#!/bin/sh -e
#
# Setup an alpine chroot.

chroot_dir=~/alpine-chroot
mirror=http://dl-cdn.alpinelinux.org/alpine/
file=apk-tools-static-2.10.3-r1.apk

clean() {
    umount "$chroot_dir/dev"  ||:
    umount "$chroot_dir/proc" ||:
    umount "$chroot_dir/sys"  ||:

    rm -rf "$chroot_dir" "/tmp/${file:-null}"
}

main() {
    [ "$(id -u)" != 0 ] && {
        echo "Run this script with sudo." >&2
        exit 1
    }

    clean

    mkdir -p "/tmp/$file"
    cd "/tmp/$file"

    wget "$mirror/latest-stable/main/x86_64/$file"
    tar xzf "$file"

    ./sbin/apk.static \
        -X "$mirror/latest-stable/main" \
        -U \
        --allow-untrusted \
        --root "$chroot_dir" \
        --initdb add alpine-base alpine-sdk ||:

    cp -f /etc/resolv.conf "$chroot_dir/etc"

    mkdir -p "$chroot_dir/etc/apk"
    echo "$mirror/edge/main" > "$chroot_dir/etc/apk/repositories"

    mount -o bind /dev "$chroot_dir/dev"
    mount -t proc proc "$chroot_dir/proc"
    mount -t sysfs sys "$chroot_dir/sys"

    trap clean EXIT INT

    chroot "$chroot_dir" /bin/sh
}

main