feat: set up FFI

Signed-off-by: Sphericalkat <me@kat.bio>

lib/readability.dart

@@ -0,0 +1,9 @@
+/// Support for doing something awesome.
+///
+/// More dartdocs go here.
+library;
+
+export 'src/readability_parser.dart';
+export 'src/article.dart';
+
+// TODO: Export any libraries intended for clients of this package.

lib/src/article.dart

@@ -0,0 +1,33 @@
+
+class Article {
+  final String? title;
+  final String? author;
+  final int length;
+  final String? excerpt;
+  final String? siteName;
+  final String? imageUrl;
+  final String? faviconUrl;
+  final String? content;
+  final String? textContent;
+  final String? language;
+  final String? publishedTime;
+
+  Article({
+    required this.title,
+    required this.author,
+    required this.length,
+    required this.excerpt,
+    required this.siteName,
+    required this.imageUrl,
+    required this.faviconUrl,
+    required this.content,
+    required this.textContent,
+    required this.language,
+    required this.publishedTime,
+  });
+
+  @override
+  String toString() {
+    return 'Article{title: $title,\n author: $author,\n length: $length,\n excerpt: $excerpt,\n siteName: $siteName,\n imageUrl: $imageUrl,\n faviconUrl: $faviconUrl,\n content: $content,\n textContent: $textContent,\n language: $language,\n publishedTime: $publishedTime}';
+  }
+}

lib/src/readability_parser.dart

@@ -0,0 +1,88 @@
+import 'dart:ffi' as ffi;
+import 'dart:ffi';
+import 'package:ffi/ffi.dart';
+import 'dart:io' show Platform;
+
+import 'package:readability/src/article.dart';
+
+final class CArticle extends Struct {
+  external Pointer<Utf8> title;
+  external Pointer<Utf8> author;
+  @Int32()
+  external int length;
+  external Pointer<Utf8> excerpt;
+  external Pointer<Utf8> site_name;
+  external Pointer<Utf8> image_url;
+  external Pointer<Utf8> favicon_url;
+  external Pointer<Utf8> content;
+  external Pointer<Utf8> text_content;
+  external Pointer<Utf8> language;
+  external Pointer<Utf8> published_time;
+  external Pointer<Utf8> err;
+
+  @Int32()
+  external int success;
+}
+
+typedef ParseFunc = CArticle Function(Pointer<Utf8> url);
+typedef ParseDart = CArticle Function(Pointer<Utf8> url);
+
+typedef FreeArticleFunc = Void Function(CArticle article);
+typedef FreeArticleDart = void Function(CArticle article);
+
+class ReadabilityParser {
+  late final DynamicLibrary _lib;
+  late final ParseDart _parse;
+  late final FreeArticleDart _freeArticle;
+
+  ReadabilityParser() {
+    _lib = ffi.DynamicLibrary.open(_getDylibPath());
+    _parse = _lib.lookupFunction<ParseFunc, ParseDart>('Parse');
+    _freeArticle =
+        _lib.lookupFunction<FreeArticleFunc, FreeArticleDart>('FreeArticle');
+  }
+
+  Article parse(String url) {
+    // Convert the URL to a native string.
+    final urlPtr = url.toNativeUtf8();
+
+    // Call the native function.
+    final article = _parse(urlPtr);
+
+    // Free the memory allocated for the URL.
+    malloc.free(urlPtr);
+
+
+    // Convert the native article to a Dart article.
+    final articleDart = Article(
+      title: article.title == nullptr ? null : article.title.toDartString(),
+      author: article.author == nullptr ? null : article.author.toDartString(),
+      length: article.length,
+      excerpt: article.excerpt == nullptr ? null : article.excerpt.toDartString(),
+      siteName: article.site_name == nullptr ? null : article.site_name.toDartString(),
+      imageUrl: article.image_url == nullptr ? null : article.image_url.toDartString(),
+      faviconUrl: article.favicon_url == nullptr ? null : article.favicon_url.toDartString(),
+      content: article.content == nullptr ? null : article.content.toDartString(),
+      textContent: article.text_content == nullptr ? null : article.text_content.toDartString(),
+      language: article.language == nullptr ? null : article.language.toDartString(),
+      publishedTime: article.published_time == nullptr ? null : article.published_time.toDartString(),
+    );
+
+    // Free the memory allocated for the article.
+    _freeArticle(article);
+
+    return articleDart;
+  }
+}
+
+String _getDylibPath() {
+  if (Platform.isWindows) {
+    return 'native/windows/x64/readability.dll';
+  } else if (Platform.isMacOS) {
+    return 'native/macos/x64/readability.dylib';
+  } else if (Platform.isLinux) {
+    return 'native/linux/x86-64/libreadability.so';
+  } else {
+    throw UnsupportedError('This platform is not supported.');
+  }
+}