from subprocess import call
import sys

if len(sys.argv) != 2:
    print("Wrong number of arguments, usage: 'python split.py input_file.csv'")
    sys.exit()

in_fname = sys.argv[1]

out_fname = ""
if len(in_fname) < 6:
    out_fname = in_fname + "_"
else:
    out_fname = in_fname[0:6] + "_"

# Reverse lines and store the result in tmp file
tmp_fname = "_in.tmp"
tmp_f = open(tmp_fname, "w")
call(["tac", in_fname], stdout=tmp_f)
tmp_f.close()

f_out = None
prev_year = 0

with open(tmp_fname) as f:
    for line in f:
        splitted_line = line.rstrip("\n").split(".")
        year = int(splitted_line[0])
        month = int(splitted_line[1])
        if year != prev_year:
            prev_year = year
            if f_out:
                f_out.close()
            f_out = open(out_fname+str(year)+".csv", 'w')
        f_out.write(line)
    f_out.close()

# Remove the tmp file
call(["rm", tmp_fname])