<?php
header('Content-Type: application/json');
header('Cache-Control: no-cache, must-revalidate');

$servername = "192.168.0.13\\SQLEXPRESS";
$username   = "opce";
$password   = "opcelasuca";
$dbname     = "history";

try {
    $pdo = new PDO(
        "sqlsrv:Server=$servername;Database=$dbname",
        $username,
        $password,
        [
            PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC
        ]
    );

    // Get parameters
    $tagName = $_GET['tag'] ?? '';
    $lastTimestamp = $_GET['last_timestamp'] ?? null;
    $limit = min((int)($_GET['limit'] ?? 500), 7200); // Max 10000 points
    
    $startTime = $_GET['start_time'] ?? null;
    $endTime   = $_GET['end_time'] ?? null;
    
    if (empty($tagName)) {
        throw new Exception('Tag name required');
    }
    
    // Build query to get latest data from archive
    $sql = "SELECT a.TimeStamp, a.Value, a.ID 
            FROM dbo.archive a
            LEFT JOIN dbo.id_names n ON a.ID = n.idnumber 
            WHERE n.name = :tag_name";
    
    $params = [':tag_name' => $tagName];
    
    if ($startTime && $endTime) {
        $sql .= " AND a.TimeStamp BETWEEN :start_time AND :end_time";
        $params[':start_time'] = $startTime;
        $params[':end_time']   = $endTime;
    } elseif ($lastTimestamp) {
        $sql .= " AND a.TimeStamp > :last_timestamp";
        $params[':last_timestamp'] = $lastTimestamp;
    }
    
    $sql .= " ORDER BY a.TimeStamp DESC OFFSET 0 ROWS FETCH NEXT :limit ROWS ONLY";
    
    $stmt = $pdo->prepare($sql);
    
    foreach ($params as $key => $value) {
        $stmt->bindValue($key, $value);
    }
    $stmt->bindValue(':limit', $limit, PDO::PARAM_INT);
    
    $stmt->execute();
    $results = $stmt->fetchAll();
    
    // Reverse to get chronological order
    $results = array_reverse($results);
    
    // Format data for Chart.js
    $data = [];
    foreach ($results as $row) {
        $data[] = [
            'x'         => $row['TimeStamp'],
            'y'         => (float)$row['Value'],
            'timestamp' => $row['TimeStamp']
        ];
    }
    
    $response = [
        'success'          => true,
        'data'             => $data,
        'count'            => count($data),
        'latest_timestamp' => !empty($data) ? end($data)['timestamp'] : null,
        'tag'              => $tagName
    ];
    
} catch (Exception $e) {
    $response = [
        'success' => false,
        'error'   => $e->getMessage()
    ];
}

echo json_encode($response);
?>