#!/usr/bin/env bash
# -*- coding: utf-8 -*-
# region header
# Copyright Torben Sickert (info["~at~"]torben.website) 16.12.2012

# License
# -------

# This library written by Torben Sickert stands under a creative commons naming
# 3.0 unported license. See https://creativecommons.org/licenses/by/3.0/deed.de
# endregion
# shellcheck disable=SC2016,SC2034,SC2155
# region imports
# shellcheck source=./module.sh
source "$(dirname "${BASH_SOURCE[0]}")/module.sh"
bl.module.import bashlink.exception
bl.module.import bashlink.logging
# endregion
# region variables
declare -gr BL_CHANGEROOT__DOCUMENTATION__='
    The changeroot module implements utility functions concerning advanced
    change roots with kernel filesystem application interfaces.
'
declare -agr BL_CHANGEROOT__DEPENDENCIES__=(
    chroot
    mountpoint mount umount
    mkdir
)
declare -agr BL_CHANGEROOT__OPTIONAL_DEPENDENCIES__=(fakeroot fakechroot)
declare -agr BL_CHANGEROOT_KERNEL_API_LOCATIONS=(
    /proc
    /sys
    /sys/firmware/efi/efivars
    /dev
    /dev/pts
    /dev/shm
    /run
)
# endregion
# region functions
alias bl.changeroot=bl_changeroot
bl_changeroot() {
    local -r __documentation__='
        This function performs a linux change root if needed and provides all
        kernel api filesystems in target root by using a change root interface
        with minimal needed rights.

        ```bash
            changeroot /new_root /usr/bin/env bash some arguments
        ```
    '
    if [ "$1" = / ]; then
        shift
        "$@"
        return $?
    fi
    bl_changeroot_with_kernel_api "$@"
}
alias bl.changeroot.with_fake_fallback=bl_changeroot_with_fake_fallback
bl_changeroot_with_fake_fallback() {
    # shellcheck disable=SC1004
    local -r __documentation__='
        Perform the available change root program wich needs at least rights.

        ```bash
            bl_changeroot_with_fake_fallback /new_root /usr/bin/env bash \
                some arguments
        ```
    '
    if (( UID == 0 )); then
        chroot "$@"
        return $?
    fi
    fakeroot fakechroot chroot "$@"
}
alias bl.changeroot.with_kernel_api=bl_changeroot_with_kernel_api
bl_changeroot_with_kernel_api() {
    # shellcheck disable=SC1004
    local -r __documentation__='
        Performs a change root by mounting needed host locations in change root
        environment.

        ```bash
            bl_changeroot_with_kernel_api \
                /new_root \
                /usr/bin/env bash some arguments
        ```
    '
    local new_root_location="$1"
    if [[ ! "$new_root_location" =~ .*/$ ]]; then
        new_root_location+=/
    fi
    local -a created_locations=()
    local -a mounted_locations=()
    local mountpoint_path
    for mountpoint_path in "${BL_CHANGEROOT_KERNEL_API_LOCATIONS[@]}"; do
        mountpoint_path="${mountpoint_path#/}"
        if [ ! -e "${new_root_location}${mountpoint_path}" ]; then
            mkdir --parents "${new_root_location}${mountpoint_path}"
            created_locations+=("${new_root_location}${mountpoint_path}")
        fi
        if ! mountpoint -q "${new_root_location}${mountpoint_path}"; then
            if [ "$mountpoint_path" = proc ]; then
                mount "/${mountpoint_path}" \
                    "${new_root_location}${mountpoint_path}" --types \
                    "$mountpoint_path" --options nosuid,noexec,nodev
            elif [ "$mountpoint_path" = sys ]; then
                mount "/${mountpoint_path}" \
                    "${new_root_location}${mountpoint_path}" --types sysfs \
                    --options nosuid,noexec,nodev
            elif [ "$mountpoint_path" = dev ]; then
                mount udev "${new_root_location}${mountpoint_path}" --types \
                    devtmpfs --options mode=0755,nosuid
            elif [ "$mountpoint_path" = 'dev/pts' ]; then
                mount devpts "${new_root_location}${mountpoint_path}" \
                    --types devpts --options mode=0620,gid=5,nosuid,noexec
            elif [ "$mountpoint_path" = 'dev/shm' ]; then
                mount shm "${new_root_location}${mountpoint_path}" --types \
                    tmpfs --options mode=1777,nosuid,nodev
            elif [ "$mountpoint_path" = run ]; then
                mount "/${mountpoint_path}" \
                    "${new_root_location}${mountpoint_path}" --types tmpfs \
                    --options nosuid,nodev,mode=0755
            elif [ "$mountpoint_path" = tmp ]; then
                mount run "${new_root_location}${mountpoint_path}" --types \
                    tmpfs --options mode=1777,strictatime,nodev,nosuid
            elif [ -f "/${mountpoint_path}" ]; then
                mount "/${mountpoint_path}" \
                    "${new_root_location}${mountpoint_path}" --bind
            else
                bl.logging.warn \
                    "Mountpoint \"/${mountpoint_path}\" couldn't be handled."
                continue
            fi
            mounted_locations+=("$mountpoint_path")
        fi
    done
    local -i return_code=0
    bl.changeroot.with_fake_fallback "$@" || \
        return_code=$?
    local -i current_return_code=0
    for mountpoint_path in $(bl.array.reverse "${mounted_locations[*]}"); do
        if mountpoint -q "${new_root_location}${mountpoint_path}" || \
            [ -f "/${mountpoint_path}" ]
        then
            # If unmounting doesn't work try to unmount in lazy mode (when
            # mountpoints are not needed anymore).
            if ! umount "${new_root_location}${mountpoint_path}"; then
                bl.logging.warn "Unmounting \"${new_root_location}${mountpoint_path}\" fails so unmount it in force mode."
                if ! umount -f "${new_root_location}${mountpoint_path}"; then
                    bl.logging.warn "Unmounting \"${new_root_location}${mountpoint_path}\" in force mode fails so unmount it if mountpoint isn't busy anymore."
                    umount -l "${new_root_location}${mountpoint_path}"
                fi
            fi
            # NOTE: "return_code" remains with an error code if there was
            # given one in all iterations.
            current_return_code=$?
            ((current_return_code != 0)) && \
                return_code="$current_return_code"
        else
            bl.logging.warn \
                "Location \"${new_root_location}${mountpoint_path}\" should be a mountpoint but isn't."
        fi
    done
    local created_location
    for created_location in $(bl.array.reverse "${created_locations[*]}"); do
        rm --force --recursive "$created_location"
    done
    return $return_code
}
# endregion
# region vim modline
# vim: set tabstop=4 shiftwidth=4 expandtab:
# vim: foldmethod=marker foldmarker=region,endregion:
# endregion