#!/bin/bash

# CREDIT TO THESE TUTORIALS:
# petr.io/en/blog/2015/11/09/read-only-raspberry-pi-with-jessie
# hallard.me/raspberry-pi-read-only
# k3a.me/how-to-make-raspberrypi-truly-read-only-reliable-and-trouble-free

if [ $(id -u) -ne 0 ]; then
	echo "Installer must be run as root."
	echo "Try 'sudo bash $0'"
	exit 1
fi

clear

echo "This script configures a Raspberry Pi"
echo "SD card to boot into read-only mode,"
echo "obviating need for clean shutdown."
echo "NO FILES ON THE CARD CAN BE CHANGED"
echo "WHEN PI IS BOOTED IN THIS STATE. Either"
echo "the filesystems must be remounted in"
echo "read/write mode, card must be mounted"
echo "R/W on another system, or an optional"
echo "jumper can be used to enable read/write"
echo "on boot."
echo
echo "Links to original tutorials are in"
echo "script source. THIS IS A ONE-WAY"
echo "OPERATION. THERE IS NO SCRIPT TO"
echo "REVERSE THIS SETUP! ALL other system"
echo "config should be complete before using"
echo "this script. MAKE A BACKUP FIRST."
echo
echo "Run time ~5 minutes. Reboot required."
echo
echo -n "CONTINUE? [y/N] "
read
if [[ ! "$REPLY" =~ ^(yes|y|Y)$ ]]; then
	echo "Canceled."
	exit 0
fi

# FEATURE PROMPTS ----------------------------------------------------------
# Installation doesn't begin until after all user input is taken.

INSTALL_RW_JUMPER=0
INSTALL_HALT=0
INSTALL_WATCHDOG=0

# Given a list of strings representing options, display each option
# preceded by a number (1 to N), display a prompt, check input until
# a valid number within the selection range is entered.
selectN() {
	for ((i=1; i<=$#; i++)); do
		echo $i. ${!i}
	done
	echo
	REPLY=""
	while :
	do
		echo -n "SELECT 1-$#: "
		read
		if [[ $REPLY -ge 1 ]] && [[ $REPLY -le $# ]]; then
			return $REPLY
		fi
	done
}

SYS_TYPES=(Pi\ 3\ /\ Pi\ Zero\ W All\ other\ models)
WATCHDOG_MODULES=(bcm2835_wdog bcm2708_wdog)
OPTION_NAMES=(NO YES)

# echo -n "Enable boot-time read/write jumper? [y/N] "
# read
# if [[ "$REPLY" =~ (yes|y|Y)$ ]]; then
# 	INSTALL_RW_JUMPER=1
# 	echo -n "GPIO pin for R/W jumper: "
# 	read
# 	RW_PIN=$REPLY
# fi
# 
# echo -n "Install GPIO-halt utility? [y/N] "
# read
# if [[ "$REPLY" =~ (yes|y|Y)$ ]]; then
# 	INSTALL_HALT=1
# 	echo -n "GPIO pin for halt button: "
# 	read
# 	HALT_PIN=$REPLY
# fi
# 
# echo -n "Enable kernel panic watchdog? [y/N] "
# read
# if [[ "$REPLY" =~ (yes|y|Y)$ ]]; then
# 	INSTALL_WATCHDOG=1
# 	echo "Target system type:"
# 	selectN "${SYS_TYPES[0]}" \
# 		"${SYS_TYPES[1]}"
# 	WD_TARGET=$?
# fi

# VERIFY SELECTIONS BEFORE CONTINUING --------------------------------------

# echo
# if [ $INSTALL_RW_JUMPER -eq 1 ]; then
# 	echo "Boot-time R/W jumper: YES (GPIO$RW_PIN)"
# else
# 	echo "Boot-time R/W jumper: NO"
# fi
# if [ $INSTALL_HALT -eq 1 ]; then
# 	echo "Install GPIO-halt: YES (GPIO$HALT_PIN)"
# else
# 	echo "Install GPIO-halt: NO"
# fi
# if [ $INSTALL_WATCHDOG -eq 1 ]; then
# 	echo "Enable watchdog: YES (${SYS_TYPES[WD_TARGET-1]})"
# else
# 	echo "Enable watchdog: NO"
# fi
# echo
# echo -n "CONTINUE? [y/N] "
# read
# if [[ ! "$REPLY" =~ ^(yes|y|Y)$ ]]; then
# 	echo "Canceled."
# 	exit 0
# fi

# START INSTALL ------------------------------------------------------------
# All selections have been validated at this point...

# Given a filename, a regex pattern to match and a replacement string:
# Replace string if found, else no change.
# (# $1 = filename, $2 = pattern to match, $3 = replacement)
replace() {
	grep $2 $1 >/dev/null
	if [ $? -eq 0 ]; then
		# Pattern found; replace in file
		sed -i "s/$2/$3/g" $1 >/dev/null
	fi
}

# Given a filename, a regex pattern to match and a replacement string:
# If found, perform replacement, else append file w/replacement on new line.
replaceAppend() {
	grep $2 $1 >/dev/null
	if [ $? -eq 0 ]; then
		# Pattern found; replace in file
		sed -i "s/$2/$3/g" $1 >/dev/null
	else
		# Not found; append on new line (silently)
		echo $3 | sudo tee -a $1 >/dev/null
	fi
}

# Given a filename, a regex pattern to match and a string:
# If found, no change, else append file with string on new line.
append1() {
	grep $2 $1 >/dev/null
	if [ $? -ne 0 ]; then
		# Not found; append on new line (silently)
		echo $3 | sudo tee -a $1 >/dev/null
	fi
}

# Given a filename, a regex pattern to match and a string:
# If found, no change, else append space + string to last line --
# this is used for the single-line /boot/cmdline.txt file.
append2() {
	grep $2 $1 >/dev/null
	if [ $? -ne 0 ]; then
		# Not found; insert in file before EOF
		sed -i "s/\'/ $3/g" $1 >/dev/null
	fi
}

echo
echo "Starting installation..."

echo "Removing unwanted packages..."
#apt-get remove -y --force-yes --purge triggerhappy logrotate dbus \
# dphys-swapfile xserver-common lightdm fake-hwclock
# Let's keep dbus...that includes avahi-daemon, a la 'raspberrypi.local',
# also keeping xserver & lightdm for GUI login (WIP, not working yet)
apt-get remove -y --force-yes --purge triggerhappy logrotate \
 dphys-swapfile fake-hwclock
apt-get -y --force-yes autoremove --purge

# Replace log management with busybox (use logread if needed)
echo "Installing ntp and busybox-syslogd..."
apt-get -y --force-yes install ntp busybox-syslogd; dpkg --purge rsyslog

echo "Configuring system..."

# Add fastboot, noswap and/or ro to end of /boot/cmdline.txt
append2 /boot/cmdline.txt fastboot fastboot
append2 /boot/cmdline.txt noswap noswap
append2 /boot/cmdline.txt ro^o^t ro

# Move /var/spool to /tmp
rm -rf /var/spool
ln -s /tmp /var/spool

# Change spool permissions in var.conf (rondie/Margaret fix)
replace /usr/lib/tmpfiles.d/var.conf "spool\s*0755" "spool 1777"

# Move dhcpd.resolv.conf to tmpfs
touch /tmp/dhcpcd.resolv.conf
rm /etc/resolv.conf
ln -s /tmp/dhcpcd.resolv.conf /etc/resolv.conf

# Make edits to fstab
# make / ro
# tmpfs /var/log tmpfs nodev,nosuid 0 0
# tmpfs /var/tmp tmpfs nodev,nosuid 0 0
# tmpfs /tmp     tmpfs nodev,nosuid 0 0
replace /etc/fstab "vfat\s*defaults\s" "vfat    defaults,ro "
replace /etc/fstab "ext4\s*defaults,noatime\s" "ext4    defaults,noatime,ro "
cat << EOF >> /etc/fstab
tmpfs /var/log tmpfs nodev,nosuid 0 0
tmpfs /var/tmp tmpfs nodev,nosuid 0 0
tmpfs /var/lib/ntp tmpfs nodev,nosuid 0 0
tmpfs /var/lib/pyheatpump tmpfs nodev,nosuid 0 0
tmpfs /var/run tmpfs nodev,nosuid 0 0
tmpfs /tmp tmpfs nodev,nosuid 0 0
EOF

# PROMPT FOR REBOOT --------------------------------------------------------

echo "Done."
echo
echo "Settings take effect on next boot."
echo
echo -n "REBOOT NOW? [y/N] "
read
if [[ ! "$REPLY" =~ ^(yes|y|Y)$ ]]; then
	echo "Exiting without reboot."
	exit 0
fi
echo "Reboot started..."
reboot
exit 0