#!/usr/bin/python3

'''\
Simple database for: http://rosettacode.org/wiki/Simple_database

'''

import argparse
from argparse import Namespace
import datetime
import shlex


def parse_args():
    'Set up, parse, and return arguments'

    parser = argparse.ArgumentParser(epilog=globals()['__doc__'])

    parser.add_argument('command', choices='add pl plc pa'.split(),
                        help='''\
add: Add a new entry
pl:  Print the latest entry
plc: Print the latest entry for each category/tag
pa:  Print all entries sorted by a date''')
    parser.add_argument('-d', '--description',
                        help='A description of the item. (e.g., title, name)')
    parser.add_argument('-t', '--tag',
                        help=('''A category or tag (genre, topic, relationship '''
                              '''such as “friend” or “family”)'''))
    parser.add_argument('-f', '--field', nargs=2, action='append',
                        help='Other optional fields with value (can be repeated)')

    return parser

def do_add(args, dbname):
    'Add a new entry'
    if args.description is None:
        args.description = ''
    if args.tag is None:
        args.tag = ''
    del args.command
    print('Writing record to %s' % dbname)
    with open(dbname, 'a') as db:
        db.write('%r\n' % args)

def do_pl(args, dbname):
    'Print the latest entry'
    print('Getting last record from %s' % dbname)
    with open(dbname, 'r') as db:
        for line in db: pass
    record = eval(line)
    del record._date
    print(str(record))

def do_plc(args, dbname):
    'Print the latest entry for each category/tag'
    print('Getting latest record for each tag from %s' % dbname)
    with open(dbname, 'r') as db:
        records = [eval(line) for line in db]
    tags = set(record.tag for record in records)
    records.reverse()
    for record in records:
        if record.tag in tags:
            del record._date
            print(str(record))
            tags.discard(record.tag)
            if not tags: break

def do_pa(args, dbname):
    'Print all entries sorted by a date'
    print('Getting all records by date from %s' % dbname)
    with open(dbname, 'r') as db:
        records = [eval(line) for line in db]
    for record in records:
        del record._date
        print(str(record))

def test():
    import time
    parser = parse_args()
    for cmdline in [
                    """-d Book -f title 'Windy places' -f type hardback --tag DISCOUNT add""",
                    """-d Book -f title 'RC spammers'  -f type paperback -t   DISCOUNT add""",
                    """-d Book -f title 'Splat it' -f type hardback -f special 'first edition' -t PREMIUM add""",
                    """pl""",
                    """plc""",
                    ]:
        args = parser.parse_args(shlex.split(cmdline))
        now = datetime.datetime.utcnow()
        args._date = now.isoformat()
        do_command[args.command](args, dbname)
        time.sleep(0.5)



do_command = dict(add=do_add, pl=do_pl, plc=do_plc, pa=do_pa)
dbname = '_simple_db_db.py'


if __name__ == '__main__':
    if 0:
        test()
    else:
        parser = parse_args()
        args = parser.parse_args()
        now = datetime.datetime.utcnow()
        args._date = now.isoformat()
        do_command[args.command](args, dbname)