<?php
header('Content-Type: application/json');
require_once __DIR__ . '/../db/config.php';

try {
    $pdo = db();

    // For the dashboard, we'll fetch the latest reading from any node as a general overview.
    $stmt = $pdo->query("
        SELECT
            `temperature`,
            `humidity`,
            `co2`,
            `gas_level`,
            `pressure`,
            `light_level`
        FROM `sensor_readings`
        ORDER BY `timestamp` DESC
        LIMIT 1
    ");

    $latest_data = $stmt->fetch(PDO::FETCH_ASSOC);

    // If the database is empty, provide default zero values to prevent frontend errors.
    if (!$latest_data) {
        $latest_data = [
            'temperature' => 0,
            'humidity' => 0,
            'co2' => 0,
            'gas_level' => 0,
            'pressure' => 1000, // A more realistic default for pressure
            'light_level' => 0,
        ];
    }

    // These thresholds will be used by the frontend to determine the gauge color.
    $thresholds = [
        'temperature' => ['max' => 50, 'warning' => 28, 'critical' => 35],
        'humidity' => ['max' => 100, 'warning' => 60, 'critical' => 80],
        'co2' => ['max' => 5000, 'warning' => 1000, 'critical' => 2000],
        'gas_level' => ['max' => 1000, 'warning' => 300, 'critical' => 500],
        'pressure' => ['max' => 1100, 'warning' => 1030, 'critical' => 1050],
        'light_level' => ['max' => 1000, 'warning' => 500, 'critical' => 750],
    ];

    $response = [
        'data' => $latest_data,
        'thresholds' => $thresholds
    ];

    echo json_encode($response);

} catch (PDOException $e) {
    http_response_code(500);
    // In a production environment, you might want to log this error instead of echoing it.
    echo json_encode(['error' => 'Database error: ' . $e->getMessage()]);
}