#!/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

# Direct kernel boot: the ISO's own cmdline omits console=ttyS0 (kernel + getty
# land on VGA, invisible under -nographic). Extract the kernel/initrd and the
# installer's APPEND line, then add a serial console so the install is drivable.
bsdtar -xOf "$ISO" boot/bzImage > "$work/bzImage"
bsdtar -xOf "$ISO" boot/initrd  > "$work/initrd"
APPEND_BASE="$(bsdtar -xOf "$ISO" isolinux/isolinux.cfg 2>/dev/null \
  | awk '/^[[:space:]]*APPEND/ {sub(/^[[:space:]]*APPEND[[:space:]]*/,""); print; exit}')"
[ -n "$APPEND_BASE" ] || { echo "could not read installer APPEND line" >&2; exit 1; }
APPEND="$APPEND_BASE console=ttyS0,115200"
echo "golden target: $OUT (${DISK_GB}G)  ·  seed: $SEED_ISO"
echo "kernel append: $APPEND"

# Pass values to expect via the environment ($env(...)); `expect -c` does not
# populate $argv from trailing args.
export GI_ISO="$ISO" GI_SEED="$SEED_ISO" GI_OUT="$OUT" GI_MEM="$MEM_MB" \
       GI_SMP="$SMP" GI_TIMEOUT="$INSTALL_TIMEOUT" \
       GI_KERNEL="$work/bzImage" GI_INITRD="$work/initrd" GI_APPEND="$APPEND"

expect -c '
  set timeout 600
  set iso       $env(GI_ISO)
  set seed_iso  $env(GI_SEED)
  set out       $env(GI_OUT)
  set mem       $env(GI_MEM)
  set smp       $env(GI_SMP)
  set install_timeout $env(GI_TIMEOUT)
  set kernel    $env(GI_KERNEL)
  set initrd    $env(GI_INITRD)
  set append    $env(GI_APPEND)

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

  expect {
    timeout { puts "\n!! installer never reached autologin"; exit 2 }
    "automatic login" {}
  }
  sleep 5
  send "sudo -i\r"
  sleep 2
  send "mkdir -p /mnt-seed && mount /dev/sr1 /mnt-seed && bash /mnt-seed/install.sh\r"

  set timeout $install_timeout
  expect {
    timeout { puts "\n!! install never finished"; exit 4 }
    "NINA_INSTALL_FAIL" { puts "\n!! install.sh reported failure"; exit 5 }
    "NINA_INSTALL_DONE" {}
    "NINA_INSTALL_START" { exp_continue }
  }
  set timeout 120
  expect eof
'

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