[flutter]: add markdown parser

app_flowy/lib/workspace/application/doc/share_bloc.dart

@@ -1,4 +1,5 @@
 import 'package:app_flowy/workspace/domain/i_share.dart';
+import 'package:app_flowy/workspace/infrastructure/markdown/delta_markdown.dart';
 import 'package:flowy_sdk/protobuf/flowy-workspace-infra/export.pb.dart';
 import 'package:flowy_sdk/protobuf/flowy-workspace-infra/view_create.pb.dart';
 import 'package:flowy_sdk/protobuf/flowy-workspace/errors.pb.dart';
@@ -16,7 +17,7 @@ class DocShareBloc extends Bloc<DocShareEvent, DocShareState> {
         shareMarkdown: (ShareMarkdown value) async {
           await shareManager.exportMarkdown(view.id).then((result) {
             result.fold(
-              (value) => emit(DocShareState.finish(left(value))),
+              (value) => emit(DocShareState.finish(left(_convertDeltaToMarkdown(value)))),
               (error) => emit(DocShareState.finish(right(error))),
             );
           });
@@ -28,6 +29,12 @@ class DocShareBloc extends Bloc<DocShareEvent, DocShareState> {
       );
     });
   }
+
+  ExportData _convertDeltaToMarkdown(ExportData value) {
+    final result = deltaToMarkdown(value.data);
+    value.data = result;
+    return value;
+  }
 }
 
 @freezed

app_flowy/lib/workspace/infrastructure/markdown/delta_markdown.dart

@@ -0,0 +1,30 @@
+library delta_markdown;
+
+import 'dart:convert';
+
+import 'src/delta_markdown_decoder.dart';
+import 'src/delta_markdown_encoder.dart';
+import 'src/version.dart';
+
+const version = packageVersion;
+
+/// Codec used to convert between Markdown and Quill deltas.
+const DeltaMarkdownCodec _kCodec = DeltaMarkdownCodec();
+
+String markdownToDelta(String markdown) {
+  return _kCodec.decode(markdown);
+}
+
+String deltaToMarkdown(String delta) {
+  return _kCodec.encode(delta);
+}
+
+class DeltaMarkdownCodec extends Codec<String, String> {
+  const DeltaMarkdownCodec();
+
+  @override
+  Converter<String, String> get decoder => DeltaMarkdownDecoder();
+
+  @override
+  Converter<String, String> get encoder => DeltaMarkdownEncoder();
+}

app_flowy/lib/workspace/infrastructure/markdown/src/ast.dart

@@ -0,0 +1,113 @@
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+typedef Resolver = Node? Function(String name, [String? title]);
+
+/// Base class for any AST item.
+///
+/// Roughly corresponds to Node in the DOM. Will be either an Element or Text.
+class Node {
+  void accept(NodeVisitor visitor) {}
+
+  bool isToplevel = false;
+
+  String? get textContent {
+    return null;
+  }
+}
+
+/// A named tag that can contain other nodes.
+class Element extends Node {
+  /// Instantiates a [tag] Element with [children].
+  Element(this.tag, this.children) : attributes = <String, String>{};
+
+  /// Instantiates an empty, self-closing [tag] Element.
+  Element.empty(this.tag)
+      : children = null,
+        attributes = {};
+
+  /// Instantiates a [tag] Element with no [children].
+  Element.withTag(this.tag)
+      : children = [],
+        attributes = {};
+
+  /// Instantiates a [tag] Element with a single Text child.
+  Element.text(this.tag, String text)
+      : children = [Text(text)],
+        attributes = {};
+
+  final String tag;
+  final List<Node>? children;
+  final Map<String, String> attributes;
+  String? generatedId;
+
+  /// Whether this element is self-closing.
+  bool get isEmpty => children == null;
+
+  @override
+  void accept(NodeVisitor visitor) {
+    if (visitor.visitElementBefore(this)) {
+      if (children != null) {
+        for (final child in children!) {
+          child.accept(visitor);
+        }
+      }
+      visitor.visitElementAfter(this);
+    }
+  }
+
+  @override
+  String get textContent => children == null
+      ? ''
+      : children!.map((child) => child.textContent).join();
+}
+
+/// A plain text element.
+class Text extends Node {
+  Text(this.text);
+
+  final String text;
+
+  @override
+  void accept(NodeVisitor visitor) => visitor.visitText(this);
+
+  @override
+  String get textContent => text;
+}
+
+/// Inline content that has not been parsed into inline nodes (strong, links,
+/// etc).
+///
+/// These placeholder nodes should only remain in place while the block nodes
+/// of a document are still being parsed, in order to gather all reference link
+/// definitions.
+class UnparsedContent extends Node {
+  UnparsedContent(this.textContent);
+
+  @override
+  final String textContent;
+
+  @override
+  void accept(NodeVisitor visitor);
+}
+
+/// Visitor pattern for the AST.
+///
+/// Renderers or other AST transformers should implement this.
+abstract class NodeVisitor {
+  /// Called when a Text node has been reached.
+  void visitText(Text text);
+
+  /// Called when an Element has been reached, before its children have been
+  /// visited.
+  ///
+  /// Returns `false` to skip its children.
+  bool visitElementBefore(Element element);
+
+  /// Called when an Element has been reached, after its children have been
+  /// visited.
+  ///
+  /// Will not be called if [visitElementBefore] returns `false`.
+  void visitElementAfter(Element element);
+}

app_flowy/lib/workspace/infrastructure/markdown/src/delta_markdown_decoder.dart

@@ -0,0 +1,255 @@
+import 'dart:collection';
+import 'dart:convert';
+
+import 'package:flutter_quill/models/documents/attribute.dart';
+import 'package:flutter_quill/models/quill_delta.dart';
+
+import 'ast.dart' as ast;
+import 'document.dart';
+
+class DeltaMarkdownDecoder extends Converter<String, String> {
+  @override
+  String convert(String input) {
+    final lines = input.replaceAll('\r\n', '\n').split('\n');
+
+    final markdownDocument = Document().parseLines(lines);
+
+    return jsonEncode(_DeltaVisitor().convert(markdownDocument).toJson());
+  }
+}
+
+class _DeltaVisitor implements ast.NodeVisitor {
+  static final _blockTags =
+      RegExp('h1|h2|h3|h4|h5|h6|hr|pre|ul|ol|blockquote|p|pre');
+
+  static final _embedTags = RegExp('hr|img');
+
+  late Delta delta;
+
+  late Queue<Attribute> activeInlineAttributes;
+  Attribute? activeBlockAttribute;
+  late Set<String> uniqueIds;
+
+  ast.Element? previousElement;
+  late ast.Element previousToplevelElement;
+
+  Delta convert(List<ast.Node> nodes) {
+    delta = Delta();
+    activeInlineAttributes = Queue<Attribute>();
+    uniqueIds = <String>{};
+
+    for (final node in nodes) {
+      node.accept(this);
+    }
+
+    // Ensure the delta ends with a newline.
+    if (delta.length > 0 && delta.last.value != '\n') {
+      delta.insert('\n', activeBlockAttribute?.toJson());
+    }
+
+    return delta;
+  }
+
+  @override
+  void visitText(ast.Text text) {
+    // Remove trailing newline
+    //final lines = text.text.trim().split('\n');
+
+    /*
+    final attributes = Map<String, dynamic>();
+    for (final attr in activeInlineAttributes) {
+      attributes.addAll(attr.toJson());
+    }
+
+    for (final l in lines) {
+      delta.insert(l, attributes);
+      delta.insert('\n', activeBlockAttribute.toJson());
+    }*/
+
+    final str = text.text;
+    //if (str.endsWith('\n')) str = str.substring(0, str.length - 1);
+
+    final attributes = <String, dynamic>{};
+    for (final attr in activeInlineAttributes) {
+      attributes.addAll(attr.toJson());
+    }
+
+    var newlineIndex = str.indexOf('\n');
+    var startIndex = 0;
+    while (newlineIndex != -1) {
+      final previousText = str.substring(startIndex, newlineIndex);
+      if (previousText.isNotEmpty) {
+        delta.insert(previousText, attributes.isNotEmpty ? attributes : null);
+      }
+      delta.insert('\n', activeBlockAttribute?.toJson());
+
+      startIndex = newlineIndex + 1;
+      newlineIndex = str.indexOf('\n', newlineIndex + 1);
+    }
+
+    if (startIndex < str.length) {
+      final lastStr = str.substring(startIndex);
+      delta.insert(lastStr, attributes.isNotEmpty ? attributes : null);
+    }
+  }
+
+  @override
+  bool visitElementBefore(ast.Element element) {
+    // Hackish. Separate block-level elements with newlines.
+    final attr = _tagToAttribute(element);
+
+    if (delta.isNotEmpty && _blockTags.firstMatch(element.tag) != null) {
+      if (element.isToplevel) {
+        // If the last active block attribute is not a list, we need to finish
+        // it off.
+        if (previousToplevelElement.tag != 'ul' &&
+            previousToplevelElement.tag != 'ol' &&
+            previousToplevelElement.tag != 'pre' &&
+            previousToplevelElement.tag != 'hr') {
+          delta.insert('\n', activeBlockAttribute?.toJson());
+        }
+
+        // Only separate the blocks if both are paragraphs.
+        //
+        // TODO(kolja): Determine which behavior we really want here.
+        // We can either insert an additional newline or just have the
+        // paragraphs as single lines. Zefyr will by default render two lines
+        // are different paragraphs so for now we will not add an additonal
+        // newline here.
+        //
+        // if (previousToplevelElement != null &&
+        //     previousToplevelElement.tag == 'p' &&
+        //     element.tag == 'p') {
+        //   delta.insert('\n');
+        // }
+      } else if (element.tag == 'p' &&
+          previousElement != null &&
+          !previousElement!.isToplevel &&
+          !previousElement!.children!.contains(element)) {
+        // Here we have two children of the same toplevel element. These need
+        // to be separated by additional newlines.
+
+        delta
+          // Finish off the last lower-level block.
+          ..insert('\n', activeBlockAttribute?.toJson())
+          // Add an empty line between the lower-level blocks.
+          ..insert('\n', activeBlockAttribute?.toJson());
+      }
+    }
+
+    // Keep track of the top-level block attribute.
+    if (element.isToplevel && element.tag != 'hr') {
+      // Hacky solution for horizontal rule so that the attribute is not added
+      // to the line feed at the end of the line.
+      activeBlockAttribute = attr;
+    }
+
+    if (_embedTags.firstMatch(element.tag) != null) {
+      // We write out the element here since the embed has no children or
+      // content.
+      delta.insert(attr!.toJson());
+    } else if (_blockTags.firstMatch(element.tag) == null && attr != null) {
+      activeInlineAttributes.addLast(attr);
+    }
+
+    previousElement = element;
+    if (element.isToplevel) {
+      previousToplevelElement = element;
+    }
+
+    if (element.isEmpty) {
+      // Empty element like <hr/>.
+      //buffer.write(' />');
+
+      if (element.tag == 'br') {
+        delta.insert('\n');
+      }
+
+      return false;
+    } else {
+      //buffer.write('>');
+      return true;
+    }
+  }
+
+  @override
+  void visitElementAfter(ast.Element element) {
+    if (element.tag == 'li' &&
+        (previousToplevelElement.tag == 'ol' ||
+            previousToplevelElement.tag == 'ul')) {
+      delta.insert('\n', activeBlockAttribute?.toJson());
+    }
+
+    final attr = _tagToAttribute(element);
+    if (attr == null || !attr.isInline || activeInlineAttributes.last != attr) {
+      return;
+    }
+    activeInlineAttributes.removeLast();
+
+    // Always keep track of the last element.
+    // This becomes relevant if we have something like
+    //
+    // <ul>
+    //   <li>...</li>
+    //   <li>...</li>
+    // </ul>
+    previousElement = element;
+  }
+
+  /// Uniquifies an id generated from text.
+  String uniquifyId(String id) {
+    if (!uniqueIds.contains(id)) {
+      uniqueIds.add(id);
+      return id;
+    }
+
+    var suffix = 2;
+    var suffixedId = '$id-$suffix';
+    while (uniqueIds.contains(suffixedId)) {
+      suffixedId = '$id-${suffix++}';
+    }
+    uniqueIds.add(suffixedId);
+    return suffixedId;
+  }
+
+  Attribute? _tagToAttribute(ast.Element el) {
+    switch (el.tag) {
+      case 'em':
+        return Attribute.italic;
+      case 'strong':
+        return Attribute.bold;
+      case 'ul':
+        return Attribute.ul;
+      case 'ol':
+        return Attribute.ol;
+      case 'pre':
+        return Attribute.codeBlock;
+      case 'blockquote':
+        return Attribute.blockQuote;
+      case 'h1':
+        return Attribute.h1;
+      case 'h2':
+        return Attribute.h2;
+      case 'h3':
+        return Attribute.h3;
+      case 'a':
+        final href = el.attributes['href'];
+        return LinkAttribute(href);
+      case 'img':
+        final href = el.attributes['src'];
+        return ImageAttribute(href);
+      case 'hr':
+        return DividerAttribute();
+    }
+
+    return null;
+  }
+}
+
+class ImageAttribute extends Attribute<String?> {
+  ImageAttribute(String? val) : super('image', AttributeScope.EMBEDS, val);
+}
+
+class DividerAttribute extends Attribute<String?> {
+  DividerAttribute() : super('divider', AttributeScope.EMBEDS, 'hr');
+}

app_flowy/lib/workspace/infrastructure/markdown/src/delta_markdown_encoder.dart

@@ -0,0 +1,272 @@
+import 'dart:convert';
+
+import 'package:collection/collection.dart' show IterableExtension;
+import 'package:flutter_quill/models/documents/attribute.dart';
+import 'package:flutter_quill/models/documents/nodes/embed.dart';
+import 'package:flutter_quill/models/documents/style.dart';
+import 'package:flutter_quill/models/quill_delta.dart';
+
+class DeltaMarkdownEncoder extends Converter<String, String> {
+  static const _lineFeedAsciiCode = 0x0A;
+
+  late StringBuffer markdownBuffer;
+  late StringBuffer lineBuffer;
+
+  Attribute? currentBlockStyle;
+  late Style currentInlineStyle;
+
+  late List<String> currentBlockLines;
+
+  /// Converts the [input] delta to Markdown.
+  @override
+  String convert(String input) {
+    markdownBuffer = StringBuffer();
+    lineBuffer = StringBuffer();
+    currentInlineStyle = Style();
+    currentBlockLines = <String>[];
+
+    final inputJson = jsonDecode(input) as List<dynamic>?;
+    if (inputJson is! List<dynamic>) {
+      throw ArgumentError('Unexpected formatting of the input delta string.');
+    }
+    final delta = Delta.fromJson(inputJson);
+    final iterator = DeltaIterator(delta);
+
+    while (iterator.hasNext) {
+      final operation = iterator.next();
+
+      if (operation.data is String) {
+        final operationData = operation.data as String;
+
+        if (!operationData.contains('\n')) {
+          _handleInline(lineBuffer, operationData, operation.attributes);
+        } else {
+          _handleLine(operationData, operation.attributes);
+        }
+      } else if (operation.data is Map<String, dynamic>) {
+        _handleEmbed(operation.data as Map<String, dynamic>);
+      } else {
+        throw ArgumentError('Unexpected formatting of the input delta string.');
+      }
+    }
+
+    _handleBlock(currentBlockStyle); // Close the last block
+
+    return markdownBuffer.toString();
+  }
+
+  void _handleInline(
+    StringBuffer buffer,
+    String text,
+    Map<String, dynamic>? attributes,
+  ) {
+    final style = Style.fromJson(attributes);
+
+    // First close any current styles if needed
+    final markedForRemoval = <Attribute>[];
+    // Close the styles in reverse order, e.g. **_ for _**Test**_.
+    for (final value
+        in currentInlineStyle.attributes.values.toList().reversed) {
+      // TODO(tillf): Is block correct?
+      if (value.scope == AttributeScope.BLOCK) {
+        continue;
+      }
+      if (style.containsKey(value.key)) {
+        continue;
+      }
+
+      final padding = _trimRight(buffer);
+      _writeAttribute(buffer, value, close: true);
+      if (padding.isNotEmpty) {
+        buffer.write(padding);
+      }
+      markedForRemoval.add(value);
+    }
+
+    // Make sure to remove all attributes that are marked for removal.
+    for (final value in markedForRemoval) {
+      currentInlineStyle.attributes.removeWhere((_, v) => v == value);
+    }
+
+    // Now open any new styles.
+    for (final attribute in style.attributes.values) {
+      // TODO(tillf): Is block correct?
+      if (attribute.scope == AttributeScope.BLOCK) {
+        continue;
+      }
+      if (currentInlineStyle.containsKey(attribute.key)) {
+        continue;
+      }
+      final originalText = text;
+      text = text.trimLeft();
+      final padding = ' ' * (originalText.length - text.length);
+      if (padding.isNotEmpty) {
+        buffer.write(padding);
+      }
+      _writeAttribute(buffer, attribute);
+    }
+
+    // Write the text itself
+    buffer.write(text);
+    currentInlineStyle = style;
+  }
+
+  void _handleLine(String data, Map<String, dynamic>? attributes) {
+    final span = StringBuffer();
+
+    for (var i = 0; i < data.length; i++) {
+      if (data.codeUnitAt(i) == _lineFeedAsciiCode) {
+        if (span.isNotEmpty) {
+          // Write the span if it's not empty.
+          _handleInline(lineBuffer, span.toString(), attributes);
+        }
+        // Close any open inline styles.
+        _handleInline(lineBuffer, '', null);
+
+        final lineBlock = Style.fromJson(attributes)
+            .attributes
+            .values
+            .singleWhereOrNull((a) => a.scope == AttributeScope.BLOCK);
+
+        if (lineBlock == currentBlockStyle) {
+          currentBlockLines.add(lineBuffer.toString());
+        } else {
+          _handleBlock(currentBlockStyle);
+          currentBlockLines
+            ..clear()
+            ..add(lineBuffer.toString());
+
+          currentBlockStyle = lineBlock;
+        }
+        lineBuffer.clear();
+
+        span.clear();
+      } else {
+        span.writeCharCode(data.codeUnitAt(i));
+      }
+    }
+
+    // Remaining span
+    if (span.isNotEmpty) {
+      _handleInline(lineBuffer, span.toString(), attributes);
+    }
+  }
+
+  void _handleEmbed(Map<String, dynamic> data) {
+    final embed = BlockEmbed(data.keys.first, data.values.first as String);
+
+    if (embed.type == 'image') {
+      _writeEmbedTag(lineBuffer, embed);
+      _writeEmbedTag(lineBuffer, embed, close: true);
+    } else if (embed.type == 'divider') {
+      _writeEmbedTag(lineBuffer, embed);
+      _writeEmbedTag(lineBuffer, embed, close: true);
+    }
+  }
+
+  void _handleBlock(Attribute? blockStyle) {
+    if (currentBlockLines.isEmpty) {
+      return; // Empty block
+    }
+
+    // If there was a block before this one, add empty line between the blocks
+    if (markdownBuffer.isNotEmpty) {
+      markdownBuffer.writeln();
+    }
+
+    if (blockStyle == null) {
+      markdownBuffer
+        ..write(currentBlockLines.join('\n'))
+        ..writeln();
+    } else if (blockStyle == Attribute.codeBlock) {
+      _writeAttribute(markdownBuffer, blockStyle);
+      markdownBuffer.write(currentBlockLines.join('\n'));
+      _writeAttribute(markdownBuffer, blockStyle, close: true);
+      markdownBuffer.writeln();
+    } else {
+      // Dealing with lists or a quote.
+      for (final line in currentBlockLines) {
+        _writeBlockTag(markdownBuffer, blockStyle);
+        markdownBuffer
+          ..write(line)
+          ..writeln();
+      }
+    }
+  }
+
+  String _trimRight(StringBuffer buffer) {
+    final text = buffer.toString();
+    if (!text.endsWith(' ')) {
+      return '';
+    }
+
+    final result = text.trimRight();
+    buffer
+      ..clear()
+      ..write(result);
+    return ' ' * (text.length - result.length);
+  }
+
+  void _writeAttribute(
+    StringBuffer buffer,
+    Attribute attribute, {
+    bool close = false,
+  }) {
+    if (attribute.key == Attribute.bold.key) {
+      buffer.write('**');
+    } else if (attribute.key == Attribute.italic.key) {
+      buffer.write('_');
+    } else if (attribute.key == Attribute.link.key) {
+      buffer.write(!close ? '[' : '](${attribute.value})');
+    } else if (attribute == Attribute.codeBlock) {
+      buffer.write(!close ? '```\n' : '\n```');
+    } else {
+      throw ArgumentError('Cannot handle $attribute');
+    }
+  }
+
+  void _writeBlockTag(
+    StringBuffer buffer,
+    Attribute block, {
+    bool close = false,
+  }) {
+    if (close) {
+      return; // no close tag needed for simple blocks.
+    }
+
+    if (block == Attribute.blockQuote) {
+      buffer.write('> ');
+    } else if (block == Attribute.ul) {
+      buffer.write('* ');
+    } else if (block == Attribute.ol) {
+      buffer.write('1. ');
+    } else if (block.key == Attribute.h1.key && block.value == 1) {
+      buffer.write('# ');
+    } else if (block.key == Attribute.h2.key && block.value == 2) {
+      buffer.write('## ');
+    } else if (block.key == Attribute.h3.key && block.value == 3) {
+      buffer.write('### ');
+    } else {
+      throw ArgumentError('Cannot handle block $block');
+    }
+  }
+
+  void _writeEmbedTag(
+    StringBuffer buffer,
+    BlockEmbed embed, {
+    bool close = false,
+  }) {
+    const kImageType = 'image';
+    const kDividerType = 'divider';
+
+    if (embed.type == kImageType) {
+      if (close) {
+        buffer.write('](${embed.data})');
+      } else {
+        buffer.write('![');
+      }
+    } else if (embed.type == kDividerType && close) {
+      buffer.write('\n---\n\n');
+    }
+  }
+}

app_flowy/lib/workspace/infrastructure/markdown/src/document.dart

@@ -0,0 +1,88 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'ast.dart';
+import 'block_parser.dart';
+import 'extension_set.dart';
+import 'inline_parser.dart';
+
+/// Maintains the context needed to parse a Markdown document.
+class Document {
+  Document({
+    Iterable<BlockSyntax>? blockSyntaxes,
+    Iterable<InlineSyntax>? inlineSyntaxes,
+    ExtensionSet? extensionSet,
+    this.linkResolver,
+    this.imageLinkResolver,
+  }) : extensionSet = extensionSet ?? ExtensionSet.commonMark {
+    _blockSyntaxes
+      ..addAll(blockSyntaxes ?? [])
+      ..addAll(this.extensionSet.blockSyntaxes);
+    _inlineSyntaxes
+      ..addAll(inlineSyntaxes ?? [])
+      ..addAll(this.extensionSet.inlineSyntaxes);
+  }
+
+  final Map<String, LinkReference> linkReferences = <String, LinkReference>{};
+  final ExtensionSet extensionSet;
+  final Resolver? linkResolver;
+  final Resolver? imageLinkResolver;
+  final _blockSyntaxes = <BlockSyntax>{};
+  final _inlineSyntaxes = <InlineSyntax>{};
+
+  Iterable<BlockSyntax> get blockSyntaxes => _blockSyntaxes;
+  Iterable<InlineSyntax> get inlineSyntaxes => _inlineSyntaxes;
+
+  /// Parses the given [lines] of Markdown to a series of AST nodes.
+  List<Node> parseLines(List<String> lines) {
+    final nodes = BlockParser(lines, this).parseLines();
+    // Make sure to mark the top level nodes as such.
+    for (final n in nodes) {
+      n.isToplevel = true;
+    }
+    _parseInlineContent(nodes);
+    return nodes;
+  }
+
+  /// Parses the given inline Markdown [text] to a series of AST nodes.
+  List<Node>? parseInline(String text) => InlineParser(text, this).parse();
+
+  void _parseInlineContent(List<Node> nodes) {
+    for (var i = 0; i < nodes.length; i++) {
+      final node = nodes[i];
+      if (node is UnparsedContent) {
+        final inlineNodes = parseInline(node.textContent)!;
+        nodes
+          ..removeAt(i)
+          ..insertAll(i, inlineNodes);
+        i += inlineNodes.length - 1;
+      } else if (node is Element && node.children != null) {
+        _parseInlineContent(node.children!);
+      }
+    }
+  }
+}
+
+/// A [link reference
+/// definition](http://spec.commonmark.org/0.28/#link-reference-definitions).
+class LinkReference {
+  /// Construct a [LinkReference], with all necessary fields.
+  ///
+  /// If the parsed link reference definition does not include a title, use
+  /// `null` for the [title] parameter.
+  LinkReference(this.label, this.destination, this.title);
+
+  /// The [link label](http://spec.commonmark.org/0.28/#link-label).
+  ///
+  /// Temporarily, this class is also being used to represent the link data for
+  /// an inline link (the destination and title), but this should change before
+  /// the package is released.
+  final String label;
+
+  /// The [link destination](http://spec.commonmark.org/0.28/#link-destination).
+  final String destination;
+
+  /// The [link title](http://spec.commonmark.org/0.28/#link-title).
+  final String title;
+}

app_flowy/lib/workspace/infrastructure/markdown/src/extension_set.dart

@@ -0,0 +1,64 @@
+import 'block_parser.dart';
+import 'inline_parser.dart';
+
+/// ExtensionSets provide a simple grouping mechanism for common Markdown
+/// flavors.
+///
+/// For example, the [gitHubFlavored] set of syntax extensions allows users to
+/// output HTML from their Markdown in a similar fashion to GitHub's parsing.
+class ExtensionSet {
+  ExtensionSet(this.blockSyntaxes, this.inlineSyntaxes);
+
+  /// The [ExtensionSet.none] extension set renders Markdown similar to
+  /// [Markdown.pl].
+  ///
+  /// However, this set does not render _exactly_ the same as Markdown.pl;
+  /// rather it is more-or-less the CommonMark standard of Markdown, without
+  /// fenced code blocks, or inline HTML.
+  ///
+  /// [Markdown.pl]: http://daringfireball.net/projects/markdown/syntax
+  static final ExtensionSet none = ExtensionSet([], []);
+
+  /// The [commonMark] extension set is close to compliance with [CommonMark].
+  ///
+  /// [CommonMark]: http://commonmark.org/
+  static final ExtensionSet commonMark =
+      ExtensionSet([const FencedCodeBlockSyntax()], [InlineHtmlSyntax()]);
+
+  /// The [gitHubWeb] extension set renders Markdown similarly to GitHub.
+  ///
+  /// This is different from the [gitHubFlavored] extension set in that GitHub
+  /// actually renders HTML different from straight [GitHub flavored Markdown].
+  ///
+  /// (The only difference currently is that [gitHubWeb] renders headers with
+  /// linkable IDs.)
+  ///
+  /// [GitHub flavored Markdown]: https://github.github.com/gfm/
+  static final ExtensionSet gitHubWeb = ExtensionSet([
+    const FencedCodeBlockSyntax(),
+    const HeaderWithIdSyntax(),
+    const SetextHeaderWithIdSyntax(),
+    const TableSyntax()
+  ], [
+    InlineHtmlSyntax(),
+    StrikethroughSyntax(),
+    EmojiSyntax(),
+    AutolinkExtensionSyntax(),
+  ]);
+
+  /// The [gitHubFlavored] extension set is close to compliance with the [GitHub
+  /// flavored Markdown spec].
+  ///
+  /// [GitHub flavored Markdown]: https://github.github.com/gfm/
+  static final ExtensionSet gitHubFlavored = ExtensionSet([
+    const FencedCodeBlockSyntax(),
+    const TableSyntax()
+  ], [
+    InlineHtmlSyntax(),
+    StrikethroughSyntax(),
+    AutolinkExtensionSyntax(),
+  ]);
+
+  final List<BlockSyntax> blockSyntaxes;
+  final List<InlineSyntax> inlineSyntaxes;
+}

app_flowy/lib/workspace/infrastructure/markdown/src/html_renderer.dart

@@ -0,0 +1,121 @@
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'ast.dart';
+import 'block_parser.dart';
+import 'document.dart';
+import 'extension_set.dart';
+import 'inline_parser.dart';
+
+/// Converts the given string of Markdown to HTML.
+String markdownToHtml(String markdown,
+    {Iterable<BlockSyntax>? blockSyntaxes,
+    Iterable<InlineSyntax>? inlineSyntaxes,
+    ExtensionSet? extensionSet,
+    Resolver? linkResolver,
+    Resolver? imageLinkResolver,
+    bool inlineOnly = false}) {
+  final document = Document(
+      blockSyntaxes: blockSyntaxes,
+      inlineSyntaxes: inlineSyntaxes,
+      extensionSet: extensionSet,
+      linkResolver: linkResolver,
+      imageLinkResolver: imageLinkResolver);
+
+  if (inlineOnly) {
+    return renderToHtml(document.parseInline(markdown)!);
+  }
+
+  // Replace windows line endings with unix line endings, and split.
+  final lines = markdown.replaceAll('\r\n', '\n').split('\n');
+
+  return '${renderToHtml(document.parseLines(lines))}\n';
+}
+
+/// Renders [nodes] to HTML.
+String renderToHtml(List<Node> nodes) => HtmlRenderer().render(nodes);
+
+/// Translates a parsed AST to HTML.
+class HtmlRenderer implements NodeVisitor {
+  HtmlRenderer();
+
+  static final _blockTags = RegExp('blockquote|h1|h2|h3|h4|h5|h6|hr|p|pre');
+
+  late StringBuffer buffer;
+  late Set<String> uniqueIds;
+
+  String render(List<Node> nodes) {
+    buffer = StringBuffer();
+    uniqueIds = <String>{};
+
+    for (final node in nodes) {
+      node.accept(this);
+    }
+
+    return buffer.toString();
+  }
+
+  @override
+  void visitText(Text text) {
+    buffer.write(text.text);
+  }
+
+  @override
+  bool visitElementBefore(Element element) {
+    // Hackish. Separate block-level elements with newlines.
+    if (buffer.isNotEmpty && _blockTags.firstMatch(element.tag) != null) {
+      buffer.write('\n');
+    }
+
+    buffer.write('<${element.tag}');
+
+    // Sort the keys so that we generate stable output.
+    final attributeNames = element.attributes.keys.toList()
+      ..sort((a, b) => a.compareTo(b));
+
+    for (final name in attributeNames) {
+      buffer.write(' $name="${element.attributes[name]}"');
+    }
+
+    // attach header anchor ids generated from text
+    if (element.generatedId != null) {
+      buffer.write(' id="${uniquifyId(element.generatedId!)}"');
+    }
+
+    if (element.isEmpty) {
+      // Empty element like <hr/>.
+      buffer.write(' />');
+
+      if (element.tag == 'br') {
+        buffer.write('\n');
+      }
+
+      return false;
+    } else {
+      buffer.write('>');
+      return true;
+    }
+  }
+
+  @override
+  void visitElementAfter(Element element) {
+    buffer.write('</${element.tag}>');
+  }
+
+  /// Uniquifies an id generated from text.
+  String uniquifyId(String id) {
+    if (!uniqueIds.contains(id)) {
+      uniqueIds.add(id);
+      return id;
+    }
+
+    var suffix = 2;
+    var suffixedId = '$id-$suffix';
+    while (uniqueIds.contains(suffixedId)) {
+      suffixedId = '$id-${suffix++}';
+    }
+    uniqueIds.add(suffixedId);
+    return suffixedId;
+  }
+}

app_flowy/lib/workspace/infrastructure/markdown/src/util.dart

@@ -0,0 +1,71 @@
+import 'dart:convert';
+
+import 'package:charcode/charcode.dart';
+
+String escapeHtml(String html) =>
+    const HtmlEscape(HtmlEscapeMode.element).convert(html);
+
+// Escape the contents of [value], so that it may be used as an HTML attribute.
+
+// Based on http://spec.commonmark.org/0.28/#backslash-escapes.
+String escapeAttribute(String value) {
+  final result = StringBuffer();
+  int ch;
+  for (var i = 0; i < value.codeUnits.length; i++) {
+    ch = value.codeUnitAt(i);
+    if (ch == $backslash) {
+      i++;
+      if (i == value.codeUnits.length) {
+        result.writeCharCode(ch);
+        break;
+      }
+      ch = value.codeUnitAt(i);
+      switch (ch) {
+        case $quote:
+          result.write('&quot;');
+          break;
+        case $exclamation:
+        case $hash:
+        case $dollar:
+        case $percent:
+        case $ampersand:
+        case $apostrophe:
+        case $lparen:
+        case $rparen:
+        case $asterisk:
+        case $plus:
+        case $comma:
+        case $dash:
+        case $dot:
+        case $slash:
+        case $colon:
+        case $semicolon:
+        case $lt:
+        case $equal:
+        case $gt:
+        case $question:
+        case $at:
+        case $lbracket:
+        case $backslash:
+        case $rbracket:
+        case $caret:
+        case $underscore:
+        case $backquote:
+        case $lbrace:
+        case $bar:
+        case $rbrace:
+        case $tilde:
+          result.writeCharCode(ch);
+          break;
+        default:
+          result.write('%5C');
+          result.writeCharCode(ch);
+      }
+    } else if (ch == $quote) {
+      result.write('%22');
+    } else {
+      result.writeCharCode(ch);
+    }
+  }
+  return result.toString();
+}

app_flowy/lib/workspace/infrastructure/markdown/src/version.dart

@@ -0,0 +1,2 @@
+// Generated code. Do not modify.
+const packageVersion = '0.0.2';

app_flowy/lib/workspace/presentation/stack_page/doc/doc_stack_page.dart

@@ -8,6 +8,7 @@ import 'package:flowy_infra/size.dart';
 import 'package:flowy_infra_ui/flowy_infra_ui.dart';
 import 'package:flowy_infra_ui/style_widget/text.dart';
 import 'package:flowy_infra_ui/widget/rounded_button.dart';
+import 'package:flowy_log/flowy_log.dart';
 import 'package:flowy_sdk/protobuf/flowy-workspace-infra/export.pb.dart';
 import 'package:flowy_sdk/protobuf/flowy-workspace-infra/view_create.pb.dart';
 import 'package:flowy_sdk/protobuf/flowy-workspace/errors.pb.dart';
@@ -117,9 +118,7 @@ class DocShareButton extends StatelessWidget {
         // TODO: Handle this case.
         break;
       case ExportType.Markdown:
-        FlutterClipboard.copy(exportData.data).then(
-          (value) => print('copied'),
-        );
+        FlutterClipboard.copy(exportData.data).then((value) => Log.info('copied to clipboard'));
         break;
       case ExportType.Text:
         // TODO: Handle this case.

app_flowy/pubspec.lock

@@ -253,13 +253,6 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "6.1.2"
-  file_picker:
-    dependency: "direct main"
-    description:
-      name: file_picker
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "4.2.1"
   fixnum:
     dependency: transitive
     description:

app_flowy/pubspec.yaml

@@ -66,7 +66,6 @@ dependencies:
   url_launcher: ^6.0.2
   # file_picker: ^4.2.1
   clipboard: ^0.1.3
-  delta_markdown: '>=0.3.0'
 
   # The following adds the Cupertino Icons font to your application.
   # Use with the CupertinoIcons class for iOS style icons.