#!/bin/sh -eu
# fp6-img modem-preserving installer for the Fairphone 6.
#
# Why this exists: this device's bootloader ZEROES the modem's NV storage
# (modemst1/modemst2) whenever the boot partition is written over fastboot —
# after a classic `fastboot flash boot`, cellular (incl. eSIM access) is dead
# until restored. Isolated by experiment, 2026-08-09 (fp6 journal/modem).
#
# This installer never lets the bootloader write boot:
#   1. fastboot erase dtbo          (verified safe)
#   2. fastboot flash userdata      (rootfs; not a boot write - believed safe,
#                                    final isolation pending; step 5 verifies)
#   3. fastboot boot boot.img       (RAM boot - writes nothing; verified safe)
#   4. dd boot.img to boot_a from the booted Linux over USB networking
#      (kernel block layer - the bootloader never sees it)
#   5. read back the modem NV and tell you the truth either way
#
# Requirements on this machine: fastboot, ssh. Phone: bootloader unlocked,
# in fastboot mode (Vol-down + Power), connected over USB.
# Run from a directory containing boot.img and fairphone-fp6.img.

PHONE=172.16.42.1
BOOT=${BOOT:-boot.img}
ROOTFS=${ROOTFS:-fairphone-fp6.img}

say() { printf '\n== %s ==\n' "$*"; }
die() { printf 'ERROR: %s\n' "$*" >&2; exit 1; }

# --- preflight ---------------------------------------------------------------
command -v fastboot >/dev/null || die "fastboot not found (install android-tools)"
command -v ssh >/dev/null || die "ssh not found"
[ -f "$BOOT" ] || die "$BOOT not found (download it from the release)"
[ -f "$ROOTFS" ] || die "$ROOTFS not found (download it from the release)"
fastboot devices 2>/dev/null | grep -q fastboot || \
	die "no device in fastboot mode (Vol-down + Power, USB connected)"

cat <<'EOF'
This will REPLACE the operating system on the connected Fairphone 6
(userdata + boot). The modem's NV storage is preserved - that is the point
of this installer. Press Enter to continue, Ctrl-C to abort.
EOF
read -r _

# --- 1+2: safe fastboot writes -------------------------------------------------
say "erasing dtbo (one-time; safe - does not touch modem NV)"
fastboot erase dtbo

say "flashing rootfs to userdata (this is the big one, be patient)"
fastboot flash userdata "$ROOTFS"

# --- 3: RAM-boot the kernel, no write -----------------------------------------
say "RAM-booting the new system (nothing is written)"
fastboot boot "$BOOT"

say "waiting for the phone to come up on the USB network ($PHONE)"
# The phone side is reliable (it always configures 172.16.42.1 on its USB
# gadget); when this step times out the problem is almost always THIS
# machine's side of the USB link: the gadget shows up as a new network
# interface here, and either nothing configures an address on it, or a
# network manager grabs it with the wrong profile (we have seen
# NetworkManager hand it an unrelated LAN address). The phone runs a DHCP
# server on the link, but host managers don't always ask.
i=0
until (exec 3<>"/dev/tcp/$PHONE/22") 2>/dev/null; do
	i=$((i+1))
	if [ $i -gt 40 ]; then
		cat >&2 <<'EOF'
ERROR: phone did not appear on 172.16.42.1 after 400s.

The phone has most likely booted fine - this machine just hasn't configured
its side of the USB network link. Fix it by hand:

  1. find the new interface:   ip link   (usually enp*u* or usb0, appeared
     when the phone booted; unplug/replug USB and watch if unsure)
  2. give this machine an address on it:
        sudo ip link set <iface> up
        sudo ip addr add 172.16.42.2/24 dev <iface>
  3. verify:                   ping 172.16.42.1
  4. re-run this script - every step is safe to repeat.

If a network manager keeps reclaiming the interface, tell it to ignore it,
e.g.: sudo nmcli device set <iface> managed no
EOF
		exit 1
	fi
	sleep 10
done
exec 3<&- 3>&- 2>/dev/null || true
sleep 8

# --- 4: write boot from Linux ---------------------------------------------------
# One authenticated ssh connection is opened and kept alive (ControlMaster);
# sudo self-answers with the image's default password via an askpass helper
# (sudo -S would eat the first bytes of the boot image from stdin).
PW=147147
CTL="/tmp/fp6-install-ssh-$$"
SSHOPTS="-o StrictHostKeyChecking=accept-new -o UserKnownHostsFile=/dev/null \
	-o ControlMaster=auto -o ControlPath=$CTL -o ControlPersist=120"
SUDO="SUDO_ASKPASS=/tmp/.fp6-install-pw sudo -A"

if command -v sshpass >/dev/null; then
	say "connecting (default credentials, no typing needed)"
	SSHCMD="sshpass -p $PW ssh $SSHOPTS"
else
	say "connecting - type the password ONCE (fresh image default: 147147)"
	SSHCMD="ssh $SSHOPTS"
fi
# shellcheck disable=SC2086
$SSHCMD "user@$PHONE" \
	"printf '#!/bin/sh\necho $PW\n' > /tmp/.fp6-install-pw && chmod 700 /tmp/.fp6-install-pw && echo CONNECTED" \
	|| die "could not connect to the phone"

say "writing boot.img to boot_a from inside Linux"
# shellcheck disable=SC2086
cat "$BOOT" | ssh $SSHOPTS "user@$PHONE" \
	"$SUDO dd of=/dev/disk/by-partlabel/boot_a bs=1M conv=fsync status=none && sync && echo BOOT-WRITTEN"

say "verifying modem NV survived"
# shellcheck disable=SC2086
Z=$(ssh $SSHOPTS "user@$PHONE" \
	"$SUDO od -An -tx1 -N4096 /dev/disk/by-partlabel/modemst1 | sort -u | wc -l" 2>/dev/null || echo 0)
if [ "$Z" -gt 2 ]; then
	echo "modem NV intact - cellular will work."
else
	cat <<'EOF'
WARNING: the modem NV reads empty. If this device previously ran stock
Android, its factory copy (fsg) is still on the device but postmarketOS
cannot restore from it yet - see the README's modem section. If you have a
modemst backup, dd it back now.
EOF
fi

say "rebooting into the installed system"
# shellcheck disable=SC2086
ssh $SSHOPTS "user@$PHONE" \
	"$SUDO setsid sh -c 'sleep 2; /sbin/reboot' </dev/null >/dev/null 2>&1 & sleep 5" || true
# shellcheck disable=SC2086
ssh $SSHOPTS -O exit "user@$PHONE" 2>/dev/null || true

cat <<'EOF'

DONE. The phone reboots into postmarketOS from its own boot partition.
Log in as user / 147147 (change it!). For VoLTE, write your carrier's
P-CSCF into /etc/imsd.env and restart imsd - see the README.
EOF