<?php

namespace SiteSync;

if ( ! defined( 'ABSPATH' ) ) {
    exit;
}

/**
 * Handles the persistent state for the Site Sync plugin, including sync checkpoints, tombstones, and mappings.
 */
class State {
    public const OPTION_KEY       = 'site_sync_state';
    private const TOMBSTONE_LIMIT = 200;

    /**
     * Default state structure for Site Sync plugin.
     *
     * @var array
     */
    private $defaults = array(
        'last_sent'     => array(
            'posts' => array(
				'modified' => null,
				'id'       => 0,
			),
            'terms' => array(
				'modified' => null,
				'id'       => 0,
			),
            'media' => array(
				'modified' => null,
				'id'       => 0,
			),
        ),
        'last_received' => array(
            'posts' => array(
				'modified' => null,
				'id'       => 0,
			),
            'terms' => array(
				'modified' => null,
				'id'       => 0,
			),
            'media' => array(
				'modified' => null,
				'id'       => 0,
			),
        ),
        'last_counts'   => array(
            'sent'     => array(
                'posts'      => 0,
                'terms'      => 0,
                'media'      => 0,
                'tombstones' => 0,
            ),
            'received' => array(
                'applied' => 0,
                'skipped' => 0,
                'errors'  => 0,
            ),
        ),
        'mappings'      => array(
            'posts' => array(), // phpcs:ignore local_id => array( 'peer' => peer_id, 'peer_site' => site_uuid )
            'terms' => array(),
            'media' => array(),
        ),
        'last_deleted'  => array(
            'posts' => 0,
            'terms' => 0,
            'media' => 0,
        ),
        'tombstones'    => array(),
        'last_run'      => null,
        'last_error'    => null,
    );

    /**
     * Retrieves the current persistent state for the Site Sync plugin.
     *
     * @return array The current state array merged with defaults.
     */
    public function get(): array {
        $stored = get_option( self::OPTION_KEY, array() );
        $data   = is_array( $stored ) ? $stored : array();

        return array_merge( $this->defaults, $data );
    }

    /**
     * Updates the persistent state with the provided data.
     *
     * @param array $data The data to merge into the current state.
     */
    public function update( array $data ): void {
        $state = $this->get();
        $state = array_merge( $state, $data );
        update_option( self::OPTION_KEY, $state );
    }

    /**
     * Records the results of a sync run, including summary counts and errors.
     *
     * @param array $summary An array containing 'counts' and optionally 'error' from the sync run.
     */
    public function record_run( array $summary ): void {
        $state               = $this->get();
        $state['last_run']   = current_time( 'mysql' );
        $state['last_error'] = $summary['error'] ?? null;

        if ( isset( $summary['counts'] ) && is_array( $summary['counts'] ) ) {
            $state['last_counts'] = $this->merge_counts( $summary['counts'] );
        }

        update_option( self::OPTION_KEY, $state );
    }

    /**
     * Reset checkpoints and tombstone queue to force a full resend on next sync.
     */
    public function reset(): void {
        $state                  = $this->get();
        $state['last_sent']     = $this->defaults['last_sent'];
        $state['last_received'] = $this->defaults['last_received'];
        $state['tombstones']    = array();
        $state['last_counts']   = $this->defaults['last_counts'];
        $state['last_error']    = null;
        update_option( self::OPTION_KEY, $state );
    }

    /**
     * Adds a tombstone item to the queue, ensuring no duplicates based on external_id and type.
     *
     * @param array $item The tombstone item to enqueue. Should contain 'external_id', 'type', and optionally 'taxonomy'.
     *
     * @return void
     */
    public function enqueue_tombstone( array $item ): void {
        // Avoid duplicates: check if same external_id/type already queued.
        $state = $this->get();
        if ( ! empty( $item['external_id'] ) && ! empty( $item['type'] ) ) {
            $existing = array_filter(
                $state['tombstones'],
                function ( $t ) use ( $item ) {
                    return isset( $t['external_id'], $t['type'] )
                        && $t['external_id'] === $item['external_id']
                        && $t['type'] === $item['type']
                        && ( ! isset( $item['taxonomy'] ) || ( $t['taxonomy'] ?? '' ) === ( $item['taxonomy'] ?? '' ) );
                }
            );
            if ( ! empty( $existing ) ) {
                return;
            }
        }

        $state['tombstones'][] = $item;
        if ( count( $state['tombstones'] ) > self::TOMBSTONE_LIMIT ) {
            $state['tombstones'] = array_slice( $state['tombstones'], -self::TOMBSTONE_LIMIT );
        }
        update_option( self::OPTION_KEY, $state );
    }

    /**
     * Removes and returns up to $limit tombstone items from the queue.
     *
     * @param int $limit The maximum number of tombstone items to consume.
     * @return array The consumed tombstone items.
     */
    public function consume_tombstones( int $limit = 50 ): array {
        $state               = $this->get();
        $queue               = $state['tombstones'] ?? array();
        $items               = array_slice( $queue, 0, $limit );
        $state['tombstones'] = array_slice( $queue, $limit );
        update_option( self::OPTION_KEY, $state );

        return $items;
    }

    /**
     * Returns up to $limit tombstone items from the queue without removing them.
     *
     * @param int $limit The maximum number of tombstone items to return.
     * @return array The tombstone items.
     */
    public function peek_tombstones( int $limit = 50 ): array {
        $state = $this->get();
        $queue = $state['tombstones'] ?? array();

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

    /**
     * Merges provided counts with the default counts, ensuring all values are integers.
     *
     * @param array $counts The counts to merge, containing 'sent' and 'received' arrays.
     * @return array The merged counts array.
     */
    private function merge_counts( array $counts ): array {
        $defaults = $this->defaults['last_counts'];
        $sent     = $counts['sent'] ?? array();
        $received = $counts['received'] ?? array();

        $mergedSent     = array_merge( $defaults['sent'], array_map( 'intval', $sent ) );
        $mergedReceived = array_merge( $defaults['received'], array_map( 'intval', $received ) );

        return array(
            'sent'     => $mergedSent,
            'received' => $mergedReceived,
        );
    }
}