<?php
defined($security_key) or exit;

//------------------------------------------
// Appointments
//------------------------------------------

//Connect to DB
$pdo = dbConnect($dbname);

//NEW ARRAY
$criterias = [];   

//Check for $_GET variables and build up clause
if(isset($get_content) && $get_content!=''){    
    //GET VARIABLES FROM URL
    $requests = explode("&", $get_content);     
    //Check for keys and values
    foreach ($requests as $y){
        $v = explode("=", $y);
        //INCLUDE VARIABLES IN ARRAY
        $criterias[$v[0]] = $v[1]; 
    }
} 
//GET SLOTS PER DEALER
if(isset($criterias['action']) && $criterias['action'] == 'get_slots' && isset($criterias['dealer_id']) && isset($criterias['year']) && isset($criterias['month'])){
    
    //DECODE DEALER_ID
    $dealer_id = decodeUuid($criterias['dealer_id']);
    
    $year = (int)$criterias['year'];
    $month = (int)$criterias['month'];

    // Get the number of days in the month
    $num_days = cal_days_in_month(CAL_GREGORIAN, $month, $year);
    
    //GET OPENING_HOURS
    $sql_opening_hours = 'SELECT opening_hours FROM dealers WHERE rowID = ?';
    $stmt = $pdo->prepare($sql_opening_hours);
    $stmt->execute([$dealer_id]);
    $opening_hours = $stmt->fetch(PDO::FETCH_ASSOC);
    
    $opening_hours = json_decode($opening_hours['opening_hours'],true);

    if (empty($opening_hours)){
        // Define opening hours
        $opening_hours = [
            1 => ['start' => '09:00', 'end' => '17:00'], // Monday
            2 => ['start' => '09:00', 'end' => '17:00'], // Tuesday
            3 => ['start' => '09:00', 'end' => '17:00'], // Wednesday
            4 => ['start' => '09:00', 'end' => '17:00'], // Thursday
            5 => ['start' => '09:00', 'end' => '17:00'], // Friday
            6 => ['start' => '09:00', 'end' => '17:00'], // Saturday
            7 => null // Sunday - Closed
        ];
    } else {
        // Convert all string "null" values to actual null
        foreach ($opening_hours as $day => $hours) {
            if ($hours === "null") {
                $opening_hours[$day] = null;
            }
        }
    }
  
    // Initialize an array to store the available slots for the entire month
    $all_available_slots = [];
    
    // Initialize a counter for the slot IDs
    $id_counter = 1;
    
    // Iterate over each day in the month
    for ($day = 1; $day <= $num_days; $day++) {
        // Create a full date string
        $full_date = sprintf("%04d-%02d-%02d", $year, $month, $day);
        
        // Determine the day of the week (1 = Monday, 7 = Sunday)
        $day_of_week = date('N', strtotime($full_date));
        
        // Check if the day is open
        if ($opening_hours[$day_of_week] === null) {
            continue; // Skip closed days (Sunday)
        }

        // Get existing booked/unavailable slots for the day
        $booked_slots_sql = "SELECT start_time, end_time FROM appointment_slots 
                            WHERE DATE(start_time) = ? AND dealer_id = ? AND is_available = false";
        $stmt = $pdo->prepare($booked_slots_sql);
        $stmt->execute([$full_date, $dealer_id]);
        $booked_result = $stmt->fetchAll(PDO::FETCH_ASSOC);
        
        // Store booked slots for the day
        $booked_slots = [];

        foreach ($booked_result as $row){
            $booked_slots[] = [
                'start' => substr($row['start_time'], 11, 5),
                'end' => substr($row['end_time'], 11, 5)
            ];
        }

        // Generate all possible slots for the day
        $start_time = new DateTime($full_date . ' ' . $opening_hours[$day_of_week]['start']);
        $end_time = new DateTime($full_date . ' ' . $opening_hours[$day_of_week]['end']);
        $interval = new DateInterval('PT1H');
        
        // Iterate through each hour and check availability
        while ($start_time < $end_time) {
            $slot_end = clone $start_time;
            $slot_end->add($interval);
            
            // Check if this slot is booked
            $is_available = true;
            foreach ($booked_slots as $booked) {
                $booked_start = new DateTime($full_date . ' ' . $booked['start']);
                $booked_end = new DateTime($full_date . ' ' . $booked['end']);
                
                if (($start_time >= $booked_start && $start_time < $booked_end) ||
                    ($slot_end > $booked_start && $slot_end <= $booked_end)) {
                    $is_available = false;
                    break;
                }
            }

            // If the slot is available, add it to the list
            if ($is_available) {
                $all_available_slots[] = [
                    'id' => $id_counter++,
                    'start_time' => $start_time->format('Y-m-d H:i:s'),
                    'end_time' => $slot_end->format('Y-m-d H:i:s')
                ];
            }
            
            $start_time->add($interval);
        }
    }

    $messages = $all_available_slots;
} else {
    $messages =['success' => false, 'slots' => ''];
}

//------------------------------------------
//JSON_ENCODE
//------------------------------------------
$messages = json_encode($messages, JSON_UNESCAPED_UNICODE);

//Send results
echo $messages;

?>