#! /usr/bin/python3
# ===================================================================
# parse a string containing a phone number and return it in
# canonical form
# ===================================================================
# recognized phone number formats are:
#     (999) 999-9999
#     9999999999
#     999-999-9999
#     999-9999
#     9999999
#
# Notes:
#    1. extra spaces in the middle are removed
#    2. starting and ending spaces are removed
#    3. returned  canonical form is 999-9999 or 999-999-9999
#
# ===================================================================
# Definition:
# A canonical form means that values can be described or represented
# in multiple ways, and one of those ways is chosen as the favored
# canonical form.
# ===================================================================

import re

# ---- phone number regular expressions

rex2 = []
rex2.append(re.compile(r'^\s*(\d\d\d)-(\d\d\d\d)\s*$'))
rex2.append(re.compile(r'^\s*(\d\d\d)(\d\d\d\d)\s*$'))

rex3 = []
rex3.append(re.compile(r'^\s*\((\d\d\d)\)\s*(\d\d\d)-(\d\d\d\d)\s*$'))
rex3.append(re.compile(r'^\s*(\d\d\d)(\d\d\d)(\d\d\d\d)\s*$'))
rex3.append(re.compile(r'^\s*(\d\d\d)-(\d\d\d)-(\d\d\d\d)\s*$'))

# -------------------------------------------------------------------
# ----parse Phone Number string
# -------------------------------------------------------------------

def ParsePhoneNumber(s):

    # ---- is there a string to parse?

    if len(s) < 1:
        ##print('empty phone number string')
        return '' 

    # ---- test phone number string
    # ---- match any of the phone number regrex patterns?

    ##print(f'Test string = {s}')

    for p in rex3:
        m = p.match(s)
        if m:
            return f'{m.group(1)}-{m.group(2)}-{m.group(3)}'

    for p in rex2:
        m = p.match(s)
        if m:
            return f'{m.group(1)}-{m.group(2)}'

    return ''

# -------------------------------------------------------------------
# ---- main
# -------------------------------------------------------------------

if __name__ == '__main__':

    import user_interface as ui

    if not ui.running_python3():
        print('end program - not running Python3')
        quit()

    while True:                # loop

        ui.clear_screen()
        print()
        s = ui.get_user_input('Enter phone number: ')
        if not s:              # empty string?
            break

        pn = ParsePhoneNumber(s)

        print()
        if not pn:
            print('Not a recognized phone number')
        else:
            print(f'Phone number is {pn}')

        ui.pause()

    print()