/**
 */
namespace _zeitbild.frontend.resources.backend
{
	
	/**
	 */
	var _data : _zeitbild.frontend.type_datamodel;
	
	
	/**
	 */
	export async function init(
	) : Promise<void>
	{
		const path : string = "data.json";
		if (_data === undefined) {
			_data = lib_plankton.call.convey(
				await lib_plankton.file.read(path),
				[
					lib_plankton.json.decode,
					(data_raw : any) => (
						({
							"users": data_raw["users"],
							"calendars": (
								data_raw["calendars"]
								.map(
									(calendar_entry_raw : any) => ({
										"id": calendar_entry_raw["id"],
										"object": (
											((calendar_object_raw) => {
												switch (calendar_object_raw["kind"]) {
													default: {
														return calendar_object_raw;
														break;
													}
													case "concrete": {
														return {
															"kind": "concrete",
															"data": {
																"name": calendar_object_raw["data"]["name"],
																"private": (
																	calendar_object_raw["data"]["private"]
																	??
																	false
																),
																"users": calendar_object_raw["data"]["users"],
																"events": (
																	calendar_object_raw["data"]["events"]
																	.map(
																		(event_raw : any) => ({
																			"name": event_raw["name"],
																			"begin": event_raw["begin"],
																			"end": (
																				(
																					(
																						event_raw["end"]
																						??
																						null
																					)
																					===
																					null
																				)
																				?
																				null
																				:
																				event_raw["end"]
																			),
																			"location": (
																				event_raw["location"]
																				??
																				null
																			),
																			"description": (
																				event_raw["description"]
																				??
																				null
																			),
																		})
																	)
																),
															},
														};
														break;
													}
												}
											}) (calendar_entry_raw["object"])
										),
									})
								)
							),
						}) as type_datamodel
					),
				]
			);
		}
		else {
			// do nothing
		}
		return Promise.resolve<void>(undefined);
	}
	
	
	/**
	 */
	export async function calendar_list(
	) : Promise<
		 Array<
			{
				key : type_calendar_id;
				preview : {
					name : string;
				}
			}
		>
	>
	{
		await init();
		return Promise.resolve(
			_data.calendars
			.map(
				(calendar_entry) => {
					switch (calendar_entry.object.kind) {
						case "concrete": {
							return {
								"key": calendar_entry.id,
								"preview": {
									"name": calendar_entry.object.data.name,
								}
							};
							break;
						}
						case "collection": {
							return {
								"key": calendar_entry.id,
								"preview": {
									"name": calendar_entry.object.data.name,
								}
							};
						}
						case "caldav": {
							return {
								"key": calendar_entry.id,
								"preview": {
									"name": "(imported)",
								}
							};
						}
					}
				}
			)
		);
	}
	
	
	/**
	 */
	export async function calendar_read(
		calendar_id : type_calendar_id
	) : Promise<type_calendar_object>
	{
		await init();
		const hits = (
			_data.calendars
			.filter(
				(calendar_entry) => (calendar_entry.id === calendar_id)
			)
		);
		if (hits.length <= 0) {
			return Promise.reject<type_calendar_object>(new Error("not found"));
		}
		else {
			return Promise.resolve<type_calendar_object>(hits[0].object);
		}
	}

	
	/**
	 * @todo prevent loops
	 */
	export async function calendar_gather_events(
		calendar_id : type_calendar_id,
		from_pit : _zeitbild.frontend.helpers.type_pit,
		to_pit : _zeitbild.frontend.helpers.type_pit
	) : Promise<
		Array<
			{
				calendar_id : type_calendar_id;
				calendar_name : string;
				event : type_event;
			}
		>
	>
	{
		await init();
		const calendar_object : type_calendar_object = await calendar_read(
			calendar_id
		);
		lib_plankton.log.info(
			"calendar_gather_events",
			{
				"calendar_id": calendar_id,
			}
		);
		switch (calendar_object.kind) {
			case "concrete": {
				return Promise.resolve(
					calendar_object.data.events
					.filter(
						(event) => _zeitbild.frontend.helpers.pit_is_between(
							_zeitbild.frontend.helpers.pit_from_datetime(event.begin),
							from_pit,
							to_pit
						)
					)
					.map(
						(event) => ({
							"calendar_id": calendar_id,
							"calendar_name": calendar_object.data.name,
							"event": event
						})
					)
				);
				break;
			}
			case "collection": {
				return (
					Promise.all(
						calendar_object.data.sources
						.map(
							(source_calendar_id) => calendar_gather_events(
								source_calendar_id,
								from_pit,
								to_pit
							)
						)
					)
					.then(
						(entries) => Promise.resolve(
							entries
							.reduce(
								(x, y) => x.concat(y),
								[]
							)
						)
					)
				);
				break;
			}
			case "caldav": {
				const url : lib_plankton.url.type_url = lib_plankton.url.decode(
					calendar_object.data.source_url
				);
				const http_request : lib_plankton.http.type_request = {
					"version": "HTTP/2",
					"scheme": ((url.scheme === "https") ? "https" : "http"),
					"host": url.host,
					"path": (url.path ?? "/"),
					"query": url.query,
					"method": lib_plankton.http.enum_method.get,
					"headers": {},
					"body": null,
				};
				// TODO: cache?
				const http_response : lib_plankton.http.type_response = await lib_plankton.http.call(
					http_request,
					{
					}
				);
				const vcalendar : lib_plankton.ical.type_vcalendar = lib_plankton.ical.ics_decode(
					http_response.body.toString(),
					{
					}
				);
				return Promise.resolve(
					vcalendar.vevents
					.map(
						(vevent : lib_plankton.ical.type_vevent) => (
							(vevent.dtstart !== undefined)
							?
							{
								"name": (
									(vevent.summary !== undefined)
									?
									vevent.summary
									:
									"???"
								),
								"begin": _zeitbild.frontend.helpers.ical_dt_to_own_datetime(vevent.dtstart),
								"end": (
									(vevent.dtend !== undefined)
									?
									_zeitbild.frontend.helpers.ical_dt_to_own_datetime(vevent.dtend)
									:
									null
								),
								"location": (
									(vevent.location !== undefined)
									?
									vevent.location
									:
									null
								),
								"description": (
									(vevent.description !== undefined)
									?
									vevent.description
									:
									null
								),
							}
							:
							null
						)
					)
					.filter(
						(event) => (event !== null)
					)
					.filter(
						(event) => _zeitbild.frontend.helpers.pit_is_between(
							_zeitbild.frontend.helpers.pit_from_datetime(event.begin),
							from_pit,
							to_pit
						)
					)
					.map(
						(event) => ({
							"calendar_id": calendar_id,
							"calendar_name": calendar_object.data.name,
							"event": event,
						})
					)
				);
				break;
			}
		}
	}

}