markdown/extensions/tables.py

"""
Tables Extension for Python-Markdown
====================================

Added parsing of tables to Python-Markdown.

See <https://Python-Markdown.github.io/extensions/tables>
for documentation.

Original code Copyright 2009 [Waylan Limberg](http://achinghead.com)

All changes Copyright 2008-2014 The Python Markdown Project

License: [BSD](https://opensource.org/licenses/bsd-license.php)

"""

from . import Extension
from ..blockprocessors import BlockProcessor
import xml.etree.ElementTree as etree
import re
PIPE_NONE = 0
PIPE_LEFT = 1
PIPE_RIGHT = 2


class TableProcessor(BlockProcessor):
    """ Process Tables. """

    RE_CODE_PIPES = re.compile(r'(?:(\\\\)|(\\`+)|(`+)|(\\\|)|(\|))')
    RE_END_BORDER = re.compile(r'(?<!\\)(?:\\\\)*\|$')

    def __init__(self, parser):
        self.border = False
        self.separator = ''
        super().__init__(parser)

    def test(self, parent, block):
        """
        Ensure first two rows (column header and separator row) are valid table rows.

        Keep border check and separator row do avoid repeating the work.
        """
        is_table = False
        rows = [row.strip(' ') for row in block.split('\n')]
        if len(rows) > 1:
            header0 = rows[0]
            self.border = PIPE_NONE
            if header0.startswith('|'):
                self.border |= PIPE_LEFT
            if self.RE_END_BORDER.search(header0) is not None:
                self.border |= PIPE_RIGHT
            row = self._split_row(header0)
            row0_len = len(row)
            is_table = row0_len > 1

            # Each row in a single column table needs at least one pipe.
            if not is_table and row0_len == 1 and self.border:
                for index in range(1, len(rows)):
                    is_table = rows[index].startswith('|')
                    if not is_table:
                        is_table = self.RE_END_BORDER.search(rows[index]) is not None
                    if not is_table:
                        break

            if is_table:
                row = self._split_row(rows[1])
                is_table = (len(row) == row0_len) and set(''.join(row)) <= set('|:- ')
                if is_table:
                    self.separator = row

        return is_table

    def run(self, parent, blocks):
        """ Parse a table block and build table. """
        block = blocks.pop(0).split('\n')
        header = block[0].strip(' ')
        rows = [] if len(block) < 3 else block[2:]

        # Get alignment of columns
        align = []
        for c in self.separator:
            c = c.strip(' ')
            if c.startswith(':') and c.endswith(':'):
                align.append('center')
            elif c.startswith(':'):
                align.append('left')
            elif c.endswith(':'):
                align.append('right')
            else:
                align.append(None)

        # Build table
        table = etree.SubElement(parent, 'table')
        thead = etree.SubElement(table, 'thead')
        self._build_row(header, thead, align)
        tbody = etree.SubElement(table, 'tbody')
        if len(rows) == 0:
            # Handle empty table
            self._build_empty_row(tbody, align)
        else:
            for row in rows:
                self._build_row(row.strip(' '), tbody, align)

    def _build_empty_row(self, parent, align):
        """Build an empty row."""
        tr = etree.SubElement(parent, 'tr')
        count = len(align)
        while count:
            etree.SubElement(tr, 'td')
            count -= 1

    def _build_row(self, row, parent, align):
        """ Given a row of text, build table cells. """
        tr = etree.SubElement(parent, 'tr')
        tag = 'td'
        if parent.tag == 'thead':
            tag = 'th'
        cells = self._split_row(row)
        # We use align here rather than cells to ensure every row
        # contains the same number of columns.
        for i, a in enumerate(align):
            c = etree.SubElement(tr, tag)
            try:
                c.text = cells[i].strip(' ')
            except IndexError:  # pragma: no cover
                c.text = ""
            if a:
                c.set('align', a)

    def _split_row(self, row):
        """ split a row of text into list of cells. """
        if self.border:
            if row.startswith('|'):
                row = row[1:]
            row = self.RE_END_BORDER.sub('', row)
        return self._split(row)

    def _split(self, row):
        """ split a row of text with some code into a list of cells. """
        elements = []
        pipes = []
        tics = []
        tic_points = []
        tic_region = []
        good_pipes = []

        # Parse row
        # Throw out \\, and \|
        for m in self.RE_CODE_PIPES.finditer(row):
            # Store ` data (len, start_pos, end_pos)
            if m.group(2):
                # \`+
                # Store length of each tic group: subtract \
                tics.append(len(m.group(2)) - 1)
                # Store start of group, end of group, and escape length
                tic_points.append((m.start(2), m.end(2) - 1, 1))
            elif m.group(3):
                # `+
                # Store length of each tic group
                tics.append(len(m.group(3)))
                # Store start of group, end of group, and escape length
                tic_points.append((m.start(3), m.end(3) - 1, 0))
            # Store pipe location
            elif m.group(5):
                pipes.append(m.start(5))

        # Pair up tics according to size if possible
        # Subtract the escape length *only* from the opening.
        # Walk through tic list and see if tic has a close.
        # Store the tic region (start of region, end of region).
        pos = 0
        tic_len = len(tics)
        while pos < tic_len:
            try:
                tic_size = tics[pos] - tic_points[pos][2]
                if tic_size == 0:
                    raise ValueError
                index = tics[pos + 1:].index(tic_size) + 1
                tic_region.append((tic_points[pos][0], tic_points[pos + index][1]))
                pos += index + 1
            except ValueError:
                pos += 1

        # Resolve pipes.  Check if they are within a tic pair region.
        # Walk through pipes comparing them to each region.
        #     - If pipe position is less that a region, it isn't in a region
        #     - If it is within a region, we don't want it, so throw it out
        #     - If we didn't throw it out, it must be a table pipe
        for pipe in pipes:
            throw_out = False
            for region in tic_region:
                if pipe < region[0]:
                    # Pipe is not in a region
                    break
                elif region[0] <= pipe <= region[1]:
                    # Pipe is within a code region.  Throw it out.
                    throw_out = True
                    break
            if not throw_out:
                good_pipes.append(pipe)

        # Split row according to table delimeters.
        pos = 0
        for pipe in good_pipes:
            elements.append(row[pos:pipe])
            pos = pipe + 1
        elements.append(row[pos:])
        return elements


class TableExtension(Extension):
    """ Add tables to Markdown. """

    def extendMarkdown(self, md):
        """ Add an instance of TableProcessor to BlockParser. """
        if '|' not in md.ESCAPED_CHARS:
            md.ESCAPED_CHARS.append('|')
        md.parser.blockprocessors.register(TableProcessor(md.parser), 'table', 75)


def makeExtension(**kwargs):  # pragma: no cover
    return TableExtension(**kwargs)