"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) {
		return pipe([
			updateStream({ prefix }),
			simpleSink((item) => {
				return Promise.try(() => {
					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();
	};
};