<?php
/**
 * Low-volume milestones derived from persisted local experiment rows by cron.
 * No visitor, cart, checkout or tracking request contacts the hosted service.
 *
 * @package abtestkit
 */

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

define( 'ABTESTKIT_CONNECTED_MILESTONE_BASELINE_PREFIX', 'abtestkit_connected_milestone_baseline_' );
define( 'ABTESTKIT_CONNECTED_MILESTONE_EVENT_PREFIX', 'abtestkit_connected_milestone_event_' );
define( 'ABTESTKIT_CONNECTED_MILESTONE_CURSOR_OPTION', 'abtestkit_connected_milestone_cursor' );

/** An indexed, local high-water mark; old rows never become invented firsts. */
function abtestkit_connected_milestone_latest_row( string $test_id ) {
    global $wpdb;
    // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Indexed event lookup must observe the latest persisted row.
    $id = $wpdb->get_var( $wpdb->prepare( 'SELECT MAX(id) FROM %i WHERE ab_test_id = %s', ABTESTKIT_EVENTS_TABLE, $test_id ) );
    return '' === $wpdb->last_error ? (int) $id : new WP_Error( 'abtestkit_connected_milestone_storage_unavailable' );
}

function abtestkit_connected_milestone_baseline_key( string $test_id ) : string {
    return ABTESTKIT_CONNECTED_MILESTONE_BASELINE_PREFIX . hash( 'sha256', $test_id );
}

function abtestkit_connected_milestone_event_key( string $site_ref, string $test_ref, string $name ) : string {
    return ABTESTKIT_CONNECTED_MILESTONE_EVENT_PREFIX . hash( 'sha256', $site_ref . '|' . $test_ref . '|' . $name );
}

/** Called only after a newly created test has been committed, before traffic. */
function abtestkit_connected_milestone_seed_new_test( string $test_id ) : void {
    $connection = abtestkit_hosted_get_connection();
    if ( ! is_array( $connection ) ) {
        return;
    }
    $latest = abtestkit_connected_milestone_latest_row( $test_id );
    if ( is_wp_error( $latest ) ) {
        abtestkit_connected_collection_gap( $latest->get_error_code() );
        return;
    }
    $key = abtestkit_connected_milestone_baseline_key( $test_id );
    if ( ! add_option( $key, array( 'site_ref' => (string) $connection['site_ref'], 'row_id' => $latest ), '', 'no' ) && null === get_option( $key, null ) ) {
        abtestkit_connected_collection_gap( 'milestone_baseline_write_failed' );
    }
}

/** A different hosted site starts an honest new observation window. */
function abtestkit_connected_milestone_baseline( string $test_id, string $site_ref ) {
    $key = abtestkit_connected_milestone_baseline_key( $test_id );
    $stored = get_option( $key, null );
    if ( null === $stored || ( is_array( $stored ) && ( $stored['site_ref'] ?? '' ) !== $site_ref ) ) {
        $latest = abtestkit_connected_milestone_latest_row( $test_id );
        if ( is_wp_error( $latest ) ) {
            return $latest;
        }
        $baseline = array( 'site_ref' => $site_ref, 'row_id' => $latest );
        if ( null === $stored ) {
            add_option( $key, $baseline, '', 'no' );
        } else {
            update_option( $key, $baseline, false );
        }
        $saved = get_option( $key, null );
        return $saved === $baseline ? null : new WP_Error( 'abtestkit_connected_milestone_baseline_write_failed' );
    }
    if ( ! is_array( $stored ) || ! is_int( $stored['row_id'] ?? null ) || $stored['row_id'] < 0 ) {
        return new WP_Error( 'abtestkit_connected_milestone_baseline_invalid' );
    }
    return $stored['row_id'];
}

/** Existence checks use fixed indexed queries and return no visitor data. */
function abtestkit_connected_milestone_has_row( string $test_id, int $after_id, string $type, string $constraint = '' ) {
    global $wpdb;

    if ( 'order' === $constraint ) {
        // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Indexed milestone lookup must observe current persisted evidence.
        $found = $wpdb->get_var( $wpdb->prepare( 'SELECT id FROM %i WHERE ab_test_id = %s AND event_type = %s AND id > %d AND order_id > 0 LIMIT 1', ABTESTKIT_EVENTS_TABLE, $test_id, $type, $after_id ) );
    } elseif ( 'revenue' === $constraint ) {
        // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Indexed milestone lookup must observe current persisted evidence.
        $found = $wpdb->get_var( $wpdb->prepare( 'SELECT id FROM %i WHERE ab_test_id = %s AND event_type = %s AND id > %d AND order_id > 0 AND amount > 0 LIMIT 1', ABTESTKIT_EVENTS_TABLE, $test_id, $type, $after_id ) );
    } elseif ( '' === $constraint ) {
        // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Indexed milestone lookup must observe current persisted evidence.
        $found = $wpdb->get_var( $wpdb->prepare( 'SELECT id FROM %i WHERE ab_test_id = %s AND event_type = %s AND id > %d LIMIT 1', ABTESTKIT_EVENTS_TABLE, $test_id, $type, $after_id ) );
    } else {
        return new WP_Error( 'abtestkit_connected_milestone_constraint_invalid' );
    }

    return '' === $wpdb->last_error ? null !== $found : new WP_Error( 'abtestkit_connected_milestone_storage_unavailable' );
}

/** Reserve a single immutable event ID before touching the bounded outbox. */
function abtestkit_connected_milestone_reserve( string $name, array $test, string $site_ref, string $test_ref ) {
    $key = abtestkit_connected_milestone_event_key( $site_ref, $test_ref, $name );
    $marker = get_option( $key, null );
    if ( null !== $marker ) {
        return $marker;
    }
    $payload = abtestkit_connected_test_payload( $test, 'observed' );
    $installation = ABTestKit_Connected_Installation::get_or_create();
    $event_id = ABTestKit_Connected_Event::new_id();
    if ( is_wp_error( $payload ) || is_wp_error( $installation ) || is_wp_error( $event_id ) ) {
        return new WP_Error( 'abtestkit_connected_milestone_event_unavailable' );
    }
    $event = array(
        'schema_version' => 1,
        'event_id' => $event_id,
        'installation_id' => (string) $installation['installation_id'],
        'event_name' => $name,
        'occurred_at' => time(),
        'plugin_version' => abtestkit_hosted_sync_plugin_version(),
        'test_ref' => $test_ref,
        'payload' => $payload,
    );
    if ( is_wp_error( ABTestKit_Connected_Event::validate( $event, time() ) ) ) {
        return new WP_Error( 'abtestkit_connected_milestone_event_invalid' );
    }
    add_option( $key, array( 'event' => $event, 'acknowledged' => false ), '', 'no' );
    $marker = get_option( $key, null );
    return is_array( $marker ) ? $marker : new WP_Error( 'abtestkit_connected_milestone_reservation_failed' );
}

/** An unacknowledged event is replayed with its original ID, never recreated. */
function abtestkit_connected_milestone_queue_marker( string $key, array $marker ) : bool {
    if ( ! is_bool( $marker['acknowledged'] ?? null ) || ! is_array( $marker['event'] ?? null ) ) {
        abtestkit_connected_collection_gap( 'milestone_marker_invalid' );
        return false;
    }
    if ( $marker['acknowledged'] ) {
        return true;
    }
    if ( ! empty( $marker['expired'] ) ) {
        return false;
    }
    if ( (int) ( $marker['event']['occurred_at'] ?? 0 ) <= time() - ABTestKit_Connected_Event::MAX_AGE ) {
        $marker['expired'] = true;
        update_option( $key, $marker, false );
        abtestkit_connected_collection_gap( 'milestone_expired' );
        return false;
    }
    $queued = ABTestKit_Connected_Outbox::enqueue( $marker['event'], time() );
    if ( is_wp_error( $queued ) ) {
        abtestkit_connected_collection_gap( $queued->get_error_code() );
        return false;
    }
    return true;
}

/** At most 20 tests and 20 milestone enqueues per 15-minute cron tick. */
function abtestkit_connected_collect_persisted_milestones() : void {
    global $wpdb;
    if ( ! abtestkit_connected_platform_can_create_or_launch() ) {
        return;
    }
    $connection = abtestkit_hosted_get_connection();
    $tests = get_option( 'abtestkit_page_tests', array() );
    if ( ! is_array( $connection ) || ! is_array( $tests ) || ! $tests ) {
        return;
    }
    $tests = array_values( $tests );
    $total = count( $tests );
    $cursor = (int) get_option( ABTESTKIT_CONNECTED_MILESTONE_CURSOR_OPTION, 0 ) % $total;
    $processed = 0;
    $queued = 0;
    while ( $processed < min( 20, $total ) && $queued < 20 ) {
        $test = $tests[ $cursor ] ?? null;
        $cursor = ( $cursor + 1 ) % $total;
        ++$processed;
        if ( ! is_array( $test ) || empty( $test['id'] ) ) {
            continue;
        }
        $test_id = (string) $test['id'];
        $baseline = abtestkit_connected_milestone_baseline( $test_id, (string) $connection['site_ref'] );
        if ( is_wp_error( $baseline ) ) {
            abtestkit_connected_collection_gap( $baseline->get_error_code() );
            continue;
        }
        if ( null === $baseline ) {
            continue;
        }
        $payload = abtestkit_connected_test_payload( $test, 'observed' );
        if ( is_wp_error( $payload ) || 'draft' === $payload['status'] ) {
            continue;
        }
        $ref = abtestkit_connected_test_ref_record( $test_id );
        if ( is_wp_error( $ref ) ) {
            abtestkit_connected_collection_gap( $ref->get_error_code() );
            continue;
        }
        $site_ref = (string) $connection['site_ref'];
        $test_ref = (string) $ref['test_ref'];
        $names = array( 'first_impression_recorded', 'both_variants_recorded', 'first_conversion_recorded' );
        if ( 'purchase' === $payload['goal'] ) {
            $names[] = 'first_order_attributed';
            $names[] = 'first_revenue_attributed';
        }
        $variants = null;
        foreach ( $names as $name ) {
            if ( $queued >= 20 ) {
                break;
            }
            $key = abtestkit_connected_milestone_event_key( $site_ref, $test_ref, $name );
            $marker = get_option( $key, null );
            if ( is_array( $marker ) && ( ! empty( $marker['acknowledged'] ) || ! empty( $marker['expired'] ) ) ) {
                continue;
            }
            if ( null === $marker ) {
                $found = false;
                if ( in_array( $name, array( 'first_impression_recorded', 'both_variants_recorded' ), true ) ) {
                    if ( null === $variants ) {
                        // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Indexed milestone lookup must observe current persisted evidence.
                        $variants = $wpdb->get_col( $wpdb->prepare( "SELECT DISTINCT variant FROM %i WHERE ab_test_id = %s AND event_type = 'impression' AND id > %d AND variant IN ('A','B') LIMIT 2", ABTESTKIT_EVENTS_TABLE, $test_id, $baseline ) );
                        if ( '' !== $wpdb->last_error ) {
                            abtestkit_connected_collection_gap( 'milestone_storage_unavailable' );
                            break;
                        }
                    }
                    $found = 'first_impression_recorded' === $name ? ! empty( $variants ) : in_array( 'A', $variants, true ) && in_array( 'B', $variants, true );
                } elseif ( 'first_conversion_recorded' === $name ) {
                    $found = abtestkit_connected_milestone_has_row( $test_id, $baseline, 'purchase' === $payload['goal'] ? 'purchase' : 'click' );
                } elseif ( 'first_order_attributed' === $name ) {
                    $found = abtestkit_connected_milestone_has_row( $test_id, $baseline, 'purchase', 'order' );
                } elseif ( 'first_revenue_attributed' === $name ) {
                    $found = abtestkit_connected_milestone_has_row( $test_id, $baseline, 'purchase', 'revenue' );
                }
                if ( is_wp_error( $found ) ) {
                    abtestkit_connected_collection_gap( $found->get_error_code() );
                    break;
                }
                if ( ! $found ) {
                    continue;
                }
                $marker = abtestkit_connected_milestone_reserve( $name, $test, $site_ref, $test_ref );
            }
            if ( is_wp_error( $marker ) || ! is_array( $marker ) || ! abtestkit_connected_milestone_queue_marker( $key, $marker ) ) {
                if ( is_wp_error( $marker ) ) {
                    abtestkit_connected_collection_gap( $marker->get_error_code() );
                } elseif ( ! is_array( $marker ) ) {
                    abtestkit_connected_collection_gap( 'milestone_marker_invalid' );
                }
                break;
            }
            ++$queued;
        }
    }
    update_option( ABTESTKIT_CONNECTED_MILESTONE_CURSOR_OPTION, $cursor, false );
}

/** Called only after a complete hosted batch response and local acknowledgement. */
function abtestkit_connected_milestone_mark_acknowledged( array $event, string $site_ref ) : void {
    $name = (string) ( $event['event_name'] ?? '' );
    if ( ! in_array( $name, array( 'first_impression_recorded', 'both_variants_recorded', 'first_conversion_recorded', 'first_order_attributed', 'first_revenue_attributed' ), true ) ) {
        return;
    }
    $key = abtestkit_connected_milestone_event_key( $site_ref, (string) ( $event['test_ref'] ?? '' ), $name );
    $marker = get_option( $key, null );
    if ( ! is_array( $marker ) || ! hash_equals( (string) ( $marker['event']['event_id'] ?? '' ), (string) ( $event['event_id'] ?? '' ) ) ) {
        abtestkit_connected_collection_gap( 'milestone_ack_marker_missing' );
        return;
    }
    $marker['acknowledged'] = true;
    update_option( $key, $marker, false );
    if ( get_option( $key, null ) !== $marker ) {
        abtestkit_connected_collection_gap( 'milestone_ack_write_failed' );
    }
}