fix: markdown does not support nested lists

lib/src/plugins/markdown/decoder/document_markdown_decoder.dart

@@ -41,13 +41,13 @@
           [convertLineToNode(lines[i], customInlineSyntaxes)],
         );
         i++;
-      } else if (lines[i].startsWith("```")) {
-        String codeBlock = "";
-        codeBlock += "${lines[i]}\n";
+      } else if (lines[i].startsWith('```')) {
+        String codeBlock = '';
+        codeBlock += '${lines[i]}\n';
         int tempLinePointer = i;
         i++;
-        while (i < lines.length && !lines[i].endsWith("```")) {
-          codeBlock += "${lines[i]}\n";
+        while (i < lines.length && !lines[i].endsWith('```')) {
+          codeBlock += '${lines[i]}\n';
           i++;
         }
 
@@ -73,6 +73,53 @@
 
         document.insert([i], [node]);
         i++;
+      } else if (i + 1 < lines.length && isNestedList(lines[i], lines[i + 1])) {
+        String text = lines[i];
+        int tempLinePointer = i;
+        int currentIndent = getIndentLevel(lines[i]);
+        i++;
+
+        while (i < lines.length &&
+            (lines[i].trimLeft().startsWith('- ') ||
+                lines[i].trimLeft().startsWith('* ')) &&
+            getIndentLevel(lines[i]) > currentIndent) {
+          text += '\n${lines[i]}';
+          i++;
+        }
+        List<String> listLines = text.split('\n');
+        Node? rootList;
+        Node? currentParent;
+        int indentLevel = 0;
+
+        for (String line in listLines) {
+          currentIndent = getIndentLevel(line);
+          Node newNode =
+              convertLineToNode(line.trimLeft(), customInlineSyntaxes);
+
+          if (rootList == null) {
+            rootList = newNode;
+            currentParent = newNode;
+          } else if (currentIndent > indentLevel) {
+            currentParent!.insert(newNode);
+            currentParent = newNode;
+          } else {
+            while (
+                currentIndent <= indentLevel && currentParent!.parent != null) {
+              currentParent = currentParent.parent;
+              indentLevel--;
+            }
+            if (currentParent != rootList) {
+              currentParent!.parent!.insert(newNode);
+            } else {
+              rootList.insert(newNode);
+            }
+            currentParent = newNode;
+          }
+          indentLevel = currentIndent;
+        }
+        if (rootList != null) {
+          document.insert([tempLinePointer], [rootList]);
+        }
       } else {
         document.insert(
           [i],
@@ -85,6 +132,24 @@
     return document;
   }
 
+  bool isNestedList(String line1, String line2) {
+    if ((line1.trimLeft().startsWith('- ') ||
+            line1.trimLeft().startsWith('* ')) &&
+        (line2.trimLeft().startsWith('- ') ||
+            line2.trimLeft().startsWith('* '))) {
+      return getIndentLevel(line2) > getIndentLevel(line1);
+    }
+    return false;
+  }
+
+  int getIndentLevel(String line) {
+    int indent = 0;
+    while (indent < line.length && line[indent] == ' ') {
+      indent++;
+    }
+    return (indent / 2).floor();
+  }
+
   Node convertLineToNode(
     String line,
     List<md.InlineSyntax> customInlineSyntaxes,

test/plugins/markdown/decoder/document_markdown_decoder_test.dart

@@ -627,6 +627,120 @@ void main() async {
   }
 }
 ''';
+    const example4 = '''
+{
+  "document": {
+    "type": "page",
+    "children": [
+      {
+        "type": "heading",
+        "data": {
+          "delta": [
+            {
+              "insert": "Welcome to AppFlowy"
+            }
+          ],
+          "level": 1
+        }
+      },
+      {
+        "type": "paragraph",
+        "data": {
+          "delta": []
+        }
+      },
+      {
+        "type": "heading",
+        "data": {
+          "delta": [
+            {
+              "insert": "Tasks"
+            }
+          ],
+          "level": 2
+        }
+      },
+      {
+        "type": "paragraph",
+        "data": {
+          "delta": []
+        }
+      },
+      {
+        "type": "bulleted_list",
+        "children": [
+          {
+            "type": "bulleted_list",
+            "children": [
+              {
+                "type": "bulleted_list",
+                "data": {
+                  "delta": [
+                    {
+                      "insert": "Task Two"
+                    }
+                  ]
+                }
+              }
+            ],
+            "data": {
+              "delta": [
+                {
+                  "insert": "Task One + Parent"
+                }
+              ]
+            }
+          },
+          {
+            "type": "bulleted_list",
+            "data": {
+              "delta": [
+                {
+                  "insert": "Task Three"
+                }
+              ]
+            }
+          }
+        ],
+        "data": {
+          "delta": [
+            {
+              "insert": "Task Parent One"
+            }
+          ]
+        }
+      },
+      {
+        "type": "bulleted_list",
+        "data": {
+          "delta": [
+            {
+              "insert": "Task Four"
+            }
+          ]
+        }
+      },
+      {
+        "type": "bulleted_list",
+        "data": {
+          "delta": [
+            {
+              "insert": "Task Five"
+            }
+          ]
+        }
+      },
+      {
+        "type": "paragraph",
+        "data": {
+          "delta": []
+        }
+      }
+    ]
+  }
+}
+''';
+
     setUpAll(() {
       TestWidgetsFlutterBinding.ensureInitialized();
     });
@@ -698,6 +812,24 @@ void main(){
       expect(result.toJson(), data);
     });
 
+    test('test nested list', () async {
+      const markdown = '''
+# Welcome to AppFlowy
+
+## Tasks
+
+- Task Parent One
+  - Task One + Parent
+    - Task Two
+  - Task Three
+- Task Four
+- Task Five
+''';
+      final result = DocumentMarkdownDecoder().convert(markdown);
+      final data = jsonDecode(example4);
+      expect(result.toJson(), data);
+    });
+
     test('decode uncommon markdown table', () async {
       const markdown = r'''
   |  ## \|a|_c_|