Move chat history operations into Client

lib/client.js

@@ -39,6 +39,7 @@ export default class Client extends EventTarget {
 	batches = new Map();
 	autoReconnect = true;
 	reconnectTimeoutID = null;
+	pendingHistory = Promise.resolve(null);
 
 	constructor(params) {
 		super();
@@ -359,4 +360,55 @@ export default class Client extends EventTarget {
 			this.send(msg);
 		});
 	}
+
+	roundtripChatHistory(params) {
+		// Don't send multiple CHATHISTORY commands in parallel, we can't
+		// properly handle batches and errors.
+		this.pendingHistory = this.pendingHistory.catch(() => {}).then(() => {
+			var msg = {
+				command: "CHATHISTORY",
+				params,
+			};
+			return this.roundtrip(msg, (event) => {
+				var msg = event.detail.message;
+
+				switch (msg.command) {
+				case "BATCH":
+					var enter = msg.params[0].startsWith("+");
+					var name = msg.params[0].slice(1);
+					if (enter) {
+						break;
+					}
+					var batch = this.batches.get(name);
+					if (batch.type == "chathistory") {
+						return batch;
+					}
+					break;
+				case "FAIL":
+					if (msg.params[0] == "CHATHISTORY") {
+						throw msg;
+					}
+					break;
+				}
+			});
+		});
+		return this.pendingHistory;
+	}
+
+	/* Fetch history in ascending order. */
+	fetchHistoryBetween(target, after, before, limit) {
+		var max = Math.min(limit, CHATHISTORY_PAGE_SIZE);
+		var params = ["AFTER", target, "timestamp=" + after.time, max];
+		return this.roundtripChatHistory(params).then((batch) => {
+			limit -= batch.messages.length;
+			if (limit <= 0) {
+				throw new Error("Cannot fetch all chat history: too many messages");
+			}
+			if (batch.messages.length == max) {
+				// There are still more messages to fetch
+				after.time = batch.messages[batch.messages.length - 1].tags.time;
+				return this.fetchHistoryBetween(target, after, before, limit);
+			}
+		});
+	}
 }