from .. import rate as oxrrate

def format_one_rate(rate, from_amt, from_curr, to_curr):
    return "{:g} {} = {:g} {}".format(
        from_amt, from_curr, rate.convert(from_amt, from_curr, to_curr), to_curr)

def format_rate_pair(rate, from_curr, to_curr):
    yield format_one_rate(rate, 1, from_curr, to_curr)
    yield format_one_rate(rate, 1, to_curr, from_curr)

def run(config, stdout, stderr):
    loaders = config.get_loaders()
    with loaders.historical(config.args.date, config.args.base) as rate_json:
        rate = oxrrate.Rate.from_json_file(rate_json)
    if loaders.should_cache():
        config.cache.save_rate(rate)
    if not config.args.from_currency:
        for from_curr in sorted(rate.rates):
            print(*format_rate_pair(rate, from_curr, config.args.to_currency),
                  sep='\n', file=stdout)
    elif config.args.amount is None:
        print(*format_rate_pair(rate, config.args.from_currency, config.args.to_currency),
              sep='\n', file=stdout)
    else:
        print(format_one_rate(rate, config.args.amount,
                              config.args.from_currency, config.args.to_currency),
              file=stdout)