LayoutReader.read handling levels incorrectly

[solvingproblemswithtechnology]

I want to use nlm-ingestor from C#, so I was layout_reader.py to create the code. And I found a really bad bug regarding level handling.

It will hard to explain for me, but I'll do my best and provide the test data I'm using.

Given the following structure:

heading 1
    heading 2
    heading 2
        para 3
    heading 2
para 1

When the reader goes to read the last para, in the if block['tag'] == 'para': it doesn't take into account the level change to change its parent.

Since my knowledge of python is limited, I'll paste some visual debugging information to make it easier to understand:

In this image, you can see a Level 0 header with another Level 0 header as children:

And in this image, you can see a Level 0 paragraph inside a Level 2 header:

This is the translated code with the bug:

public Block Read(List<Block> blocksJson)
{
	var root = new Block();
	Block parent = root;
	var parentStack = new Stack<Block>();
	parentStack.Push(root);
	var prevNode = root;
	var listStack = new Stack<Block>();

	foreach (var block in blocksJson)
	{
		if (block.Tag.ToString() != "list_item" && listStack.Count > 0)
			listStack.Clear();

		Block node = null;

		switch (block.Tag)
		{
			case "para":
				node = new Paragraph(block);
				parent.AddChild(node);
				break;
			case "table":
				node = new Table(block, prevNode);
				parent.AddChild(node);
				break;
			case "list_item":
				node = new ListItem(block);

				if (prevNode.Tag == "para" && prevNode.Level == node.Level)
					listStack.Push(prevNode);
				else if (prevNode.Tag == "list_item")
				{
					if (node.Level > prevNode.Level)
						listStack.Push(prevNode);
					else
					{
						while (listStack.Count > 0 && listStack.Peek().Level > node.Level)
							listStack.Pop();
					}
				}

				if (listStack.Count > 0)
					listStack.Peek().AddChild(node);
				else
					parent.AddChild(node);

				break;
			case "header":
				node = new Section(block);

				if (node.Level > parent.Level)
				{
					parentStack.Push(node);
					parent.AddChild(node);
				}
				else
				{
					while (parentStack.Count > 1 && parentStack.Peek().Level > node.Level)
						parentStack.Pop();

					parentStack.Peek().AddChild(node);
					parentStack.Push(node);
				}

				parent = node;
				break;
		}

		prevNode = node;
	}

	return root;
}

Here's the fixed method, handling the level change within the rest of the cases. I know it's not pretty, I didn't refactor it yet:

public Block Read(List<Block> blocksJson)
{
	var root = new Block();
	Block parent = root;
	var parentStack = new Stack<Block>();
	parentStack.Push(root);
	var prevNode = root;
	var listStack = new Stack<Block>();

	foreach (var block in blocksJson)
	{
		if (block.Tag != "list_item" && listStack.Count > 0)
			listStack.Clear();

		Block node = null;

		switch (block.Tag)
		{
			case "header":
				node = new Section(block);

				if (node.Level > parent.Level)
				{
					parentStack.Push(node);
					parent.AddChild(node);
				}
				else
				{
					while (parentStack.Count > 1 && parent.Level >= node.Level)
					{
						parentStack.Pop();
						parent = parentStack.Peek();
					}

					parent.AddChild(node);
					parentStack.Push(node);
				}

				parent = node;
				break;
			case "para":
				node = new Paragraph(block);

			        if (node.Level < parent.Level)
			        {
				        while (parentStack.Count > 1 && parentStack.Peek().Level > node.Level)
					        parentStack.Pop();
        
				        parent = parentStack.Peek();
			        }

				parent.AddChild(node);
				break;
			case "table":
				node = new Table(block, prevNode);

			        if (node.Level < parent.Level)
			        {
				        while (parentStack.Count > 1 && parentStack.Peek().Level > node.Level)
					        parentStack.Pop();
        
				        parent = parentStack.Peek();
			        }

				parent.AddChild(node);
				break;
			case "list_item":
				node = new ListItem(block);

				if (prevNode.Tag == "para" && prevNode.Level == node.Level)
					listStack.Push(prevNode);
				else if (prevNode.Tag == "list_item")
				{
					if (node.Level > prevNode.Level)
						listStack.Push(prevNode);
					else
					{
						while (listStack.Count > 0 && listStack.Peek().Level > node.Level)
							listStack.Pop();
					}
				}

				if (listStack.Count > 0)
					listStack.Peek().AddChild(node);
				else
				{
					if (node.Level < parent.Level)
					{
						while (parentStack.Count > 1 && parentStack.Peek().Level > node.Level)
							parentStack.Pop();

						parent = parentStack.Peek();
					}

					parent.AddChild(node);
				}

				break;
		}

		prevNode = node;
	}

	return root;
}

Here's the first case fixed. You can notice that there's no Level 0 header and that there's more Level 1 items in there:

The second case, now there's no childrens as it should:

Here's the used json for testing:
https://gist.github.com/solvingproblemswithtechnology/a1d79d1892284375855a7205d5eb4ea5

P.S.: Thanks for your understanding, currently I'm not knowledgable enough on python to fix this issue with confidence, but I tried to add all the context.