#!/usr/bin/python3

"""This scripts allows migration of records between pyzor engines types."""



import sys
import logging
import optparse

import pyzor
import pyzor.engines


def get_engine(engine, dsn, mode='c'):
    engine_class = pyzor.engines.database_classes[engine].single_threaded
    engine_instance = engine_class(dsn, mode)
    return engine_instance


def migrate(options):
    ok_count = 0
    fail_count = 0
    print_interval = 100000

    source_engine = get_engine(options.source_engine, options.source_dsn,
                               mode='r')
    destination_engine = get_engine(options.destination_engine,
                                    options.destination_dsn)

    it = iter(source_engine.items())
    while True:
        try:
            key, record = next(it)
            destination_engine[key] = record
            if options.delete:
                del source_engine[key]
            ok_count += 1
            if ok_count % print_interval == 0:
                print("%s records transferred..." % ok_count)
        except StopIteration:
            break
        except Exception as e:
            fail_count += 1
            print("Record %s failed: %s" % (key, str(e)))

    print("Migration complete, %s records transferred successfully, %s "
          "records failed" % (ok_count, fail_count))

if __name__ == '__main__':
    """Parse command-line arguments and execute the script."""
    description = """This scripts allows migrating pyzor records between 
different engine types. It's arguments are pyzor's DSN, which differ according
to the engine type. See pyzor documentation for more details.   
    """
    logging.basicConfig()
    parser = optparse.OptionParser(description=description)
    parser.add_option("--se", "--source-engine", action="store", default=None,
                      dest="source_engine",
                      help="select source database backend")
    parser.add_option("--sd", "--source-dsn", action="store", default=None,
                      dest="source_dsn", help="data source DSN")
    parser.add_option("--de", "--destination-engine", action="store",
                      default=None, dest="destination_engine", help="select "
                      "destination database backend")
    parser.add_option("--dd", "--destination-dsn", action="store",
                      default=None, dest="destination_dsn",
                      help="destination DSN")
    parser.add_option("--delete", action="store_true", dest="delete",
                      default=False, help="delete old records")

    opts, args = parser.parse_args()

    if not (opts.source_engine and opts.source_dsn and opts.destination_engine
            and opts.destination_dsn):
        print("options --se/--sd/--de/--dd are required")
        sys.exit(1)

    if opts.source_engine not in pyzor.engines.database_classes:
        print("Unsupported source engine: %s" % opts.source_engine)
        sys.exit(1)

    if opts.destination_engine not in pyzor.engines.database_classes:
        print("Unsupported destination engine: %s" % opts.destination_engine)
        sys.exit(1)

    migrate(opts)