import subprocess
from typing import List

from PyInquirer import prompt


def _run_shell_command(cmd: List[str]) -> str:
    return subprocess.check_output(cmd).decode("UTF-8").strip()


class SwapModule:

    def run(self):
        actions = {
            "Create/Resize temp. swap": self._create_resize_swap,
            "Create/Resize persistent swap": self._create_resize_persistent_swap,
            "Delete swap": self._delete_swap,
            "Make temp. swap persistent": self._make_swap_persistent,
            "Get swap location": self._get_swap_location,
            "Get swap size": self._get_swap_size,
            "Show swapiness": self._show_swapiness,
            "Adjust temp. swapiness": self._adjust_swapiness_temp,
            "Check fstab for entry": self._fstab_entry_exists
        }
        menu = [
            {
                'type': 'list',
                'message': 'Select action',
                'name': 'action',
                'choices': list(map(lambda x: {"name": x}, actions.keys()))
            }
        ]
        selected_action = prompt(menu)['action']
        actions[selected_action]()

    def _create_resize_persistent_swap(self):
        self._create_resize_swap()
        self._make_swap_persistent()

    def _get_swap_location(self):
        output_swaps = _run_shell_command(["cat", "/proc/swaps"])
        try:
            swap_location = output_swaps.split()[5]
            print("Swap is located here:", swap_location)
            return swap_location
        except IndexError:
            print("Swap file doesn´t exist!")
            return None

    def _get_swap_size(self):
        swap_size = _run_shell_command(['swapon', '--show'])
        try:
            swap_size = swap_size.split()[7]
            print("Swap is {}b big!".format(swap_size))
        except IndexError:
            print("Swap file doesn´t exist!")

    def _create_resize_swap(self):
        output_swapon = _run_shell_command(['swapon', '--show'])
        if output_swapon is not "":
            swap_size = output_swapon.split()[7]
            print("")
            print("Swap already installed! You can resize it!")
            print("Curr. swap size: {}b".format(swap_size))
            resize = input("How big should your swap become (numbers in Gigabyte)? ")
            resize_swapfile = "sudo swapoff /swapfile && " + \
                              "sudo fallocate -l {}G /swapfile && ".format(resize) + \
                              "sudo mkswap /swapfile && " + \
                              "sudo swapon /swapfile"
            subprocess.call(resize_swapfile, shell=True)
            output_free = _run_shell_command(["free", "-h"])
            print(output_free.strip())

        else:
            size = input("How big should the swap be (numbers in Gigabyte)? ")
            create_swapfile = "sudo fallocate -l {}G /swapfile && ".format(size) + \
                              "sudo chmod 600 /swapfile && " + \
                              "sudo mkswap /swapfile && " + \
                              "sudo swapon /swapfile"
            subprocess.call(create_swapfile, shell=True)

            output_free = _run_shell_command(["free", "-h"])
            print(output_free.strip())

    def _make_swap_persistent(self):
        swap_location = self._get_swap_location()
        if swap_location is None:
            print("Swap file doesn't exist!")
            return
        backup_fstab = "sudo cp /etc/fstab /etc/fstab.bak"
        enable_persistence = "echo '{} none swap sw 0 0' | sudo tee -a /etc/fstab".format(swap_location)
        if self._fstab_entry_exists():
            print("Swap is already persistent!")
        else:
            subprocess.call(backup_fstab, shell=True)
            subprocess.call(enable_persistence, shell=True)
            print("Swap is now persistent!")

    def _show_swapiness(self):
        print(_run_shell_command(["cat", "/proc/sys/vm/swappiness"]))

    def _adjust_swapiness_temp(self):
        options = {
            "Light": 25,
            "Default": 60,
            "Aggressive": 100
        }
        menu = [
            {
                'type': 'list',
                'message': 'Select action',
                'name': 'action',
                'choices': list(map(lambda x: {"name": x}, options.keys()))
            }
        ]
        selected_swapiness = prompt(menu)['action']

        adjust = "sudo sysctl vm.swappiness=" + str(options[selected_swapiness])
        subprocess.call(adjust, shell=True)
        print("Temporary swapiness is " + str(options[selected_swapiness]))

    def _delete_swap(self):
        swap_location = self._get_swap_location()
        if swap_location is None:
            return
        disable_swapfile = "sudo swapoff {} && ".format(swap_location) + \
                           "sudo rm {}".format(swap_location)
        if self._fstab_entry_exists():
            with open("/etc/fstab", "r") as fstab_out:
                content = fstab_out.readlines()
            with open("/etc/fstab", "w") as fstab_in:
                content = content[:-1]
                for line in content:
                    fstab_in.write(line)
        else:
            print("No entry in /etc/fstab!")
        subprocess.call(disable_swapfile, shell=True)
        output_swapon = _run_shell_command(['swapon', '--show'])
        output_free = _run_shell_command(["free", "-h"])
        if not output_swapon:
            print("Swap deleted!")
            print(output_free.strip())

    def _fstab_entry_exists(self):
        swap_location = self._get_swap_location()
        fstab_entry = "{} none swap sw 0 0\n".format(swap_location)
        with open("/etc/fstab", "r") as fstab_file:
            line = fstab_file.readlines()[-1]
            if line != fstab_entry:
                print("No entry in /etc/fstab")
                return False
            else:
                print("fstab entry:", line.strip())
                return True