<?php

namespace WooOrderCart\Monitoring;

use WP_REST_Request;
use WP_REST_Response;

class CheckoutPpcpShippingCallbackTraceProbe {
    private static ?self $instance = null;

    private const ROUTE = '/paypal/v1/shipping-callback';
    private const TRACE_LINK_TRANSIENT_PREFIX = 'ipscmi_order_cart_ppcp_shipping_trace_';
    private const TRACE_LINK_TTL = 1800;

    /**
     * @var array<string,array<string,mixed>>
     */
    private $active_callbacks = [];

    public static function instance(): self {
        return self::$instance ??= new self();
    }

    private function __construct() {
        if ( ! CheckoutTraceConfig::is_enabled() ) {
            return;
        }

        add_filter( 'rest_request_before_callbacks', [ $this, 'capture_callback_request' ], 10, 3 );
        add_filter( 'rest_request_after_callbacks', [ $this, 'capture_callback_response' ], 10, 3 );
    }

    /**
     * @param mixed $response
     * @param array<int,mixed> $handler
     * @return mixed
     */
    public function capture_callback_request( $response, array $handler, WP_REST_Request $request ) {
        if ( ! $this->is_shipping_callback_request( $request ) ) {
            return $response;
        }

        $request_summary = $this->summarize_request( $request );
        $trace_id = $this->resolve_trace_id( $request, (string) ( $request_summary['cart_token_hash'] ?? '' ) );

        $this->active_callbacks[ $trace_id ] = $request_summary;
        register_shutdown_function( [ $this, 'capture_shutdown_error' ], $trace_id );

        CheckoutTraceService::record(
            [
                'traceId' => $trace_id,
                'event' => 'ppcp_shipping_callback_received',
                'step' => 'payment',
                'status' => 'start',
                'origin' => 'backend',
                'gatewayId' => 'ppcp-gateway',
                'providerKey' => 'ppcp',
                'context' => $request_summary,
            ]
        );

        return $response;
    }

    /**
     * @param mixed $response
     * @param array<int,mixed> $handler
     * @return mixed
     */
    public function capture_callback_response( $response, array $handler, WP_REST_Request $request ) {
        if ( ! $this->is_shipping_callback_request( $request ) ) {
            return $response;
        }

        $request_summary = $this->summarize_request( $request );
        $trace_id = $this->resolve_trace_id( $request, (string) ( $request_summary['cart_token_hash'] ?? '' ) );
        $response_summary = $this->summarize_response( $response );
        $status_code = (int) ( $response_summary['status_code'] ?? 0 );

        CheckoutTraceService::record(
            [
                'traceId' => $trace_id,
                'event' => $status_code >= 400 ? 'ppcp_shipping_callback_failed' : 'ppcp_shipping_callback_completed',
                'step' => 'payment',
                'status' => $status_code >= 400 ? 'error' : 'success',
                'origin' => 'backend',
                'gatewayId' => 'ppcp-gateway',
                'providerKey' => 'ppcp',
                'message' => (string) ( $response_summary['response_issue'] ?? $response_summary['response_code'] ?? '' ),
                'context' => array_merge( $request_summary, $response_summary ),
            ]
        );

        unset( $this->active_callbacks[ $trace_id ] );

        return $response;
    }

    public function capture_shutdown_error( string $trace_id ): void {
        if ( ! isset( $this->active_callbacks[ $trace_id ] ) ) {
            return;
        }

        $error = error_get_last();
        if ( ! is_array( $error ) || ! $this->is_fatal_error_type( (int) ( $error['type'] ?? 0 ) ) ) {
            return;
        }

        CheckoutTraceService::record(
            [
                'traceId' => $trace_id,
                'event' => 'ppcp_shipping_callback_shutdown_error',
                'step' => 'payment',
                'status' => 'critical',
                'origin' => 'backend',
                'gatewayId' => 'ppcp-gateway',
                'providerKey' => 'ppcp',
                'message' => 'PayPal shipping callback ended with a fatal PHP error.',
                'context' => array_merge(
                    $this->active_callbacks[ $trace_id ],
                    [
                        'fatal_error_type' => (int) ( $error['type'] ?? 0 ),
                        'fatal_error_file_basename' => basename( (string) ( $error['file'] ?? '' ) ),
                        'fatal_error_line' => (int) ( $error['line'] ?? 0 ),
                        'fatal_error_message_length' => strlen( (string) ( $error['message'] ?? '' ) ),
                    ]
                ),
            ]
        );
    }

    /**
     * @return array<string,mixed>
     */
    public function summarize_request( WP_REST_Request $request ): array {
        $params = $this->get_request_params( $request );
        $body = $this->get_request_body( $request );
        $cart_token = trim( (string) ( $params['cart_token'] ?? $request->get_param( 'cart_token' ) ?? '' ) );
        $shipping_address = isset( $params['shipping_address'] ) && is_array( $params['shipping_address'] )
            ? $params['shipping_address']
            : [];
        $shipping_option = isset( $params['shipping_option'] ) && is_array( $params['shipping_option'] )
            ? $params['shipping_option']
            : [];
        $purchase_units = isset( $params['purchase_units'] ) && is_array( $params['purchase_units'] )
            ? $params['purchase_units']
            : [];
        $first_purchase_unit = isset( $purchase_units[0] ) && is_array( $purchase_units[0] )
            ? $purchase_units[0]
            : [];

        return [
            'route' => $this->get_request_route( $request ),
            'request_method' => $this->get_request_method( $request ),
            'has_cart_token' => '' !== $cart_token,
            'cart_token_hash' => self::hash_identifier( $cart_token ),
            'cart_token_length' => strlen( $cart_token ),
            'request_body_length' => strlen( $body ),
            'request_key_count' => count( $params ),
            'request_keys' => $this->sanitize_keys( array_keys( $params ), 12 ),
            'callback_id_length' => strlen( trim( (string) ( $params['id'] ?? '' ) ) ),
            'purchase_unit_count' => count( $purchase_units ),
            'purchase_unit_reference_id_length' => strlen( trim( (string) ( $first_purchase_unit['reference_id'] ?? '' ) ) ),
            'has_shipping_address' => [] !== $shipping_address,
            'shipping_address_summary' => $this->summarize_paypal_shipping_address( $shipping_address ),
            'has_shipping_option' => [] !== $shipping_option,
            'shipping_option_summary' => $this->summarize_paypal_shipping_option( $shipping_option ),
        ];
    }

    /**
     * @param mixed $response
     * @return array<string,mixed>
     */
    public function summarize_response( $response ): array {
        $summary = [
            'status_code' => 200,
            'response_code' => '',
            'response_name' => '',
            'response_issue' => '',
            'response_purchase_unit_count' => 0,
            'response_shipping_option_count' => 0,
        ];

        if ( function_exists( 'is_wp_error' ) && is_wp_error( $response ) ) {
            $summary['status_code'] = 500;
            if ( is_object( $response ) && method_exists( $response, 'get_error_code' ) ) {
                $summary['response_code'] = sanitize_key( (string) $response->get_error_code() );
            }

            return $summary;
        }

        if ( ! $response instanceof WP_REST_Response ) {
            return $summary;
        }

        $summary['status_code'] = (int) $response->get_status();
        $data = $response->get_data();

        if ( ! is_array( $data ) ) {
            return $summary;
        }

        $purchase_units = isset( $data['purchase_units'] ) && is_array( $data['purchase_units'] )
            ? $data['purchase_units']
            : [];
        $first_purchase_unit = isset( $purchase_units[0] ) && is_array( $purchase_units[0] )
            ? $purchase_units[0]
            : [];
        $shipping_options = isset( $first_purchase_unit['shipping_options'] ) && is_array( $first_purchase_unit['shipping_options'] )
            ? $first_purchase_unit['shipping_options']
            : [];

        $summary['response_code'] = sanitize_key( (string) ( $data['code'] ?? '' ) );
        $summary['response_name'] = sanitize_key( (string) ( $data['name'] ?? '' ) );
        $summary['response_issue'] = $this->extract_response_issue( $data );
        $summary['response_purchase_unit_count'] = count( $purchase_units );
        $summary['response_shipping_option_count'] = count( $shipping_options );

        return $summary;
    }

    /**
     * @param array<string,mixed> $context
     * @return array<string,mixed>
     */
    public static function remember_trace_for_callback_url( string $callback_url, string $trace_id, array $context = [] ): array {
        $summary = self::summarize_callback_url( $callback_url );
        $cart_token_hash = (string) ( $summary['callback_cart_token_hash'] ?? '' );
        $trace_id = sanitize_key( $trace_id );

        if ( '' === $trace_id || '' === $cart_token_hash || ! function_exists( 'set_transient' ) ) {
            $summary['stored_trace_link'] = false;

            return $summary;
        }

        set_transient(
            self::TRACE_LINK_TRANSIENT_PREFIX . $cart_token_hash,
            [
                'trace_id' => $trace_id,
                'created_at' => gmdate( 'c' ),
                'context' => [
                    'payment_method' => sanitize_key( (string) ( $context['payment_method'] ?? '' ) ),
                    'funding_source' => sanitize_key( (string) ( $context['funding_source'] ?? '' ) ),
                ],
            ],
            self::TRACE_LINK_TTL
        );

        $summary['stored_trace_link'] = true;

        return $summary;
    }

    /**
     * @return array<string,mixed>
     */
    public static function summarize_callback_url( string $callback_url ): array {
        $parts = '' !== trim( $callback_url ) ? wp_parse_url( $callback_url ) : [];
        $query = [];

        if ( is_array( $parts ) && isset( $parts['query'] ) ) {
            parse_str( (string) $parts['query'], $query );
        }

        $cart_token = trim( (string) ( $query['cart_token'] ?? '' ) );

        return [
            'has_callback_url' => '' !== trim( $callback_url ),
            'callback_url_scheme' => sanitize_key( (string) ( is_array( $parts ) ? ( $parts['scheme'] ?? '' ) : '' ) ),
            'callback_url_host' => sanitize_text_field( (string) ( is_array( $parts ) ? ( $parts['host'] ?? '' ) : '' ) ),
            'callback_url_path' => sanitize_text_field( (string) ( is_array( $parts ) ? ( $parts['path'] ?? '' ) : '' ) ),
            'has_callback_cart_token' => '' !== $cart_token,
            'callback_cart_token_hash' => self::hash_identifier( $cart_token ),
            'callback_cart_token_length' => strlen( $cart_token ),
        ];
    }

    public static function hash_identifier( string $value ): string {
        $value = trim( $value );

        return '' === $value ? '' : substr( hash( 'sha256', $value ), 0, 16 );
    }

    private function resolve_trace_id( WP_REST_Request $request, string $cart_token_hash ): string {
        $trace_id = $this->get_trace_id_from_request( $request );

        if ( '' !== $trace_id ) {
            return $trace_id;
        }

        if ( '' !== $cart_token_hash && function_exists( 'get_transient' ) ) {
            $stored = get_transient( self::TRACE_LINK_TRANSIENT_PREFIX . $cart_token_hash );
            if ( is_array( $stored ) && '' !== sanitize_key( (string) ( $stored['trace_id'] ?? '' ) ) ) {
                return sanitize_key( (string) $stored['trace_id'] );
            }
        }

        return 'ppcpshipping' . ( '' !== $cart_token_hash ? $cart_token_hash : 'missing' );
    }

    private function get_trace_id_from_request( WP_REST_Request $request ): string {
        $headers = [ 'x-ips-checkout-trace', 'x-ips-checkout-trace-id' ];

        foreach ( $headers as $header ) {
            $value = method_exists( $request, 'get_header' ) ? (string) $request->get_header( $header ) : '';
            if ( '' !== trim( $value ) ) {
                return sanitize_key( $value );
            }
        }

        return '';
    }

    private function is_shipping_callback_request( WP_REST_Request $request ): bool {
        $route = $this->get_request_route( $request );
        if ( false === strpos( $route, self::ROUTE ) ) {
            return false;
        }

        return 'POST' === strtoupper( $this->get_request_method( $request ) );
    }

    private function get_request_route( WP_REST_Request $request ): string {
        if ( method_exists( $request, 'get_route' ) ) {
            return sanitize_text_field( (string) $request->get_route() );
        }

        return sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ?? '' ) );
    }

    private function get_request_method( WP_REST_Request $request ): string {
        if ( method_exists( $request, 'get_method' ) ) {
            return strtoupper( sanitize_key( (string) $request->get_method() ) );
        }

        return strtoupper( sanitize_key( (string) ( $_SERVER['REQUEST_METHOD'] ?? 'POST' ) ) );
    }

    /**
     * @return array<string,mixed>
     */
    private function get_request_params( WP_REST_Request $request ): array {
        if ( method_exists( $request, 'get_params' ) ) {
            $params = $request->get_params();

            return is_array( $params ) ? $params : [];
        }

        if ( method_exists( $request, 'get_json_params' ) ) {
            $params = $request->get_json_params();

            return is_array( $params ) ? $params : [];
        }

        return [];
    }

    private function get_request_body( WP_REST_Request $request ): string {
        if ( method_exists( $request, 'get_body' ) ) {
            return (string) $request->get_body();
        }

        $params = $this->get_request_params( $request );
        $encoded = wp_json_encode( $params );

        return false !== $encoded ? (string) $encoded : '';
    }

    /**
     * @param array<string,mixed> $address
     * @return array<string,mixed>
     */
    private function summarize_paypal_shipping_address( array $address ): array {
        $country_code = strtoupper( preg_replace( '/[^A-Z]/', '', (string) ( $address['country_code'] ?? '' ) ) ?: '' );

        return [
            'key_count' => count( $address ),
            'keys' => $this->sanitize_keys( array_keys( $address ), 12 ),
            'has_country_code' => '' !== $country_code,
            'country_code' => substr( $country_code, 0, 2 ),
            'has_admin_area_1' => '' !== trim( (string) ( $address['admin_area_1'] ?? '' ) ),
            'has_admin_area_2' => '' !== trim( (string) ( $address['admin_area_2'] ?? '' ) ),
            'has_postal_code' => '' !== trim( (string) ( $address['postal_code'] ?? '' ) ),
            'postal_code_length' => strlen( trim( (string) ( $address['postal_code'] ?? '' ) ) ),
            'has_address_line_1' => '' !== trim( (string) ( $address['address_line_1'] ?? '' ) ),
            'has_address_line_2' => '' !== trim( (string) ( $address['address_line_2'] ?? '' ) ),
        ];
    }

    /**
     * @param array<string,mixed> $shipping_option
     * @return array<string,mixed>
     */
    private function summarize_paypal_shipping_option( array $shipping_option ): array {
        $option_id = trim( (string) ( $shipping_option['id'] ?? '' ) );

        return [
            'key_count' => count( $shipping_option ),
            'keys' => $this->sanitize_keys( array_keys( $shipping_option ), 8 ),
            'has_id' => '' !== $option_id,
            'id_length' => strlen( $option_id ),
            'has_selected' => isset( $shipping_option['selected'] ),
        ];
    }

    /**
     * @param array<string,mixed> $data
     */
    private function extract_response_issue( array $data ): string {
        $details = isset( $data['details'] ) && is_array( $data['details'] ) ? $data['details'] : [];

        foreach ( $details as $detail ) {
            if ( ! is_array( $detail ) ) {
                continue;
            }

            $issue = sanitize_key( (string) ( $detail['issue'] ?? '' ) );
            if ( '' !== $issue ) {
                return $issue;
            }
        }

        return '';
    }

    /**
     * @param array<int|string> $keys
     * @return array<int,string>
     */
    private function sanitize_keys( array $keys, int $limit ): array {
        $sanitized = [];

        foreach ( $keys as $key ) {
            $normalized = sanitize_key( (string) $key );

            if ( '' !== $normalized ) {
                $sanitized[] = $normalized;
            }
        }

        return array_slice( array_values( array_unique( $sanitized ) ), 0, max( 1, $limit ) );
    }

    private function is_fatal_error_type( int $type ): bool {
        return in_array( $type, [ E_ERROR, E_PARSE, E_CORE_ERROR, E_COMPILE_ERROR, E_USER_ERROR ], true );
    }
}