#!/bin/bash
# mer-sdk-chroot

# TODO
#
# Support a Mer clean setup (ie no .oscrc)
# Support multiple shells (ie split setup/entry)

usage()
{
    cat <<EOF
    usage: $0 [-u <user>] [-m <all|none|root|home>] [-r <SDK root path>] [<command> <args> ..]
           $0 -h

       This is the Mer chroot SDK.
       For information see http://wiki.merproject.org/wiki/Platform_SDK

      If command is not present,
         used to enter the SDK and begin working. The SDK bash shell is a
         login shell. See below for .profile handling

      If command is present,
         used to execute an arbitrary command from within the SDK chroot
         environment. The environment variable MERSDK is set to allow
         SDK detection.

      Options:

       -u  System user to link into SDK (not needed if using sudo)
       -m  Devices to bind mount from host: none, all (default)
           root, home
       -r The root of the SDK to use - normally derived from the
          pathname of $0
       -h  Show this help

      Profile

      Entering the SDK runs the user's normal .profile and any (SDK)
      system profile entries. It will not execute the host's system
      profile entries.

      The environment variable MERSDK is set to allow .profile to
      detect the SDK.

      If the user has a ~/.mersdk.profile then it is sourced after the
      normal .profile handling (this allows the common use case of
      setting a profile to be handled).

      Hooks

      If the user specified has a .mersdkrc in their $HOME, it will be
      sourced to allow hook functions to be defined. Hooks are run as
      root. No commands should be executed immediately.

      These hooks are usually used to define symbolic links from any
      /parentroot/data type filesystems into the SDK root to setup
      system specific shared caches or filesystem layouts etc

EOF
    return 0
}

MY_SSH_AUTH_SOCK=${SSH_AUTH_SOCK#/parentroot}
[[ $MY_SSH_AUTH_SOCK ]] && MY_SSH_AUTH_SOCK="/parentroot$MY_SSH_AUTH_SOCK"

if [[ $EUID -ne 0 ]]; then
    exec sudo SSH_AGENT_PID=${SSH_AGENT_PID:-} SSH_AUTH_SOCK=${MY_SSH_AUTH_SOCK} $0 "$@"
    echo "$0 must be run as root and sudo failed; exiting"
    exit 1
fi

if cmp -s /proc/$PPID/mountinfo /proc/self/mountinfo; then
    exec unshare -m -- "$0" "$@"
    echo "$0 must be run in private namespace and unshare failed; exiting"
    exit 1
fi

# Make sure that mountpoints in the new namespace are really unshared from the
# parental namespace. See unshare(1).
# This prevents mounts in the sdk from appearing in the parent fs.
mount --make-rslave /

# Use the SUDO value if present
user=$SUDO_USER || true;

bind_mount_root="yes";
bind_mount_home="yes";

while getopts "u:m:r:" opt; do
    case $opt in
	u ) user=$OPTARG;;
	m )
	    case $OPTARG in
		all) ;;
		home)
		    bind_mount_root="no";;
		root)
		    bind_mount_home="no";;
		none)
		    bind_mount_root="no";
		    bind_mount_home="no";;
		*)  echo "Only 'none', 'all' or 'home' are permitted for -m"
		    usage
		    exit 1;;
	    esac ;;
	r ) sdkroot=$OPTARG;;
	h|\? ) usage
            exit 1;;
	: ) echo "Option -$OPTARG requires an argument." >&2
	    usage
	    exit 1;;
	* ) usage
            exit 1;;
    esac
done
shift $(($OPTIND - 1))

if [[ -z "${sdkroot}" ]] ; then
    sdkroot=$(dirname $(readlink -f $0))
else
    sdkroot=$(readlink -f $sdkroot)
fi

if [[ ! -f ${sdkroot}/etc/MerSDK ]] ; then
    echo "${sdkroot} does not look like a Mer SDK rootfs"
    echo "if you are sure it is, you may mark it by running"
    echo "echo 'MerSDK' | sudo tee ${sdkroot}/etc/MerSDK"
    exit 1
fi

if ! [[ $(basename $(dirname $sdkroot)) == "sdks" ]]; then
    echo "Non-standard SDK installation layout - cannot determine location for "
    echo "SDK targets and toolings. Expected layout is:"
    echo ""
    echo "    <path/to/SDKs...>/"
    echo "    ├── sdks/"
    echo "    │   ├── <sdk_1>/"
    echo "    │   ├── <sdk_2>/"
    echo "    │   └── .../"
    echo "    ├── targets/"
    echo "    │   ├── <targets_1>/"
    echo "    │   ├── <targets_2>/"