#!/usr/bin/env bash
# Bake the golden NixOS qcow2: boot the minimal ISO headless under qemu, drive a
# scripted nixos-install over the serial console, power off. Output is a golden
# disk image; Kiln (or boot-overlay.sh) boots throwaway overlays from it.
#
# Usage: build-golden.sh <nixos.iso> <nina-linux-binary> <out-golden.qcow2>
# Tunables via env: DISK_GB (20), MEM_MB (4096), SMP (2), INSTALL_TIMEOUT (2400)
set -euo pipefail

ISO="${1:?usage: build-golden.sh <iso> <nina-bin> <out.qcow2>}"
NINA="${2:?need nina linux binary}"
OUT="${3:?need output qcow2 path}"
HERE="$(cd "$(dirname "$0")" && pwd)"
DISK_GB="${DISK_GB:-20}"
MEM_MB="${MEM_MB:-4096}"
SMP="${SMP:-2}"
INSTALL_TIMEOUT="${INSTALL_TIMEOUT:-2400}"

for f in "$ISO" "$NINA"; do [ -f "$f" ] || { echo "missing: $f" >&2; exit 1; }; done

work="$(mktemp -d)"
trap 'rm -rf "$work"' EXIT

# Seed media: our config + install script + nina, as an ISO the installer mounts.
seed="$work/seed"
mkdir -p "$seed"
cp "$HERE/configuration.nix" "$seed/configuration.nix"
cp "$HERE/install.sh" "$seed/install.sh"
cp "$NINA" "$seed/nina"
SEED_ISO="$work/seed.iso"
hdiutil makehybrid -quiet -iso -joliet -default-volume-name NINASEED -o "$SEED_ISO" "$seed"

# Fresh blank disk for the install target.
qemu-img create -f qcow2 "$OUT" "${DISK_GB}G" >/dev/null
echo "golden target: $OUT (${DISK_GB}G)  ·  seed: $SEED_ISO"

expect -c '
  set timeout 600
  set iso       [lindex $argv 0]
  set seed_iso  [lindex $argv 1]
  set out       [lindex $argv 2]
  set mem       [lindex $argv 3]
  set smp       [lindex $argv 4]
  set install_timeout [lindex $argv 5]

  spawn qemu-system-x86_64 \
    -machine q35 -accel tcg -cpu max -smp $smp -m $mem \
    -drive file=$out,if=virtio,format=qcow2 \
    -drive file=$iso,media=cdrom,readonly=on \
    -drive file=$seed_iso,media=cdrom,readonly=on \
    -boot d \
    -netdev user,id=n0 -device virtio-net-pci,netdev=n0 \
    -nographic

  # Reach an installer root shell (autologin on the ISO serial console).
  expect {
    timeout { puts "\n!! no shell prompt from installer"; exit 2 }
    -re {\[root@nixos[^\]]*\]#} {}
    -re {nixos@nixos} { send "sudo -i\r"; exp_continue }
    -re {login:} { send "root\r"; exp_continue }
  }
  send "\r"
  expect -re {\[root@nixos[^\]]*\]#}

  # Mount seed media and run the installer script.
  send "mkdir -p /mnt-seed && mount /dev/sr1 /mnt-seed && echo NINA_SEED_OK\r"
  expect {
    timeout { puts "\n!! seed mount failed"; exit 3 }
    "NINA_SEED_OK" {}
  }
  send "bash /mnt-seed/install.sh\r"

  set timeout $install_timeout
  expect {
    timeout { puts "\n!! install timed out"; exit 4 }
    "NINA_INSTALL_DONE" {}
    "NINA_INSTALL_START" { exp_continue }
  }
  # qemu exits when the guest powers off.
  set timeout 120
  expect eof
' "$ISO" "$SEED_ISO" "$OUT" "$MEM_MB" "$SMP" "$INSTALL_TIMEOUT"

echo "=== golden image built: $OUT ==="
qemu-img info "$OUT" | sed 's/^/  /'