import json
import argparse
import os

program_name = 'SplitOCR'
program_description = 'Splits the given frt file into frt files for it\'s component pages.'
parser = argparse.ArgumentParser(prog=program_name, description=program_description, add_help=False)
# Constant values for printing.
red_error = '\033[91mError:\033[0m'
yellow_warning = '\033[93mWARNING:\033[0m'
blue_okay = '\033[94mOK\033[0m'
# Constant values for script.
NUM_PAGES_TAG = 'numPages'
ORIG_SRC_TYPE_TAG = 'originalSourceType'
ORIG_SRC_FILE_TAG = 'originalSourceFile'
FIXED_UP_TAG = 'fixedUp'
PAGES_TAG = 'pages'


# Parses the pages into a list of dicts form the given file.
def parse_pages(file_name):
    """
    Parses the pages from the given '.frt' file into a list of dictionaries containing the json info for the pages.
    
    :param file_name: The source '.frt' file to parse the pages form.
    :return: A list of dictionaries containing the json data for each page.
    """
    pages_result = []
    with open(file_name) as reader:
        frt_json = json.load(reader)
    num_pages = frt_json[NUM_PAGES_TAG]
    orig_src_type = frt_json[ORIG_SRC_TYPE_TAG]
    orig_src_file = frt_json[ORIG_SRC_FILE_TAG]
    fixed_up = frt_json[FIXED_UP_TAG]
    pages_json = frt_json[PAGES_TAG]

    print('Parsing %s pages from %s', num_pages, file_name)

    for page in pages_json:
        # There is only one page!
        pages_result.append({NUM_PAGES_TAG: '1',
                             ORIG_SRC_TYPE_TAG: orig_src_type,
                             ORIG_SRC_FILE_TAG: orig_src_file,
                             FIXED_UP_TAG: fixed_up,
                             PAGES_TAG: page})
    return pages_result


# Writes the data from
def write_pages(pages_array, file_name, overwrite):
    """
    Writes the pages in the passed list to a file named [file_name].[page_idx].frt
    
    :param pages_array: The list of page dictionaries parsed from file_name to write.
    :param file_name: The source file the dictionaries in pages_array were parsed from.
    :param overwrite: Weather or not to overwrite files if they exist.
        If set to True, they will be overwritten, if set to false, they will not.
    |
    :return: nothing.
    """
    for i in range(len(pages_array)):
        new_file = file_name.replace('.frt', '.{:04d}.frt'.format(i))
        # If the file exists and we aren't auto overwriting,
        if os.path.exists(new_file) and not overwrite:
            # Ask for permission.
            yes_or_no('%s File will be overwritten (%s)\n'
                      '   Continue (y/n)? ', yellow_warning, new_file)

        page = pages_array[i]
        with open(new_file, 'w+') as writer:
            json.dump(page, writer, indent=1)


def main(in_file, auto_overwrite):
    pages = parse_pages(in_file)
    write_pages(pages, in_file, auto_overwrite)


def check_args(in_file):
    fatal_error = False

    if not in_file.endswith('.frt'):
        print('%s File is not the correct type (.frt): %s', red_error, in_file)
        fatal_error = True
    if not os.path.exists(in_file):
        print('%s File does not exist: %s', red_error, in_file)
        fatal_error = True

    if fatal_error:
        parser.print_help()
        print('Fatal error occurred, Exiting...')
        exit(-1)


# Will ask the user to input yes or no and if they input yes the program will continue to execute. If however, they
# input no, the program will exit with status 0. 0 status is used here because there was no error, the user just chose
# to exit rather than continue executing.
def yes_or_no(message):
    decision = input(message)
    if decision.lower() == 'y' or decision.lower() == 'yes':
        print('%s continuing...', blue_okay)
        return
    elif decision.lower() == 'n' or decision.lower() == 'no':
        exit(0)
    else:
        yes_or_no('   Invalid input, enter Y(es) or N(o): ')


if __name__ == '__main__':
    required_args = parser.add_argument_group('Required')
    optional_args = parser.add_argument_group('Optional')

    required_args.add_argument('-i', '--input_file', required=True,
                               help='The input frt file to split the pages out of.')
    optional_args.add_argument('-w', '--overwrite', required=False, action='set_true',
                               help='If used, previous files will be overwritten without asking permission.')
    optional_args.add_argument('-h', '--help', action='help', help='Prints the help message.')