<?php

namespace Yoast\WP\SEO\Premium\Repositories;

use Yoast\WP\Lib\Model;
use Yoast\WP\Lib\ORM;

/**
 * Class Prominent_Words_Repository.
 */
class Prominent_Words_Repository {

	/**
	 * Class constructor.
	 *
	 * Empty constructor is necessary for BC.
	 *
	 * @see \Yoast\WP\SEO\Repositories\Prominent_Words_Repository
	 */
	public function __construct() {
	}

	/**
	 * Starts a query for this repository.
	 *
	 * @return ORM
	 */
	public function query() {
		return Model::of_type( 'Prominent_Words' );
	}

	/**
	 * Finds the prominent words for a given post (indexable).
	 *
	 * @param int $indexable_id The indexable ID.
	 *
	 * @return array The list of prominent words items found by the indexable id.
	 */
	public function find_by_indexable_id( $indexable_id ) {
		return $this->query()->where( 'indexable_id', $indexable_id )->find_many();
	}

	/**
	 * Finds the prominent words based on a list of indexable ids.
	 * The method also computes the document frequency of each word and adds it as a separate property on the objects.
	 *
	 * @param int[] $ids The ids of indexables to get prominent words for.
	 *
	 * @return array The list of prominent words items found by indexable ids.
	 */
	public function find_by_list_of_ids( $ids ) {
		if ( empty( $ids ) ) {
			return [];
		}

		$prominent_words = $this->query()->where_in( 'indexable_id', $ids )->find_many();
		$prominent_stems = \wp_list_pluck( $prominent_words, 'stem' );
		$document_freqs  = $this->query()
			->select( 'stem' )
			->select_expr( 'COUNT(id)', 'count' )
			->where_in( 'stem', $prominent_stems )
			->group_by( 'stem' )
			->find_array();

		$stem_counts = [];
		foreach ( $document_freqs as $document_freq ) {
			$stem_counts[ $document_freq['stem'] ] = $document_freq['count'];
		}
		foreach ( $prominent_words as $prominent_word ) {
			if ( ! \array_key_exists( $prominent_word->stem, $stem_counts ) ) {
				continue;
			}
			$prominent_word->df = (int) $stem_counts[ $prominent_word->stem ];
		}

		return $prominent_words;
	}

	/**
	 * Finds all indexable ids which have prominent words with stems from the list.
	 *
	 * @param array $stems        The stems of prominent words to search for.
	 * @param int   $limit        The number of indexable ids to return in 1 call.
	 * @param int   $page         From which page (batch) to begin.
	 * @param int[] $excluded_ids The indexable IDs to exclude.
	 *
	 * @return array The list of indexable ids.
	 */
	public function find_ids_by_stems( $stems, $limit, $page, $excluded_ids = [] ) {
		if ( empty( $stems ) ) {
			return [];
		}

		$offset = ( ( $page - 1 ) * $limit );

		$stem_placeholders = \implode( ', ', \array_fill( 0, \count( $stems ), '%s' ) );

		$query = Model::of_type( 'Indexable' )
			->table_alias( 'i' )
			->select( 'id' )
			->where_raw(
				'i.id IN ( SELECT DISTINCT pw.indexable_id FROM ' . Model::get_table_name( 'Prominent_Words' ) . ' pw WHERE pw.stem IN (' . $stem_placeholders . ') )',
				$stems
			)
			->where_raw( '( i.post_status NOT IN ( \'draft\', \'auto-draft\', \'trash\' ) OR i.post_status IS NULL )' )
			->limit( $limit )
			->offset( $offset );

		if ( ! empty( $excluded_ids ) ) {
			$query = $query->where_not_in( 'id', $excluded_ids );
		}

		$results = $query->find_array();

		return \wp_list_pluck( $results, 'id' );
	}

	/**
	 * Deletes multiple prominent words from the database in one query.
	 *
	 * @param int   $indexable_id   The id of the indexable which needs to have
	 *                              some of its prominent words deleted.
	 * @param array $outdated_stems The array with to-be-deleted prominent word stems.
	 *
	 * @return bool Whether the delete was successful.
	 */
	public function delete_by_indexable_id_and_stems( $indexable_id, $outdated_stems ) {
		// Check if the data are of the right format.
		if ( ( ! $indexable_id ) || empty( $outdated_stems ) || ! \is_array( $outdated_stems ) ) {
			return false;
		}

		return $this->query()
			->where( 'indexable_id', $indexable_id )
			->where_in( 'stem', $outdated_stems )
			->delete_many();
	}

	/**
	 * Counts the number of documents in which each of the given stems occurs.
	 *
	 * @param string[] $stems The stems of the words for which to find the document frequencies.
	 *
	 * @return array The list of stems and their respective document frequencies. Each entry has a 'stem' and a 'document_frequency' parameter.
	 */
	public function count_document_frequencies( $stems ) {
		if ( empty( $stems ) ) {
			return [];
		}

		/*
		 * Count in how many documents each stem occurs by querying the database.
		 * Returns "Prominent_Words" with two properties: 'stem' and 'document_frequency'.
		 */
		$raw_doc_frequencies = $this->query()
			->select( 'stem' )
			->select_expr( 'COUNT( stem )', 'document_frequency' )
			->where_in( 'stem', $stems )
			->group_by( 'stem' )
			->find_many();

		// We want to change the raw document frequencies into a map mapping stems to document frequency.
		$stems = \array_map(
			static function( $item ) {
				return $item->stem;
			},
			$raw_doc_frequencies
		);

		$doc_frequencies = \array_fill_keys( $stems, 0 );
		foreach ( $raw_doc_frequencies as $raw_doc_frequency ) {
			$doc_frequencies[ $raw_doc_frequency->stem ] = (int) $raw_doc_frequency->document_frequency;
		}

		return $doc_frequencies;
	}
}
