add: Megalodon, initial mastodon api

packages/megalodon/src/parser.ts

@@ -0,0 +1,94 @@
+import { EventEmitter } from "events";
+import Entity from "./entity";
+
+/**
+ * Parser
+ * Parse response data in streaming.
+ **/
+export class Parser extends EventEmitter {
+	private message: string;
+
+	constructor() {
+		super();
+		this.message = "";
+	}
+
+	public parse(chunk: string) {
+		// skip heartbeats
+		if (chunk === ":thump\n") {
+			this.emit("heartbeat", {});
+			return;
+		}
+
+		this.message += chunk;
+		chunk = this.message;
+
+		const size: number = chunk.length;
+		let start = 0;
+		let offset = 0;
+		let curr: string | undefined;
+		let next: string | undefined;
+
+		while (offset < size) {
+			curr = chunk[offset];
+			next = chunk[offset + 1];
+
+			if (curr === "\n" && next === "\n") {
+				const piece: string = chunk.slice(start, offset);
+
+				offset += 2;
+				start = offset;
+
+				if (!piece.length) continue; // empty object
+
+				const root: Array<string> = piece.split("\n");
+
+				// should never happen, as long as mastodon doesn't change API messages
+				if (root.length !== 2) continue;
+
+				// remove event and data markers
+				const event: string = root[0].substr(7);
+				const data: string = root[1].substr(6);
+
+				let jsonObj = {};
+				try {
+					jsonObj = JSON.parse(data);
+				} catch (err) {
+					// delete event does not have json object
+					if (event !== "delete") {
+						this.emit(
+							"error",
+							new Error(
+								`Error parsing API reply: '${piece}', error message: '${err}'`,
+							),
+						);
+						continue;
+					}
+				}
+				switch (event) {
+					case "update":
+						this.emit("update", jsonObj as Entity.Status);
+						break;
+					case "notification":
+						this.emit("notification", jsonObj as Entity.Notification);
+						break;
+					case "conversation":
+						this.emit("conversation", jsonObj as Entity.Conversation);
+						break;
+					case "delete":
+						// When delete, data is an ID of the deleted status
+						this.emit("delete", data);
+						break;
+					default:
+						this.emit(
+							"error",
+							new Error(`Unknown event has received: ${event}`),
+						);
+						continue;
+				}
+			}
+			offset++;
+		}
+		this.message = chunk.slice(start, size);
+	}
+}