import re
import openpyxl
from typing import Union, IO


class XlsxReplacement:
    def __init__(self, file: Union[str, IO]):
        self.file = file
        self.xlsx = openpyxl.load_workbook(file, read_only=True, data_only=True)
        self.re_replace = re.compile('\[\[(?:(\w+):)?([a-zA-Z]+\d+)\]\]')
        self.errors = []

    def find_replace_text(self, text: str):
        if '[[' not in text:
            return text

        return self.re_replace.sub(self._regex_replacement, text)

    def _regex_replacement(self, match):
        sheet, cell = match.groups()
        if sheet is None:
            sheet = self.xlsx.active
        else:
            try:
                sheet = self.xlsx[sheet]
            except IndexError:
                self.errors.append('Unknown sheet {sheet}'.format(sheet=sheet))
                return 'ERR Unknown sheet'
        try:
            return str(sheet[cell].value)
        except (IndexError, ValueError):
            self.errors.append('Unknown cell {sheet}:{cell}'.format(sheet=sheet, cell=cell))
            return 'ERR Unknown cell'