<?php
/**
 * Comments and replies.
 *
 * @package SpaceBay
 */

namespace SpaceBay\Feed;

use SpaceBay\Content\Reactions;
use SpaceBay\Content\Renderer;
use SpaceBay\Database\Tables;
use SpaceBay\Moderation\Moderation;
use SpaceBay\Support\RateLimit;
use SpaceBay\Support\Time;
use WP_Error;

defined( 'ABSPATH' ) || exit;

/**
 * Comments on posts, with nested replies up to MAX_DEPTH levels.
 */
final class Comments {

	/**
	 * Longest comment, in characters.
	 *
	 * @var int
	 */
	const MAX_LENGTH = 5000;

	/**
	 * Deepest reply level; a top-level comment is level 1.
	 *
	 * @var int
	 */
	const MAX_DEPTH = 5;

	/**
	 * Most descendants returned with one page of top-level comments.
	 *
	 * @var int
	 */
	const MAX_DESCENDANTS = 500;

	/**
	 * Columns read from the comments table.
	 *
	 * @var string
	 */
	const COLUMNS = 'id, post_id, parent_id, user_id, message, message_rendered, status, is_pinned, reactions_count, created_at, updated_at';

	/**
	 * Finds a comment.
	 *
	 * @param int $id Comment ID.
	 * @return array|null
	 */
	public static function find( $id ) {
		global $wpdb;

		$row = $wpdb->get_row( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table, single row by primary key.
			$wpdb->prepare( 'SELECT ' . self::COLUMNS . ' FROM %i WHERE id = %d', Tables::name( 'comments' ), absint( $id ) ), // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared -- COLUMNS is a class constant.
			ARRAY_A
		);

		return $row ? self::normalize( $row ) : null;
	}

	/**
	 * Lists top-level comments of a post, oldest first, with all their replies.
	 *
	 * @param int $post_id  Post ID.
	 * @param int $page     Page number, from 1.
	 * @param int $per_page Top-level comments per page.
	 * @return array{items: array[], total: int}
	 */
	public static function for_post( $post_id, $page = 1, $per_page = 20 ) {
		global $wpdb;

		$table    = Tables::name( 'comments' );
		$per_page = max( 1, min( 50, absint( $per_page ) ) );
		$offset   = ( max( 1, absint( $page ) ) - 1 ) * $per_page;

		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared -- Paged comment list; COLUMNS is a class constant.
		$total = (int) $wpdb->get_var(
			$wpdb->prepare( 'SELECT COUNT(id) FROM %i WHERE post_id = %d AND parent_id = 0 AND status = %s', $table, absint( $post_id ), 'published' )
		);
		$top   = $wpdb->get_results(
			$wpdb->prepare(
				'SELECT ' . self::COLUMNS . ' FROM %i WHERE post_id = %d AND parent_id = 0 AND status = %s ORDER BY is_pinned DESC, created_at ASC, id ASC LIMIT %d OFFSET %d',
				$table,
				absint( $post_id ),
				'published',
				$per_page,
				$offset
			),
			ARRAY_A
		);

		$items = array_map( array( __CLASS__, 'normalize' ), (array) $top );
		// phpcs:enable

		$ids = wp_list_pluck( $items, 'id' );

		if ( $ids ) {
			$items = array_merge( $items, self::descendants( $ids, self::MAX_DESCENDANTS ) );
		}

		return array(
			'items' => $items,
			'total' => $total,
		);
	}

	/**
	 * Adds a comment or reply.
	 *
	 * @param array $post    Post row.
	 * @param array $space   Space row of the post.
	 * @param array $input   Raw input: message, parent_id.
	 * @param int   $user_id Author.
	 * @return array|WP_Error The new comment row.
	 */
	public static function create( array $post, array $space, array $input, $user_id ) {
		global $wpdb;

		if ( ! PostAccess::can_comment( $space, $user_id ) ) {
			return new WP_Error( 'spacebay_cannot_comment', __( 'Join this space to comment.', 'spacebay' ), array( 'status' => 403 ) );
		}

		$parent_id = absint( $input['parent_id'] ?? 0 );

		if ( $parent_id ) {
			$parent = self::find( $parent_id );

			if ( ! $parent || $parent['post_id'] !== $post['id'] || 'published' !== $parent['status'] ) {
				return new WP_Error( 'spacebay_bad_parent', __( 'The comment you are replying to no longer exists.', 'spacebay' ), array( 'status' => 400 ) );
			}

			// A reply keeps its real parent; at the depth cap it lands beside the comment it answers.
			$parent_id = self::depth( $parent ) >= self::max_depth() ? $parent['parent_id'] : $parent['id'];
		}

		$limited = RateLimit::hit( 'comment', $user_id, 20 );

		if ( is_wp_error( $limited ) ) {
			return $limited;
		}

		$screen = Moderation::screen( array( 'message' => (string) ( $input['message'] ?? '' ) ), $space, $user_id, 'comment' );

		if ( is_wp_error( $screen ) ) {
			return $screen;
		}

		$rendered = self::render( $screen['texts']['message'] );

		if ( is_wp_error( $rendered ) ) {
			return $rendered;
		}

		$now    = Time::now();
		$status = '' === $screen['hold'] ? 'published' : 'pending';

		$wpdb->insert( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.
			Tables::name( 'comments' ),
			array(
				'post_id'          => $post['id'],
				'parent_id'        => $parent_id,
				'user_id'          => absint( $user_id ),
				'message'          => $rendered['text'],
				'message_rendered' => $rendered['html'],
				'status'           => $status,
				'created_at'       => $now,
				'updated_at'       => $now,
			)
		);

		$comment = self::find( (int) $wpdb->insert_id );
		delete_transient( 'spacebay_admin_stats' );

		if ( 'pending' === $status ) {
			Moderation::held( 'comment', $comment, $screen['hold'], $screen['note'] );

			return $comment;
		}

		Posts::touch( $post['id'] );

		/**
		 * Fires after a comment is added, including when a moderator
		 * approves a comment that was held for review.
		 *
		 * @since 1.0.0
		 *
		 * @param array $comment  Comment row.
		 * @param array $post     Post row.
		 * @param int[] $mentions IDs of mentioned members.
		 */
		do_action( 'spacebay_comment_created', $comment, $post, $rendered['mentions'] );

		return $comment;
	}

	/**
	 * Edits the text of a comment.
	 *
	 * @param array  $comment Comment row.
	 * @param string $message New text.
	 * @param array  $space   Space row, used to check blocked words.
	 * @param int    $user_id Editor.
	 * @return array|WP_Error Updated row.
	 */
	public static function update( array $comment, $message, array $space = array(), $user_id = 0 ) {
		global $wpdb;

		if ( $user_id ) {
			$limited = RateLimit::hit( 'edit', $user_id, 20 );

			if ( is_wp_error( $limited ) ) {
				return $limited;
			}
		}

		if ( $space ) {
			$screen = Moderation::screen( array( 'message' => (string) $message ), $space, $user_id, 'comment_edit' );

			if ( is_wp_error( $screen ) ) {
				return $screen;
			}

			$message = $screen['texts']['message'];
		}

		$rendered = self::render( $message );

		if ( is_wp_error( $rendered ) ) {
			return $rendered;
		}

		$wpdb->update( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.
			Tables::name( 'comments' ),
			array(
				'message'          => $rendered['text'],
				'message_rendered' => $rendered['html'],
				'updated_at'       => Time::now(),
			),
			array( 'id' => $comment['id'] )
		);

		return self::find( $comment['id'] );
	}

	/**
	 * Changes the status of a comment and recounts the post's comments.
	 *
	 * @param array  $comment Comment row.
	 * @param string $status  "published" or "pending".
	 * @return array Updated row.
	 */
	public static function set_status( array $comment, $status ) {
		global $wpdb;

		$wpdb->update( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.
			Tables::name( 'comments' ),
			array( 'status' => 'pending' === $status ? 'pending' : 'published' ),
			array( 'id' => $comment['id'] )
		);
		Posts::touch( $comment['post_id'] );
		delete_transient( 'spacebay_admin_stats' );

		return self::find( $comment['id'] );
	}

	/**
	 * The depth cap, filterable.
	 *
	 * @return int
	 */
	public static function max_depth() {
		/**
		 * Filters the deepest reply level (a top-level comment is level 1).
		 *
		 * @since 1.0.0
		 *
		 * @param int $max Depth cap, default 5.
		 */
		return max( 1, (int) apply_filters( 'spacebay_comment_max_depth', self::MAX_DEPTH ) );
	}

	/**
	 * Depth of a comment: 1 for a top-level comment.
	 *
	 * @param array $comment Comment row.
	 * @return int
	 */
	public static function depth( array $comment ) {
		$depth = 1;
		$seen  = array( $comment['id'] => true );

		while ( $comment['parent_id'] && ! isset( $seen[ $comment['parent_id'] ] ) ) {
			$comment = self::find( $comment['parent_id'] );

			if ( ! $comment ) {
				break;
			}

			$seen[ $comment['id'] ] = true;
			++$depth;
		}

		return $depth;
	}

	/**
	 * IDs of the direct children of comments.
	 *
	 * @param int[] $parent_ids Comment IDs.
	 * @param int   $user_id    Only children by this user, 0 for all.
	 * @return int[]
	 */
	private static function child_ids( array $parent_ids, $user_id = 0 ) {
		global $wpdb;

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

		$placeholders = implode( ',', array_fill( 0, count( $parent_ids ), '%d' ) );

		if ( $user_id ) {
			$ids = $wpdb->get_col( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Cleanup query.
				$wpdb->prepare( // phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber -- The IN() list has one %d per ID.
					"SELECT id FROM %i WHERE parent_id IN ($placeholders) AND user_id = %d", // phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare, WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, WordPress.DB.PreparedSQL.NotPrepared -- Placeholders are %d only.
					array_merge( array( Tables::name( 'comments' ) ), $parent_ids, array( $user_id ) )
				)
			);
		} else {
			$ids = $wpdb->get_col( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Cleanup query.
				$wpdb->prepare( // phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber -- The IN() list has one %d per ID.
					"SELECT id FROM %i WHERE parent_id IN ($placeholders)", // phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare, WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, WordPress.DB.PreparedSQL.NotPrepared -- Placeholders are %d only.
					array_merge( array( Tables::name( 'comments' ) ), $parent_ids )
				)
			);
		}

		return array_map( 'intval', (array) $ids );
	}

	/**
	 * Published (or all) descendants of comments at any depth, oldest first.
	 *
	 * Reads one level per query, so the cost follows the depth, not the number
	 * of comments.
	 *
	 * @param int[] $root_ids Comment IDs.
	 * @param int   $limit    Most rows to return.
	 * @param bool  $all      Include pending comments.
	 * @return array[] Comment rows.
	 */
	private static function descendants( array $root_ids, $limit, $all = false ) {
		global $wpdb;

		$level  = array_map( 'absint', $root_ids );
		$seen   = array_fill_keys( $level, true );
		$found  = array();
		$rounds = 0;
		$size   = 0;

		while ( $level && $size < $limit && $rounds < 100 ) {
			++$rounds;
			$placeholders = implode( ',', array_fill( 0, count( $level ), '%d' ) );
			$columns      = self::COLUMNS;

			if ( $all ) {
				$rows = $wpdb->get_results( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- One query per level.
					$wpdb->prepare( // phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber -- The IN() list has one %d per ID.
						"SELECT $columns FROM %i WHERE parent_id IN ($placeholders) ORDER BY created_at ASC, id ASC", // phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare, WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, WordPress.DB.PreparedSQL.NotPrepared -- Placeholders are %d only; COLUMNS is a class constant.
						array_merge( array( Tables::name( 'comments' ) ), $level )
					),
					ARRAY_A
				);
			} else {
				$rows = $wpdb->get_results( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- One query per level.
					$wpdb->prepare( // phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber -- The IN() list has one %d per ID.
						"SELECT $columns FROM %i WHERE parent_id IN ($placeholders) AND status = %s ORDER BY created_at ASC, id ASC", // phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare, WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, WordPress.DB.PreparedSQL.NotPrepared -- Placeholders are %d and %s only; COLUMNS is a class constant.
						array_merge( array( Tables::name( 'comments' ) ), $level, array( 'published' ) )
					),
					ARRAY_A
				);
			}

			$level = array();

			foreach ( (array) $rows as $row ) {
				$row = self::normalize( $row );

				if ( isset( $seen[ $row['id'] ] ) ) {
					continue;
				}

				$seen[ $row['id'] ] = true;
				$found[]            = $row;
				$level[]            = $row['id'];
				++$size;
			}
		}

		usort(
			$found,
			static function ( $a, $b ) {
				$by_time = strcmp( $a['created_at'], $b['created_at'] );

				return 0 !== $by_time ? $by_time : $a['id'] <=> $b['id'];
			}
		);

		return array_slice( $found, 0, $limit );
	}

	/**
	 * Deletes a comment and its replies.
	 *
	 * With $keep_replies, replies by other members are kept and move up to the
	 * deleted comment's own parent (top level when it had none). The author's
	 * own direct replies are deleted with it, and the replies to those move up
	 * as well. Without it, every descendant is deleted.
	 *
	 * @param array $comment      Comment row.
	 * @param bool  $keep_replies Keep other members' replies.
	 * @return array{ids: int[], parent_id: int, promoted_ids: int[]} Deleted IDs, the
	 *               parent the kept replies now hang on, and their IDs.
	 */
	public static function delete( array $comment, $keep_replies = false ) {
		global $wpdb;

		$table    = Tables::name( 'comments' );
		$promoted = array();

		if ( $keep_replies ) {
			$own      = self::child_ids( array( $comment['id'] ), $comment['user_id'] );
			$ids      = array_merge( array( $comment['id'] ), $own );
			$promoted = array_values( array_diff( self::child_ids( array( $comment['id'] ) ), $own ) );
			$promoted = array_values( array_unique( array_merge( $promoted, self::child_ids( $own ) ) ) );

			if ( $promoted ) {
				$placeholders = implode( ',', array_fill( 0, count( $promoted ), '%d' ) );
				$wpdb->query( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.
					$wpdb->prepare( "UPDATE %i SET parent_id = %d WHERE id IN ($placeholders)", array_merge( array( $table, $comment['parent_id'] ), $promoted ) ) // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared, WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare, WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber -- One %d per ID.
				);
			}
		} else {
			$ids = array_merge( array( $comment['id'] ), wp_list_pluck( self::descendants( array( $comment['id'] ), PHP_INT_MAX, true ), 'id' ) );
		}

		$ids = array_map( 'intval', $ids );

		Reactions::delete_for( 'comment', $ids );

		foreach ( $ids as $id ) {
			$wpdb->delete( $table, array( 'id' => $id ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.
		}

		Posts::touch( $comment['post_id'] );
		delete_transient( 'spacebay_admin_stats' );

		/**
		 * Fires after a comment and its replies are deleted.
		 *
		 * @since 1.0.0
		 * @since 1.0.0 Added the $ids parameter.
		 *
		 * @param array $comment The deleted comment row.
		 * @param int[] $ids     IDs of every deleted comment: the comment and the replies deleted with it.
		 */
		do_action( 'spacebay_comment_deleted', $comment, $ids );

		return array(
			'ids'          => $ids,
			'parent_id'    => (int) $comment['parent_id'],
			'promoted_ids' => $promoted,
		);
	}

	/**
	 * Deletes all comments of a post.
	 *
	 * @param int $post_id Post ID.
	 * @return void
	 */
	public static function delete_for_post( $post_id ) {
		global $wpdb;

		$table = Tables::name( 'comments' );
		$ids   = $wpdb->get_col( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Cleanup query.
			$wpdb->prepare( 'SELECT id FROM %i WHERE post_id = %d', $table, absint( $post_id ) )
		);

		Reactions::delete_for( 'comment', array_map( 'intval', (array) $ids ) );
		$wpdb->delete( $table, array( 'post_id' => absint( $post_id ) ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.
	}

	/**
	 * Deletes all comments written by a user.
	 *
	 * @param int $user_id User ID.
	 * @return void
	 */
	public static function delete_for_user( $user_id ) {
		global $wpdb;

		$rows = $wpdb->get_results( // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Cleanup query.
			$wpdb->prepare( 'SELECT ' . self::COLUMNS . ' FROM %i WHERE user_id = %d', Tables::name( 'comments' ), absint( $user_id ) ), // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared -- COLUMNS is a class constant.
			ARRAY_A
		);

		foreach ( (array) $rows as $row ) {
			$comment = self::find( (int) $row['id'] );

			if ( $comment ) {
				self::delete( $comment );
			}
		}
	}

	/**
	 * Renders and validates comment text.
	 *
	 * @param string $message Raw text.
	 * @return array|WP_Error Renderer output.
	 */
	private static function render( $message ) {
		$rendered = Renderer::render( (string) $message );

		if ( '' === $rendered['text'] ) {
			return new WP_Error( 'spacebay_comment_empty', __( 'Please write a comment first.', 'spacebay' ), array( 'status' => 400 ) );
		}

		if ( mb_strlen( $rendered['text'] ) > self::MAX_LENGTH ) {
			return new WP_Error(
				'spacebay_comment_too_long',
				sprintf(
					/* translators: %s: Maximum number of characters. */
					__( 'Comments can be up to %s characters long.', 'spacebay' ),
					number_format_i18n( self::MAX_LENGTH )
				),
				array( 'status' => 400 )
			);
		}

		return $rendered;
	}

	/**
	 * Casts a comment row.
	 *
	 * @param array $row Raw row.
	 * @return array
	 */
	public static function normalize( array $row ) {
		return array(
			'id'               => (int) $row['id'],
			'post_id'          => (int) $row['post_id'],
			'parent_id'        => (int) $row['parent_id'],
			'user_id'          => (int) $row['user_id'],
			'message'          => (string) $row['message'],
			'message_rendered' => (string) $row['message_rendered'],
			'status'           => $row['status'],
			'reactions_count'  => (int) $row['reactions_count'],
			'created_at'       => $row['created_at'],
			'updated_at'       => $row['updated_at'],
		);
	}
}