#!/bin/sh

# System initialization sequence:
#
# /init
#  |
#  +--(1) /etc/01_prepare.sh
#  |
#  +--(2) /etc/02_overlay.sh (this file)
#          |
#          +-- /etc/03_init.sh
#               |
#               +-- /sbin/init
#                    |
#                    +--(1) /etc/04_bootscript.sh
#                    |       |
#                    |       +-- /etc/autorun/* (all scripts)
#                    |
#                    +--(2) /bin/sh (Alt + F1, main console)
#                    |
#                    +--(2) /bin/sh (Alt + F2)
#                    |
#                    +--(2) /bin/sh (Alt + F3)
#                    |
#                    +--(2) /bin/sh (Alt + F4)

# Create the new mountpoint in RAM.
mount -t tmpfs none /mnt

# Create folders for all critical file systems.
mkdir /mnt/dev
mkdir /mnt/sys
mkdir /mnt/proc
mkdir /mnt/tmp
mkdir /mnt/var
echo "Created folders for all critical file systems."

# Copy root folders in the new mountpoint.
echo -e "Copying the root file system to \\e[94m/mnt\\e[0m."
cp -a bin etc lib lib64 root sbin src usr var /mnt 2>/dev/null

setvar DEFAULT_OVERLAY_DIR = ""/tmp/minimal/overlay""
setvar DEFAULT_UPPER_DIR = ""/tmp/minimal/rootfs""
setvar DEFAULT_WORK_DIR = ""/tmp/minimal/work""

echo "Searching available devices for overlay content."
for DEVICE in /dev/*  {
  setvar DEV = $(echo "${DEVICE##*/}")
  setvar SYSDEV = $(echo "/sys/class/block/$DEV")

  case (DEV) {
    *loop* { continue }
  }

  if test ! -d $SYSDEV  {
    continue
  }

  mkdir -p /tmp/mnt/device
  setvar DEVICE_MNT = '/tmp/mnt/device'

  setvar OVERLAY_DIR = """"
  setvar OVERLAY_MNT = """"
  setvar UPPER_DIR = """"
  setvar WORK_DIR = """"

  mount $DEVICE $DEVICE_MNT 2>/dev/null
  if test -d $DEVICE_MNT/minimal/rootfs -a -d $DEVICE_MNT/minimal/work  {
    # folder
    echo -e "  Found \\e[94m/minimal\\e[0m folder on device \\e[31m$DEVICE\\e[0m."
    touch $DEVICE_MNT/minimal/rootfs/minimal.pid 2>/dev/null
    if test -f $DEVICE_MNT/minimal/rootfs/minimal.pid  {
      # read/write mode
      echo -e "  Device \\e[31m$DEVICE\\e[0m is mounted in read/write mode."

      rm -f $DEVICE_MNT/minimal/rootfs/minimal.pid

      setvar OVERLAY_DIR = "$DEFAULT_OVERLAY_DIR"
      setvar OVERLAY_MNT = "$DEVICE_MNT"
      setvar UPPER_DIR = "$DEVICE_MNT/minimal/rootfs"
      setvar WORK_DIR = "$DEVICE_MNT/minimal/work"
    } else {
      # read only mode
      echo -e "  Device \\e[31m$DEVICE\\e[0m is mounted in read only mode."

      setvar OVERLAY_DIR = "$DEVICE_MNT/minimal/rootfs"
      setvar OVERLAY_MNT = "$DEVICE_MNT"
      setvar UPPER_DIR = "$DEFAULT_UPPER_DIR"
      setvar WORK_DIR = "$DEFAULT_WORK_DIR"
    }
  } elif test -f $DEVICE_MNT/minimal.img  {
    #image
    echo -e "  Found \\e[94m/minimal.img\\e[0m image on device \\e[31m$DEVICE\\e[0m."

    mkdir -p /tmp/mnt/image
    setvar IMAGE_MNT = '/tmp/mnt/image'

    setvar LOOP_DEVICE = $(losetup -f)
    losetup $LOOP_DEVICE $DEVICE_MNT/minimal.img

    mount $LOOP_DEVICE $IMAGE_MNT
    if test -d $IMAGE_MNT/rootfs -a -d $IMAGE_MNT/work  {
      touch $IMAGE_MNT/rootfs/minimal.pid 2>/dev/null
      if test -f $IMAGE_MNT/rootfs/minimal.pid  {
        # read/write mode
        echo -e "  Image \\e[94m$DEVICE/minimal.img\\e[0m is mounted in read/write mode."

        rm -f $IMAGE_MNT/rootfs/minimal.pid

        setvar OVERLAY_DIR = "$DEFAULT_OVERLAY_DIR"
        setvar OVERLAY_MNT = "$IMAGE_MNT"
        setvar UPPER_DIR = "$IMAGE_MNT/rootfs"
        setvar WORK_DIR = "$IMAGE_MNT/work"
      } else {
        # read only mode
        echo -e "  Image \\e[94m$DEVICE/minimal.img\\e[0m is mounted in read only mode."

        setvar OVERLAY_DIR = "$IMAGE_MNT/rootfs"
        setvar OVERLAY_MNT = "$IMAGE_MNT"
        setvar UPPER_DIR = "$DEFAULT_UPPER_DIR"
        setvar WORK_DIR = "$DEFAULT_WORK_DIR"
      }
    } else {
      umount $IMAGE_MNT
      rm -rf $IMAGE_MNT
    }
  }

  if test $OVERLAY_DIR != "" -a $UPPER_DIR != "" -a $WORK_DIR != ""  {
    mkdir -p $OVERLAY_DIR
    mkdir -p $UPPER_DIR
    mkdir -p $WORK_DIR

    mount -t overlay -o lowerdir=$OVERLAY_DIR:/mnt,upperdir=$UPPER_DIR,workdir=$WORK_DIR none /mnt 2>/dev/null

    setvar OUT = ""$?
    if test ! $OUT = "0"  {
      echo -e "  \\e[31mMount failed (probably on vfat).\\e[0m"

      umount $OVERLAY_MNT 2>/dev/null
      rmdir $OVERLAY_MNT 2>/dev/null

      rmdir $DEFAULT_OVERLAY_DIR 2>/dev/null
      rmdir $DEFAULT_UPPER_DIR 2>/dev/null
      rmdir $DEFAULT_WORK_DIR 2>/dev/null
    } else {
      # All done, time to go.
      echo -e "  Overlay data from device \\e[31m$DEVICE\\e[0m has been merged."
      break
    }
  } else {
    echo -e "  Device \\e[31m$DEVICE\\e[0m has no proper overlay structure."
  }

  umount $DEVICE_MNT 2>/dev/null
  rm -rf $DEVICE_MNT 2>/dev/null
}

# Move critical file systems to the new mountpoint.
mount --move /dev /mnt/dev
mount --move /sys /mnt/sys
mount --move /proc /mnt/proc
mount --move /tmp /mnt/tmp
echo -e "Mount locations \\e[94m/dev\\e[0m, \\e[94m/sys\\e[0m, \\e[94m/tmp\\e[0m and \\e[94m/proc\\e[0m have been moved to \\e[94m/mnt\\e[0m."

# The new mountpoint becomes file system root. All original root folders are
# deleted automatically as part of the command execution. The '/sbin/init'
# process is invoked and it becomes the new PID 1 parent process.
echo "Switching from initramfs root area to overlayfs root area."
exec switch_root /mnt /etc/03_init.sh

echo "(/etc/02_overlay.sh) - there is a serious bug..."

# Wait until any key has been pressed.
read -n1 -s