#!/usr/bin/python3
"""Plot data from HN “who is hiring”/“who wants to be hired” posts.

This uses Matplotlib without Numpy.

"""

from matplotlib.pyplot import figure, plot, gca, savefig, xticks, legend, ylim
from matplotlib.pyplot import subplots, ylabel
import csv
import sys

def plot_hiring(data, outfilename):
    hiring = [int(n) for what, month, year, n in data if what == 'hiring']
    hired = [int(n) for what, month, year, n in data if what == 'hired']
    hired_months = ['%s%s' % (month[:3], year[-2:]) for what, month, year, n in data if what == 'hired']
    months = ['%s%s' % (month[:3], year[-2:]) for what, month, year, n in data if what == 'hiring']
    if months != hired_months:
        raise ValueError(data)

    subplots(figsize=(12, 9))
    ylabel('comments in thread')
    ylim(0, 1300)
    plot(hiring[::-1], label='Who is hiring?')
    plot(hired[::-1], label='Who wants to be hired?')
    legend()
    xticks(range(len(months)), months[::-1], rotation='vertical')
    savefig(outfilename)

def main(args):
    if len(args) != 3:
        sys.stderr.write(f"Usage: {args[0]} whoishiring.csv hiring.png")
        return 1

    plot_hiring(list(csv.reader(open(args[1]))), args[2])

if __name__ == '__main__':
    sys.exit(main(sys.argv))