feat: improve API error handling & add exchange rate updates

- Switched to using cURL for fetching data from CoinGecko API, with added error handling for failed requests. This reduces the chances of runtime errors and ensures fallback to previous data.
- Implemented periodic updates to exchange rates every 5 seconds in `main.js` to keep the rates current.
- Added OpenGraph meta tags on `index.php` for better social media integration.
- Minor CSS adjustments for better table rendering.
- Moved `import` statements for Bootstrap CSS and JS to the top in `main.js`.

coingecko.php

@@ -15,7 +15,22 @@ $currentTime = time();
 // Check if five seconds have passed since the last update
 if (($currentTime - $previousData['time']) >= 5) {
 	// Fetch the available currencies from CoinGecko API
-	$availableCurrencies = json_decode(file_get_contents("https://api.coingecko.com/api/v3/simple/supported_vs_currencies"), true);
+	$availableCurrenciesApi = "https://api.coingecko.com/api/v3/simple/supported_vs_currencies";
+
+	$currenciesCh = curl_init($availableCurrenciesApi);
+	curl_setopt($currenciesCh, CURLOPT_RETURNTRANSFER, true);
+	$availableCurrenciesJson = curl_exec($currenciesCh);
+
+	$currenciesHttpCode = curl_getinfo($currenciesCh, CURLINFO_HTTP_CODE);
+
+	curl_close($currenciesCh);
+
+	if ($currenciesHttpCode == 200) {
+		$availableCurrencies = json_decode($availableCurrenciesJson, true);
+	} else {
+		$availableCurrencies = array_keys($previousData);
+		unset($availableCurrencies[array_search('time', $availableCurrencies)]);
+	}
 
 	// Remove excluded currencies
 	$availableCurrencies = array_diff($availableCurrencies, $excludedCurrencies);
@@ -29,14 +44,11 @@ if (($currentTime - $previousData['time']) >= 5) {
 	curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
 	$json = curl_exec($ch);
 
-	if (curl_errno($ch)) {
-		echo 'Curl error: ' . curl_error($ch);
-		curl_close($ch);
-		exit;
-	}
-
+	$httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
 	curl_close($ch);
     
+	// If the request worked and was not rate-limited
+    if ($httpCode == 200) {
         // Decode the fetched data
         $fetchedData = json_decode($json, true);
         $moneroData = $fetchedData['monero'];
@@ -66,7 +78,8 @@ if (($currentTime - $previousData['time']) >= 5) {
         
         $output = $newData;
     } 
+}
 
 // Output the data
 header('Content-Type: application/json');
-echo json_encode($newData, JSON_PRETTY_PRINT);
+echo json_encode($output, JSON_PRETTY_PRINT);

index.php

@@ -59,8 +59,10 @@ $xmr_in_fiat = strtr($xmr_in_fiat, ",", " ");
     <meta name="description" lang="<?php echo $lang_meta; ?>" content="<?php echo $meta_description; ?>" />
     <meta name="keywords" lang="<?php echo $lang_meta; ?>" content="<?php echo $meta_keywords; ?>" />
 
-
-    <!-- TODO: Add corresponding OpenGraph tags -->
+    <meta property="og:title" content="<?php echo $page_title; ?>" />
+    <meta property="og:description" content="<?php echo $meta_description; ?>" />
+    <meta property="og:image" content="img/mstile-310x150.png" />
+    <meta property="og:type" content="website" />
 
     <link rel="apple-touch-icon-precomposed" sizes="57x57" href="img/apple-touch-icon-57x57.png" />
     <link rel="apple-touch-icon-precomposed" sizes="114x114" href="img/apple-touch-icon-114x114.png" />
@@ -161,7 +163,7 @@ $xmr_in_fiat = strtr($xmr_in_fiat, ",", " ");
     </div>
 
     <script>
-        const exchangeRates = <?php echo json_encode($exchangeRates); ?>;
+        var exchangeRates = <?php echo json_encode($exchangeRates); ?>;
     </script>
     <script src="js/main.js"></script>
 

src/css/custom.css

@@ -34,6 +34,7 @@ a.fiat-tooltip {
 table.table {
     max-width: 472px;
     margin: auto;
+    --bs-table-bg: transparent;
 }
 
 .input-group-text {

src/js/main.js

@@ -1,3 +1,8 @@
+import 'bootstrap/dist/css/bootstrap.min.css';
+import 'bootstrap/dist/js/bootstrap.bundle.min';
+
+import '../css/custom.css';
+
 import Tooltip from "bootstrap/js/dist/tooltip";
 var tooltipTriggerList = [].slice.call(
   document.querySelectorAll('[data-toggle="tooltip"]')
@@ -7,8 +12,54 @@ var tooltipList = tooltipTriggerList.map(function (tooltipTriggerEl) {
 });
 console.log(tooltipList);
 
-import 'bootstrap/dist/css/bootstrap.min.css';
-import '../css/custom.css';
+let lastModifiedField = 'xmr';
+
+document.addEventListener('DOMContentLoaded', function () {
+  // Add event listeners to track the last modified input field
+  document.getElementById("xmrInput").addEventListener('input', function () {
+    lastModifiedField = 'xmr';
+  });
+
+  document.getElementById("fiatInput").addEventListener('input', function () {
+    lastModifiedField = 'fiat';
+  });
+
+  // Fetch updated exchange rates every 5 seconds
+  setInterval(fetchUpdatedExchangeRates, 5000);
+});
+
+function fetchUpdatedExchangeRates() {
+  fetch('/coingecko.php')
+    .then(response => response.json())
+    .then(data => {
+      // Update the exchangeRates object with the new values
+      for (const [currency, value] of Object.entries(data)) {
+        exchangeRates[currency.toUpperCase()] = value.lastValue;
+      }
+
+      updateTimeElement(data.time);
+
+      // Re-execute the appropriate conversion function
+      if (lastModifiedField === 'xmr') {
+        xmrConvert();
+      } else {
+        fiatConvert();
+      }
+    })
+    .catch(error => console.error('Error fetching exchange rates:', error));
+}
+
+function updateTimeElement(unixTimestamp) {
+  const date = new Date(unixTimestamp * 1000);
+  const hours = String(date.getHours()).padStart(2, '0');
+  const minutes = String(date.getMinutes()).padStart(2, '0');
+  const seconds = String(date.getSeconds()).padStart(2, '0');
+  const formattedTime = `${hours}:${minutes}:${seconds}`;
+
+  const u = document.querySelector('u');
+  u.textContent = formattedTime;
+  u.parentElement.innerHTML = u.parentElement.innerHTML.replace('Europe/Berlin', Intl.DateTimeFormat().resolvedOptions().timeZone);
+}
 
 function copyToClipBoardXMR() {
   var content = document.getElementById('xmrInput');