/**
 * External dependencies
 */
import { select, dispatch } from '@wordpress/data-controls';
import { addQueryArgs } from '@wordpress/url';

/**
 * Internal dependencies
 */
import { receiveCollection, receiveCollectionError } from './actions';
import { STORE_KEY as SCHEMA_STORE_KEY } from '../schema/constants';
import { STORE_KEY, DEFAULT_EMPTY_ARRAY } from './constants';
import { apiFetchWithHeaders } from '../shared-controls';

/**
 * Check if the store needs invalidating due to a change in last modified headers.
 *
 * @param {number} timestamp Last update timestamp.
 */
function* invalidateModifiedCollection( timestamp ) {
	const lastModified = yield select( STORE_KEY, 'getCollectionLastModified' );

	if ( ! lastModified ) {
		yield dispatch( STORE_KEY, 'receiveLastModified', timestamp );
	} else if ( timestamp > lastModified ) {
		yield dispatch( STORE_KEY, 'invalidateResolutionForStore' );
		yield dispatch( STORE_KEY, 'receiveLastModified', timestamp );
	}
}

/**
 * Resolver for retrieving a collection via a api route.
 *
 * @param {string} namespace
 * @param {string} resourceName
 * @param {Object} query
 * @param {Array}  ids
 */
export function* getCollection( namespace, resourceName, query, ids ) {
	const route = yield select(
		SCHEMA_STORE_KEY,
		'getRoute',
		namespace,
		resourceName,
		ids
	);
	const queryString = addQueryArgs( '', query );
	if ( ! route ) {
		yield receiveCollection( namespace, resourceName, queryString, ids );
		return;
	}

	try {
		const {
			response = DEFAULT_EMPTY_ARRAY,
			headers,
		} = yield apiFetchWithHeaders( { path: route + queryString } );

		if ( headers && headers.get && headers.has( 'last-modified' ) ) {
			// Do any invalidation before the collection is received to prevent
			// this query running again.
			yield invalidateModifiedCollection(
				parseInt( headers.get( 'last-modified' ), 10 )
			);
		}

		yield receiveCollection( namespace, resourceName, queryString, ids, {
			items: response,
			headers,
		} );
	} catch ( error ) {
		yield receiveCollectionError(
			namespace,
			resourceName,
			queryString,
			ids,
			error
		);
	}
}

/**
 * Resolver for retrieving a specific collection header for the given arguments
 *
 * Note: This triggers the `getCollection` resolver if it hasn't been resolved
 * yet.
 *
 * @param {string} header
 * @param {string} namespace
 * @param {string} resourceName
 * @param {Object} query
 * @param {Array}  ids
 */
export function* getCollectionHeader(
	header,
	namespace,
	resourceName,
	query,
	ids
) {
	// feed the correct number of args in for the select so we don't resolve
	// unnecessarily. Any undefined args will be excluded. This is important
	// because resolver resolution is cached by both number and value of args.
	const args = [ namespace, resourceName, query, ids ].filter(
		( arg ) => typeof arg !== 'undefined'
	);
	//we call this simply to do any resolution of the collection if necessary.
	yield select( STORE_KEY, 'getCollection', ...args );
}