"use strict";

class GatewayRepo {
	constructor({ database }) {
		this.db = database;
	}
	
	add(...gateways) {
		const statement = this.db.prepare(`INSERT INTO gateways (
			id,
			latitude, longitude,
			altitude
		) VALUES (
			:id,
			:latitude, :longitude,
			:altitude
		)`);
		
		for(let gateway of gateways)
			statement.run(gateway);
	}
	
	/**
	 * Determines whether a gateway exists in the dayabase with the given name.
	 * @param	{string}	id	The id of the gateway.
	 * @return	{bool}		Whether a gateway with the given name exists in the database.
	 */
	exists(id) {
		// Note that normally a count wouldn't be appropriate here just to test for existence, but it's ok because it's guaranteed that there will only ever be a single entry with a given id.
		let statement = this.db.prepare(`SELECT COUNT(id) AS count
		FROM gateways
		WHERE id = :id`);
		
		let count = statement.get({ id }).count;
		
		return count > 0;
	}
	
	/**
	 * Returns a garteway by it's id.
	 * @param	{string}	id	The id to fetcht he gateway for.
	 * @return	{object}	The information recorded about the gateway with the specified id .
	 */
	get_by_id(id) {
		return this.db.prepare(`SELECT * FROM gateways WHERE id = :id`).get({ id });
	}
	
	/**
	 * Iterates over all the gateways in the table.
	 * TODO: Use Symbol.iterator here?
 	 * @return	{Generator}	A generator that can be used with for..of
	 */
	iterate() {
		return this.db.prepare(`SELECT * FROM gateways`).iterate();
	}
	
	/**
	 * Returns the average location of allt he currently registered gateways.
	 * @return {{latitude: number, longitude: number}} The lat longg coordinates of the average location of all the gateways.
	 */
	get_average_location() {
		let count = 0, lat_sum = 0, lng_sum = 0;
		for(let gateway of this.iterate()) {
			lat_sum += gateway.latitude;
			lng_sum += gateway.longitude;
			count++;
		}
		
		return {
			latitude: lat_sum / count,
			longitude: lng_sum / count
		};
	}
}

export default GatewayRepo;