/*
This file is part of »munin«.

Copyright 2025 'Fenris Wolf' <fenris@folksprak.org>

»munin« is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

»munin« is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License
along with »munin«. If not, see <http://www.gnu.org/licenses/>.
 */


namespace _munin.logic
{
	
	/**
	 * @todo Tests schreiben
	 */
	function shall_remind(
		event : _munin.type_event,
		reminder : type_reminder,
		{
			"pit": pit = lib_plankton.pit.now(),
			"interval": interval = 1,
		} : {
			pit ?: lib_plankton.pit.type_pit;
			interval ?: int;
		} = {
		}
	) : boolean
	{
		const window_from : lib_plankton.pit.type_pit = lib_plankton.pit.shift_hour(
			pit,
			0
		);
		const window_to : lib_plankton.pit.type_pit = lib_plankton.pit.shift_hour(
			pit,
			interval
		);
		const event_begin : lib_plankton.pit.type_pit = lib_plankton.pit.from_datetime(
			event.begin
		);
		const reminder_time : lib_plankton.pit.type_pit = lib_plankton.pit.shift_hour(
			event_begin,
			(-reminder)
		);
		return lib_plankton.pit.is_between(
			reminder_time,
			window_from,
			window_to
		);
	}
	
	
	/**
	 */
	function frequency_anchor(
		frequency : _munin.enum_frequency,
		{
			"pit": pit = lib_plankton.pit.now(),
		} : {
			pit ?: lib_plankton.pit.type_pit,
		} = {
		}
	) : lib_plankton.pit.type_pit
	{
		switch (frequency)
		{
			case _munin.enum_frequency.hourly: return lib_plankton.pit.trunc_hour(pit);
			case _munin.enum_frequency.daily: return lib_plankton.pit.trunc_day(pit);
			case _munin.enum_frequency.weekly: return lib_plankton.pit.trunc_week(pit);
			case _munin.enum_frequency.monthly: return lib_plankton.pit.trunc_month(pit);
			default:
			{
				throw (new Error("unhandled frequency: " + frequency));
				break;
			}
		}
	}
	
	
	/**
	 */
	export function reminder_due(
		reminder : type_reminder_new,
		{
			"pit": pit = lib_plankton.pit.now(),
			"interval": interval = 1,
		} : {
			pit ?: lib_plankton.pit.type_pit;
			interval ?: int;
		} = {
		}
	) : boolean
	{
		const anchor : lib_plankton.pit.type_pit = frequency_anchor(
			reminder.frequency,
			{"pit": pit}
		);
		// 0 ≤ ((p - a(p)) - o) < i
		const x : float = (
			(
				(
					lib_plankton.pit.to_unix_timestamp(pit)
					-
					lib_plankton.pit.to_unix_timestamp(anchor)
				)
				/
				(60 * 60)
			)
			-
			reminder.offset
		);
		return ((0 <= x) && (x < interval));
	}
	
	
	/**
	 */
	export function reminder_event_in_window(
		reminder : type_reminder_new,
		event : _munin.type_event,
		{
			"pit": pit = lib_plankton.pit.now(),
			"interval": interval = 1,
		} : {
			pit ?: lib_plankton.pit.type_pit;
			interval ?: int;
		} = {
		}
	) : boolean
	{
		const anchor : lib_plankton.pit.type_pit = frequency_anchor(
			reminder.frequency,
			{"pit": pit}
		);
		const window_from : lib_plankton.pit.type_pit = lib_plankton.pit.shift_hour(
			anchor,
			reminder.from
		);
		const window_to : lib_plankton.pit.type_pit = lib_plankton.pit.shift_hour(
			anchor,
			reminder.to
		);
		const event_begin : lib_plankton.pit.type_pit = lib_plankton.pit.from_datetime(
			event.begin
		);
		return lib_plankton.pit.is_between(
			event_begin,
			window_from,
			window_to
		);
	}
		
	
	/**
	 */
	function shall_remind_new(
		reminder : type_reminder_new,
		event : _munin.type_event,
		{
			"pit": pit = lib_plankton.pit.now(),
			"interval": interval = 1,
		} : {
			pit ?: lib_plankton.pit.type_pit;
			interval ?: int;
		} = {
		}
	) : boolean
	{
		return (
			reminder_due(
				reminder,
				{"pit": pit, "interval": interval}
			)
			&&
			reminder_event_in_window(
				reminder,
				event,
				{"pit": pit, "interval": interval}
			)
		);
	}
	
		
	/**
	 */
	async function run_iteration(
		conf : _munin.conf.type_conf,
		sources : Array<_munin.type_source>,
		targets : Array<_munin.type_target>,
		{
			"dry_run": dry_run = false,
		} : {
			dry_run ?: boolean;
		} = {
		}
	) : Promise<void>
	{
		const now : lib_plankton.pit.type_pit = lib_plankton.pit.now();
		const events : Array<_munin.type_event> = (
			(await Promise.all(sources.map(source => source.fetch())))
			.reduce((x, y) => x.concat(y), [])
		);
		for (const target of targets) {
			for (const reminder_hours of target.reminders) {
				for (const event of events) {
					const remind : boolean = shall_remind(
						event,
						reminder_hours,
						{
							"pit": now,
							"interval": conf.settings.interval,
						}
					);
					if (! remind) {
						// do nothing
					}
					else {
						lib_plankton.log._info(
							"munin.remind.do",
							{
								"details": {
									"event": event,
									"target": target.show(),
								}
							}
						);
						if (dry_run) {
							// do nothing
						}
						else {
							try {
								await target.send(conf.labels, event);
							}
							catch (error) {
								lib_plankton.log.error(
									"munin.remind.error",
									{
										"details": {
											"message": String(error),
										}
									}
								);
							}
						}
					}
				}
			}
		}
	}
	
	
	/**
	 */
	export async function run(
		conf : _munin.conf.type_conf,
		{
			"single_run": single_run = false,
			"dry_run": dry_run = false,
		} : {
			single_run ?: boolean;
			dry_run ?: boolean;
		} = {
		}
	) : Promise<void>
	{
		const sources : Array<_munin.type_source> = conf.sources.map(
			source_raw => _munin.sources.factory(source_raw)
		);
		const targets : Array<_munin.type_target> = conf.targets.map(
			target_raw => _munin.targets.factory(target_raw)
		);
		lib_plankton.log._info(
			"munin.run.start",
			{
				"details": {
				}
			}
		);
		if (single_run) {
			await run_iteration(conf, sources, targets, {"dry_run": dry_run});
		}
		else {
			while (true) {
				await run_iteration(conf, sources, targets, {"dry_run": dry_run});
				await lib_plankton.call.sleep(conf.settings.interval * 60 * 60);
			}
		}
	}
	
}