"use strict";

const dateFns = require("date-fns");

const pipe = require("@promistream/pipe");
const combineSequentialStreaming = require("@promistream/combine-sequential-streaming");
const fromIterable = require("@promistream/from-iterable");
const fromNodeStream = require("@promistream/from-node-stream");

const createTypeTaggingStream = require("./streams/tag-type");

module.exports = function ({ db, knex }) {
	return function (tx, { timestamp, prefix }) {
		// NOTE: This returns snake_cased keys! As we're bypassing the Objection internals, no casemapping occurs.
		// FIXME/REFACTOR: That needs to be changed in the refactor, for consistency across database backends

		// NOTE: This is a hacky workaround - if we don't do this, then for some reason also entries *at* the exact timestamp are included, which is not what we want.
		// FIXME: Verify that this doesn't break anything, eg. when an entry is created inbetween the original timestamp and +1ms.
		let actualTimestamp = (timestamp != null)
			? dateFns.addMilliseconds(timestamp, 1)
			: undefined;

		function applyWhereClauses(query, idField) {
			if (timestamp != null) {
				// FIXME: An error in the query here throws an error, resulting in an abort handling bug in a promistream
				query = query.whereRaw(`updated_at > ?`, [ actualTimestamp ]);
			}

			if (prefix != null) {
				query = query.whereRaw(`${idField} LIKE ?`, [ `${prefix.replace(/%/g, "\\%")}%` ]);
			}

			return query;
		}

		function* streamGenerator() {
			yield pipe([
				fromNodeStream.fromReadable(
					applyWhereClauses(db.Item.query(tx), "id").toKnexQuery().stream()
				),
				createTypeTaggingStream("item")
			]);
			
			yield pipe([
				fromNodeStream.fromReadable(
					// NOTE: We are only interested in aliases which don't point at themselves
					applyWhereClauses(db.Alias.query(tx).where("alias", "!=", knex.ref("item_id")), "alias").toKnexQuery().stream()
				),
				createTypeTaggingStream("alias")
			]);

			yield pipe([
				fromNodeStream.fromReadable(
					applyWhereClauses(db.TaskResult.query(tx), "item_id").toKnexQuery().stream()
				),
				createTypeTaggingStream("taskResult")
			]);
		}

		return pipe([
			fromIterable(streamGenerator()),
			combineSequentialStreaming()
		]);
	}
};