#!/bin/bash

IMG_FILE=rootfs.img
IMG_SIZE=100 # MB

function log() {
  echo "$*"
}

function yes_or_no() {
  while true; do
    read -p "$* [y/n]: " yn
    case $yn in
    [Yy]*) return 0 ;;
    [Nn]*)
      echo "Aborted"
      return 1
      ;;
    esac
  done
}

function setup_lb() {
  sudo losetup -fP --show ${IMG_FILE}
}

if [ ! -d mnt ]; then
  mkdir mnt
fi

if [ -f "${IMG_FILE}" ]; then
  log "${IMG_FILE} already exists"
  if ! yes_or_no "Continue?"; then
    exit 1
  fi
fi

# build img
dd if=/dev/zero of=${IMG_FILE} bs=1M count=${IMG_SIZE}

parted -s ${IMG_FILE} mktable msdos
parted -s ${IMG_FILE} mkpart primary ext2 0 100%

LB_DEV="$(setup_lb)"

if [ -z "${LB_DEV}" ]; then
  log "Failed to setup loobback"
  exit 1
fi

sudo mkfs.ext2 -L rootfs "${LB_DEV}p1"
sudo mount "${LB_DEV}p1" mnt