<?php

declare(strict_types=1);
/**
 * SPDX-FileCopyrightText: 2016-2024 Nextcloud GmbH and Nextcloud contributors
 * SPDX-FileCopyrightText: 2016 ownCloud, Inc.
 * SPDX-License-Identifier: AGPL-3.0-only
 */

namespace OC;

use OCP\AppFramework\QueryException;
use OCP\Capabilities\ICapability;
use OCP\Capabilities\IInitialStateExcludedCapability;
use OCP\Capabilities\IPublicCapability;
use OCP\ILogger;
use Psr\Log\LoggerInterface;

class CapabilitiesManager {
	/**
	 * Anything above 0.1s to load the capabilities of an app qualifies for bad code
	 * and should be cached within the app.
	 */
	public const ACCEPTABLE_LOADING_TIME = 0.1;

	/** @var \Closure[] */
	private array $capabilities = [];

	public function __construct(
		private LoggerInterface $logger,
	) {
	}

	/**
	 * Get an array of all the capabilities that are registered at this manager
	 *
	 * @param bool $public get public capabilities only
	 * @throws \InvalidArgumentException
	 * @return array<string, mixed>
	 */
	public function getCapabilities(bool $public = false, bool $initialState = false) : array {
		$capabilities = [];
		$slowCapabilities = [];
		foreach ($this->capabilities as $capability) {
			try {
				$c = $capability();
			} catch (QueryException $e) {
				$this->logger->error('CapabilitiesManager', [
					'exception' => $e,
				]);
				continue;
			}

			if ($c instanceof ICapability) {
				if (!$public || $c instanceof IPublicCapability) {
					if ($initialState && ($c instanceof IInitialStateExcludedCapability)) {
						// Remove less important capabilities information that are expensive to query
						// that we would otherwise inject to every page load
						continue;
					}

					$startTime = microtime(true);
					$capabilities = array_replace_recursive($capabilities, $c->getCapabilities());
					$timeSpent = microtime(true) - $startTime;

					if ($timeSpent > self::ACCEPTABLE_LOADING_TIME) {
						$slowCapabilities[get_class($c)] = $timeSpent;
					}
				}
			} else {
				throw new \InvalidArgumentException('The given Capability (' . get_class($c) . ') does not implement the ICapability interface');
			}
		}

		if ($slowCapabilities !== []) {
			$this->logSlowCapabilities($slowCapabilities);
		}

		return $capabilities;
	}

	/**
	 * Log a single message for all capabilities that took too long to generate,
	 * using the highest log level applicable to the slowest one.
	 *
	 * @param array<string, float> $slowCapabilities Map of class name to time spent in seconds
	 */
	private function logSlowCapabilities(array $slowCapabilities): void {
		$slowestTime = max($slowCapabilities);
		$logLevel = match (true) {
			$slowestTime > self::ACCEPTABLE_LOADING_TIME * 16 => ILogger::FATAL,
			$slowestTime > self::ACCEPTABLE_LOADING_TIME * 8 => ILogger::ERROR,
			$slowestTime > self::ACCEPTABLE_LOADING_TIME * 4 => ILogger::WARN,
			$slowestTime > self::ACCEPTABLE_LOADING_TIME * 2 => ILogger::INFO,
			default => ILogger::DEBUG,
		};

		$durations = [];
		foreach ($slowCapabilities as $className => $timeSpent) {
			$durations[] = $className . ' (' . round($timeSpent, 2) . 's)';
		}

		$this->logger->log(
			$logLevel,
			'Generating the capabilities of the following apps took longer than {acceptable} seconds: {capabilities}',
			[
				'acceptable' => self::ACCEPTABLE_LOADING_TIME,
				'capabilities' => implode(', ', $durations),
			]
		);
	}

	/**
	 * In order to improve lazy loading a closure can be registered which will be called in case
	 * capabilities are actually requested
	 *
	 * $callable has to return an instance of OCP\Capabilities\ICapability
	 *
	 * @param \Closure $callable
	 */
	public function registerCapability(\Closure $callable) {
		$this->capabilities[] = $callable;
	}
}