Add support for CHATHISTORY TARGETS

The main motivation is to avoid missing direct messages coming from
other users.

A nice side-effect is that we no longer need to issue CHATHISTORY
queries for each channel we JOIN: instead, we can only fetch
history for targets known to have new messages available (as indicated
by CHATHISTORY TARGETS).

We use read receipts instead of delivery receipts, so that reloading
the webapp restores the exact same state (ie, unread messages are
re-fetched).

References: https://github.com/ircv3/ircv3-specifications/pull/450

components/app.js

@@ -450,6 +450,20 @@ export default class App extends Component {
 		this.saveReceipts();
 	}
 
+	latestReceipt(type) {
+		var last = null;
+		this.receipts.forEach((receipts, target) => {
+			var delivery = receipts[type];
+			if (target == "*" || !delivery || !delivery.time) {
+				return;
+			}
+			if (!last || delivery.time > last.time) {
+				last = delivery;
+			}
+		});
+		return last;
+	}
+
 	addMessage(netID, bufName, msg) {
 		var client = this.clients.get(netID);
 
@@ -608,6 +622,21 @@ export default class App extends Component {
 					params: [this.state.connectParams.autojoin.join(",")],
 				});
 			}
+
+			var lastReceipt = this.latestReceipt(ReceiptType.READ);
+			if (lastReceipt && lastReceipt.time && client.enabledCaps["draft/chathistory"] && (!client.enabledCaps["soju.im/bouncer-networks"] || client.params.bouncerNetwork)) {
+				var now = irc.formatDate(new Date());
+				client.fetchHistoryTargets(now, lastReceipt.time).then((targets) => {
+					targets.forEach((target) => {
+						var from = this.getReceipt(target, ReceiptType.READ);
+						if (!from) {
+							from = lastReceipt;
+						}
+						var to = { time: msg.tags.time || irc.formatDate(new Date()) };
+						this.fetchBacklog(client, target.name, from, to);
+					});
+				});
+			}
 			break;
 		case irc.RPL_MYINFO:
 			// TODO: parse available modes
@@ -729,17 +758,6 @@ export default class App extends Component {
 				this.switchBuffer({ network: netID, name: channel });
 				this.switchToChannel = null;
 			}
-
-			var receipt = this.getReceipt(channel, ReceiptType.READ);
-			if (client.isMyNick(msg.prefix.name) && receipt && client.enabledCaps["draft/chathistory"] && client.enabledCaps["server-time"]) {
-				var after = receipt;
-				var before = { time: msg.tags.time || irc.formatDate(new Date()) };
-				client.fetchHistoryBetween(channel, after, before, CHATHISTORY_MAX_SIZE).catch((err) => {
-					this.setState({ error: "Failed to fetch history: " + err });
-					this.receipts.delete(channel);
-					this.saveReceipts();
-				});
-			}
 			break;
 		case "PART":
 			var channel = msg.params[0];
@@ -886,6 +904,7 @@ export default class App extends Component {
 		case "PONG":
 		case "BATCH":
 		case "TAGMSG":
+		case "CHATHISTORY":
 			// Ignore these
 			break;
 		default:
@@ -928,6 +947,14 @@ export default class App extends Component {
 		return irc.STD_CHANNEL_TYPES.indexOf(name[0]) >= 0;
 	}
 
+	fetchBacklog(client, target, after, before) {
+		client.fetchHistoryBetween(target, after, before, CHATHISTORY_MAX_SIZE).catch((err) => {
+			this.setState({ error: "Failed to fetch history for '" + taregt + "': " + err });
+			this.receipts.delete(channel);
+			this.saveReceipts();
+		});
+	}
+
 	open(target) {
 		var netID = getActiveNetworkID(this.state);
 		var client = this.clients.get(netID);

lib/client.js

@@ -575,6 +575,24 @@ export default class Client extends EventTarget {
 		});
 	}
 
+	fetchHistoryTargets(t1, t2) {
+		var msg = {
+			command: "CHATHISTORY",
+			params: ["TARGETS", "timestamp=" + t1, "timestamp=" + t2, 1000],
+		};
+		return this.fetchBatch(msg, "draft/chathistory-targets").then((batch) => {
+			return batch.messages.map((msg) => {
+				if (msg.command != "CHATHISTORY" || msg.params[0] != "TARGETS") {
+					throw new Error("Cannot fetch chat history targets: unexpected message " + msg);
+				}
+				return {
+					name: msg.params[1],
+					latestMessage: msg.params[2],
+				};
+			});
+		});
+	}
+
 	listBouncerNetworks() {
 		if (!this.enabledCaps["soju.im/bouncer-networks"]) {
 			return Promise.reject(new Error("Server doesn't support the BOUNCER extension"));