/**
 * Internal dependencies
 */
import { MAX_LAMBDA_PAYLOAD, getApiUrl } from '../utils/helpers';
import { getChunksBySize } from '../utils/helpers/get-chunks-by-size';
import type { Session } from '../types';
import type { StoredEvent } from '../utils/storage';

type EventChunk = ReadonlyArray< StoredEvent >;

export async function sync(
	events: ReadonlyArray< StoredEvent >,
	session: Session
): Promise< ReadonlyArray< number > > {
	if ( ! events.length ) {
		return [];
	} //end if

	return track( events, session );
} //end sync()

async function track(
	events: ReadonlyArray< StoredEvent >,
	session: Session
): Promise< ReadonlyArray< number > > {
	if ( session.isStagingSite ) {
		events.forEach(
			( event ) =>
				console.info( '[Staging] Event', JSON.stringify( event.event ) ) // eslint-disable-line
		);
		return events.map( ( event ) => event.id );
	} //end if

	const chunks = getChunksBySize< StoredEvent >( {
		input: [ ...events ],
		bytesSize: MAX_LAMBDA_PAYLOAD,
		sizeCalcFunction: ( item ) => JSON.stringify( item.event ).length,
	} );

	const { api, site, id } = session;
	const url = getApiUrl( api, `/site/${ site }/session/${ id }`, {
		a: site,
	} );
	const acknowledgedIds: number[] = [];

	for ( const chunk of chunks ) {
		const wasSent = await sendChunk( url, chunk );
		if ( wasSent ) {
			acknowledgedIds.push( ...chunk.map( ( event ) => event.id ) );
		} //end if
	} //end for

	return acknowledgedIds;
} //end track()

async function sendChunk( url: string, chunk: EventChunk ): Promise< boolean > {
	try {
		const response = await fetch( url, {
			method: 'POST',
			mode: 'cors',
			body: JSON.stringify( chunk.map( ( item ) => item.event ) ),
			headers: {
				'Content-Type': 'application/json',
				'Access-Control-Allow-Origin': '*',
			},
		} );
		return response.ok;
	} catch {
		return false;
	}
}