<?php
/**
 * Decides what to do when an incoming record already exists.
 *
 * @package Transtrix
 */

namespace Transtrix\Import;

defined( 'ABSPATH' ) || exit;

/**
 * Decides; never writes.
 *
 * Keeping the decision separate from the write is what lets the dry run report
 * exactly what the real run will do, using the same code path.
 */
class Conflict_Resolver {

	const SKIP       = 'skip';
	const UPDATE     = 'update';
	const CREATE_NEW = 'create-new';

	/**
	 * The chosen strategy.
	 *
	 * @var string
	 */
	private $strategy;

	/**
	 * Constructor.
	 *
	 * @param string $strategy One of skip, update, create-new.
	 */
	public function __construct( string $strategy = self::SKIP ) {
		$this->strategy = in_array( $strategy, self::strategies(), true ) ? $strategy : self::SKIP;
	}

	/**
	 * The strategies a caller may pass.
	 *
	 * @return string[]
	 */
	public static function strategies(): array {
		return array( self::SKIP, self::UPDATE, self::CREATE_NEW );
	}

	/**
	 * The strategy in force.
	 *
	 * @return string
	 */
	public function strategy(): string {
		return $this->strategy;
	}

	/**
	 * Decide what happens to one incoming post record.
	 *
	 * @param array<string,mixed> $record One post record from the package.
	 * @return array{action:string,existing_id:int} Action is create, update or skip.
	 */
	public function resolve( array $record ): array {
		$existing = $this->find_existing( $record );

		if ( 0 === $existing ) {
			return array(
				'action'      => 'create',
				'existing_id' => 0,
			);
		}

		if ( self::CREATE_NEW === $this->strategy ) {
			return array(
				'action'      => 'create',
				'existing_id' => 0,
			);
		}

		if ( self::UPDATE === $this->strategy ) {
			return array(
				'action'      => 'update',
				'existing_id' => $existing,
			);
		}

		return array(
			'action'      => 'skip',
			'existing_id' => $existing,
		);
	}

	/**
	 * Find the local post matching an incoming record.
	 *
	 * Slug plus post type, because ids do not survive a move between sites and
	 * a title is not unique.
	 *
	 * A draft has no slug — WordPress assigns one on publish — so a record with
	 * an empty slug falls back to an exact title match inside the post type.
	 * Without the fallback every re-import creates another copy of every draft.
	 *
	 * @param array<string,mixed> $record One post record.
	 * @return int Local post id, or 0.
	 */
	private function find_existing( array $record ): int {
		$post_type = isset( $record['post_type'] ) ? (string) $record['post_type'] : 'post';
		$slug      = isset( $record['post_name'] ) ? (string) $record['post_name'] : '';

		if ( '' === $slug ) {
			return $this->find_by_title( $record, $post_type );
		}

		return $this->find_by( 'post_name', $slug, $post_type );
	}

	/**
	 * Find a slugless record by its exact title.
	 *
	 * Only reached for records WordPress never gave a slug — drafts, and the
	 * auto-draft and pending states beside them.
	 *
	 * @param array<string,mixed> $record    One post record.
	 * @param string              $post_type The record's post type.
	 * @return int Local post id, or 0.
	 */
	private function find_by_title( array $record, string $post_type ): int {
		$title = isset( $record['post_title'] ) ? (string) $record['post_title'] : '';

		if ( '' === $title ) {
			return 0;
		}

		return $this->find_by( 'post_title', $title, $post_type );
	}

	/**
	 * The newest local post of a type whose column equals a value.
	 *
	 * Read from the posts table, not get_posts(): plugins narrow every query on
	 * pre_get_posts (WP Travel Engine's Fixed Departure Dates hides expired
	 * trips everywhere, admin and CLI included), and a post the resolver cannot
	 * see is a post it duplicates — then a rollback deleting that duplicate
	 * takes the original's packages with it. Same reasoning as Object_Query.
	 *
	 * Trash and auto-drafts are not matches, as with get_posts( 'any' ).
	 *
	 * @param string $column    post_name or post_title.
	 * @param string $value     Value to match exactly.
	 * @param string $post_type The record's post type.
	 * @return int Local post id, or 0.
	 */
	private function find_by( string $column, string $value, string $post_type ): int {
		global $wpdb;

		// A query filter must not hide an existing post, so this reads the table.
		if ( 'post_title' === $column ) {
			// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- a query WordPress has no API for; nothing to cache.
			$found = $wpdb->get_var( $wpdb->prepare( "SELECT ID FROM {$wpdb->posts} WHERE post_title = %s AND post_type = %s AND post_status NOT IN ( 'trash', 'auto-draft' ) ORDER BY post_date DESC, ID DESC LIMIT 1", $value, $post_type ) );
		} else {
			// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- a query WordPress has no API for; nothing to cache.
			$found = $wpdb->get_var( $wpdb->prepare( "SELECT ID FROM {$wpdb->posts} WHERE post_name = %s AND post_type = %s AND post_status NOT IN ( 'trash', 'auto-draft' ) ORDER BY post_date DESC, ID DESC LIMIT 1", $value, $post_type ) );
		}

		return (int) $found;
	}
}