Redo LiveArray to watch all returned IDs for removal from the selector.

There is still a big TODO here in that the globalWatcher mechanism assumes one database.  Need to re-structure this whole thing around a db instance.

packages/gallery/src/interface/album.js

@@ -6,7 +6,6 @@ import { LiveArray } from '../utils/livearray.js';
 export function AlbumView(vm, model) {
 	const { remove, db } = model;
 	let data = null;
-	let currentMemberLen = -1;
 	let title = null;
 
 	function removeImageFromAlbum(id, rev) {
@@ -15,14 +14,13 @@ export function AlbumView(vm, model) {
 
 	return function(vm, model, key, opts) {
 		const { doc, remove } = model;
-		const { props, members } = doc;
+		const { props } = doc;
 
-		if (title !== props.title || currentMemberLen !== members.length) {
+		if (title !== props.title) {
 			if (data) {
 				data.cleanup();
 			}
 			title = props.title;
-			currentMemberLen = members.length;
 			const SELECTOR = Object.assign(
 				{
 					[`tags.${title}`]: { $eq: true }

packages/gallery/src/utils/comparators.js

@@ -0,0 +1,9 @@
+import { extractID } from './conversion.js';
+import { equals } from './set.js';
+
+export function pouchDocArrayComparator(a, b) {
+	const aIDs = a.map(extractID);
+	const bIDs = b.map(extractID);
+
+	return equals(new Set(...aIDs), new Set(...bIDs));
+}

packages/gallery/src/utils/conversion.js

@@ -35,3 +35,7 @@ export function deepAssign(to, ...rest) {
 	}
 	return to;
 }
+
+export function extractID(doc) {
+	return doc._id;
+}

packages/gallery/src/utils/livearray.js

@@ -1,35 +1,96 @@
 import { observable, computed } from 'frptools';
-import { group, groupEnd, log } from '../services/console.js';
-import { Watcher } from './watcher.js';
+import { matchesSelector } from 'pouchdb-selector-core';
 
+import { getDatabase } from '../services/db.js';
+import { Watcher } from './watcher.js';
+import { pouchDocArrayComparator } from './comparators.js';
+import { difference } from './set.js';
+
+// The point of the globalWatcher mechanism is that PouchDB.changes doesn't register when a document changes in such a way that removes it from the selector specifications.
+// For Example: a selector looks for images with a specific tag. If a change removes that tag, the changes API will not register a change event.  globalWatcher watches the document IDs for exactly this type of change and triggers the LiveArray to refresh.
+
+const globalWatcher = Watcher(getDatabase(), {}, true);
+const watchingIDs = new Map();
+let globalWatcherSubscription = null;
+
+function checkDocs(id, deleted, doc) {
+	// Is the changed doc one that we're watching?
+	if (watchingIDs.has(id)) {
+		const refresherMap = watchingIDs.get(id);
+		// if the doc doesn't match a watching selector, then refresh its LA
+		[...refresherMap.keys()]
+			.filter(s => !matchesSelector(doc, s))
+			.forEach(s => refresherMap.get(s)());
+		return;
+	}
+}
+
+function addID(id, selector, refresher) {
+	if (!watchingIDs.has(id)) {
+		watchingIDs.set(id, new Map());
+	}
+	watchingIDs.get(id).set(selector, refresher);
+	if (globalWatcherSubscription === null) {
+		globalWatcherSubscription = globalWatcher(checkDocs);
+	}
+}
+
+function removeID(id, selector) {
+	if (watchingIDs.has(id)) {
+		const idSet = watchingIDs.get(id);
+		idSet.delete(selector);
+		if (idSet.size === 0) {
+			watchingIDs.delete(selector);
+			if (watchingIDs.size === 0) {
+				globalWatcherSubscription();
+				globalWatcherSubscription = null;
+			}
+		}
+	}
+}
+
+// LiveArray is a subscribable property function that always returns the db results that match the provided selector and calls subscribers when the results change.
 export function LiveArray(db, selector, watcher) {
 	const _watcher = watcher || Watcher(db, selector);
-	const data = observable({ docs: [] });
-	const docs = computed(r => r.docs, [data]);
 	let changeSub = null;
 
-	const accessor = docs;
-	accessor.ready = observable(false);
-	accessor.cleanup = () => {
-		docs.detach();
+	const ready = observable(false);
+	const data = observable({ docs: [] });
+	const docs = computed(r => r.docs, [data], pouchDocArrayComparator);
+
+	const idSet = () => docs().reduce((acc, d) => acc.add(d._id), new Set());
+	const addThisID = id => addID(id, selector, refresh);
+	const removeThisID = id => removeID(id, selector);
+
+	const cleanup = () => {
+		docs.unsubscribeAll();
+		ready.unsubscribeAll();
 		if (changeSub) {
 			changeSub();
+			changeSub = null;
 		}
-		accessor.ready.unsubscribeAll();
+		[...idSet()].forEach(removeThisID);
 		data({ docs: [] });
 	};
 
-	async function refresh() {
-		group('LiveArray Refreshing');
-		log(selector);
+	const refresh = async function refresh() {
+		const oldIdSet = idSet();
 		data(await db.find({ selector }));
-		log(data());
-		groupEnd('LiveArray Refreshing');
-	}
+		const currentIDSet = idSet();
+		// Removes IDs not in the new set
+		[...difference(oldIdSet, currentIDSet)].forEach(removeThisID);
+		// Add IDs in the new set
+		[...difference(currentIDSet, oldIdSet)].forEach(addThisID);
+	};
+
+	docs.ready = ready;
+	docs.cleanup = cleanup;
+	docs.selector = selector;
+	docs.db = db;
 
 	refresh().then(() => {
 		changeSub = _watcher(refresh);
-		accessor.ready(true);
+		ready(true);
 	});
-	return accessor;
+	return docs;
 }

packages/gallery/src/utils/set.js

@@ -0,0 +1,14 @@
+export function equals(a, b) {
+	return (
+		[...a].reduce((acc, d) => acc && b.has(d), true) &&
+		[...b].reduce((acc, d) => acc && a.has(d), true)
+	);
+}
+
+export function intersection(a, b) {
+	return new Set([...a].filter(x => b.has(x)));
+}
+
+export function difference(a, b) {
+	return new Set([...a].filter(x => !b.has(x)));
+}