#!/bin/sh

case $1 in
    prereqs)
        exit 0
        ;;
esac

set -e
# set -x
total_mem=$(free | awk '/^Mem:/{print $2}')
tmpfs_size=$(( $total_mem / 20 *  17 ))
free_mem_thres=$(( $total_mem / 20 * 18 ))
tmp_mnt='/mnt/ramdisk-convfs'
root_mnt='/mnt/root-convfs'
root_dev=''
flash_dev=''
block_flash=''
aboot_flag=''
backup_file=''

# Get the fullpath of flash device, e.g., /dev/sda
get_flash_dev() {
    for dev in $(ls /sys/block); do
        local is_mmc=$(echo "$dev" | grep 'mmcblk.*boot.*' | cat)
        if [ -n "$is_mmc" ]; then
            continue
        fi
        local devid=$(realpath "/sys/block/$dev/device")
        local is_device=$(echo "$devid" | grep '^/sys/devices/' | cat)
        local is_flash=$(echo "$devid" | grep "$block_flash" | cat)
        if [ -n "$is_device" -a -n "$is_flash" ]; then
            flash_dev="/dev/$dev"
            return 0
        fi
    done
    return 1
}

# Wait for root_dev to be ready
wait_for_root_dev() {
    local try_rounds=30
    while [ $try_rounds -gt 0 ]; do
        if [ -e "$root_dev" ]; then
            return 0
        fi
        sleep 1
        try_rounds=$(( $try_rounds - 1 ))
    done
    return 1
}

# Alway run cleanup before exit
cleanup() {
    if grep -q "$root_mnt" /proc/mounts; then
        umount "$root_mnt"
    fi
    if grep -q "$tmp_mnt" /proc/mounts; then
        umount "$tmp_mnt"
    fi
    [ -e "$root_mnt" ] && rmdir "$root_mnt"
    [ -e "$tmp_mnt" ] && rmdir "$tmp_mnt"
}
trap cleanup EXIT

notification() {
cat << EOF
A failure happend in modifying the root file system which stopped the upgrade. Manual interventions are needed to fix the issue. Note that:
1) files in the old root file system may have been lost and the old partition table may have been corrupted;
2) The files in the old root file system were copied to $tmp_mnt;
3) The old partition table was dumped to the file $tmp_mnt/$backup_file by sfdisk;
4) Quitting the current shell will lose all files mentioned above permanently.
EOF
}

run_cmd() {
    if ! eval "$1"; then
        echo "$2"
        notification
        sh
        exit 1
    fi
}

# Extract kernel parameters
set -- $(cat /proc/cmdline)
for x in "$@"; do
    case "$x" in
        block_flash=*)
            block_flash="${x#block_flash=}"
            ;;
        Aboot=*)
            aboot_flag="${x#Aboot=}"
    esac
done
root_dev="$ROOT"

#Check aboot and root_dev is vfat
[ -z "$aboot_flag" ] && exit 0
if [ -z "$root_dev" ]; then
    echo "Error: root device name is not provided"
    exit 1
fi
if ! wait_for_root_dev; then
    echo "Error: timeout in waiting for $root_dev"
    exit 1
fi
blkid | grep "$root_dev.*vfat" -q || exit 0


# Get flash dev name
if [ -z "$block_flash" ]; then
    echo "Error: flash device info is not provided"
    exit 1
fi
if ! get_flash_dev; then
    echo "Error: flash device is not found"
    exit 1
fi

# Check memory size for tmpfs
free_mem=$(free | awk '/^Mem:/{print $4}')
if [ "$free_mem" -lt "$free_mem_thres" ]; then
    echo "Error: memory is not enough"
    exit 1
fi

# Backup partition table
mkdir -p "$root_mnt"
mount "$root_dev" "$root_mnt"
backup_file=backup.$(date +%Y-%m-%d.%H-%M-%S)
sfdisk -d "$flash_dev" > "$root_mnt/$backup_file"

# Check total size of files in root
total_file_size=$(du -s "$root_mnt" | awk '{print $1}')
if [ "$total_file_size" -gt "$tmpfs_size" ]; then
    echo "Error: total file size is too large"
    exit 1
fi

# Create tmpfs, and copy files to tmpfs
mkdir -p "$tmp_mnt"
mount -t tmpfs -o size="${tmpfs_size}k" tmpfs "$tmp_mnt"
cp -a "$root_mnt/." "$tmp_mnt/"
umount "$root_mnt"

#### Lines below will modify the root file system, so any failure will be trapped to shell for manual interventions.

# Create a new partition table (content in flash_dev will be deleted)
err_msg="Error: repartitioning $flash_dev failed"
cmd="echo ';' | sfdisk $flash_dev"
run_cmd "$cmd" "$err_msg"

sleep 5
err_msg="Error: timeout in waiting for $root_dev after repartition"
cmd="wait_for_root_dev"
run_cmd "$cmd" "$err_msg"

err_msg="Error: formatting to ext4 failed"
cmd="mke2fs -t ext4 -m2 -F -O '^huge_file' $root_dev"
run_cmd "$cmd" "$err_msg"

err_msg="Error: mounting $root_dev to $root_mnt failed"
cmd="mount -t ext4 $root_dev $root_mnt"
run_cmd "$cmd" "$err_msg"

err_msg="Error: copying files form $tmp_mnt to $root_mnt failed"
cmd="cp -a $tmp_mnt/. $root_mnt/"
run_cmd "$cmd" "$err_msg"