"""
Copyright 2020 Oliver Smith

This file is part of pmbootstrap.

pmbootstrap is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

pmbootstrap is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with pmbootstrap.  If not, see <http://www.gnu.org/licenses/>.
"""
import logging
import os
import re
import pmb.chroot
import pmb.config
import pmb.helpers.pmaports
import pmb.helpers.run


def folder_size(args, path):
    """
    Run `du` to calculate the size of a folder (this is less code and
    faster than doing the same task in pure Python). This result is only
    approximatelly right, but good enough for pmbootstrap's use case (#760).

    :returns: folder size in bytes
    """
    output = pmb.helpers.run.root(args, ["du", "--summarize",
                                         "--block-size=1",
                                         path], output_return=True)

    # Only look at last line to filter out sudo garbage (#1766)
    last_line = output.split("\n")[-2]

    ret = int(last_line.split("\t")[0])
    return ret


def check_grsec(args):
    """
    Check if the current kernel is based on the grsec patchset, and if
    the chroot_deny_chmod option is enabled. Raise an exception in that
    case, with a link to the issue. Otherwise, do nothing.
    """
    path = "/proc/sys/kernel/grsecurity/chroot_deny_chmod"
    if not os.path.exists(path):
        return

    raise RuntimeError("You're running a kernel based on the grsec"
                       " patchset. This is not supported.")


def check_binfmt_misc(args):
    """
    Check if the 'binfmt_misc' module is loaded by checking, if
    /proc/sys/fs/binfmt_misc/ exists. If it exists, then do nothing.
    Otherwise, raise an exception pointing to user to the Wiki.
    """
    path = "/proc/sys/fs/binfmt_misc/status"
    if os.path.exists(path):
        return

    link = "https://postmarketos.org/binfmt_misc"
    raise RuntimeError("It appears that your system has not loaded the"
                       " module 'binfmt_misc'. This is required to run"
                       " foreign architecture programs with QEMU (eg."
                       " armhf on x86_64):\n See: <" + link + ">")


def migrate_success(args, version):
    logging.info("Migration to version " + str(version) + " done")
    with open(args.work + "/version", "w") as handle:
        handle.write(str(version) + "\n")


def migrate_work_folder(args):
    # Read current version
    current = 0
    path = args.work + "/version"
    if os.path.exists(path):
        with open(path, "r") as f:
            current = int(f.read().rstrip())

    # Compare version, print warning or do nothing
    required = pmb.config.work_version
    if current == required:
        return
    logging.info("WARNING: Your work folder version needs to be migrated"
                 " (from version " + str(current) + " to " + str(required) +
                 ")!")

    # 0 => 1
    if current == 0:
        # Ask for confirmation
        logging.info("Changelog:")
        logging.info("* Building chroots have a different username (#709)")
        logging.info("Migration will do the following:")
        logging.info("* Zap your chroots")
        logging.info("* Adjust '" + args.work + "/config_abuild/abuild.conf'")
        if not pmb.helpers.cli.confirm(args):
            raise RuntimeError("Aborted.")

        # Zap and update abuild.conf
        pmb.chroot.zap(args, False)
        conf = args.work + "/config_abuild/abuild.conf"
        if os.path.exists(conf):
            pmb.helpers.run.root(args, ["sed", "-i",
                                        "s./home/user/./home/pmos/.g", conf])
        # Update version file
        migrate_success(args, 1)
        current = 1

    # 1 => 2
    if current == 1:
        # Ask for confirmation
        logging.info("Changelog:")
        logging.info("* Fix: cache_distfiles was writable for everyone")
        logging.info("Migration will do the following:")
        logging.info("* Fix permissions of '" + args.work +
                     "/cache_distfiles'")
        if not pmb.helpers.cli.confirm(args):
            raise RuntimeError("Aborted.")

        # Fix permissions
        dir = "/var/cache/distfiles"
        for cmd in [["chown", "-R", "root:abuild", dir],
                    ["chmod", "-R", "664", dir],
                    ["chmod", "a+X", dir]]:
            pmb.chroot.root(args, cmd)
        migrate_success(args, 2)
        current = 2

    if current == 2:
        # Ask for confirmation
        logging.info("Changelog:")
        logging.info("* Device chroots have a different user UID (#1576)")
        logging.info("Migration will do the following:")
        logging.info("* Zap your chroots")
        if not pmb.helpers.cli.confirm(args):
            raise RuntimeError("Aborted.")

        # Zap chroots
        pmb.chroot.zap(args, False)

        # Update version file
        migrate_success(args, 3)
        current = 3

    # Can't migrate, user must delete it
    if current != required:
        raise RuntimeError("Sorry, we can't migrate that automatically. Please"
                           " run 'pmbootstrap shutdown', then delete your"
                           " current work folder manually ('sudo rm -rf " +
                           args.work + "') and start over with 'pmbootstrap"
                           " init'. All your binary packages and caches will"
                           " be lost.")


def validate_hostname(hostname):
    """
    Check whether the string is a valid hostname, according to
    <http://en.wikipedia.org/wiki/Hostname#Restrictions_on_valid_host_names>
    """
    # Check length
    if len(hostname) > 63:
        logging.fatal("ERROR: Hostname '" + hostname + "' is too long.")
        return False

    # Check that it only contains valid chars
    if not re.match("^[0-9a-z-]*$", hostname):
        logging.fatal("ERROR: Hostname must only contain letters (a-z),"
                      " digits (0-9) or minus signs (-)")
        return False

    # Check that doesn't begin or end with a minus sign
    if hostname[:1] == "-" or hostname[-1:] == "-":
        logging.fatal("ERROR: Hostname must not begin or end with a minus sign")
        return False
    return True