import re
from slither.exceptions import SlitherException
from ..utils.patches import create_patch

def format(slither, patches, elements):
    for element in elements:
        _patch(slither, patches, element['source_mapping']['filename_absolute'],
               element['source_mapping']['filename_relative'],
               element['name'],
               "constant " + element['name'],
               element['source_mapping']['start'],
               element['source_mapping']['start'] + element['source_mapping']['length'])


def _patch(slither, patches, in_file, in_file_relative, match_text, replace_text, modify_loc_start, modify_loc_end):
    in_file_str = slither.source_code[in_file].encode('utf-8')
    old_str_of_interest = in_file_str[modify_loc_start:modify_loc_end]
    # Add keyword `constant` before the variable name
    (new_str_of_interest, num_repl) = re.subn(match_text, replace_text, old_str_of_interest.decode('utf-8'), 1)
    if num_repl != 0:
        create_patch(
            patches,
            "constable-states",
            in_file_relative,
            in_file,
            modify_loc_start,
            modify_loc_end,
            old_str_of_interest.decode('utf-8'),
            new_str_of_interest
        )

    else:
        raise SlitherException("State variable not found?!")