<?php
/**
 * Process Survey URLs - Updated
 * 
 * Changes from previous version:
 * - Removed ID pattern options (numeric/alphanumeric/custom)
 * - Always generates complex alphanumeric IDs (RR + 8 random chars)
 * - Accepts uid_param: the query parameter name that holds the unique respondent ID
 * - For single URL: replaces the uid_param value in the template URL
 * - For multiple URLs: extracts the uid_param value from each URL
 * - Stores uid_param in survey_url_batches table
 */

require_once 'client-session.php';
requireClientLogin();

$client_id = $_SESSION['client_id'];
$project_id = $_POST['project_id'] ?? '';
$upload_type = $_POST['upload_type'] ?? '';
$uid_param = trim($_POST['uid_param'] ?? '');

if (empty($project_id) || empty($upload_type) || empty($uid_param)) {
    $_SESSION['error'] = "Invalid request parameters. Project ID, upload type, and UID parameter name are required.";
    header('Location: manage-survey-urls.php?project_id=' . urlencode($project_id));
    exit;
}

// Validate uid_param: only letters, numbers, underscores
if (!preg_match('/^[a-zA-Z0-9_]+$/', $uid_param)) {
    $_SESSION['error'] = "UID parameter name can only contain letters, numbers, and underscores.";
    header('Location: manage-survey-urls.php?project_id=' . urlencode($project_id));
    exit;
}

try {
    $pdo = getClientDBConnection();
    
    // Verify project belongs to client
    $stmt = $pdo->prepare("
        SELECT project_id, id
        FROM projects 
        WHERE project_id = ? AND client_id = ?
    ");
    $stmt->execute([$project_id, $client_id]);
    $project = $stmt->fetch();
    
    if (!$project) {
        $_SESSION['error'] = "Project not found or access denied";
        header('Location: projects-list.php');
        exit;
    }
    
    // Get next batch number
    $stmt = $pdo->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') {
        // =============================================
        // SINGLE URL TEMPLATE MODE
        // =============================================
        $template_url = trim($_POST['template_url'] ?? '');
        $url_count = (int)($_POST['url_count'] ?? 0);
        
        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;
        }
        
        // Parse the template URL and check the uid_param exists
        $parsed = parse_url($template_url);
        if (!isset($parsed['query'])) {
            $_SESSION['error'] = "Template URL has no query parameters. The UID parameter must be in the URL query string.";
            header('Location: manage-survey-urls.php?project_id=' . urlencode($project_id));
            exit;
        }
        
        parse_str($parsed['query'], $query_params);
        
        if (!array_key_exists($uid_param, $query_params)) {
            $_SESSION['error'] = "The parameter \"$uid_param\" was not found in the template URL. Please check the URL and parameter name.";
            header('Location: manage-survey-urls.php?project_id=' . urlencode($project_id));
            exit;
        }
        
        // Generate URLs by replacing the uid_param value
        for ($i = 1; $i <= $url_count; $i++) {
            $unique_id = generateUniqueId();
            
            // Replace the uid_param value in the query string
            $new_params = $query_params;
            $new_params[$uid_param] = $unique_id;
            
            // Rebuild the URL preserving the original parameter order
            $client_url = rebuildUrlWithParam($template_url, $uid_param, $unique_id);
            $rr_proxy_url = generateProxyUrl($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') {
        // =============================================
        // MULTIPLE URLS (BULK) MODE
        // =============================================
        $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) {
            $url = trim($url);
            if (empty($url)) continue;
            
            // 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 the unique ID from the specified uid_param
            $parsed = parse_url($url);
            $unique_id = null;
            
            if (isset($parsed['query'])) {
                parse_str($parsed['query'], $params);
                if (isset($params[$uid_param]) && $params[$uid_param] !== '') {
                    $unique_id = $params[$uid_param];
                }
            }
            
            if ($unique_id === null) {
                $_SESSION['error'] = "Parameter \"$uid_param\" not found in URL at line " . ($index + 1) . ": " . htmlspecialchars($url);
                header('Location: manage-survey-urls.php?project_id=' . urlencode($project_id));
                exit;
            }
            
            // 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
            ];
        }
    }
    
    if (empty($urls_to_insert)) {
        $_SESSION['error'] = "No valid URLs to process";
        header('Location: manage-survey-urls.php?project_id=' . urlencode($project_id));
        exit;
    }
    
    // Begin transaction
    $pdo->beginTransaction();
    
    try {
        // Insert batch record with uid_param
        $stmt = $pdo->prepare("
            INSERT INTO survey_url_batches 
            (project_id, batch_number, total_urls, upload_type, uid_param, created_by)
            VALUES (?, ?, ?, ?, ?, ?)
        ");
        $stmt->execute([
            $project_id,
            $batch_number,
            count($urls_to_insert),
            $upload_type,
            $uid_param,
            $client_id
        ]);
        
        // Insert URLs
        $stmt = $pdo->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
            ]);
        }
        
        $pdo->commit();
        
        $_SESSION['success'] = "Successfully generated " . count($urls_to_insert) . " survey URLs in Batch #" . $batch_number . " (UID param: " . htmlspecialchars($uid_param) . ")";
        header('Location: view-batch-urls.php?project_id=' . urlencode($project_id) . '&batch=' . $batch_number);
        exit;
        
    } catch (Exception $e) {
        $pdo->rollBack();
        throw $e;
    }
    
} catch (Exception $e) {
    error_log("Process Survey URLs error: " . $e->getMessage());
    $_SESSION['error'] = "Error processing URLs: " . $e->getMessage();
    header('Location: manage-survey-urls.php?project_id=' . urlencode($project_id));
    exit;
}


/**
 * Generate a unique alphanumeric identifier
 * Format: RR + 8 random alphanumeric chars (e.g., RR4K7BX2M9)
 * Always complex - no simple numeric or sequential IDs
 */
function generateUniqueId() {
    $chars = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789'; // Removed confusing chars: 0,O,1,I
    $id = 'RR';
    for ($j = 0; $j < 8; $j++) {
        $id .= $chars[random_int(0, strlen($chars) - 1)];
    }
    return $id;
}


/**
 * Rebuild a URL replacing a specific query parameter's value
 * Preserves the original parameter order and all other params
 */
function rebuildUrlWithParam($original_url, $param_name, $new_value) {
    $parsed = parse_url($original_url);
    
    // Get the original query string to preserve parameter order
    $original_query = $parsed['query'] ?? '';
    
    // Split into individual param pairs
    $pairs = explode('&', $original_query);
    $new_pairs = [];
    
    foreach ($pairs as $pair) {
        if (empty($pair)) continue;
        
        $parts = explode('=', $pair, 2);
        $key = urldecode($parts[0]);
        
        if ($key === $param_name) {
            // Replace this param's value
            $new_pairs[] = urlencode($key) . '=' . urlencode($new_value);
        } else {
            // Keep original
            $new_pairs[] = $pair;
        }
    }
    
    // Rebuild URL
    $scheme = isset($parsed['scheme']) ? $parsed['scheme'] . '://' : '';
    $host = $parsed['host'] ?? '';
    $port = isset($parsed['port']) ? ':' . $parsed['port'] : '';
    $path = $parsed['path'] ?? '';
    $query = !empty($new_pairs) ? '?' . implode('&', $new_pairs) : '';
    $fragment = isset($parsed['fragment']) ? '#' . $parsed['fragment'] : '';
    
    return $scheme . $host . $port . $path . $query . $fragment;
}


/**
 * Generate RR proxy URL
 * Format: https://relevantreflex.com/s/{encoded_string}
 */
function generateProxyUrl($project_id, $unique_id) {
    $data = $project_id . '|' . $unique_id;
    $encoded = base64_encode($data);
    $encoded = strtr($encoded, '+/', '-_');
    $encoded = rtrim($encoded, '=');
    
    return 'https://relevantreflex.com/s/' . $encoded;
}
?>