<?php

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

class AIEO_Reco_Experiment {

    const OPTION = 'aieo_reco_experiment';

    const ARM_CONTROL   = 'control';
    const ARM_TREATMENT = 'treatment';
    
    const ARM_NONE = '';

    
    const SUBJECTS = array('semantic_reco_boost', 'semantic_related_diversity');

    const SUBJECT_DIVERSITY = 'semantic_related_diversity';

    
    const ARM_SETS = array(
        'semantic_reco_boost'        => array(self::ARM_CONTROL, self::ARM_TREATMENT),
        'semantic_related_diversity' => array('cap2', 'cap0', 'covis'),
    );

    
    private static $arm = null;

    
    public static function config() {
        $stored = get_option(self::OPTION, array());
        $stored = is_array($stored) ? $stored : array();
        $subject = isset($stored['subject']) ? (string) $stored['subject'] : '';
        if (!in_array($subject, self::SUBJECTS, true)) {
            $subject = self::SUBJECTS[0];
        }
        $split = isset($stored['split']) ? (int) $stored['split'] : 50;
        
        
        $split = max(5, min(95, $split));
        return array(
            'enabled'    => !empty($stored['enabled']),
            'subject'    => $subject,
            'split'      => $split,
            'salt'       => isset($stored['salt']) ? (string) $stored['salt'] : '',
            'started_at' => isset($stored['started_at']) ? (string) $stored['started_at'] : '',
        );
    }

    
    public static function is_running() {
        $c = self::config();
        return $c['enabled'] && '' !== $c['salt'];
    }

    
    public static function start($subject = '', $split = 50) {
        $subject = in_array($subject, self::SUBJECTS, true) ? $subject : self::SUBJECTS[0];
        $config  = array(
            'enabled'    => true,
            'subject'    => $subject,
            'split'      => max(5, min(95, (int) $split)),
            'salt'       => wp_generate_password(16, false, false),
            'started_at' => gmdate('Y-m-d H:i:s'),
        );
        update_option(self::OPTION, $config, false);
        self::$arm = null;
        self::flush_reco_caches();
        return self::config();
    }

    
    public static function stop() {
        $config            = self::config();
        $config['enabled'] = false;
        update_option(self::OPTION, $config, false);
        self::$arm = null;
        self::flush_reco_caches();
        return self::config();
    }

    
    private static function flush_reco_caches() {
        if (class_exists('AIEO_Recommendations_Cache')
            && method_exists('AIEO_Recommendations_Cache', 'delete_all')) {
            AIEO_Recommendations_Cache::delete_all();
        }
    }

    
    public static function arm() {
        if (null !== self::$arm) {
            return self::$arm;
        }
        $config = self::config();
        if (!$config['enabled'] || '' === $config['salt']) {
            return self::$arm = self::ARM_NONE;
        }
        $session = self::session_id();
        if ('' === $session) {
            
            
            
            
            return self::$arm = self::ARM_NONE;
        }
        $arms = self::arms_for($config['subject']);
        if (count($arms) > 2) {
            
            
            return self::$arm = self::assign_variant($session, $config['salt'], $arms);
        }
        return self::$arm = self::assign($session, $config['salt'], $config['split']);
    }

    
    public static function arms_for($subject) {
        $sets = self::ARM_SETS;
        return isset($sets[$subject])
            ? $sets[$subject]
            : array(self::ARM_CONTROL, self::ARM_TREATMENT);
    }

    
    public static function assign($session_id, $salt, $split = 50) {
        $bucket = crc32($session_id . $salt) % 100;
        return ($bucket < (int) $split) ? self::ARM_TREATMENT : self::ARM_CONTROL;
    }

    
    public static function assign_variant($session_id, $salt, array $arms) {
        $n = count($arms);
        if ($n < 1) {
            return self::ARM_NONE;
        }
        $bucket = crc32($session_id . $salt) % 100;
        $idx    = (int) floor($bucket * $n / 100);
        return $arms[min($idx, $n - 1)];
    }

    
    public static function related_diversity_arm() {
        $config = self::config();
        if (!$config['enabled'] || '' === $config['salt']
            || self::SUBJECT_DIVERSITY !== $config['subject']) {
            return '';
        }
        return self::arm();
    }

    
    public static function cache_suffix() {
        if (!self::is_running()) {
            return '';
        }
        $arm = self::arm();
        if (self::ARM_NONE === $arm) {
            return '';
        }
        
        
        $arm = preg_replace('/[^a-z0-9]/', '', strtolower($arm));
        return ('' === $arm) ? '' : '_a' . $arm;
    }

    
    public static function feature_active($subject) {
        $config = self::config();
        if (!$config['enabled'] || '' === $config['salt'] || $config['subject'] !== $subject) {
            return true; 
        }
        return self::ARM_TREATMENT === self::arm();
    }

    
    private static function session_id() {
        if (!class_exists('AIEO_Attribution')) {
            return '';
        }
        if (class_exists('AIEO_Session_Tracker')
            && method_exists('AIEO_Session_Tracker', 'is_consent_blocking_writes')
            && AIEO_Session_Tracker::is_consent_blocking_writes()) {
            return '';
        }
        return (string) AIEO_Attribution::read_visitor_key();
    }

    
    public static function reset_memo() {
        self::$arm = null;
    }
}