#!/usr/bin/python3

import sys, os
import subprocess, shlex
import time
import unittest

import scapy.all

class PcapComparison(unittest.TestCase):
    ID2T_PATH = ".."
    ID2T_LOCATION = ID2T_PATH + "/" + "id2t"
    NUM_ITERATIONS = 3

    PCAP_ENVIRONMENT_VALUE = "ID2T_SRC_PCAP"
    SEED_ENVIRONMENT_VALUE = "ID2T_SEED"

    DEFAULT_PCAP = "resources/telnet-raw.pcap"
    DEFAULT_SEED = "42"

    OUTPUT_FILES_PREFIX_LINE = "Output files created:"

    def setUp(self):
        self.generated_files = []
        self.keep_files = []

    def test_determinism(self):
        input_pcap = os.environ.get(self.PCAP_ENVIRONMENT_VALUE, self.DEFAULT_PCAP)
        seed = os.environ.get(self.SEED_ENVIRONMENT_VALUE, self.DEFAULT_SEED)

        command_args = [self.ID2T_LOCATION, "-i", input_pcap, "--seed", seed, "-a", "MembersMgmtCommAttack"]
        command = " ".join(map(shlex.quote, command_args))
        self.print_warning("The command that gets executed is:", command)

        generated_pcap = None
        for i in range(self.NUM_ITERATIONS):
            retcode, output = subprocess.getstatusoutput(command)

            self.print_warning(output)
            self.assertEqual(retcode, 0, "For some reason id2t completed with an error")

            files = self.parse_files(output)
            self.generated_files.extend(files)

            pcap = self.find_pcap(files)
            if generated_pcap is not None:
                try: self.compare_pcaps(generated_pcap, pcap)
                except AssertionError as e:
                    self.keep_files = [generated_pcap, pcap]
                    raise e
            else:
                generated_pcap = pcap

            self.print_warning()
            time.sleep(1) # let some time pass between calls because files are based on the time

    def tearDown(self):
        self.print_warning("Cleaning up files generated by the test-calls...")
        for file in self.generated_files:
            if file in self.keep_files: continue

            self.print_warning(file)
            os.remove(self.ID2T_PATH + os.path.sep + file)
        self.print_warning("Done")
        self.print_warning("The following files have been kept: " + ", ".join(self.keep_files))

    def parse_files(self, program_output: str) -> "list[str]":
        lines = program_output.split(os.linesep)

        self.assertIn(self.OUTPUT_FILES_PREFIX_LINE, lines,
                "The magic string is not in the program output anymore, has the program output structure changed?")
        index = lines.index(self.OUTPUT_FILES_PREFIX_LINE)

        return lines[index + 1:]

    def find_pcap(self, files: "list[str]") -> str:
        return next(file for file in files if file.endswith(".pcap"))

    def compare_pcaps(self, one: str, other: str):
        packetsA = list(scapy.all.rdpcap(self.ID2T_PATH + "/" + one))
        packetsB = list(scapy.all.rdpcap(self.ID2T_PATH + "/" + other))

        self.assertEqual(len(packetsA), len(packetsB), "Both pcap's have to have the same amount of packets")
        for i in range(len(packetsA)):
            p, p2 = packetsA[i], packetsB[i]

            self.assertAlmostEqual(p.time, p2.time, "Packets no %i in the pcap's don't appear at the same time" % (i + 1))
            self.compare_packets(p, p2, i + 1)

    def compare_packets(self, p, p2, packet_number):
        if p == p2:
            return

        while type(p) != scapy.packet.NoPayload or type(p2) != scapy.packet.NoPayload:
            if type(p) != type(p2):
                self.fail("Packets %i are of incompatible types: %s and %s" % (packet_number, type(p).__name__, type(p2).__name__))

            for field in p.fields:
                if p.fields[field] != p2.fields[field]:
                    packet_type = type(p).__name__
                    v, v2 = p.fields[field], p2.fields[field]

                    self.fail("Packets %i differ in field %s.%s: %s != %s" %
                                (packet_number, packet_type, field, v, v2))

            p = p.payload
            p2 = p2.payload

    def print_warning(self, *text):
        print(*text, file=sys.stderr)

if __name__ == "__main__":
    suite = unittest.TestSuite()
    suite.addTest(PcapComparison("test_determinism"))

    unittest.TextTestRunner().run(suite)