'use strict';

const knex = require('../knex');
const chunk = require('./chunk');

async function bulkUpsert(table, items, conflict, update = true, chunkSize) {
	if (items.length === 0) {
		return [];
	}

	const updated = (conflict === false && ':query ON CONFLICT DO NOTHING RETURNING *;')
	|| (conflict && update && `
		:query ON CONFLICT (${conflict})
		DO UPDATE SET ${(update === true
			? Object.keys(items[0]) // derive updating props
			: update)
			.reduce((acc, prop, index) => `${acc}${index > 0 ? ',' : ''}\n${prop} = ${conflict.includes(prop) ? table : 'EXCLUDED'}.${prop}`, '')}
		RETURNING *;
	`);

	return knex.transaction(async (transaction) => {
		const chunked = chunk(items, chunkSize);

		const queries = chunked
			.map((chunkItems) => knex.raw(updated || ':query RETURNING *;', {
				query: knex(table).insert(chunkItems),
			}).transacting(transaction));

		const responses = await Promise.all(queries);

		return responses.flat().map((response) => response.rows).flat();
	});
}

module.exports = bulkUpsert;