'use strict';

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

const chunkTarget = 50_000; // PostgreSQL allows 65,535 binding parameters, allow for a bit of margin

// improved version of bulkInsert
async function batchInsert(table, items, {
	conflict = true,
	update = false,
	concurrent = false,
	transaction,
	commit = false,
} = {}) {
	if (!table) {
		throw new Error('No table specified for batch insert');
	}

	if (conflict && update) {
		throw new Error('Batch insert conflict must specify columns, or update must be disabled');
	}

	if (!Array.isArray(items)) {
		throw new Error('Batch insert items are not an array');
	}

	if (items.length === 0) {
		return [];
	}

	// PostgreSQL's bindings limit applies to individual values, so item size needs to be taken into account
	const itemSize = items.reduce((acc, item) => Math.max(acc, Object.keys(item).length), 0);

	if (itemSize === 0) {
		throw new Error('Batch insert items are empty');
	}

	const chunks = chunk(items, Math.floor(chunkTarget / itemSize));
	const conflicts = [].concat(conflict).filter((column) => typeof column === 'string'); // conflict might be 'true'

	if (conflicts.length > 0 && !update) {
		throw new Error('Batch insert conflict columns must be specified together with update');
	}

	const trx = transaction || await knex.transaction();

	try {
		const queries = chunks.map((chunkItems) => {
			const query = trx(table)
				.insert(chunkItems)
				.returning('*');

			if (conflicts.length > 0) {
				if (Array.isArray(update)) {
					// udpate specified
					return query
						.onConflict(conflicts)
						.merge(update);
				}

				if (update) {
					// update all
					return query
						.onConflict(conflicts)
						.merge();
				}
			}

			// error on any conflict
			if (conflict) {
				return query;
			}

			// ignore duplicates, keep old entries as-is
			return query
				.onConflict()
				.ignore();
		});

		const results = concurrent
			? await Promise.all(queries)
			: await queries.reduce(async (chain, query) => {
				const acc = await chain;
				const result = await query;

				return acc.concat(result);
			}, Promise.resolve([]));

		if (!transaction || commit) {
			await trx.commit();
		}

		return results;
	} catch (error) {
		if (!transaction || commit) {
			await trx.rollback();
		}

		logger.error(`Failed batch insert: ${error.message} (${error.detail})`);

		throw error;
	}
}

module.exports = batchInsert;