Cloudflare Workers Cryptocurrency Slack Bot

index.js

addEventListener('fetch', event => {
	event.respondWith(slackWebhookHandler(event.request));
});

// SLACK_TOKEN is used to authenticate requests are from Slack.
// Keep this value secret.
let SLACK_TOKEN = 'PUTYOURTOKENHERE';
let BOT_NAME = 'Crypto-bot 🤖';
let REPO_URL = 'https://github.com/cloudflare/templates';

let jsonHeaders = new Headers([['Content-Type', 'application/json']]);

// tickerMap is a map of "ticker" symbols and CoinMarketCap API IDs.
let tickerMap = new Map([
	['BTC', 'bitcoin'],
	['ETH', 'ethereum'],
	['XRP', 'ripple'],
	['BCH', 'bitcoin-cash'],
	['LTC', 'litecoin'],
	['ADA', 'cardano'],
	['NEO', 'neo'],
	['XLM', 'stellar'],
	['EOS', 'eos'],
	['MIOTA', 'iota'],
	['XMR', 'monero'],
	['DASH', 'dash'],
	['XEM', 'nem'],
	['USDT', 'tether'],
	['TRX', 'tron'],
	['VEN', 'vechain'],
	['ETC', 'ethereum-classic'],
	['LSK', 'lisk'],
	['QTUM', 'qtum'],
	['OMG', 'omisego'],
	['NANO', 'nano'],
	['BTG', 'bitcoin-gold'],
	['BNB', 'binance-coin'],
	['ICX', 'icon'],
	['ZEC', 'zcash'],
	['DGD', 'digixdao'],
	['PPT', 'populous'],
	['STEEM', 'steem'],
	['WAVES', 'waves'],
	['BCN', 'bytecoin-bcn'],
	['STRAT', 'stratis'],
	['XVG', 'verge'],
	['MKR', 'maker'],
	['RHOC', 'rchain'],
	['SNT', 'status'],
	['DOGE', 'dogecoin'],
	['SC', 'siacoin'],
	['BTS', 'bitshares'],
	['AE', 'aeternity'],
	['REP', 'augur'],
	['DCR', 'decred'],
	['BTM', 'bytom'],
	['WTC', 'waltonchain'],
	['ONT', 'ontology'],
	['ZIL', 'zilliqa'],
	['AION', 'aion'],
	['KMD', 'komodo'],
	['ARDR', 'ardor'],
	['ARK', 'ark'],
	['CNX', 'cryptonex'],
	['KCS', 'kucoin-shares'],
	['MONA', 'monacoin'],
	['ZRX', '0x'],
	['HSR', 'hshare'],
	['ETN', 'electroneum'],
	['DGB', 'digibyte'],
	['GXS', 'gxchain'],
	['VERI', 'veritaseum'],
	['PIVX', 'pivx'],
	['BAT', 'basic-attention-token'],
	['FCT', 'factom'],
	['SYS', 'syscoin'],
	['GAS', 'gas'],
	['R', 'revain'],
	['DRGN', 'dragonchain'],
	['GNT', 'golem-network-tokens'],
	['QASH', 'qash'],
	['FUN', 'funfair'],
	['ETHOS', 'ethos'],
	['LRC', 'loopring'],
	['NAS', 'nebulas-token'],
	['RDD', 'reddcoin'],
	['XZC', 'zcoin'],
	['IOST', 'iostoken'],
	['EMC', 'emercoin'],
	['KNC', 'kyber-network'],
	['ELF', 'aelf'],
	['KIN', 'kin'],
	['SALT', 'salt'],
	['GBYTE', 'byteball'],
	['NCASH', 'nucleus-vision'],
	['PART', 'particl'],
	['MAID', 'maidsafecoin'],
	['DCN', 'dentacoin'],
	['NXT', 'nxt'],
	['LINK', 'chainlink'],
	['SMART', 'smartcash'],
	['REQ', 'request-network'],
	['POWR', 'power-ledger'],
	['BNT', 'bancor'],
	['PAY', 'tenx'],
	['CND', 'cindicator'],
	['NEBL', 'neblio'],
	['POLY', 'polymath-network'],
	['NXS', 'nexus'],
	['DENT', 'dent'],
	['ICN', 'iconomi'],
	['ENG', 'enigma-project'],
	['MNX', 'minexcoin'],
	['STORJ', 'storj'],
]);

/**
 * simpleResponse generates a simple JSON response
 * with the given status code and message.
 *
 * @param {Number} statusCode
 * @param {String} message
 */
function simpleResponse(statusCode, message) {
	let resp = {
		message: message,
		status: statusCode,
	};

	return new Response(JSON.stringify(resp), {
		headers: jsonHeaders,
		status: statusCode,
	});
}

/**
 * slackResponse builds a message for Slack with the given text
 * and optional attachment text
 *
 * @param {string} text - the message text to return
 * @param {string[]} [attachmentText] - the (optional) attachment text to add.
 */
function slackResponse(text, attachmentText) {
	let content = {
		response_type: 'in_channel',
		text: text,
		attachments: [],
	};

	if (attachmentText.length > 0) {
		attachmentText.forEach(val => {
			content.attachments.push({ text: val });
		});
	}

	try {
		return new Response(JSON.stringify(content), {
			headers: jsonHeaders,
			status: 200,
		});
	} catch (e) {
		return simpleResponse(200, 'Sorry, I had an issue generating a response. Try again in a bit!');
	}
}

/**
 * parseMessage parses the selected currency from the Slack message.
 *
 * @param {FormData} message - the message text
 * @return {string} - the currency name.
 */
function parseMessage(message) {
	// 1. Parse the message (trim command, trim whitespace, check length)
	// 2. Lookup the ticker <-> id (name) mapping
	// 3. Return the name value
	// 4. Else, just return the provided value from the message.
	try {
		let text = message.get('text').trim();
		let vals = text.split(' ');
		// Example: /slashcommand BTC EUR
		let currency = vals[0];
		let display = vals[1];

		// If we can't find the ticker => ID in our map, we
		// use the user-provided value.
		if (tickerMap.has(currency)) {
			currency = tickerMap.get(currency);
		}

		return {
			currency: currency,
			display: display,
		};
	} catch (e) {
		return null;
	}
}

/**
 * currencyRequest makes a request to the CoinMarketCap API for the
 * given currency ticker.
 * Endpoint: https://api.coinmarketcap.com/v1/ticker/{ticker}/?convert={display}
 *
 * @param {string} ticker - the crypto-currency to fetch the price for
 * @param {string} [display] - the currency to display (e.g. USD, EUR)
 * @returns {Object} - an Object containing the currency, price in USD, and price in the (optional) display currency.
 */
async function currencyRequest(currency, display) {
	let endpoint = 'https://api.coinmarketcap.com/v1/ticker/';

	if (display === '') {
		display = 'USD';
	}

	try {
		let resp = await fetch(
			`${endpoint}${currency}/?convert=${display}`,
			{ cf: { cacheTtl: 60 } } // Cache our responses for 60s.
		);

		let data = await resp.json();
		if (resp.status !== 200) {
			throw new Error(`bad status code from CoinMarketCap: HTTP ${resp.status}`);
		}

		let cachedResponse = false;
		if (resp.headers.get('cf-cache-status').toLowerCase() === 'hit') {
			cachedResponse = true;
		}

		let reply = {
			currency: data[0].name,
			symbol: data[0].symbol,
			USD: data[0].price_usd,
			percent_change_1h: `${data[0].percent_change_1h}%`,
			percent_change_24h: `${data[0].percent_change_24h}%`,
			percent_change_7d: `${data[0].percent_change_7d}%`,
			updated: new Date(parseInt(`${data[0].last_updated}000`)).toUTCString(),
			cached: cachedResponse,
		};

		return reply;
	} catch (e) {
		throw new Error(`could not fetch the selected currency: ${e}`);
	}
}

/**
 * slackWebhookHandler handles an incoming Slack
 * webhook and generates a response.
 * @param {Request} request
 */
async function slackWebhookHandler(request) {
	// As per: https://api.slack.com/slash-commands
	// - Slash commands are outgoing webhooks (POST requests)
	// - Slack authenticates via a verification token.
	// - The webhook payload is provided as POST form data

	if (request.method != 'POST') {
		return simpleResponse(
			200,
			`Hi, I'm ${BOT_NAME}, a Slack bot for fetching the latest crypto-currenncy prices. Find my source code at ${REPO_URL}`
		);
	}

	let formData;
	try {
		formData = await request.formData();
		if (formData.get('token').toString() !== SLACK_TOKEN) {
			return simpleResponse(403, 'invalid Slack verification token');
		}
	} catch (e) {
		return simpleResponse(400, 'could not decode POST form data');
	}

	try {
		let parsed = parseMessage(formData);
		if (parsed === null) {
			throw new Error('could not parse your message');
		}

		let reply = await currencyRequest(parsed.currency, parsed.display);

		return slackResponse(`Current price (${reply.currency}): 💵 $USD${reply.USD}`, [
			`1h Δ: ${reply.percent_change_1h} · 24h Δ: ${reply.percent_change_24h} · 7d Δ: ${reply.percent_change_7d}`,
			`Updated: ${reply.updated} | ${reply.cached}`,
		]);
	} catch (e) {
		return simpleResponse(200, `Sorry, I had an issue retrieving anything for that currency: ${e}`);
	}
}

license.md

Copyright (c) 2018, Cloudflare, Inc. All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.