"use strict";

const Promise = require("bluebird");
const bhttp = require("bhttp");

const pipe = require("@promistream/pipe");
const simpleSource = require("@promistream/simple-source");
const createCombineSequentialStream = require("@promistream/combine-sequential-streaming");
const createSpyStream = require("@promistream/spy");
const fromNodeStream = require("@promistream/from-node-stream");

const createNDJSONParseStream = require("./ndjson-parse-stream");

module.exports = function createUpdateStream({ prefix } = {}) {
	let lastTimestamp = new Date(0);
	// let lastTimestamp = new Date();
	
	return pipe([
		simpleSource(() => {
			function attempt() {
				return Promise.try(() => {
					// To ensure that we don't hammer the srap instance
					return Promise.delay(5 * 1000);
				}).then(() => {
					// console.log({ lastTimestamp });
					// console.log(`http://localhost:3000/updates?prefix=${encodeURIComponent(prefix)}&since=${Math.floor(lastTimestamp.getTime())}`);
					return bhttp.get(`http://localhost:3000/updates?prefix=${encodeURIComponent(prefix)}&since=${Math.floor(lastTimestamp.getTime())}`, {
						stream: true
					});
				}).then((response) => {
					if (response.statusCode === 200) {
						return fromNodeStream.fromReadable(response);
					} else {
						throw new Error(`Got unexpected status code ${response.statusCode}`);
					}
				}).catch({ code: "ECONNREFUSED" }, (_error) => {
					// Scraping server is down, try again in a minute or so
					console.warn("WARNING: Scraping server is not reachable! Retrying in a minute...");
					
					return Promise.try(() => {
						return Promise.delay(60 * 1000);
					}).then(() => {
						return attempt();
					});
				});
			}

			return attempt();
		}),
		createCombineSequentialStream(),
		createNDJSONParseStream(),
		createSpyStream((item) => {
			if (item.updatedAt != null) {
				// TODO: Can this be made significantly more performant by string-sorting the timestamps in ISO format directly, instead of going through a parsing cycle?
				let itemDate = new Date(item.updatedAt);

				if (itemDate > lastTimestamp) {
					lastTimestamp = itemDate;
				}
			}
		})
	]);
};