feed finder

2025-02-23 17:12:46 +01:00
parent ccb186a26b
commit 4112779477
6 changed files with 132 additions and 10 deletions
@@ -0,0 +1,96 @@
+import 'package:html/dom.dart';
+import 'package:http/http.dart' as http;
+
+class FeedFinder {
+  final Uri url;
+  final Document document;
+
+  late final String _base;
+
+  FeedFinder({required this.url, required this.document}) {
+    final uri = url.removeFragment();
+    _base = '${uri.scheme}://${uri.authority}';
+  }
+
+  Future<Set<String>> _verifyCandidates(Set<String> candidates) async {
+    final results = <String>{};
+
+    final client = http.Client();
+    try {
+      for (final candidate in candidates) {
+        try {
+          await client.get(Uri.parse(candidate));
+        } catch (e) {
+          continue;
+        }
+
+        results.add(candidate);
+      }
+    } finally {
+      client.close();
+    }
+
+    return results;
+  }
+
+  void _parseBody(Set<String> candidates) {
+    for (final a in document.querySelectorAll('a')) {
+      var href = a.attributes['href'];
+      if (href != null) {
+        if (href.contains('rss') ||
+            href.contains('xml') ||
+            href.contains('feed')) {
+          // Fix relative URLs
+          href = href.startsWith('/') ? _base + href : href;
+          href = href.endsWith('/') ? href.substring(0, href.length - 2) : href;
+
+          // Fix naked URLs
+          href = !href.startsWith('http') ? '$_base/$href' : href;
+
+          candidates.add(href);
+        }
+      }
+    }
+  }
+
+  void _parseHead(Set<String> candidates) {
+    for (final link in document.querySelectorAll("link[rel='alternate']")) {
+      final type = link.attributes['type'];
+      if (type != null) {
+        if (type.contains('rss') || type.contains('xml')) {
+          var href = link.attributes['href'];
+          if (href != null) {
+            // Fix relative URLs
+            href = href.startsWith('/') ? _base + href : href;
+            candidates.add(href);
+          }
+        }
+      }
+    }
+  }
+
+  Future<Set<String>> parse({
+    bool parseHead = true,
+    bool parseBody = true,
+    bool verifyCandidates = true,
+  }) async {
+    final candidates = <String>{};
+
+    // Look for feed candidates in head
+    if (parseHead) {
+      _parseHead(candidates);
+    }
+
+    // Look for feed candidates in body
+    if (parseBody) {
+      _parseBody(candidates);
+    }
+
+    // Verify candidates
+    if (verifyCandidates) {
+      return _verifyCandidates(candidates);
+    }
+
+    return candidates;
+  }
+}