#Usage: python3 network.py input.csv output.csv

import csv
import re
import sys


input_file = sys.argv[1]
output_file = sys.argv[2]

def detect_mention(text):
    mentions = []
    regex = r"(?<=^|(?<=[^a-zA-Z0-9-_\.]))@([A-Za-z]+[A-Za-z0-9_]+)"
    matches = re.finditer(regex, text)

    for matchNum, match in enumerate(matches, start=1):
       mentions.append(match.group())

    return mentions


with open(input_file) as csvinput:
    readCSV = csv.reader(csvinput, delimiter=',')

    with open(output_file, 'a') as csvoutput:
        spamwriter = csv.writer(csvoutput, delimiter=';',
        quotechar='"', quoting=csv.QUOTE_MINIMAL)

        spamwriter.writerow(['username', 'mention'])

        for row in readCSV:
            username = row[11]
            mentions = detect_mention(row[2])

            for mention in mentions:
                spamwriter.writerow([username, mention])