#!/bin/bash

# Hotplug script to automatically make symlinks to hotplugged devices.
# Requires a configuration file in /etc/hotplug.d/block called symlinks.rc
# This file should have the following format:

# /dev/muvo NOMAD MuVo NX
# /dev/other Some other device

# The first word on each line should be the desired symlink position, and the
# second argument should be the model, as found in /sys/block/sd?/device/model
# when the device is plugged in. Hence, if you plug in the device with model
# name NOMAD MuVo NX, a symlink to its device node (e.g. /dev/sda) will be 
# created in /dev/muvo. You can then set up an fstab entry to use /dev/muvo
# as the device for the MuVo USB device.

CONFIG="/etc/hotplug.d/block/symlinks.rc"

# Read the config file and figure out the symlink
# Arguments: the full model string
get_symlink () {
	# Get the model, but make it whitespace agnostic, since sometimes the name
	# is padded with whitespace
	local target_model=$(echo $1)
	local link=""
	
	link=$(cat "${CONFIG}" | grep -i "${target_model}" | awk '{ print $1 }')
	
	if test -n "${link}" ; then
		echo "${link}"
		return 0
	else
		return 1
	fi
}

# Wait for a file to appear (stolen from Wout Mertens, wmertens@gentoo.org)
wait_for_file () {
	local count=0
	while test $count -lt 10 && ! test -r "$1" ; do
		sleep 1
		count=$((count + 1))
	done
	test $count -eq 10 && return 1
	return 0
}

# Only handle block devices
test "${1}" = "block" || exit 1 # (Not called for block hotplug)

# Ensure we have a partition device
partition=$(echo "${DEVPATH}" | awk -F\/ '{ print $4 }') 
test -n "${partition}" || exit 2 # (Invalid $DEVPATH; should be /block/sd?/sd??)

# Figure which device to mount
device=$(echo "${DEVPATH}" | awk -F\/ '{ print $3 }')
test -n "${device}" || exit 2

# Get the model we're looking for
model_file="/sys/block/${device}/device/model"

wait_for_file "${model_file}"
test -r "${model_file}" || exit 3 # (Could not read model)

model=$(< ${model_file})
test -n "${model}" || exit 3

link=$(get_symlink "${model}")
test -n "${link}" || exit 4 # (Could not find link for model)

case "${ACTION}" in
	add)
		ln -sf "/dev/${partition}" "${link}"
		;;
	remove)
		test -L "${link}" && rm -f "${link}"
		;;
esac