<?php

namespace MediaWiki\Extension\AbuseFilter;

use BagOStuff;
use IBufferingStatsdDataFactory;
use MediaWiki\Config\ServiceOptions;
use Psr\Log\LoggerInterface;
use Title;

/**
 * This class is used to create, store, and retrieve profiling information for single filters and
 * groups of filters.
 * @internal
 */
class FilterProfiler {
	public const SERVICE_NAME = 'AbuseFilterFilterProfiler';

	public const CONSTRUCTOR_OPTIONS = [
		'AbuseFilterProfileActionsCap',
		'AbuseFilterConditionLimit',
		'AbuseFilterSlowFilterRuntimeLimit',
	];

	private const NULL_FILTER_PROFILE = [
		// Number of observed executions of this filter
		'count' => 0,
		// Number of observed matches of this filter
		'matches' => 0,
		// Total time spent on this filter from all observed executions (in milliseconds)
		'total-time' => 0.0,
		// Total number of conditions for this filter from all executions
		'total-cond' => 0,
	];

	private const NULL_GROUP_PROFILE = [
		// Total number of actions observed
		'total' => 0,
		// Number of actions ending by exceeding condition limit
		'overflow' => 0,
		// Total time of execution of all observed actions (in milliseconds)
		'total-time' => 0.0,
		// Total number of conditions from all observed actions
		'total-cond' => 0,
		// Total number of filters matched
		'matches' => 0,
	];

	/**
	 * @var int How long to keep profiling data in cache (in seconds)
	 */
	private const STATS_STORAGE_PERIOD = BagOStuff::TTL_DAY;

	/** @var BagOStuff */
	private $objectStash;

	/** @var ServiceOptions */
	private $options;

	/** @var string */
	private $localWikiID;

	/** @var IBufferingStatsdDataFactory */
	private $statsd;

	/** @var LoggerInterface */
	private $logger;

	/**
	 * @param BagOStuff $objectStash
	 * @param ServiceOptions $options
	 * @param string $localWikiID
	 * @param IBufferingStatsdDataFactory $statsd
	 * @param LoggerInterface $logger
	 */
	public function __construct(
		BagOStuff $objectStash,
		ServiceOptions $options,
		string $localWikiID,
		IBufferingStatsdDataFactory $statsd,
		LoggerInterface $logger
	) {
		$this->objectStash = $objectStash;
		$options->assertRequiredOptions( self::CONSTRUCTOR_OPTIONS );
		$this->options = $options;
		$this->localWikiID = $localWikiID;
		$this->statsd = $statsd;
		$this->logger = $logger;
	}

	/**
	 * @param int $filter
	 */
	public function resetFilterProfile( int $filter ): void {
		$profileKey = $this->filterProfileKey( $filter );
		$this->objectStash->delete( $profileKey );
	}

	/**
	 * Retrieve per-filter statistics.
	 *
	 * @param int $filter
	 * @return array See self::NULL_FILTER_PROFILE for the returned array structure
	 * @phan-return array{count:int,matches:int,total-time:float,total-cond:int}
	 */
	public function getFilterProfile( int $filter ): array {
		return $this->objectStash->get( $this->filterProfileKey( $filter ) )
			?: self::NULL_FILTER_PROFILE;
	}

	/**
	 * Retrieve per-group statistics.
	 *
	 * @param string $group
	 * @return array See self::NULL_GROUP_PROFILE for the returned array structure
	 * @phan-return array{total:int,overflow:int,total-time:float,total-cond:int,matches:int}
	 */
	public function getGroupProfile( string $group ): array {
		return $this->objectStash->get( $this->filterProfileGroupKey( $group ) )
			?: self::NULL_GROUP_PROFILE;
	}

	/**
	 * Record per-filter profiling data
	 *
	 * @param int $filter
	 * @param float $time Time taken, in milliseconds
	 * @param int $conds
	 * @param bool $matched
	 */
	private function recordProfilingResult( int $filter, float $time, int $conds, bool $matched ): void {
		// Note: It is important that all key information be stored together in a single
		// memcache entry to avoid race conditions where competing Apache instances
		// partially overwrite the stats.
		$profileKey = $this->filterProfileKey( $filter );
		$this->objectStash->merge(
			$profileKey,
			static function ( $cache, $key, $profile ) use ( $time, $conds, $matched ) {
				if ( $profile === false ) {
					$profile = self::NULL_FILTER_PROFILE;
				}

				$profile['count']++;
				if ( $matched ) {
					$profile['matches']++;
				}
				$profile['total-time'] += $time;
				$profile['total-cond'] += $conds;

				return $profile;
			},
			BagOStuff::TTL_HOUR
		);
	}

	/**
	 * Check if profiling data for all filters is lesser than the limit. If not, delete it and
	 * also delete per-filter profiling for all filters. Note that we don't need to reset it for
	 * disabled filters too, as their profiling data will be reset upon re-enabling anyway.
	 *
	 * @param string $group
	 * @param string[] $allFilters
	 */
	public function checkResetProfiling( string $group, array $allFilters ): void {
		$profile = $this->getGroupProfile( $group );
		$total = $profile['total'];

		if ( $total > $this->options->get( 'AbuseFilterProfileActionsCap' ) ) {
			$profileKey = $this->filterProfileGroupKey( $group );
			$this->objectStash->delete( $profileKey );
			foreach ( $allFilters as $filter ) {
				list( $filterID, $global ) = GlobalNameUtils::splitGlobalName( $filter );
				if ( $global === false ) {
					$this->resetFilterProfile( $filterID );
				}
			}
		}
	}

	/**
	 * Update global statistics
	 *
	 * @param string $group
	 * @param int $condsUsed The amount of used conditions
	 * @param float $totalTime Time taken, in milliseconds
	 * @param bool $anyMatch Whether at least one filter matched the action
	 */
	public function recordStats( string $group, int $condsUsed, float $totalTime, bool $anyMatch ): void {
		$profileKey = $this->filterProfileGroupKey( $group );

		// Note: All related data is stored in a single memcache entry and updated via merge()
		// to avoid race conditions where partial updates on competing instances corrupt the data.
		$this->objectStash->merge(
			$profileKey,
			function ( $cache, $key, $profile ) use ( $condsUsed, $totalTime, $anyMatch ) {
				if ( $profile === false ) {
					$profile = self::NULL_GROUP_PROFILE;
				}

				$profile['total']++;
				$profile['total-time'] += $totalTime;
				$profile['total-cond'] += $condsUsed;

				// Increment overflow counter, if our condition limit overflowed
				if ( $condsUsed > $this->options->get( 'AbuseFilterConditionLimit' ) ) {
					$profile['overflow']++;
				}

				// Increment counter by 1 if there was at least one match
				if ( $anyMatch ) {
					$profile['matches']++;
				}

				return $profile;
			},
			self::STATS_STORAGE_PERIOD
		);
	}

	/**
	 * Record runtime profiling data for all filters together
	 *
	 * @param int $totalFilters
	 * @param int $totalConditions
	 * @param float $runtime
	 * @codeCoverageIgnore
	 */
	public function recordRuntimeProfilingResult( int $totalFilters, int $totalConditions, float $runtime ): void {
		$keyPrefix = 'abusefilter.runtime-profile.' . $this->localWikiID . '.';

		$this->statsd->timing( $keyPrefix . 'runtime', $runtime );
		$this->statsd->timing( $keyPrefix . 'total_filters', $totalFilters );
		$this->statsd->timing( $keyPrefix . 'total_conditions', $totalConditions );
	}

	/**
	 * Record per-filter profiling, for all filters
	 *
	 * @param Title $title
	 * @param array $data Profiling data
	 * @phan-param array<string,array{time:float,conds:int,result:bool}> $data
	 */
	public function recordPerFilterProfiling( Title $title, array $data ): void {
		$slowFilterThreshold = $this->options->get( 'AbuseFilterSlowFilterRuntimeLimit' );

		foreach ( $data as $filterName => $params ) {
			list( $filterID, $global ) = GlobalNameUtils::splitGlobalName( $filterName );
			// @todo Maybe add a parameter to recordProfilingResult to record global filters
			// data separately (in the foreign wiki)
			if ( !$global ) {
				$this->recordProfilingResult(
					$filterID,
					$params['time'],
					$params['conds'],
					$params['result']
				);
			}

			if ( $params['time'] > $slowFilterThreshold ) {
				$this->recordSlowFilter(
					$title,
					$filterName,
					$params['time'],
					$params['conds'],
					$params['result'],
					$global
				);
			}
		}
	}

	/**
	 * Logs slow filter's runtime data for later analysis
	 *
	 * @param Title $title
	 * @param string $filterId
	 * @param float $runtime
	 * @param int $totalConditions
	 * @param bool $matched
	 * @param bool $global
	 */
	private function recordSlowFilter(
		Title $title,
		string $filterId,
		float $runtime,
		int $totalConditions,
		bool $matched,
		bool $global
	): void {
		$this->logger->info(
			'Edit filter {filter_id} on {wiki} is taking longer than expected',
			[
				'wiki' => $this->localWikiID,
				'filter_id' => $filterId,
				'title' => $title->getPrefixedText(),
				'runtime' => $runtime,
				'matched' => $matched,
				'total_conditions' => $totalConditions,
				'global' => $global
			]
		);
	}

	/**
	 * Get the memcache access key used to store per-filter profiling data.
	 *
	 * @param int $filter
	 * @return string
	 */
	private function filterProfileKey( int $filter ): string {
		return $this->objectStash->makeKey( 'abusefilter-profile', 'v3', $filter );
	}

	/**
	 * Memcache access key used to store overall profiling data for rule groups
	 *
	 * @param string $group
	 * @return string
	 */
	private function filterProfileGroupKey( string $group ): string {
		return $this->objectStash->makeKey( 'abusefilter-profile', 'group', $group );
	}
}