Add conversion of FrontMatterDocument to raw String

.gitignore

@@ -1,5 +1,8 @@
 # See https://www.dartlang.org/guides/libraries/private-files
 
+# Intellij & Android Studio files
+.idea/
+
 # Files and directories created by pub
 .dart_tool/
 .packages

example/front_matter.dart

@@ -1,12 +1,12 @@
 import 'dart:io';
-import 'package:front_matter/front_matter.dart' as front_matter;
+import 'package:front_matter/front_matter.dart';
 
 // Example 1 - Parse a string.
 void example1() async {
   var file = new File('example/hello-world.md');
   var fileContents = await file.readAsString();
 
-  var doc = front_matter.parse(fileContents);
+  var doc = FrontMatterDocument.fromText(fileContents);
 
   print("The author is ${doc.data['author']}");
   print("The publish date is ${doc.data['date']}");
@@ -15,7 +15,7 @@ void example1() async {
 
 // Example 2 - Read a file and parse its contents.
 void example2() async {
-  var doc = await front_matter.parseFile('example/hello-world.md');
+  final doc = await FrontMatterDocument.fromFile('example/hello-world.md');
 
   print("The author is ${doc.data['author']}");
   print("The publish date is ${doc.data['date']}");

lib/front_matter.dart

@@ -3,4 +3,3 @@ library front_matter;
 
 export 'src/front_matter_document.dart';
 export 'src/front_matter_exception.dart';
-export 'src/front_matter.dart' show parse, parseFile;

lib/src/front_matter_document.dart

@@ -1,11 +1,85 @@
+import 'dart:io';
+
+import 'package:meta/meta.dart';
 import 'package:yaml/yaml.dart';
 
+import '../front_matter.dart';
+
+// Default delimiter for YAML.
+const defaultDelimiter = '---';
+
 /// Document containing the original `value`, front matter `data` and `content`.
 class FrontMatterDocument {
-  String value, content;
+  FrontMatterDocument({@required this.data, @required this.content});
+
+  FrontMatterDocument.fromText(String text,
+      {String delimiter = defaultDelimiter}) {
+    // Remove any leading whitespace.
+    final value = text.trimLeft();
+
+    // If there's no starting delimiter, there's no front matter.
+    if (!value.startsWith(delimiter)) {
+      content = value;
+      data = YamlMap();
+      return;
+    }
+
+    // Get the index of the closing delimiter.
+    final closeIndex = value.indexOf('\n' + delimiter);
+
+    // Get the raw front matter block between the opening and closing delimiters.
+    final frontMatter = value.substring(delimiter.length, closeIndex);
+
+    if (frontMatter.isNotEmpty) {
+      try {
+        // Parse the front matter as YAML.
+        data = loadYaml(frontMatter);
+      } catch (e) {
+        throw FrontMatterException(invalidYamlError);
+      }
+    }
+
+    // The content begins after the closing delimiter index.
+    content = value.substring(closeIndex + (delimiter.length + 1)).trim();
+
+    print('content: $content');
+  }
+
+  static fromFile(String path, {String delimiter = defaultDelimiter}) async {
+    var file = File(path);
+
+    // Throw an error if file not found.
+    if (!await file.exists()) {
+      throw FrontMatterException(fileNotFoundError);
+    }
+
+    try {
+      var text = await file.readAsString();
+      return FrontMatterDocument.fromText(text, delimiter: delimiter);
+    } catch (e) {
+      // Handle downstream errors, or throw one if file is not readable as text.
+      switch (e.message) {
+        case invalidYamlError:
+          rethrow;
+        default:
+          throw FrontMatterException(fileTypeError);
+      }
+    }
+  }
+
+  String content;
 
   /// The parsed YAML front matter as a [YamlMap].
   YamlMap data;
 
-  FrontMatterDocument(this.value);
+  String get value {
+    var newValue = '---\n';
+
+    for (final d in data.entries.toList()
+      ..sort((a, b) => a.key.compareTo(b.key))) {
+      newValue += '${d.key}: ${d.value}\n';
+    }
+
+    return '$newValue---\n\n$content';
+  }
 }

test/front_matter_test.dart

@@ -1,48 +1,50 @@
 import 'package:test/test.dart';
-import 'package:front_matter/front_matter.dart' as fm;
-import 'package:front_matter/src/front_matter.dart';
-import 'package:front_matter/src/front_matter_document.dart';
-import 'package:front_matter/src/front_matter_exception.dart';
+import 'package:front_matter/front_matter.dart';
 
 /// Represents a test with default parameters.
 class Test {
-  String foo, baz, delimiter, content;
+  String foo, baz, bar, yawn, delimiter, content;
 
   Test(
       {this.foo = 'bar',
       this.baz = 'qux',
+      this.bar = 'bing',
+      this.yawn = 'snore',
       this.delimiter = defaultDelimiter,
-      this.content = '\nHello, world!'});
+      this.content = 'Hello, world!'});
 
   String get frontMatter =>
-      '${this.delimiter}\nfoo: ${this.foo}\nbaz: ${this.baz}\n${this.delimiter}';
+      '${this.delimiter}\nbar: ${this.bar}\nbaz: ${this.baz}\nfoo: ${this.foo}\nyawn: ${this.yawn}\n${this.delimiter}';
 
   /// Joins front matter to content.
-  String get value => this.frontMatter + this.content;
+  String get value => '${this.frontMatter}\n\n${this.content}';
 }
 
 void main() {
   test('return type is `FrontMatterDocument`', () {
     var text = 'foo';
-    var expected = FrontMatterDocument(text);
-    var result = fm.parse(text);
+    var expected = FrontMatterDocument.fromText(text);
+    var result = FrontMatterDocument.fromText(text);
 
     expect(result.runtimeType, equals(expected.runtimeType));
   });
 
   test('parses front matter with default options', () {
     var test = Test();
-    var result = fm.parse(test.value);
+
+    var result = FrontMatterDocument.fromText(test.value);
 
     expect(result.value, equals(test.value));
     expect(result.content, equals(test.content));
     expect(result.data['foo'], equals(test.foo));
     expect(result.data['baz'], equals(test.baz));
+    expect(result.data['bar'], equals(test.bar));
+    expect(result.data['yawn'], equals(test.yawn));
   });
 
   test('removes any leading spaces and linebreaks', () {
     var test = Test();
-    var result = fm.parse('    \n\n\n${test.value}');
+    var result = FrontMatterDocument.fromText('    \n\n\n${test.value}');
 
     expect(result.content, equals(test.content));
     expect(result.data['foo'], equals(test.foo));
@@ -53,33 +55,34 @@ void main() {
     var tests = delimiters.map((delimiter) => Test(delimiter: delimiter));
 
     tests.forEach((test) {
-      var result = fm.parse(test.value, delimiter: test.delimiter);
+      var result =
+          FrontMatterDocument.fromText(test.value, delimiter: test.delimiter);
       expect(result.content, equals(test.content));
       expect(result.data['foo'], equals(test.foo));
     });
   });
 
   test('throws FrontMatterException when YAML is invalid', () {
     var input = '---\nINVALID\n---\nfoo';
-    expect(() => fm.parse(input),
+    expect(() => FrontMatterDocument.fromText(input),
         throwsA(const TypeMatcher<FrontMatterException>()));
   });
 
   test('reads a file from disk and parses front matter', () async {
-    var result = await fm.parseFile('example/hello-world.md');
+    var result = await FrontMatterDocument.fromFile('example/hello-world.md');
     expect(result.data['author'], equals('izolate'));
   });
 
   test('throws an error if file not found', () {
     expect(
-        () async => await fm.parseFile('/path/to/nowhere'),
+        () async => await FrontMatterDocument.fromFile('/path/to/nowhere'),
         throwsA(predicate((e) =>
             e is FrontMatterException && e.message == fileNotFoundError)));
   });
 
   test('throws an error if file type is not supported', () {
     expect(
-        () async => await fm.parseFile('test/dart.jpeg'),
+        () async => await FrontMatterDocument.fromFile('test/dart.jpeg'),
         throwsA(predicate(
             (e) => e is FrontMatterException && e.message == fileTypeError)));
   });