<?php
// Start session
session_start();

// Include database configuration
require_once '../config/database.php';

// Check if user is logged in and has admin role
if (!isset($_SESSION['user_id']) || $_SESSION['role'] !== 'admin') {
    header("Location: ../login.php");
    exit();
}

// Check if bank_id is provided
if (!isset($_GET['bank_id']) || empty($_GET['bank_id'])) {
    $_SESSION['error'] = "Question bank ID is required.";
    header("Location: banks.php");
    exit();
}

$bank_id = intval($_GET['bank_id']);

// Validate question bank exists
$check_bank = $conn->prepare("SELECT title FROM question_banks WHERE id = ?");
$check_bank->bind_param("i", $bank_id);
$check_bank->execute();
$bank_result = $check_bank->get_result();

if ($bank_result->num_rows === 0) {
    $_SESSION['error'] = "Question bank not found.";
    header("Location: banks.php");
    exit();
}

$bank = $bank_result->fetch_assoc();
$bank_title = $bank['title'];

// Get all questions for this bank
$questions_query = "SELECT * FROM questions WHERE question_bank_id = ? ORDER BY id";
$stmt = $conn->prepare($questions_query);
$stmt->bind_param("i", $bank_id);
$stmt->execute();
$questions_result = $stmt->get_result();

if ($questions_result->num_rows === 0) {
    $_SESSION['error'] = "No questions found in this bank.";
    header("Location: questions.php?bank_id=" . $bank_id);
    exit();
}

// Set up CSV export
$filename = 'questions_export_' . preg_replace('/[^a-z0-9_-]/i', '_', $bank_title) . '_' . date('Y-m-d') . '.csv';

// Set headers for CSV download
header('Content-Type: text/csv');
header('Content-Disposition: attachment; filename="' . $filename . '"');

// Open output stream
$output = fopen('php://output', 'w');

// Define CSV headers
$csv_headers = [
    'question_text',
    'question_type',
    'difficulty',
    'marks',
    'is_practice',
    'explanation',
    'answer_key'
];

// Add additional headers for multiple choice options (up to 10 options)
for ($i = 1; $i <= 10; $i++) {
    $csv_headers[] = 'option_' . $i;
    $csv_headers[] = 'correct_option_' . $i;
}

// Add header for true/false answer
$csv_headers[] = 'correct_answer';

// Write CSV header row
fputcsv($output, $csv_headers);

// Process each question
while ($question = $questions_result->fetch_assoc()) {
    $row = [
        'question_text' => $question['question_text'],
        'question_type' => $question['question_type'],
        'difficulty' => $question['difficulty'],
        'marks' => $question['marks'],
        'is_practice' => $question['is_practice'] ? 'Yes' : 'No',
        'explanation' => $question['explanation'],
        'answer_key' => '' // Will be filled for short answer questions
    ];
    
    // Initialize option fields to empty
    for ($i = 1; $i <= 10; $i++) {
        $row['option_' . $i] = '';
        $row['correct_option_' . $i] = '';
    }
    
    // Initialize true/false answer
    $row['correct_answer'] = '';
    
    // Get options for this question
    $options_query = "SELECT * FROM question_options WHERE question_id = ? ORDER BY id";
    $stmt = $conn->prepare($options_query);
    $stmt->bind_param("i", $question['id']);
    $stmt->execute();
    $options_result = $stmt->get_result();
    
    // Process based on question type
    if ($question['question_type'] === 'multiple_choice') {
        $option_index = 1;
        while ($option = $options_result->fetch_assoc()) {
            if ($option_index > 10) break; // Limit to 10 options
            
            $row['option_' . $option_index] = $option['option_text'];
            $row['correct_option_' . $option_index] = $option['is_correct'] ? 'Yes' : 'No';
            $option_index++;
        }
    } 
    elseif ($question['question_type'] === 'true_false') {
        // For true/false, get the correct answer
        while ($option = $options_result->fetch_assoc()) {
            if ($option['is_correct']) {
                $row['correct_answer'] = $option['option_text']; // 'True' or 'False'
                break;
            }
        }
    }
    elseif ($question['question_type'] === 'short_answer') {
        // For short answer, get the answer key
        if ($option = $options_result->fetch_assoc()) {
            $row['answer_key'] = $option['option_text'];
        }
    }
    
    // Write question row to CSV
    fputcsv($output, $row);
}

// Close file handles
fclose($output);
exit();