<?php
/**
 * Topics and hashtags.
 *
 * @package SpaceBay
 */

namespace SpaceBay\Content;

use SpaceBay\Database\Tables;
use SpaceBay\Support\Cache;
use SpaceBay\Support\Slug;
use SpaceBay\Support\Time;
use WP_Error;

defined( 'ABSPATH' ) || exit;

/**
 * Topics are labels the community team defines; members pick up to three per
 * post. Hashtags are created automatically from #words in posts.
 */
final class Terms {

	/**
	 * Most topics allowed on one post.
	 *
	 * @var int
	 */
	const MAX_TOPICS = 3;

	/**
	 * Returns every topic, cached.
	 *
	 * @return array[]
	 */
	public static function topics() {
		return Cache::remember(
			'terms',
			'topics',
			static function () {
				global $wpdb;

				$rows = $wpdb->get_results( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table, cached by Cache::remember().
					$wpdb->prepare( 'SELECT id, title, slug, description, settings FROM %i WHERE taxonomy = %s ORDER BY title ASC', Tables::name( 'terms' ), 'topic' ),
					ARRAY_A
				);

				return array_map( array( __CLASS__, 'format_topic' ), (array) $rows );
			}
		);
	}

	/**
	 * Finds a topic by ID.
	 *
	 * @param int $id Topic ID.
	 * @return array|null
	 */
	public static function topic( $id ) {
		foreach ( self::topics() as $topic ) {
			if ( absint( $id ) === $topic['id'] ) {
				return $topic;
			}
		}

		return null;
	}

	/**
	 * Finds a topic by slug.
	 *
	 * @param string $slug Topic slug.
	 * @return array|null
	 */
	public static function topic_by_slug( $slug ) {
		foreach ( self::topics() as $topic ) {
			if ( $topic['slug'] === $slug ) {
				return $topic;
			}
		}

		return null;
	}

	/**
	 * Creates or updates a topic.
	 *
	 * @param array $input Title, description, color.
	 * @param int   $id    Topic ID to update, 0 to create.
	 * @return array|WP_Error The topic.
	 */
	public static function save_topic( array $input, $id = 0 ) {
		global $wpdb;

		$title = mb_substr( sanitize_text_field( (string) ( $input['title'] ?? '' ) ), 0, 60 );

		if ( '' === $title ) {
			return new WP_Error( 'spacebay_topic_title', __( 'Please enter a topic name.', 'spacebay' ), array( 'status' => 400 ) );
		}

		foreach ( self::topics() as $topic ) {
			if ( (int) $topic['id'] !== (int) $id && mb_strtolower( $topic['title'] ) === mb_strtolower( $title ) ) {
				return new WP_Error( 'spacebay_topic_exists', __( 'A topic with this name already exists.', 'spacebay' ), array( 'status' => 400 ) );
			}
		}

		$color = sanitize_hex_color( (string) ( $input['color'] ?? '' ) );
		$data  = array(
			'title'       => $title,
			'description' => mb_substr( sanitize_text_field( (string) ( $input['description'] ?? '' ) ), 0, 200 ),
			'settings'    => wp_json_encode( array( 'color' => $color ? strtolower( $color ) : '' ) ),
		);
		$table = Tables::name( 'terms' );

		if ( $id ) {
			if ( ! self::topic( $id ) ) {
				return new WP_Error( 'spacebay_topic_not_found', __( 'Topic not found.', 'spacebay' ), array( 'status' => 404 ) );
			}

			$wpdb->update( $table, $data, array( 'id' => absint( $id ) ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.
		} else {
			$data['taxonomy']   = 'topic';
			$data['slug']       = self::unique_slug( 'topic', $title );
			$data['created_at'] = Time::now();
			$wpdb->insert( $table, $data ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.
			$id = (int) $wpdb->insert_id;
		}

		Cache::flush( 'terms' );

		return self::topic( $id );
	}

	/**
	 * Deletes a topic and removes it from posts.
	 *
	 * @param int $id Topic ID.
	 * @return bool
	 */
	public static function delete_topic( $id ) {
		global $wpdb;

		if ( ! self::topic( $id ) ) {
			return false;
		}

		$wpdb->delete( Tables::name( 'term_relations' ), array( 'term_id' => absint( $id ) ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.
		$wpdb->delete( Tables::name( 'terms' ), array( 'id' => absint( $id ) ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.
		Cache::flush( 'terms' );

		return true;
	}

	/**
	 * Keeps only valid topic IDs, at most three.
	 *
	 * @param array $ids Requested IDs.
	 * @return int[]
	 */
	public static function valid_topic_ids( array $ids ) {
		$valid = array();

		foreach ( array_unique( array_map( 'absint', $ids ) ) as $id ) {
			if ( self::topic( $id ) ) {
				$valid[] = $id;
			}
		}

		return array_slice( $valid, 0, self::MAX_TOPICS );
	}

	/**
	 * Finds a hashtag term ID by its text.
	 *
	 * @param string $tag Lower-case hashtag without "#".
	 * @return int 0 when unknown.
	 */
	public static function hashtag_id( $tag ) {
		global $wpdb;

		return (int) $wpdb->get_var( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table, indexed lookup.
			$wpdb->prepare( 'SELECT id FROM %i WHERE taxonomy = %s AND slug = %s', Tables::name( 'terms' ), 'hashtag', self::hashtag_slug( $tag ) )
		);
	}

	/**
	 * Replaces the topics and hashtags of a post.
	 *
	 * @param int      $post_id   Post ID.
	 * @param int[]    $topic_ids Valid topic IDs.
	 * @param string[] $hashtags  Lower-case hashtags.
	 * @return void
	 */
	public static function set_post_terms( $post_id, array $topic_ids, array $hashtags ) {
		global $wpdb;

		$relations = Tables::name( 'term_relations' );
		$wpdb->delete( $relations, array( 'object_id' => absint( $post_id ) ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.

		$term_ids = $topic_ids;

		foreach ( array_slice( array_unique( $hashtags ), 0, 20 ) as $tag ) {
			$term_ids[] = self::ensure_hashtag( $tag );
		}

		foreach ( array_unique( array_filter( $term_ids ) ) as $term_id ) {
			$wpdb->insert( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.
				$relations,
				array(
					'term_id'   => (int) $term_id,
					'object_id' => absint( $post_id ),
				)
			);
		}
	}

	/**
	 * Removes all term links of posts.
	 *
	 * @param int[] $post_ids Post IDs.
	 * @return void
	 */
	public static function delete_for_posts( array $post_ids ) {
		global $wpdb;

		foreach ( array_map( 'absint', $post_ids ) as $post_id ) {
			$wpdb->delete( Tables::name( 'term_relations' ), array( 'object_id' => $post_id ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.
		}
	}

	/**
	 * Topics and hashtags of several posts.
	 *
	 * @param int[] $post_ids Post IDs.
	 * @return array<int, array{topics: array[], hashtags: string[]}>
	 */
	public static function for_posts( array $post_ids ) {
		global $wpdb;

		$post_ids = array_values( array_filter( array_map( 'absint', $post_ids ) ) );

		if ( ! $post_ids ) {
			return array();
		}

		$placeholders = implode( ',', array_fill( 0, count( $post_ids ), '%d' ) );
		$rows         = $wpdb->get_results( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom tables, one query per feed page.
			$wpdb->prepare( // phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber -- The IN() list has one %d per ID.
				"SELECT r.object_id, t.id, t.taxonomy, t.slug FROM %i r INNER JOIN %i t ON t.id = r.term_id WHERE r.object_id IN ($placeholders)", // phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare, WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber, WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- Placeholders are built from %d only.
				array_merge( array( Tables::name( 'term_relations' ), Tables::name( 'terms' ) ), $post_ids )
			),
			ARRAY_A
		);

		$map = array();

		foreach ( (array) $rows as $row ) {
			$post_id = (int) $row['object_id'];

			if ( ! isset( $map[ $post_id ] ) ) {
				$map[ $post_id ] = array(
					'topics'   => array(),
					'hashtags' => array(),
				);
			}

			if ( 'topic' === $row['taxonomy'] ) {
				$topic = self::topic( (int) $row['id'] );

				if ( $topic ) {
					$map[ $post_id ]['topics'][] = $topic;
				}
			} else {
				$map[ $post_id ]['hashtags'][] = $row['slug'];
			}
		}

		return $map;
	}

	/**
	 * Returns the ID of a hashtag, creating it when needed.
	 *
	 * @param string $tag Hashtag text.
	 * @return int
	 */
	private static function ensure_hashtag( $tag ) {
		global $wpdb;

		$id = self::hashtag_id( $tag );

		if ( $id ) {
			return $id;
		}

		$wpdb->insert( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.
			Tables::name( 'terms' ),
			array(
				'taxonomy'   => 'hashtag',
				'title'      => mb_substr( $tag, 0, 50 ),
				'slug'       => self::hashtag_slug( $tag ),
				'created_at' => Time::now(),
			)
		);

		return (int) $wpdb->insert_id;
	}

	/**
	 * Storage form of a hashtag: lower case, at most 50 characters.
	 *
	 * @param string $tag Hashtag text.
	 * @return string
	 */
	public static function hashtag_slug( $tag ) {
		return mb_substr( mb_strtolower( preg_replace( '/[^\p{L}\p{N}_]/u', '', (string) $tag ) ), 0, 50 );
	}

	/**
	 * Returns a topic slug no other topic uses.
	 *
	 * @param string $taxonomy Taxonomy.
	 * @param string $title    Title.
	 * @return string
	 */
	private static function unique_slug( $taxonomy, $title ) {
		global $wpdb;

		$base   = Slug::make( $title, 'topic' );
		$slug   = $base;
		$suffix = 2;

		while ( $wpdb->get_var( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Uniqueness check must read fresh data.
			$wpdb->prepare( 'SELECT id FROM %i WHERE taxonomy = %s AND slug = %s', Tables::name( 'terms' ), $taxonomy, $slug )
		) ) {
			$slug = $base . '-' . $suffix;
			++$suffix;
		}

		return $slug;
	}

	/**
	 * Formats a topic row.
	 *
	 * @param array $row Row.
	 * @return array
	 */
	public static function format_topic( array $row ) {
		$settings = json_decode( (string) $row['settings'], true );

		return array(
			'id'          => (int) $row['id'],
			'title'       => $row['title'],
			'slug'        => $row['slug'],
			'description' => (string) $row['description'],
			'color'       => isset( $settings['color'] ) ? (string) $settings['color'] : '',
		);
	}
}