# $Id: tableparser.py 4564 2006-05-21 20:44:42Z wiemann $

# Author: David Goodger <goodger@python.org>

# Copyright: This module has been placed in the public domain.

"""

This module defines table parser classes,which parse plaintext-graphic tables

and produce a well-formed data structure suitable for building a CALS table.

:Classes:

    - `GridTableParser`: Parse fully-formed tables represented with a grid.

    - `SimpleTableParser`: Parse simple tables, delimited by top & bottom

      borders.

:Exception class: `TableMarkupError`

:Function:

    `update_dict_of_lists()`: Merge two dictionaries containing list values.

"""

__docformat__ = 'reStructuredText'

import re

import sys

from docutils import DataError

class TableMarkupError(DataError): pass

class TableParser:

    """

    Abstract superclass for the common parts of the syntax-specific parsers.

    """

    head_body_separator_pat = None

    """Matches the row separator between head rows and body rows."""

    double_width_pad_char = '\x00'

    """Padding character for East Asian double-width text."""

    def parse(self, block):

        """

        Analyze the text `block` and return a table data structure.

        Given a plaintext-graphic table in `block` (list of lines of text; no

        whitespace padding), parse the table, construct and return the data

        necessary to construct a CALS table or equivalent.

        Raise `TableMarkupError` if there is any problem with the markup.

        """

        self.setup(block)

        self.find_head_body_sep()

        self.parse_table()

        structure = self.structure_from_cells()

        return structure

    def find_head_body_sep(self):

        """Look for a head/body row separator line; store the line index."""

        for i in range(len(self.block)):

            line = self.block[i]

            if self.head_body_separator_pat.match(line):

                if self.head_body_sep:

                    raise TableMarkupError(

                        'Multiple head/body row separators in table (at line '

                        'offset %s and %s); only one allowed.'

                        % (self.head_body_sep, i))

                else:

                    self.head_body_sep = i

                    self.block[i] = line.replace('=', '-')

        if self.head_body_sep == 0 or self.head_body_sep == (len(self.block)

                                                             - 1):

            raise TableMarkupError('The head/body row separator may not be '

                                   'the first or last line of the table.')

class GridTableParser(TableParser):

    """

    Parse a grid table using `parse()`.

    Here's an example of a grid table::

        +------------------------+------------+----------+----------+

        | Header row, column 1   | Header 2   | Header 3 | Header 4 |

        +========================+============+==========+==========+

        | body row 1, column 1   | column 2   | column 3 | column 4 |

        +------------------------+------------+----------+----------+

        | body row 2             | Cells may span columns.          |

        +------------------------+------------+---------------------+

        | body row 3             | Cells may  | - Table cells       |

        +------------------------+ span rows. | - contain           |

        | body row 4             |            | - body elements.    |

        +------------------------+------------+---------------------+

    Intersections use '+', row separators use '-' (except for one optional

    head/body row separator, which uses '='), and column separators use '|'.

    Passing the above table to the `parse()` method will result in the

    following data structure::

        ([24, 12, 10, 10],

         [[(0, 0, 1, ['Header row, column 1']),

           (0, 0, 1, ['Header 2']),

           (0, 0, 1, ['Header 3']),

           (0, 0, 1, ['Header 4'])]],

         [[(0, 0, 3, ['body row 1, column 1']),

           (0, 0, 3, ['column 2']),

           (0, 0, 3, ['column 3']),

           (0, 0, 3, ['column 4'])],

          [(0, 0, 5, ['body row 2']),

           (0, 2, 5, ['Cells may span columns.']),

           None,

           None],

          [(0, 0, 7, ['body row 3']),

           (1, 0, 7, ['Cells may', 'span rows.', '']),

           (1, 1, 7, ['- Table cells', '- contain', '- body elements.']),

           None],

          [(0, 0, 9, ['body row 4']), None, None, None]])

    The first item is a list containing column widths (colspecs). The second

    item is a list of head rows, and the third is a list of body rows. Each

    row contains a list of cells. Each cell is either None (for a cell unused

    because of another cell's span), or a tuple. A cell tuple contains four

    items: the number of extra rows used by the cell in a vertical span

    (morerows); the number of extra columns used by the cell in a horizontal

    span (morecols); the line offset of the first line of the cell contents;

    and the cell contents, a list of lines of text.

    """

    head_body_separator_pat = re.compile(r'\+=[=+]+=\+ *$')

    def setup(self, block):

        self.block = block[:]           # make a copy; it may be modified

        self.block.disconnect()         # don't propagate changes to parent

        self.bottom = len(block) - 1

        self.right = len(block[0]) - 1

        self.head_body_sep = None

        self.done = [-1] * len(block[0])

        self.cells = []

        self.rowseps = {0: [0]}

        self.colseps = {0: [0]}

    def parse_table(self):

        """

        Start with a queue of upper-left corners, containing the upper-left

        corner of the table itself. Trace out one rectangular cell, remember

        it, and add its upper-right and lower-left corners to the queue of

        potential upper-left corners of further cells. Process the queue in

        top-to-bottom order, keeping track of how much of each text column has

        been seen.

        We'll end up knowing all the row and column boundaries, cell positions

        and their dimensions.

        """

        corners = [(0, 0)]

        while corners:

            top, left = corners.pop(0)

            if top == self.bottom or left == self.right \

                  or top <= self.done[left]:

                continue

            result = self.scan_cell(top, left)

            if not result:

                continue

            bottom, right, rowseps, colseps = result

            update_dict_of_lists(self.rowseps, rowseps)

            update_dict_of_lists(self.colseps, colseps)

            self.mark_done(top, left, bottom, right)

            cellblock = self.block.get_2D_block(top + 1, left + 1,

                                                bottom, right)

            cellblock.disconnect()      # lines in cell can't sync with parent

            cellblock.replace(self.double_width_pad_char, '')

            self.cells.append((top, left, bottom, right, cellblock))

            corners.extend([(top, right), (bottom, left)])

            corners.sort()

        if not self.check_parse_complete():

            raise TableMarkupError('Malformed table; parse incomplete.')

    def mark_done(self, top, left, bottom, right):

        """For keeping track of how much of each text column has been seen."""

        before = top - 1

        after = bottom - 1

        for col in range(left, right):

            assert self.done[col] == before

            self.done[col] = after

    def check_parse_complete(self):

        """Each text column should have been completely seen."""

        last = self.bottom - 1

        for col in range(self.right):

            if self.done[col] != last:

                return None

        return 1

    def scan_cell(self, top, left):

        """Starting at the top-left corner, start tracing out a cell."""

        assert self.block[top][left] == '+'

        result = self.scan_right(top, left)

        return result

    def scan_right(self, top, left):

        """

        Look for the top-right corner of the cell, and make note of all column

        boundaries ('+').

        """

        colseps = {}

        line = self.block[top]

        for i in range(left + 1, self.right + 1):

            if line[i] == '+':

                colseps[i] = [top]

                result = self.scan_down(top, left, i)

                if result:

                    bottom, rowseps, newcolseps = result

                    update_dict_of_lists(colseps, newcolseps)

                    return bottom, i, rowseps, colseps

            elif line[i] != '-':

                return None

        return None

    def scan_down(self, top, left, right):

        """

        Look for the bottom-right corner of the cell, making note of all row

        boundaries.

        """

        rowseps = {}

        for i in range(top + 1, self.bottom + 1):

            if self.block[i][right] == '+':

                rowseps[i] = [right]

                result = self.scan_left(top, left, i, right)

                if result:

                    newrowseps, colseps = result

                    update_dict_of_lists(rowseps, newrowseps)

                    return i, rowseps, colseps

            elif self.block[i][right] != '|':

                return None

        return None

    def scan_left(self, top, left, bottom, right):

        """

        Noting column boundaries, look for the bottom-left corner of the cell.

        It must line up with the starting point.

        """

        colseps = {}

        line = self.block[bottom]

        for i in range(right - 1, left, -1):

            if line[i] == '+':

                colseps[i] = [bottom]

            elif line[i] != '-':

                return None

        if line[left] != '+':

            return None

        result = self.scan_up(top, left, bottom, right)

        if result is not None:

            rowseps = result

            return rowseps, colseps

        return None

    def scan_up(self, top, left, bottom, right):

        """

        Noting row boundaries, see if we can return to the starting point.

        """

        rowseps = {}

        for i in range(bottom - 1, top, -1):

            if self.block[i][left] == '+':

                rowseps[i] = [left]

            elif self.block[i][left] != '|':

                return None

        return rowseps

    def structure_from_cells(self):

        """

        From the data collected by `scan_cell()`, convert to the final data

        structure.

        """

        rowseps = self.rowseps.keys()   # list of row boundaries

        rowseps.sort()

        rowindex = {}

        for i in range(len(rowseps)):

            rowindex[rowseps[i]] = i    # row boundary -> row number mapping

        colseps = self.colseps.keys()   # list of column boundaries

        colseps.sort()

        colindex = {}

        for i in range(len(colseps)):

            colindex[colseps[i]] = i    # column boundary -> col number map

        colspecs = [(colseps[i] - colseps[i - 1] - 1)

                    for i in range(1, len(colseps))] # list of column widths

        # prepare an empty table with the correct number of rows & columns

        onerow = [None for i in range(len(colseps) - 1)]

        rows = [onerow[:] for i in range(len(rowseps) - 1)]

        # keep track of # of cells remaining; should reduce to zero

        remaining = (len(rowseps) - 1) * (len(colseps) - 1)

        for top, left, bottom, right, block in self.cells:

            rownum = rowindex[top]

            colnum = colindex[left]

            assert rows[rownum][colnum] is None, (

                  'Cell (row %s, column %s) already used.'

                  % (rownum + 1, colnum + 1))

            morerows = rowindex[bottom] - rownum - 1

            morecols = colindex[right] - colnum - 1

            remaining -= (morerows + 1) * (morecols + 1)

            # write the cell into the table

            rows[rownum][colnum] = (morerows, morecols, top + 1, block)

        assert remaining == 0, 'Unused cells remaining.'

        if self.head_body_sep:          # separate head rows from body rows

            numheadrows = rowindex[self.head_body_sep]

            headrows = rows[:numheadrows]

            bodyrows = rows[numheadrows:]

        else:

            headrows = []

            bodyrows = rows

        return (colspecs, headrows, bodyrows)

class SimpleTableParser(TableParser):

    """

    Parse a simple table using `parse()`.

    Here's an example of a simple table::

        =====  =====

        col 1  col 2

        =====  =====

        1      Second column of row 1.

        2      Second column of row 2.

               Second line of paragraph.

        3      - Second column of row 3.

               - Second item in bullet

                 list (row 3, column 2).

        4 is a span

        ------------

        5

        =====  =====

    Top and bottom borders use '=', column span underlines use '-', column

    separation is indicated with spaces.

    Passing the above table to the `parse()` method will result in the

    following data structure, whose interpretation is the same as for

    `GridTableParser`::

        ([5, 25],

         [[(0, 0, 1, ['col 1']),

           (0, 0, 1, ['col 2'])]],

         [[(0, 0, 3, ['1']),

           (0, 0, 3, ['Second column of row 1.'])],

          [(0, 0, 4, ['2']),

           (0, 0, 4, ['Second column of row 2.',

                      'Second line of paragraph.'])],

          [(0, 0, 6, ['3']),

           (0, 0, 6, ['- Second column of row 3.',

                      '',

                      '- Second item in bullet',

                      '  list (row 3, column 2).'])],

          [(0, 1, 10, ['4 is a span'])],

          [(0, 0, 12, ['5']),

           (0, 0, 12, [''])]])

    """

    head_body_separator_pat = re.compile('=[ =]*$')

    span_pat = re.compile('-[ -]*$')

    def setup(self, block):

        self.block = block[:]           # make a copy; it will be modified

        self.block.disconnect()         # don't propagate changes to parent

        # Convert top & bottom borders to column span underlines:

        self.block[0] = self.block[0].replace('=', '-')

        self.block[-1] = self.block[-1].replace('=', '-')

        self.head_body_sep = None

        self.columns = []

        self.border_end = None

        self.table = []

        self.done = [-1] * len(block[0])

        self.rowseps = {0: [0]}

        self.colseps = {0: [0]}

    def parse_table(self):

        """

        First determine the column boundaries from the top border, then

        process rows.  Each row may consist of multiple lines; accumulate

        lines until a row is complete.  Call `self.parse_row` to finish the

        job.

        """

        # Top border must fully describe all table columns.

        self.columns = self.parse_columns(self.block[0], 0)

        self.border_end = self.columns[-1][1]

        firststart, firstend = self.columns[0]

        offset = 1                      # skip top border

        start = 1

        text_found = None

        while offset < len(self.block):

            line = self.block[offset]

            if self.span_pat.match(line):

                # Column span underline or border; row is complete.

                self.parse_row(self.block[start:offset], start,

                               (line.rstrip(), offset))

                start = offset + 1

                text_found = None

            elif line[firststart:firstend].strip():

                # First column not blank, therefore it's a new row.

                if text_found and offset != start:

                    self.parse_row(self.block[start:offset], start)

                start = offset

                text_found = 1

            elif not text_found:

                start = offset + 1

            offset += 1

    def parse_columns(self, line, offset):

        """

        Given a column span underline, return a list of (begin, end) pairs.

        """

        cols = []

        end = 0

        while 1:

            begin = line.find('-', end)

            end = line.find(' ', begin)

            if begin < 0:

                break

            if end < 0:

                end = len(line)

            cols.append((begin, end))

        if self.columns:

            if cols[-1][1] != self.border_end:

                raise TableMarkupError('Column span incomplete at line '

                                       'offset %s.' % offset)

            # Allow for an unbounded rightmost column:

            cols[-1] = (cols[-1][0], self.columns[-1][1])

        return cols

    def init_row(self, colspec, offset):

        i = 0

        cells = []

        for start, end in colspec:

            morecols = 0

            try:

                assert start == self.columns[i][0]

                while end != self.columns[i][1]:

                    i += 1

                    morecols += 1

            except (AssertionError, IndexError):

                raise TableMarkupError('Column span alignment problem at '

                                       'line offset %s.' % (offset + 1))

            cells.append([0, morecols, offset, []])

            i += 1

        return cells

    def parse_row(self, lines, start, spanline=None):

        """

        Given the text `lines` of a row, parse it and append to `self.table`.

        The row is parsed according to the current column spec (either

        `spanline` if provided or `self.columns`).  For each column, extract

        text from each line, and check for text in column margins.  Finally,

        adjust for insigificant whitespace.

        """

        if not (lines or spanline):

            # No new row, just blank lines.

            return

        if spanline:

            columns = self.parse_columns(*spanline)

            span_offset = spanline[1]

        else:

            columns = self.columns[:]

            span_offset = start

        self.check_columns(lines, start, columns)

        row = self.init_row(columns, start)

        for i in range(len(columns)):

            start, end = columns[i]

            cellblock = lines.get_2D_block(0, start, len(lines), end)

            cellblock.disconnect()      # lines in cell can't sync with parent

            cellblock.replace(self.double_width_pad_char, '')

            row[i][3] = cellblock

        self.table.append(row)

    def check_columns(self, lines, first_line, columns):

        """

        Check for text in column margins and text overflow in the last column.

        Raise TableMarkupError if anything but whitespace is in column margins.

        Adjust the end value for the last column if there is text overflow.

        """

        # "Infinite" value for a dummy last column's beginning, used to

        # check for text overflow:

        columns.append((sys.maxint, None))

        lastcol = len(columns) - 2

        for i in range(len(columns) - 1):

            start, end = columns[i]

            nextstart = columns[i+1][0]

            offset = 0

            for line in lines:

                if i == lastcol and line[end:].strip():

                    text = line[start:].rstrip()

                    new_end = start + len(text)

                    columns[i] = (start, new_end)

                    main_start, main_end = self.columns[-1]

                    if new_end > main_end:

                        self.columns[-1] = (main_start, new_end)

                elif line[end:nextstart].strip():

                    raise TableMarkupError('Text in column margin at line '

                                           'offset %s.' % (first_line + offset))

                offset += 1

        columns.pop()

    def structure_from_cells(self):

        colspecs = [end - start for start, end in self.columns]

        first_body_row = 0

        if self.head_body_sep:

            for i in range(len(self.table)):

                if self.table[i][0][2] > self.head_body_sep:

                    first_body_row = i

                    break

        return (colspecs, self.table[:first_body_row],

                self.table[first_body_row:])

def update_dict_of_lists(master, newdata):

    """

    Extend the list values of `master` with those from `newdata`.

    Both parameters must be dictionaries containing list values.

    """

    for key, values in newdata.items():

        master.setdefault(key, []).extend(values)