import os

from collections import namedtuple

class ValidationError(ValueError):
    pass

Validator = namedtuple('Validator', 'type validate extension')
DataFile = namedtuple('DataFile', 'path separator')

def validate_stx(lines):
    iterator = iter(lines)
    line = next(iterator)
    if not line.startswith('Report_Format\t2'):
        raise ValidationError('1 Unsupported File;' + line)
    for line in iterator:
        if line.startswith('Probe_Name\t'):
            break
    else:
        raise ValidationError('1 Unsupported File')
    for line in iterator:
        probe_name, rest = line.split('\t', 1)
        separator = ',' if rest.count(',') > rest.count('.') else '.'
        return separator
    else:
        raise ValidationError('No Data Present')


def validate_dat(lines):
    iterator = iter(lines)
    if not next(iterator).startswith('Report_Format\t2'):
        raise ValidationError('Unsupported File')
    for line in iterator:
        if line.startswith('Dot_Number\t'):
            break
    else:
        raise ValidationError('Unsupported File')
    for line in iterator:
        probe_name, rest = line.split('\t', 3)
        separator = ',' if rest.count(',') > rest.count('.') else '.'
        return separator
    else:
        raise ValidationError('No Data Present')

def validate_csv(lines):
    pass

validation_map = {
    '.stx': Validator('Signalyse Statistic Files', validate_stx, '.stx'),
    '.dat': Validator('Signalyse Data Files', validate_dat, '.dat'),
    '.csv': Validator('Sensovation Data Files', validate_csv, '.csv')
}

def guess_validator(unvalidated):
    # get the validation method by examining the first file
    _, extension = os.path.splitext(unvalidated[0])
    return validation_map.get(extension, None)

def validate_files(unvalidated, selected_validator):
    # get the validation method by examining the first file
    for file_path in unvalidated:
        try:
            with open(file_path, mode='r', encoding='utf-8') as file_handle:
                separator = selected_validator.validate(file_handle)
                yield DataFile(file_path, separator)
        except (IOError, UnicodeError, ValidationError) as e:
            print(e)