEnd(amount) {
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const txn = await this._openTxn();
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const liveFragment = await txn.timelineFragments.liveFragment(this._roomId);
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// room hasn't been synced yet
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if (!liveFragment) {
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return [];
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}
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this._fragmentIdComparer.add(liveFragment);
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const liveFragmentEntry = FragmentBoundaryEntry.end(liveFragment, this._fragmentIdComparer);
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const eventKey = liveFragmentEntry.asEventKey();
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const entries = await this._readFrom(eventKey, Direction.Backward, amount, txn);
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entries.unshift(liveFragmentEntry);
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return entries;
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}
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// reads distance up and down from eventId
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// or just expose eventIdToKey?
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readAtEventId(eventId, distance) {
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return null;
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}
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}
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