#!/bin/sh

# This contains the COMPLETE list of binaries that this script needs
# to function.  The only exception is the QEMU binary since it is not
# known in advance which one wil be required.
readonly LIBTOOLS="cp echo cat printf which mountpoint mount umount modprobe"

info_msg() {
    # This function handles the printing that is bold within all
    # scripts.  This is a convenience function so that the rather ugly
    # looking ASCII escape codes live in only one place.
    printf "\033[1m%s\n\033[m" "$@"
}

die() {
    # This function is registered in all the scripts to make sure that
    # the important mounts get cleaned up and the $ROOTFS location is
    # removed.
    printf "FATAL: %s\n" "$@"
    umount_pseudofs
    [ -d "$ROOTFS" ] && rm -rf "$ROOTFS"
    exit 1
}

check_tools() {
    # All scripts within mklive declare the tools they will use in a
    # variable called "REQTOOLS".  This function checks that these
    # tools are available and prints out the path to each tool that
    # will be used.  This can be useful to figure out what is broken
    # if a different version of something is used than was expected.
    for tool in $LIBTOOLS $REQTOOLS ; do
        if ! which "$tool" > /dev/null ; then
            die "Required tool $f is not available on this system!"
        fi
    done

    info_msg "The following tools will be used:"
    for tool in $LIBTOOLS $REQTOOLS ; do
        which "$tool"
    done
}

mount_pseudofs() {
    # This function ensures that the psuedofs mountpoints are present
    # in the chroot.  Strictly they are not necessary to have for many
    # commands, but bind-mounts are cheap and it isn't too bad to just
    # mount them all the time.
    for f in dev proc sys; do
        # In a naked chroot there is nothing to bind the mounts to, so
        # we need to create directories for these first.
        [ ! -d "$ROOTFS/$f" ] && mkdir -p "$ROOTFS/$f"
        if ! mountpoint -q "$ROOTFS/$f" ; then
            # It is VERY important that this only happen if the
            # pseudofs isn't already mounted.  If it already is then
            # this is virtually impossible to troubleshoot because it
            # looks like the subsequent umount just isn't working.
            mount -r --bind /$f "$ROOTFS/$f"
        fi
    done
}

umount_pseudofs() {
    # This function cleans up the mounts in the chroot.  Failure to
    # clean up these mounts will prevent the tmpdir from being
    # deletable instead throwing the error "Device or Resource Busy".
    # The '-f' option is passed to umount to account for the
    # contingency where the psuedofs mounts are not present.
    if [ -d "${ROOTFS}" ]; then
        for f in dev proc sys; do
            umount -f "$ROOTFS/$f" >/dev/null 2>&1
        done
    fi
}

run_cmd_target() {
    info_msg "Running $* for target $XBPS_TARGET_ARCH ..."
    if [ "$XBPS_TARGET_ARCH" = "$(xbps-uhelper arch)" ] ; then
        # This is being run on the same architecture as the host,
        # therefore we should set XBPS_ARCH.
        if ! eval XBPS_ARCH="$XBPS_TARGET_ARCH" "$@" ; then
            die "Could not run command $*"
        fi
    else
        # This is being run on a foriegn arch, therefore we should set
        # XBPS_TARGET_ARCH.  In this case XBPS will not attempt
        # certain actions and will require reconfiguration later.
        if ! eval XBPS_TARGET_ARCH="$XBPS_TARGET_ARCH" "$@" ; then
            die "Could not run command $*"
        fi
    fi
}

run_cmd() {
    # This is a general purpose function to run commands that a user
    # may wish to see.  For example its useful to see the tar/xz
    # pipeline to not need to delve into the scripts to see what
    # options its set up with.
    info_msg "Running $*"
    eval "$@"
}

run_cmd_chroot() {
    # General purpose chroot function which makes sure the chroot is
    # prepared.  This function takes 2 arguments, the location to
    # chroot to and the command to run.

    # This is an idempotent function, it is safe to call every time
    # before entering the chroot.  This has the advantage of making
    # execution in the chroot appear as though it "Just Works(tm)".
    register_binfmt

    # Before we step into the chroot we need to make sure the
    # pseudo-filesystems are ready to go.  Not all commands will need
    # this, but its still a good idea to call it here anyway.
    mount_pseudofs

    # With assurance that things will run now we can jump into the
    # chroot and run stuff!
    chroot "$1" sh -c "$2"
}

cleanup_chroot() {
    # This function cleans up the chroot shims that are used by QEMU
    # to allow builds on alien platforms.  It takes no arguments but
    # expects the global $ROOTFS variable to be set.

    # Un-Mount the pseudofs mounts if they were mounted
    umount_pseudofs

    # If a QEMU binary was copied in, remove that as well
    if [ -x "$ROOTFS/usr/bin/$QEMU_BIN" ] ; then
        rm "$ROOTFS/usr/bin/$QEMU_BIN"
    fi
}

# TODO: Figure out how to register the binfmt for x86_64 and for i686
# to facilitate building on alien build systems.
register_binfmt() {
    # This function sets up everything that is needed to be able to
    # chroot into a ROOTFS and be able to run commands there.  This
    # really matters on platforms where the host architecture is
    # different from the target, and you wouldn't be able to run
    # things like xbps-reconfigure -a.  This function is idempotent
    # (You can run it multiple times without modifying state).  This
    # function takes no arguments, but does expect the global variable
    # $XBPS_TARGET_ARCH to be set.

    # This select sets up the "magic" bytes in /proc that let the
    # kernel select an alternate interpreter.  More values for this
    # map can be obtained from here:
    # https://github.com/qemu/qemu/blob/master/scripts/qemu-binfmt-conf.sh

    # If the XBPS_TARGET_ARCH is unset but the PLATFORM is known, it
    # may be possible to set the architecture from the static
    # platforms map.
    if [ -z "$XBPS_TARGET_ARCH" ] && [ ! -z "$PLATFORM" ] ; then
        set_target_arch_from_platform
    fi

    case "${XBPS_TARGET_ARCH}" in
        armv*)
            _cpu=arm
            _magic="\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28\x00"
            _mask="\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff"
            QEMU_BIN=qemu-arm-static
            ;;
        aarch64*)
            _cpu=aarch64
            _magic="\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xb7"
            _mask="\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff"
            QEMU_BIN=qemu-aarch64-static
            ;;
        mipsel*)
            _cpu=mipsel
            _magic="\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x08\x00"
            _mask="\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff"
            QEMU_BIN=qemu-mipsel-static
            ;;
        *86*)
            info_msg "FIXME: Assuming that x86 instructions are native"
            QEMU_BIN=NATIVE
            ;;
        *)
            die "Unknown target architecture!"
            ;;
    esac

    # In the special case where the build is native we can return
    # without doing anything else
    if [ "$QEMU_BIN" = "NATIVE" ] ; then
        return
    fi

    # For builds that do not match the host architecture, the correct
    # qemu binary will be required.
    if ! $QEMU_BIN -version >/dev/null 2>&1; then
        die "$QEMU_BIN binary is missing in your system, exiting."
    fi

    # In order to use the binfmt system the binfmt_misc mountpoint
    # must exist inside of proc
    if ! mountpoint -q /proc/sys/fs/binfmt_misc ; then
        modprobe -q binfmt_misc
        mount -t binfmt_misc binfmt_misc /proc/sys/fs/binfmt_misc 2>/dev/null
    fi

    # Only register if the map is incomplete
    if [ ! -f /proc/sys/fs/binfmt_misc/qemu-$_cpu ] ; then
        echo ":qemu-$_cpu:M::$_magic:$_mask:/usr/bin/$QEMU_BIN:" > /proc/sys/fs/binfmt_misc/register 2>/dev/null
    fi

    # If the static binary isn't in the chroot then the chroot will
    # fail.  The kernel knows about the map but without the static
    # version there's no interpreter in the chroot, only the
    # dynamically linked one in the host.  To simplify things we just
    # use the static one always and make sure it shows up at the same
    # place in the host and the chroot.
    if [ ! -x "$ROOTFS/usr/bin/$QEMU_BIN" ] ; then
        cp -f "$(which "$QEMU_BIN")" "$ROOTFS/usr/bin" ||
            die "Could not install $QEMU_BIN to $ROOTFS/usr/bin/"
    fi
}

set_target_arch_from_platform() {
    # This function maintains a lookup from platform to target
    # architecture.  This is required for scripts that need to know
    # the target architecture, but don't necessarily need to know it
    # internally (i.e. only run_cmd_chroot).
    case "$PLATFORM" in
        bananapi*) XBPS_TARGET_ARCH="armv7l";;
        beaglebone*) XBPS_TARGET_ARCH="armv7l";;
        cubieboard2*|cubietruck*) XBPS_TARGET_ARCH="armv7l";;
        dockstar*) XBPS_TARGET_ARCH="armv5tel";;
        odroid-u2*) XBPS_TARGET_ARCH="armv7l";;
        odroid-c2*) XBPS_TARGET_ARCH="aarch64";;
        rpi3*) XBPS_TARGET_ARCH="aarch64";;
        rpi2*) XBPS_TARGET_ARCH="armv7l";;
        rpi*) XBPS_TARGET_ARCH="armv6l";;
        usbarmory*) XBPS_TARGET_ARCH="armv7l";;
        ci20*) XBPS_TARGET_ARCH="mipsel";;
        i686*) XBPS_TARGET_ARCH="i686";;
        x86_64*) XBPS_TARGET_ARCH="x86_64";;
        GCP*) XBPS_TARGET_ARCH="x86_64";;
        *) die "$PROGNAME: Unable to compute target architecture from platform";;
    esac

    if [ -z "${PLATFORM##*-musl}" ] ; then
        XBPS_TARGET_ARCH="${XBPS_TARGET_ARCH}-musl"
    fi
}

set_cachedir() {
    # The package artifacts are cacheable, but they need to be isolated
    # from the host cache.
    : "${XBPS_CACHEDIR:=--cachedir=$PWD/xbps-cache/${XBPS_TARGET_ARCH}}"
}

# These should all resolve even if they won't have the appropriate
# repodata files for the selected architecture.
: "${XBPS_REPOSITORY:=--repository=http://repo.voidlinux.eu/current \
                      --repository=http://repo.voidlinux.eu/current/musl \
                      --repository=http://repo.voidlinux.eu/current/aarch64}"