gsender

/*
 * Copyright (C) 2021 Sienci Labs Inc.
 *
 * This file is part of gSender.
 *
 * gSender is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, under version 3 of the License.
 *
 * gSender is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with gSender.  If not, see <https://www.gnu.org/licenses/>.
 *
 * Contact for information regarding this program and its license
 * can be sent through gSender@sienci.com or mailed to the main office
 * of Sienci Labs Inc. in Waterloo, Ontario, Canada.
 *
 */

import events from "events";

class Feeder extends events.EventEmitter {
	state = {
		hold: false,
		holdReason: null,
		queue: [],
		pending: false,
		changed: false,
		outstanding: 0,
		interval: null,
	};

	dataFilter = null;

	// @param {object} [options] The options object.
	// @param {function} [options.dataFilter] A function to be used to handle the data. The function accepts two arguments: The data to be sent to the controller, and the context.
	constructor(options) {
		super();

		if (typeof options.dataFilter === "function") {
			this.dataFilter = options.dataFilter;
		}

		this.on("change", () => {
			this.state.changed = true;
		});
	}

	toJSON() {
		return {
			hold: this.state.hold,
			holdReason: this.state.holdReason,
			queue: this.state.queue.length,
			pending: this.state.pending,
			changed: this.state.changed,
		};
	}

	feed(data = [], context = {}) {
		// Clear pending state when the feeder queue is empty
		console.log(data);
		if (this.state.queue.length === 0) {
			this.state.pending = false;
		}

		data = [].concat(data);
		if (data.length > 0) {
			this.state.queue = this.state.queue.concat(
				data.map((command) => {
					return { command: command, context: context };
				}),
			);
			this.emit("change");
		}
	}

	hold(reason) {
		if (this.state.hold) {
			return;
		}
		this.state.hold = true;
		this.state.holdReason = reason;
		this.emit("hold");
		this.emit("change");
	}

	unhold() {
		if (!this.state.hold) {
			return;
		}
		this.state.hold = false;
		this.state.holdReason = null;
		this.emit("unhold");
		this.emit("change");
	}

	clear() {
		this.state.queue = [];
		this.state.pending = false;
		this.state.outstanding = 0;
		this.state.interval && clearInterval(this.state.interval);
		this.emit("change");
	}

	reset() {
		this.state.hold = false;
		this.state.holdReason = null;
		this.state.queue = [];
		this.state.pending = false;
		this.state.outstanding = 0;
		this.state.interval = null;
		this.emit("change");
	}

	size() {
		return this.state.queue.length;
	}

	next() {
		if (this.state.queue.length === 0 && !this.state.hold) {
			this.state.pending = false;
			this.emit("complete"); // indicate feeder is complete
			return this.state.pending;
		}

		while (!this.state.hold && this.state.queue.length > 0) {
			let { command, context } = this.state.queue.shift();
			console.log(command);

			if (this.dataFilter) {
				command = this.dataFilter(command, context) || "";
				if (!command) {
					// Ignore blank lines
					continue;
				}
			}

			this.state.pending = true;
			this.state.outstanding++;
			this.emit("data", command, context);
			this.emit("change");
			break;
		}

		// Clear pending state when the feeder queue is empty
		if (this.state.queue.length === 0 && !this.state.hold) {
			this.state.pending = false;
			this.emit("complete"); // indicate feeder is complete
		}

		return this.state.pending;
	}

	isPending() {
		return this.state.pending;
	}

	// Returns true if any state have changes
	peek() {
		const changed = this.state.changed;
		this.state.changed = false;
		return changed;
	}

	ack() {
		if (this.state.outstanding > 0) {
			this.state.outstanding--;
		}
	}

	hasOutstanding() {
		return this.state.outstanding > 0;
	}
}

export default Feeder;