"use strict";

const Promise = require("bluebird");
const matchValue = require("match-value");
const pipe = require("@promistream/pipe");
const simpleSink = require("@promistream/simple-sink");
const updateStream = require("./update-stream");

module.exports = function ({ knex }) {
	return function createSynchronizer(tableName, prefix, mapper, { getLastTimestamp } = {}) {
		return Promise.try(() => {
			if (getLastTimestamp != null) {
				// NOTE: Must be a Date object! FIXME: Change this?
				return getLastTimestamp();
			} else {
				return null;
			}
		}).then((lastTimestamp) => {
			return pipe([
				updateStream({ prefix, since: lastTimestamp }),
				simpleSink((item) => {
					return Promise.try(() => {
						// TODO: debug-log item processing?
						// console.log("[sync] processing item", item);
						return matchValue(item.type, {
							item: () => {
								let result = mapper(item);
	
								if (result != null) {
									return knex(tableName)
										.insert(result)
										.onConflict("id").merge();
								}
							},
							alias: () => {
								return knex(tableName)
									.delete()
									.where({ id: item.alias });
							},
							taskResult: () => {
								// Ignore these for now
							}
						});
					}).then(() => {
						// FIXME: This placeholder `.then` is necessary to make this work *at all*. Investigate why this isn't working otherwise, and whether that's a bug in simple-sink
					});
				})
			]).read();
		});
	};
};