<?php
session_start();
require_once 'includes/db-config.php';
require_once 'includes/auth-check.php';

// Check if user is logged in
if (!isset($_SESSION['client_id'])) {
    header('Location: login.php');
    exit;
}

$client_id = $_SESSION['client_id'];

if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    header('Location: projects-list.php');
    exit;
}

$project_id = $_POST['project_id'] ?? '';
$upload_type = $_POST['upload_type'] ?? '';

if (empty($project_id) || empty($upload_type)) {
    $_SESSION['error'] = "Invalid request parameters";
    header('Location: manage-survey-urls.php?project_id=' . urlencode($project_id));
    exit;
}

try {
    $shopPdo = getShopDBConnection();
    
    // Verify project belongs to client
    $stmt = $shopPdo->prepare("
        SELECT project_id 
        FROM projects 
        WHERE project_id = ? AND client_id = ?
    ");
    $stmt->execute([$project_id, $client_id]);
    
    if (!$stmt->fetch()) {
        $_SESSION['error'] = "Project not found or access denied";
        header('Location: projects-list.php');
        exit;
    }
    
    // Get next batch number
    $stmt = $shopPdo->prepare("
        SELECT COALESCE(MAX(batch_number), 0) + 1 AS next_batch 
        FROM survey_url_batches 
        WHERE project_id = ?
    ");
    $stmt->execute([$project_id]);
    $batch_number = $stmt->fetchColumn();
    
    $urls_to_insert = [];
    
    if ($upload_type === 'single') {
        // Process single URL template
        $template_url = $_POST['template_url'] ?? '';
        $id_pattern = $_POST['id_pattern'] ?? 'numeric';
        $url_count = (int)($_POST['url_count'] ?? 0);
        $custom_prefix = $_POST['custom_prefix'] ?? '';
        
        if (empty($template_url) || $url_count < 1 || $url_count > 5000) {
            $_SESSION['error'] = "Invalid template URL or count";
            header('Location: manage-survey-urls.php?project_id=' . urlencode($project_id));
            exit;
        }
        
        // Check if template has {ID} placeholder
        if (strpos($template_url, '{ID}') === false) {
            $_SESSION['error'] = "Template URL must contain {ID} placeholder";
            header('Location: manage-survey-urls.php?project_id=' . urlencode($project_id));
            exit;
        }
        
        // Generate URLs
        for ($i = 1; $i <= $url_count; $i++) {
            $unique_id = generateUniqueId($i, $id_pattern, $custom_prefix);
            $client_url = str_replace('{ID}', $unique_id, $template_url);
            $rr_proxy_url = generateProxyUrl($project_id, $unique_id);
            
            $urls_to_insert[] = [
                'client_url' => $client_url,
                'rr_proxy_url' => $rr_proxy_url,
                'unique_identifier' => $unique_id
            ];
        }
        
    } else if ($upload_type === 'multiple') {
        // Process multiple URLs
        $bulk_urls = $_POST['bulk_urls'] ?? '';
        $lines = array_filter(array_map('trim', explode("\n", $bulk_urls)));
        
        if (empty($lines)) {
            $_SESSION['error'] = "No URLs provided";
            header('Location: manage-survey-urls.php?project_id=' . urlencode($project_id));
            exit;
        }
        
        if (count($lines) > 5000) {
            $_SESSION['error'] = "Maximum 5,000 URLs allowed per batch. You provided " . count($lines) . " URLs.";
            header('Location: manage-survey-urls.php?project_id=' . urlencode($project_id));
            exit;
        }
        
        $unique_ids_used = [];
        
        foreach ($lines as $index => $url) {
            // Validate URL
            if (!filter_var($url, FILTER_VALIDATE_URL)) {
                $_SESSION['error'] = "Invalid URL at line " . ($index + 1) . ": " . htmlspecialchars($url);
                header('Location: manage-survey-urls.php?project_id=' . urlencode($project_id));
                exit;
            }
            
            // Extract or generate unique identifier
            $unique_id = extractUniqueIdFromUrl($url);
            
            // Ensure unique ID is unique within this batch
            $counter = 1;
            $original_id = $unique_id;
            while (in_array($unique_id, $unique_ids_used)) {
                $unique_id = $original_id . '_' . $counter;
                $counter++;
            }
            $unique_ids_used[] = $unique_id;
            
            $rr_proxy_url = generateProxyUrl($project_id, $unique_id);
            
            $urls_to_insert[] = [
                'client_url' => $url,
                'rr_proxy_url' => $rr_proxy_url,
                'unique_identifier' => $unique_id
            ];
        }
    }
    
    // Begin transaction
    $shopPdo->beginTransaction();
    
    try {
        // Insert batch record
        $stmt = $shopPdo->prepare("
            INSERT INTO survey_url_batches 
            (project_id, batch_number, total_urls, upload_type, created_by)
            VALUES (?, ?, ?, ?, ?)
        ");
        $stmt->execute([
            $project_id,
            $batch_number,
            count($urls_to_insert),
            $upload_type,
            $client_id
        ]);
        
        // Insert URLs
        $stmt = $shopPdo->prepare("
            INSERT INTO survey_urls 
            (project_id, batch_number, client_url, rr_proxy_url, unique_identifier, created_by)
            VALUES (?, ?, ?, ?, ?, ?)
        ");
        
        foreach ($urls_to_insert as $url_data) {
            $stmt->execute([
                $project_id,
                $batch_number,
                $url_data['client_url'],
                $url_data['rr_proxy_url'],
                $url_data['unique_identifier'],
                $client_id
            ]);
        }
        
        $shopPdo->commit();
        
        $_SESSION['success'] = "Successfully generated " . count($urls_to_insert) . " survey URLs in Batch #" . $batch_number;
        header('Location: view-batch-urls.php?project_id=' . urlencode($project_id) . '&batch=' . $batch_number);
        exit;
        
    } catch (Exception $e) {
        $shopPdo->rollBack();
        throw $e;
    }
    
} catch (Exception $e) {
    $_SESSION['error'] = "Error processing URLs: " . $e->getMessage();
    header('Location: manage-survey-urls.php?project_id=' . urlencode($project_id));
    exit;
}

/**
 * Generate unique identifier based on pattern
 */
function generateUniqueId($index, $pattern, $prefix = '') {
    switch ($pattern) {
        case 'numeric':
            return (string)$index;
            
        case 'alphanumeric':
            return 'A' . str_pad($index, 4, '0', STR_PAD_LEFT);
            
        case 'custom':
            $cleanPrefix = preg_replace('/[^a-zA-Z0-9]/', '', $prefix);
            return strtoupper($cleanPrefix) . str_pad($index, 5, '0', STR_PAD_LEFT);
            
        default:
            return (string)$index;
    }
}

/**
 * Generate RR proxy URL
 * Format: https://relevantreflex.com/s/{encoded_string}
 */
function generateProxyUrl($project_id, $unique_id) {
    // Create a short encoded string that maps to project_id + unique_id
    $data = $project_id . '|' . $unique_id;
    $encoded = base64_encode($data);
    // Make it URL-safe
    $encoded = strtr($encoded, '+/', '-_');
    $encoded = rtrim($encoded, '=');
    
    return 'https://relevantreflex.com/s/' . $encoded;
}

/**
 * Extract unique identifier from URL
 * Looks for common patterns like uid=, id=, user=, etc.
 */
function extractUniqueIdFromUrl($url) {
    // Parse URL
    $parsed = parse_url($url);
    
    // Check query string
    if (isset($parsed['query'])) {
        parse_str($parsed['query'], $params);
        
        // Look for common parameter names
        $common_params = ['uid', 'id', 'user', 'userid', 'user_id', 'respondent', 'resp_id'];
        
        foreach ($common_params as $param) {
            if (isset($params[$param]) && !empty($params[$param])) {
                return $params[$param];
            }
        }
        
        // If no common param found, use first parameter value
        if (!empty($params)) {
            return reset($params);
        }
    }
    
    // Fallback: generate from URL hash
    return substr(md5($url), 0, 10);
}