<?php
// =====================================================================
// Database Helper
// Provides PDO Connection to Database and shared miscellaneous
// Functions for all API Endpoints.
// =====================================================================

require_once __DIR__ . '/init.php';


// ---------------------------------------------------------------------
// JSON Response
// Creates JSON Response including HTTP Status Code and HTTP Header 
// for every API Endpoint and terminates the Script.
// ---------------------------------------------------------------------
function json_response($data, $status_code = 200) {
    // Defines HTTP Status Code and HTTP Header
    // 1XX Informational, 2XX Successful, 3XX Redirection,
    // 4XX Client Error, 5XX Server Error
    http_response_code($status_code);
    header('Content-Type: application/json; charset=utf-8');
    // Converts PHP-Array to JSON-String
    echo json_encode($data, JSON_UNESCAPED_UNICODE);
    exit;
}


// ---------------------------------------------------------------------
// Error Response
// Creates standardized Error Responses with Error Message and HTTP Status
// Code. Uses json_response() for consistent Formatting.
// ---------------------------------------------------------------------
function error_response($message, $status_code = 400) {
    json_response(['error' => $message], $status_code);
}


// ---------------------------------------------------------------------
// Validate Required Fields
// Checks if specified Fields exist in the given Data Array and are
// non-empty. Returns an Array of missing Field Names, or an empty
// Array if all Fields are present.
// ---------------------------------------------------------------------
function validate_required($data, $fields) {
    $missing = [];

    foreach ($fields as $field) {
        // Checks if Fields exists in Data Array and are not empty
        if (!isset($data[$field]) || trim($data[$field]) === '') {
            $missing[] = $field;
        }
    }
    // Returns Array of missing Fields or emty Array
    return $missing;
}


// ---------------------------------------------------------------------
// Get POST Input
// Reads POST Parameters. Returns an associative Array.
// Fallback to JSON Request Body if no POST Data is present.
// ---------------------------------------------------------------------
function get_input() {
    // Checks for standard POST Requests
    if (!empty($_POST)) {
        return array_map('trim', $_POST);
    }

    // Fall back for JSON POST Requests
    $json = file_get_contents('php://input');
    $data = json_decode($json, true);

    if (is_array($data)) {
        return array_map('trim', $data);
    }

    return [];
}


// ---------------------------------------------------------------------
// Get PDO Connection
// Returns PDO Instance wrapped in a Function to prevent global 
// Variable Dependencies in Endpoint Files.
// ---------------------------------------------------------------------
function get_db() {
    global $pdo;

    if (!$pdo) {
        error_response('Database Connection failed.', 500);
    }

    return $pdo;
}