spaces = [

    (0, 1), # we assume this is a over-and-underlined header

    (2, 1),

    (1, 1),

    (1, 0),

    (1, 0),

    ]

# http://sphinx-doc.org/rest.html :

#   for the Python documentation, this convention is used which you may follow:

#   # with overline, for parts

#   * with overline, for chapters

#   =, for sections

#   -, for subsections

#   ^, for subsubsections

#   ", for paragraphs

pystyles = ['#', '*', '=', '-', '^', '"']

# match on a header line underlined with one of the valid characters

headermatch = re.compile(r'''\n*(.+)\n([][!"#$%&'()*+,./:;<=>?@\\^_`{|}~-])\2{2,}\n+''', flags=re.MULTILINE)

def main():

        s = open(fn).read()

        # find levels and their styles

        lastpos = 0

        styles = []

        for markup in headermatch.findall(s):

            style = markup[1]

            if style in styles:

                stylepos = styles.index(style)

                if stylepos > lastpos + 1:

                    print 'bad style %r with level %s - was at %s' % (style, stylepos, lastpos)

            else:

                stylepos = len(styles)

                if stylepos > lastpos + 1:

                    print 'bad new style %r - expected %r' % (style, styles[lastpos + 1])

                else:

                    styles.append(style)

            lastpos = stylepos

        # remove superfluous spacing (may however be restored by header spacing)

        s = re.sub(r'''(\n\n)\n*''', r'\1', s, flags=re.MULTILINE)

        if styles:

            newstyles = pystyles[pystyles.index(styles[0]):]

            def subf(m):

                title, style = m.groups()

                level = styles.index(style)

                before, after = spaces[level]

                newstyle = newstyles[level]

                return '\n' * (before + 1) + title + '\n' + newstyle * len(title) + '\n' * (after + 1)

            s = headermatch.sub(subf, s)

        # remove superfluous spacing when headers are adjacent

        s = re.sub(r'''(\n.+\n([][!"#$%&'()*+,./:;<=>?@\\^_`{|}~-])\2{2,}\n\n\n)\n*''', r'\1', s, flags=re.MULTILINE)

        # fix trailing space and spacing before link sections

        s = s.strip() + '\n'

        s = re.sub(r'''\n+((?:\.\. _[^\n]*\n)+)$''', r'\n\n\n\1', s)

        open(fn, 'w').write(s)

if __name__ == '__main__':

    main()