<?php

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

class AIEO_Reco_Experiment_Report {

    
    const Z_CI = 1.96;

    
    const Z_MDE = 2.80;

    
    public static function build($days = 60) {
        global $wpdb;
        $config = AIEO_Reco_Experiment::config();
        $since  = self::window_start($config, $days);

        $rollup = $wpdb->prefix . 'aieo_reco_arm_daily';
        $rows   = array();
        $source = 'rollup';

        if (self::table_exists($rollup)) {
            $rows = (array) $wpdb->get_results($wpdb->prepare(
                "SELECT surface, arm,
                        SUM(impressions) impressions, SUM(clicks) clicks,
                        SUM(suppressions) suppressions,
                        SUM(assisted_adds) assisted_adds,
                        SUM(assisted_purchases) assisted_purchases,
                        SUM(sessions) sessions,
                        SUM(click_sessions) click_sessions,
                        SUM(add_sessions) add_sessions
                   FROM `{$rollup}`
                  WHERE stat_date >= %s
                  GROUP BY surface, arm",
                substr($since, 0, 10)
            ), ARRAY_A);
        }

        
        
        
        
        
        if (empty($rows)) {
            $rows   = self::live_rows($since);
            $source = 'live';
        }

        $by_surface = array();
        $totals     = array();
        foreach ($rows as $r) {
            $surface = (string) $r['surface'];
            $arm     = (string) $r['arm'];
            if (!isset($by_surface[$surface])) {
                $by_surface[$surface] = array();
            }
            $by_surface[$surface][$arm] = self::measures($r);
            if (!isset($totals[$arm])) {
                $totals[$arm] = self::measures(array());
            }
            foreach (array('impressions', 'clicks', 'suppressions', 'assisted_adds', 'assisted_purchases', 'sessions', 'click_sessions', 'add_sessions') as $k) {
                
                
                
                
                $totals[$arm][$k] += isset($r[$k]) ? (int) $r[$k] : 0;
            }
        }

        $arms_order = class_exists('AIEO_Reco_Experiment') && method_exists('AIEO_Reco_Experiment', 'arms_for')
            ? AIEO_Reco_Experiment::arms_for($config['subject'])
            : array(AIEO_Reco_Experiment::ARM_CONTROL, AIEO_Reco_Experiment::ARM_TREATMENT);
        $multi = count($arms_order) > 2;

        $surfaces = array();
        foreach ($by_surface as $surface => $arms) {
            $surfaces[] = array(
                'surface' => $surface,
                'arms'    => $arms,
                
                'ctr'     => self::compare($arms, 'click_sessions', 'sessions'),
                'add'     => self::compare($arms, 'add_sessions', 'sessions'),
                
                'ctr_imp' => self::rates($arms, 'clicks', 'impressions'),
                'add_imp' => self::rates($arms, 'assisted_adds', 'impressions'),
                'pairs'   => $multi ? self::arm_pairs($arms, $arms_order) : array(),
            );
        }
        
        usort($surfaces, static function ($a, $b) {
            $an = self::arm_total($a['arms'], 'impressions');
            $bn = self::arm_total($b['arms'], 'impressions');
            return ($bn === $an) ? strcmp($a['surface'], $b['surface']) : (($bn > $an) ? 1 : -1);
        });

        return array(
            'config'     => $config,
            'since'      => $since,
            'source'     => $source,
            'surfaces'   => $surfaces,
            'totals'     => $totals,
            
            
            
            'arms_order' => $arms_order,
            'pairs'      => $multi ? self::arm_pairs($totals, $arms_order) : array(),
            
            
            
            'ctr'        => self::compare($totals, 'click_sessions', 'sessions'),
            'add'        => self::compare($totals, 'add_sessions', 'sessions'),
            
            
            'ctr_imp'    => self::rates($totals, 'clicks', 'impressions'),
            'add_imp'    => self::rates($totals, 'assisted_adds', 'impressions'),
            
            
            
            'unassigned' => isset($totals[AIEO_Reco_Experiment::ARM_NONE])
                ? $totals[AIEO_Reco_Experiment::ARM_NONE]
                : self::measures(array()),
        );
    }

    
    public static function compare(array $arms, $num, $den) {
        $c = isset($arms[AIEO_Reco_Experiment::ARM_CONTROL]) ? $arms[AIEO_Reco_Experiment::ARM_CONTROL] : null;
        $t = isset($arms[AIEO_Reco_Experiment::ARM_TREATMENT]) ? $arms[AIEO_Reco_Experiment::ARM_TREATMENT] : null;
        $n1 = $c ? (int) $c[$den] : 0;
        $n2 = $t ? (int) $t[$den] : 0;
        $x1 = $c ? (int) $c[$num] : 0;
        $x2 = $t ? (int) $t[$num] : 0;

        $core = self::compare_counts($x1, $n1, $x2, $n2);
        
        return array(
            'control_n'   => $n1,
            'treatment_n' => $n2,
            'control'     => $core['base'],
            'treatment'   => $core['other'],
            'diff'        => $core['diff'],
            'ci_low'      => $core['ci_low'],
            'ci_high'     => $core['ci_high'],
            'significant' => $core['significant'],
            'mde'         => $core['mde'],
            'verdict'     => str_replace(
                array('other_wins', 'base_wins'),
                array('treatment_wins', 'control_wins'),
                $core['verdict']
            ),
        );
    }

    
    public static function compare_pair(array $arms, $num, $den, $base_key, $other_key) {
        $b = isset($arms[$base_key]) ? $arms[$base_key] : null;
        $o = isset($arms[$other_key]) ? $arms[$other_key] : null;
        $out = self::compare_counts(
            $b ? (int) $b[$num] : 0,
            $b ? (int) $b[$den] : 0,
            $o ? (int) $o[$num] : 0,
            $o ? (int) $o[$den] : 0
        );
        $out['base_arm']  = $base_key;
        $out['other_arm'] = $other_key;
        return $out;
    }

    
    
    public static function compare_counts($x1, $n1, $x2, $n2) {
        $out = array(
            'base_n'      => $n1,
            'other_n'     => $n2,
            'base'        => ($n1 > 0) ? $x1 / $n1 : null,
            'other'       => ($n2 > 0) ? $x2 / $n2 : null,
            'diff'        => null,
            'ci_low'      => null,
            'ci_high'     => null,
            'significant' => false,
            'mde'         => null,
            'verdict'     => 'no_data',
        );
        if ($n1 < 1 || $n2 < 1) {
            return $out;
        }

        $p1 = $x1 / $n1;
        $p2 = $x2 / $n2;
        $d  = $p2 - $p1;
        $se = sqrt(($p1 * (1 - $p1) / $n1) + ($p2 * (1 - $p2) / $n2));

        $out['diff']    = $d;
        $out['ci_low']  = $d - self::Z_CI * $se;
        $out['ci_high'] = $d + self::Z_CI * $se;
        
        $out['significant'] = ($out['ci_low'] > 0) || ($out['ci_high'] < 0);

        
        
        
        
        $pbar        = ($x1 + $x2) / ($n1 + $n2);
        $harmonic_n  = (2 * $n1 * $n2) / ($n1 + $n2); 
        $out['mde']  = ($harmonic_n > 0 && $pbar > 0 && $pbar < 1)
            ? self::Z_MDE * sqrt(2 * $pbar * (1 - $pbar) / $harmonic_n)
            : null;

        if ($out['significant']) {
            $out['verdict'] = ($d > 0) ? 'other_wins' : 'base_wins';
        } elseif (null !== $out['mde'] && abs($d) < $out['mde']) {
            $out['verdict'] = 'underpowered';
        } else {
            $out['verdict'] = 'no_difference';
        }
        return $out;
    }

    
    private static function arm_pairs(array $arms, array $order) {
        $base = $order[0];
        $out  = array();
        foreach (array_slice($order, 1) as $other) {
            $out[] = array(
                'other' => $other,
                'ctr'   => self::compare_pair($arms, 'click_sessions', 'sessions', $base, $other),
                'add'   => self::compare_pair($arms, 'add_sessions', 'sessions', $base, $other),
            );
        }
        return $out;
    }

    
    private static function measures(array $r) {
        return array(
            'impressions'        => isset($r['impressions']) ? (int) $r['impressions'] : 0,
            'clicks'             => isset($r['clicks']) ? (int) $r['clicks'] : 0,
            
            
            
            
            'suppressions'       => isset($r['suppressions']) ? (int) $r['suppressions'] : 0,
            'assisted_adds'      => isset($r['assisted_adds']) ? (int) $r['assisted_adds'] : 0,
            'assisted_purchases' => isset($r['assisted_purchases']) ? (int) $r['assisted_purchases'] : 0,
            'sessions'           => isset($r['sessions']) ? (int) $r['sessions'] : 0,
            'click_sessions'     => isset($r['click_sessions']) ? (int) $r['click_sessions'] : 0,
            'add_sessions'       => isset($r['add_sessions']) ? (int) $r['add_sessions'] : 0,
        );
    }

    private static function arm_total(array $arms, $key) {
        $n = 0;
        foreach ($arms as $arm => $m) {
            if (AIEO_Reco_Experiment::ARM_NONE === $arm) { continue; }
            $n += (int) $m[$key];
        }
        return $n;
    }

    
    private static function live_rows($since) {
        global $wpdb;
        $reco    = $wpdb->prefix . 'aieo_reco_events';
        $addcart = $wpdb->prefix . 'aieo_addcart_events';
        if (!self::table_exists($reco) || !self::table_exists($addcart)) {
            return array();
        }
        
        
        
        
        if (!class_exists('AIEO_Display_Conditions')) { return array(); }
        $shown      = AIEO_Display_Conditions::raw_types_sql('shown');
        $engaged    = AIEO_Display_Conditions::raw_types_sql('engaged');
        $suppressed = AIEO_Display_Conditions::raw_types_sql('suppressed');

        return (array) $wpdb->get_results($wpdb->prepare(
            "SELECT r.surface, r.arm,
                    COUNT(DISTINCT CASE WHEN r.event_type IN ({$shown}) THEN r.id END)      AS impressions,
                    COUNT(DISTINCT CASE WHEN r.event_type IN ({$engaged}) THEN r.id END)    AS clicks,
                    COUNT(DISTINCT CASE WHEN r.event_type IN ({$suppressed}) THEN r.id END) AS suppressions,
                    COUNT(DISTINCT CASE WHEN e.id IS NOT NULL THEN r.id END) AS assisted_adds,
                    COUNT(DISTINCT CASE WHEN e.order_id > 0 THEN r.id END)   AS assisted_purchases,
                    -- Suppressed rows are the page views where the surface did
                    -- NOT appear, so they can never contribute to a numerator.
                    -- Counting them here would inflate every per-session rate.
                    COUNT(DISTINCT CASE WHEN r.event_type NOT IN ({$suppressed}) THEN r.session_id END) AS sessions,
                    COUNT(DISTINCT CASE WHEN r.event_type IN ({$engaged}) THEN r.session_id END) AS click_sessions,
                    COUNT(DISTINCT CASE WHEN e.id IS NOT NULL THEN r.session_id END) AS add_sessions
               FROM `{$reco}` r
               LEFT JOIN `{$addcart}` e
                 ON e.session_id = r.session_id
                AND e.product_id = r.target_pid
                AND e.ts_added   > r.ts
                AND e.ts_added   < DATE_ADD(r.ts, INTERVAL 7 DAY)
                AND r.event_type IN ('impression','reco_click')
              WHERE r.ts >= %s
              GROUP BY r.surface, r.arm",
            $since
        ), ARRAY_A);
    }

    
    private static function window_start(array $config, $days) {
        $days  = max(1, (int) $days);
        $floor = gmdate('Y-m-d H:i:s', time() - $days * DAY_IN_SECONDS);
        if ('' !== $config['started_at'] && $config['started_at'] > $floor) {
            return $config['started_at'];
        }
        return $floor;
    }

    
    public static function rates(array $arms, $num, $den) {
        $c  = isset($arms[AIEO_Reco_Experiment::ARM_CONTROL]) ? $arms[AIEO_Reco_Experiment::ARM_CONTROL] : null;
        $t  = isset($arms[AIEO_Reco_Experiment::ARM_TREATMENT]) ? $arms[AIEO_Reco_Experiment::ARM_TREATMENT] : null;
        $n1 = $c ? (int) $c[$den] : 0;
        $n2 = $t ? (int) $t[$den] : 0;
        $p1 = ($n1 > 0) ? ((int) $c[$num]) / $n1 : null;
        $p2 = ($n2 > 0) ? ((int) $t[$num]) / $n2 : null;
        return array(
            'control'     => $p1,
            'treatment'   => $p2,
            'control_n'   => $n1,
            'treatment_n' => $n2,
            'diff'        => (null !== $p1 && null !== $p2) ? ($p2 - $p1) : null,
        );
    }

    private static function table_exists($table) {
        global $wpdb;
        return (string) $wpdb->get_var($wpdb->prepare('SHOW TABLES LIKE %s', $table)) === $table;
    }
}