from __future__ import absolute_import
# Copyright (c) 2010-2015 openpyxl

"""
Collection of utilities used within the package and also available for client code
"""

import datetime
import re

from openpyxl.compat import basestring
from openpyxl.utils.exceptions import CellCoordinatesException

# constants
COORD_RE = re.compile('^[$]?([A-Z]+)[$]?(\d+)$')
ABSOLUTE_RE = re.compile(
'''^[$]?
(?P<min_col>[A-Z]+)
[$]?
(?P<min_row>\d+)
(:[$]?
(?P<max_col>[A-Z]+)
[$]?
(?P<max_row>\d+))?$''',
re.VERBOSE)


def get_column_interval(start, end):
    if isinstance(start, basestring):
        start = column_index_from_string(start)
    if isinstance(end, basestring):
        end = column_index_from_string(end)
    return [get_column_letter(x) for x in range(start, end + 1)]


def coordinate_from_string(coord_string):
    """Convert a coordinate string like 'B12' to a tuple ('B', 12)"""
    match = COORD_RE.match(coord_string.upper())
    if not match:
        msg = 'Invalid cell coordinates (%s)' % coord_string
        raise CellCoordinatesException(msg)
    column, row = match.groups()
    row = int(row)
    if not row:
        msg = "There is no row 0 (%s)" % coord_string
        raise CellCoordinatesException(msg)
    return (column, row)


def absolute_coordinate(coord_string):
    """Convert a coordinate to an absolute coordinate string (B12 -> $B$12)"""
    m = ABSOLUTE_RE.match(coord_string.upper())
    if m:
        parts = m.groups()
        if all(parts[-2:]):
            return '$%s$%s:$%s$%s' % (parts[0], parts[1], parts[3], parts[4])
        else:
            return '$%s$%s' % (parts[0], parts[1])
    else:
        return coord_string

def _get_column_letter(col_idx):
    """Convert a column number into a column letter (3 -> 'C')

    Right shift the column col_idx by 26 to find column letters in reverse
    order.  These numbers are 1-based, and can be converted to ASCII
    ordinals by adding 64.

    """
    # these indicies corrospond to A -> ZZZ and include all allowed
    # columns
    if not 1 <= col_idx <= 18278:
        raise ValueError("Invalid column index {0}".format(col_idx))
    letters = []
    while col_idx > 0:
        col_idx, remainder = divmod(col_idx, 26)
        # check for exact division and borrow if needed
        if remainder == 0:
            remainder = 26
            col_idx -= 1
        letters.append(chr(remainder+64))
    return ''.join(reversed(letters))


_COL_STRING_CACHE = {}
_STRING_COL_CACHE = {}
for i in range(1, 18279):
    col = _get_column_letter(i)
    _STRING_COL_CACHE[i] = col
    _COL_STRING_CACHE[col] = i


def get_column_letter(idx,):
    """Convert a column index into a column letter
    (3 -> 'C')
    """
    try:
        return _STRING_COL_CACHE[idx]
    except KeyError:
        raise ValueError("Invalid column index {0}".format(idx))


def column_index_from_string(str_col):
    """Convert a column name into a numerical index
    ('A' -> 1)
    """
    # we use a function argument to get indexed name lookup
    try:
        return _COL_STRING_CACHE[str_col.upper()]
    except KeyError:
        raise ValueError("{0} is not a valid column name".format(str_col))


def range_boundaries(range_string):
    """
    Convert a range string into a tuple of boundaries:
    (min_col, min_row, max_col, max_row)
    Cell coordinates will be converted into a range with the cell at both end
    """
    m = ABSOLUTE_RE.match(range_string)
    min_col, min_row, sep, max_col, max_row = m.groups()
    min_col = column_index_from_string(min_col)
    min_row = int(min_row)

    if max_col is None or max_row is None:
        max_col = min_col
        max_row = min_row
    else:
        max_col = column_index_from_string(max_col)
        max_row = int(max_row)

    return min_col, min_row, max_col, max_row


def cells_from_range(range_string):
    """
    Get individual addresses for every cell in a range.
    Yields one row at a time.
    """
    min_col, min_row, max_col, max_row = range_boundaries(range_string)
    for row in range(min_row, max_row+1):
        yield tuple('%s%d' % (get_column_letter(col), row)
                    for col in range(min_col, max_col+1))
