<?php
/**
 * AILinkMaster InLink Score (AILM Rank) Engine.
 * Local responsibilities: graph collection, SaaS dispatch, and result persistence.
 * The proprietary scoring formula runs exclusively on the SaaS server.
 */

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

class AILM_PageRank_Engine {

    const GRAPH_TRANSIENT = 'ailm_pr_graph';

    /** @var AILM_OpenAI_Provider */
    private $provider;

    public function __construct() {
        add_action( 'wp_ajax_ailm_pr_collect_batch', [ $this, 'ajax_collect_batch' ] );
        add_action( 'wp_ajax_ailm_pr_compute',       [ $this, 'ajax_compute' ] );
    }

    /**
     * Returns the stored AILM Rank score for a given post.
     *
     * @param int $post_id
     * @return float
     */
    public static function get_post_pr( int $post_id ): float {
        $pr = get_post_meta( $post_id, '_ailm_pagerank', true );
        return $pr !== '' ? floatval( $pr ) : 0.0;
    }

    // -------------------------------------------------------------------------
    // Private helpers
    // -------------------------------------------------------------------------

    /**
     * Lazy-load and cache the SaaS provider instance.
     */
    private function get_provider(): AILM_OpenAI_Provider {
        if ( null === $this->provider ) {
            if ( ! class_exists( 'AILM_OpenAI_Provider' ) ) {
                require_once dirname( dirname( __DIR__ ) ) . '/modules/ai-core/providers/class-ailm-openai-provider.php';
            }
            $this->provider = new AILM_OpenAI_Provider();
        }
        return $this->provider;
    }

    // -------------------------------------------------------------------------
    // AJAX: Step 1 — collect graph
    // -------------------------------------------------------------------------

    /**
     * Builds the full link graph from AILM_Link_Repository and stores it
     * in a transient for the subsequent compute step.
     * The JS client calls this first (offset=0), then checks done=true on offset=1.
     */
    public function ajax_collect_batch(): void {
        check_ajax_referer( 'ailm_orphan_nonce', 'nonce' );

        if ( ! current_user_can( 'manage_options' ) ) {
            wp_send_json_error( 'Permission denied.' );
        }

        $offset = isset( $_POST['offset'] ) ? absint( $_POST['offset'] ) : 0;

        if ( 0 === $offset ) {
            delete_transient( self::GRAPH_TRANSIENT );

            $graph = AILM_Link_Repository::get_click_enriched_graph();
            set_transient( self::GRAPH_TRANSIENT, $graph, HOUR_IN_SECONDS );

            wp_send_json_success( [
                'done'        => false,
                'next_offset' => 1,
                'processed'   => count( $graph['nodes'] ),
            ] );
        }

        wp_send_json_success( [ 'done' => true ] );
    }

    // -------------------------------------------------------------------------
    // AJAX: Step 2 — dispatch to SaaS and persist results
    // -------------------------------------------------------------------------

    /**
     * Retrieves the graph from the transient, serializes it, sends it to the
     * SaaS compute endpoint, and saves the returned scores to postmeta.
     */
    public function ajax_compute(): void {
        check_ajax_referer( 'ailm_orphan_nonce', 'nonce' );

        if ( ! current_user_can( 'manage_options' ) ) {
            wp_send_json_error( 'Permission denied.' );
        }

        $graph = get_transient( self::GRAPH_TRANSIENT );
        if ( ! $graph || empty( $graph['nodes'] ) ) {
            wp_send_json_error( 'No graph data found. Please collect data first.' );
        }

        // Determine front page ID for Click Depth BFS on the server.
        $front_page_id = (int) get_option( 'page_on_front' );
        if ( ! $front_page_id ) {
            $front_page_id = (int) get_option( 'page_for_posts' );
        }

        // Convert node keys to strings (JSON requires string keys).
        $nodes = array_fill_keys( array_map( 'strval', array_keys( $graph['nodes'] ) ), 0 );

        // Convert edges: [ from_id => [ to_id => weight ] ] with string keys.
        $edges = [];
        foreach ( $graph['edges'] as $from_id => $targets ) {
            $str_from = (string) $from_id;
            $edges[ $str_from ] = [];
            foreach ( $targets as $to_id => $weight ) {
                $edges[ $str_from ][ (string) $to_id ] = (float) $weight;
            }
        }

        $response = $this->get_provider()->saas_compute_pagerank( $nodes, $edges, $front_page_id );

        if ( is_wp_error( $response ) ) {
            wp_send_json_error( 'SaaS error: ' . $response->get_error_message() );
        }

        if ( empty( $response['scores'] ) || ! is_array( $response['scores'] ) ) {
            wp_send_json_error( 'Invalid response from SaaS server.' );
        }

        // Persist scores returned by SaaS.
        foreach ( $response['scores'] as $post_id => $score ) {
            update_post_meta( (int) $post_id, '_ailm_pagerank', (float) $score );
        }

        delete_transient( self::GRAPH_TRANSIENT );

        // Purge dashboard caches so the new scores appear immediately.
        wp_cache_delete( 'ailm_dashboard_frozen_maps',    'ailm_cache_group' );
        wp_cache_delete( 'ailm_dashboard_manual_links',   'ailm_cache_group' );
        wp_cache_delete( 'ailm_dashboard_internal_links', 'ailm_cache_group' );

        wp_send_json_success( [
            'message'    => 'AILM Rank successfully computed.',
            'node_count' => $response['node_count'] ?? count( $response['scores'] ),
        ] );
    }
}