<?php
/**
 * SPDX-FileCopyrightText: 2017 Nextcloud GmbH and Nextcloud contributors
 * SPDX-License-Identifier: AGPL-3.0-or-later
 */
namespace OCA\Comments\Collaboration;

use OCP\Collaboration\AutoComplete\ISorter;
use OCP\Comments\ICommentsManager;

class CommentersSorter implements ISorter {
	public function __construct(
		private ICommentsManager $commentsManager,
	) {
	}

	public function getId(): string {
		return 'commenters';
	}

	/**
	 * Sorts people who commented on the given item atop (descelating) of the
	 * others
	 *
	 * @param array &$sortArray
	 * @param array $context
	 */
	public function sort(array &$sortArray, array $context): void {
		$commenters = $this->retrieveCommentsInformation($context['itemType'], $context['itemId']);
		if (count($commenters) === 0) {
			return;
		}

		foreach ($sortArray as $type => &$byType) {
			if (!isset($commenters[$type])) {
				continue;
			}

			// at least on PHP 5.6 usort turned out to be not stable. So we add
			// the current index to the value and compare it on a draw
			$i = 0;
			$workArray = array_map(function ($element) use (&$i) {
				return [$i++, $element];
			}, $byType);

			usort($workArray, function ($a, $b) use ($commenters, $type) {
				$r = $this->compare($a[1], $b[1], $commenters[$type]);
				if ($r === 0) {
					$r = $a[0] - $b[0];
				}
				return $r;
			});

			// and remove the index values again
			$byType = array_column($workArray, 1);
		}
	}

	/**
	 * @return array<string, array<string, int>>
	 */
	protected function retrieveCommentsInformation(string $type, string $id): array {
		$comments = $this->commentsManager->getForObject($type, $id);
		if (count($comments) === 0) {
			return [];
		}

		$actors = [];
		foreach ($comments as $comment) {
			if (!isset($actors[$comment->getActorType()])) {
				$actors[$comment->getActorType()] = [];
			}
			if (!isset($actors[$comment->getActorType()][$comment->getActorId()])) {
				$actors[$comment->getActorType()][$comment->getActorId()] = 1;
			} else {
				$actors[$comment->getActorType()][$comment->getActorId()]++;
			}
		}
		return $actors;
	}

	protected function compare(array $a, array $b, array $commenters): int {
		$a = $a['value']['shareWith'];
		$b = $b['value']['shareWith'];

		$valueA = $commenters[$a] ?? 0;
		$valueB = $commenters[$b] ?? 0;

		return $valueB - $valueA;
	}
}