How to write parser?

[Suliman via Digitalmars-d-learn]

I am trying to learn how to write text parser. I have example doc 
with follow format:

#Header
my header text
##SubHeader
my sub header text

###Sub3Header
my sub 3 text

#Header21
my header2 text

##SubHeader21
my header2 text

###SubHeader22
my header3 text


I would like to wrap all level(#) tags to HTML div's, to get it's 
look like:

<div 1>
#Header
my header text
<div 2>
##SubHeader
my sub header text

###Sub3Header
my sub 3 text
</div 3>
</div 2>
</div 1>

<div 1>#Header21
my header2 text

<div 2>##SubHeader21
my header2 text

<div 3>###SubHeader22
my header3 text
</div 3>
</div 2>
</div 1>

It's seems that I wrong understand parser logic. I am trying to 
do it's in next way:

        bool isH1Open;
        bool isH2Open;
        bool isH3Open;

        string newcontent;

        foreach(line; content.lineSplitter)
        {
                if(line.length > 3) // to prevent access to line < 3 symblos
                {
                        if(!isH1Open && line[0] == '#' && line[1] != '#')
                        {
                                isH1Open = true;
                                line = `<div 1>` ~ "\n" ~ line ;
                                newcontent ~= line;
                                continue;
                        }


                        if(isH2Open && line[1] == '#' && line[2] != '#')
                        {
                                isH2Open = false;
                                line = "\n" ~ `</div 2>` ~ "\n";
                                newcontent ~= line;
                                continue;
                        }

                        if(isH1Open && line[0] == '#' && line[1] != '#')
                        {
                                isH1Open = false;
                                line = "\n" ~ `</div 1>` ~ "\n";
                                newcontent ~= line;
                                continue;
                        }

        
                        if(!isH2Open && line[1] == '#' && line[2] != '#')
                        {
                                isH2Open = true;
                                line = "\n" ~ `<div 2>` ~ "\n" ~ line ;
                                newcontent ~= line;
                                continue;
                        }


                }

But I am getting wrong output:

<div 1>
#Header
<div 2>
##SubHeader
</div 1>

</div 2>
<div 1>
#Header31
<div 2>
##SubHeader31

it's there any better way to parse such format?