#!/usr/bin/env -S nix shell nixpkgs#bash --command bash
#
# vm.sh - Incus VM launcher for musicfs-server
#
# Creates and manages an Incus VM that runs the `musicfs-server` gRPC binary,
# live-sharing the host's ~/Music via a virtiofs disk device.
#
# The server binary is built on the host (cargo) and shipped into the VM as a
# *self-contained bundle*: when the host toolchain is nix-based (devenv), the
# resulting ELF interpreter points at /nix/store/.../ld-linux-x86-64.so.2 which
# does not exist inside a stock Debian/Ubuntu VM. This script detects that,
# retargets the interpreter + rpath to an absolute in-VM path via patchelf, and
# bundles the few required shared objects alongside the binary. The VM therefore
# needs zero package installs to run the server.
#
# Usage:
#   scripts/vm.sh up         create VM (if missing), share music, build+ship server, start it
#   scripts/vm.sh redeploy   rebuild + push + restart server (VM kept running)
#   scripts/vm.sh restart    restart the in-VM systemd service (no rebuild)
#   scripts/vm.sh logs       tail server logs (journalctl -f)
#   scripts/vm.sh status     show VM + service status
#   scripts/vm.sh shell      open a shell in the VM
#   scripts/vm.sh down       stop the VM
#   scripts/vm.sh destroy    delete the VM (and its disk) permanently
#
# Configuration (override via env, e.g. IMAGE=images:ubuntu/24.04 scripts/vm.sh up):
#   VM_NAME       name of the Incus instance          (default: musicfs)
#   IMAGE         Incus image alias                   (default: images:debian/12)
#   MUSIC_SOURCE  host path to the music library       (default: $HOME/Music)
#   MUSIC_MOUNT   where it appears inside the VM       (default: /music)
#   LISTEN_PORT   gRPC port (host:vm forwarded)        (default: 50051)
#   RUST_LOG      tracing filter for the server        (default: info)
#   READONLY      mount music as read-only (0=writable) (default: 1)
#   VM_IP         static IPv4 for the VM                (default: auto-detected from incusbr0, gateway.145)
#
set -euo pipefail

# ─────────────────────────────── config ────────────────────────────────
VM_NAME="${VM_NAME:-musicfs}"
IMAGE="${IMAGE:-images:debian/12}"
MUSIC_SOURCE="${MUSIC_SOURCE:-$HOME/Music}"
MUSIC_MOUNT="${MUSIC_MOUNT:-/music}"
LISTEN_PORT="${LISTEN_PORT:-50051}"
RUST_LOG="${RUST_LOG:-info}"
detect_static_ip() {
  if [[ -n "${VM_IP:-}" ]]; then echo "$VM_IP"; return; fi
  local bridge_cidr
  bridge_cidr="$(incus network get incusbr0 ipv4.address 2>/dev/null || true)"
  if [[ -z "$bridge_cidr" ]]; then echo ""; return; fi
  local gateway="${bridge_cidr%%/*}"
  echo "${gateway%.*}.145"
}

SERVER_DIR="/opt/musicfs"
LOG_DIR="/var/log/musicfs"
BIN_NAME="musicfs-server"
UNIT_NAME="musicfs-server.service"

# ─────────────────────────────── helpers ───────────────────────────────
log()  { printf '\033[1;34m[vm]\033[0m %s\n' "$*" >&2; }
warn() { printf '\033[1;33m[vm warn]\033[0m %s\n' "$*" >&2; }
die()  { printf '\033[1;31m[vm error]\033[0m %s\n' "$*" >&2; exit 1; }

require() { command -v "$1" >/dev/null 2>&1 || die "missing required command: $1 (run inside 'devenv shell')"; }

vm_exists()  { incus list "$VM_NAME" -f csv -c n 2>/dev/null | grep -qx "$VM_NAME"; }
vm_running() { incus list "$VM_NAME" -f csv -c n,s 2>/dev/null | grep -q "$VM_NAME,.*RUNNING"; }

device_exists() { incus config device show "$VM_NAME" 2>/dev/null | grep -q "^$1:"; }

# incus -c 4 emits "<ip> (<iface>)"; keep only the address.
vm_ip() {
  local ip
  ip="$(incus list "$VM_NAME" -f csv -c 4 2>/dev/null | head -1 | awk '{print $1}')"
  if [[ -n "$ip" ]]; then echo "$ip"; return; fi
  detect_static_ip
}

# ──────────────────────────── build + bundle ───────────────────────────
# Emits the host path to the prepared bundle dir on stdout.
build_bundle() {
  require cargo
  require readelf
  log "building $BIN_NAME (release)..."
  cargo build --release --bin "$BIN_NAME"

  local bin="target/release/$BIN_NAME"
  local interp
  # readelf prints "      [Requesting program interpreter: /path]" — capture the path.
  interp="$(readelf -l "$bin" | sed -n 's/.*interpreter: \(.*\)\]$/\1/p')"
  [ -n "$interp" ] || die "could not read ELF interpreter from $bin"
  log "binary interpreter: $interp"

  local bundle="target/vm-bundle"
  rm -rf "$bundle"; mkdir -p "$bundle/lib"
  cp "$bin" "$bundle/server"

  case "$interp" in
    /nix/store/*)
      log "nix-built binary detected; bundling glibc + libgcc_s for the VM..."
      require patchelf
      local libc libm libgcc
      libc="$(ldd "$bin"  | sed -n 's#.*libc.so.6 => \([^ ]*\).*#\1#p')"
      libm="$(ldd "$bin"  | sed -n 's#.*libm.so.6 => \([^ ]*\).*#\1#p')"
      libgcc="$(ldd "$bin"| sed -n 's#.*libgcc_s.so.1 => \([^ ]*\).*#\1#p')"
      [ -n "$libc" ]   || die "could not resolve libc.so.6"
      [ -n "$libm" ]   || die "could not resolve libm.so.6"
      [ -n "$libgcc" ] || die "could not resolve libgcc_s.so.1"
      cp "$interp" "$bundle/lib/ld-linux-x86-64.so.2"
      cp "$libc"   "$bundle/lib/libc.so.6"
      cp "$libm"   "$bundle/lib/libm.so.6"
      cp "$libgcc" "$bundle/lib/libgcc_s.so.1"
      patchelf --set-interpreter "$SERVER_DIR/lib/ld-linux-x86-64.so.2" "$bundle/server"
      patchelf --set-rpath       "$SERVER_DIR/lib"                      "$bundle/server"
      ;;
    /*)
      warn "standard interpreter detected; shipping binary as-is."
      warn "  (this only works if the VM's glibc >= the build host's glibc)."
      ;;
    *)
      die "unexpected interpreter '$interp'; refusing to ship."
      ;;
  esac
  chmod +x "$bundle/server"
  echo "$bundle"
}

# ───────────────────────────── VM lifecycle ────────────────────────────
create_vm() {
  require incus
  if vm_exists; then log "VM '$VM_NAME' already exists."; return 0; fi

  [ -d "$MUSIC_SOURCE" ] || die "MUSIC_SOURCE '$MUSIC_SOURCE' is not a directory"
  log "creating VM '$VM_NAME' from $IMAGE ..."
  incus init "$IMAGE" "$VM_NAME" --vm

  local static_ip
  static_ip="$(detect_static_ip)"
  if [[ -n "$static_ip" ]]; then
    log "reserving static IP: $static_ip"
    incus config device add "$VM_NAME" eth0 nic \
      network=incusbr0 name=eth0 ipv4.address="$static_ip"
  fi

  if ! device_exists music; then
    local ro_flag="readonly=true"
    local mode="read-only"
    if [[ "$READONLY" == "0" ]]; then
      ro_flag="readonly=false"
      mode="read-write"
    fi
    log "sharing music: $MUSIC_SOURCE -> $MUSIC_MOUNT ($mode, virtiofs)"
    incus config device add "$VM_NAME" music disk \
      source="$MUSIC_SOURCE" path="$MUSIC_MOUNT" "$ro_flag"
  fi

  # No proxy: Incus VM proxies need NAT mode + a *static* instance IP (DHCP is
  # rejected). Server binds 0.0.0.0 and the VM is on incusbr0 -> reach it at
  # its bridge IP (shown by `status`).
}

start_vm() {
  if vm_running; then return 0; fi
  log "starting VM '$VM_NAME'..."
  incus start "$VM_NAME"
}

wait_for_vm() {
  log "waiting for VM agent to accept commands..."
  local i
  for ((i = 0; i < 90; i++)); do
    if incus exec "$VM_NAME" -- true 2>/dev/null; then return 0; fi
    sleep 2
  done
  die "VM '$VM_NAME' did not become reachable (incus-agent not up in time)"
}

# Push the bundle + install a systemd unit, then (re)start the service.
deploy() {
  local bundle; bundle="$(build_bundle)"
  log "deploying bundle to $VM_NAME:$SERVER_DIR ..."
  incus exec "$VM_NAME" -- systemctl stop "$UNIT_NAME" 2>/dev/null || true
  incus exec "$VM_NAME" -- mkdir -p "$SERVER_DIR/lib" "$LOG_DIR"
  incus file push "$bundle/server" "$VM_NAME$SERVER_DIR/server" --mode=0755
  # Ship the bundled libs one by one (robust across incus file-push versions).
  if [ -n "$(ls -A "$bundle/lib" 2>/dev/null)" ]; then
    local f
    for f in "$bundle/lib"/*; do
      incus file push "$f" "$VM_NAME$SERVER_DIR/lib/"
    done
  fi

  log "installing systemd unit ($UNIT_NAME)..."
  install_unit

  log "enabling + (re)starting $UNIT_NAME ..."
  incus exec "$VM_NAME" -- systemctl daemon-reload
  incus exec "$VM_NAME" -- systemctl enable "$UNIT_NAME" >/dev/null 2>&1 || true
  incus exec "$VM_NAME" -- systemctl restart "$UNIT_NAME"

  sleep 1
  if incus exec "$VM_NAME" -- systemctl is-active --quiet "$UNIT_NAME"; then
    log "musicfs-server is running."
  else
    warn "service did not reach active state quickly; check: scripts/vm.sh logs"
  fi
}

install_unit() {
  local unit
  unit=$(cat <<EOF
[Unit]
Description=musicfs gRPC server
After=network-online.target
Wants=network-online.target

[Service]
Type=simple
WorkingDirectory=$SERVER_DIR
ExecStart=$SERVER_DIR/server --source $MUSIC_MOUNT --listen 0.0.0.0:$LISTEN_PORT --log-dir $LOG_DIR
Environment=RUST_LOG=$RUST_LOG
Restart=on-failure
RestartSec=2

[Install]
WantedBy=multi-user.target
EOF
)
  printf '%s\n' "$unit" | incus exec "$VM_NAME" -- tee "/etc/systemd/system/$UNIT_NAME" >/dev/null
}

# ────────────────────────────── subcommands ────────────────────────────
cmd_up() {
  require incus
  create_vm
  start_vm
  wait_for_vm
  deploy
  print_status
}

cmd_redeploy() {
  require incus
  vm_exists     || die "VM '$VM_NAME' does not exist. Run 'up' first."
  vm_running    || die "VM '$VM_NAME' is not running. Run 'up' first."
  wait_for_vm
  deploy
  print_status
}

cmd_restart() {
  require incus
  vm_running || die "VM '$VM_NAME' is not running."
  incus exec "$VM_NAME" -- systemctl restart "$UNIT_NAME"
  log "restarted."
}

cmd_logs()    { require incus; vm_running || die "VM not running."; incus exec "$VM_NAME" -- journalctl -u "$UNIT_NAME" -f; }

cmd_shell()   { require incus; vm_running || die "VM not running."; exec incus exec "$VM_NAME" -- bash; }

cmd_down()    { require incus; vm_running || { log "already stopped."; return; }; incus stop "$VM_NAME"; log "stopped."; }

cmd_destroy() {
  require incus
  vm_exists || { log "nothing to destroy."; return; }
  incus delete -f "$VM_NAME"
  log "VM '$VM_NAME' deleted."
}

print_status() {
  local ip; ip="$(vm_ip)"
  local state="missing"; vm_exists  && state="$(incus list "$VM_NAME" -f csv -c s 2>/dev/null | head -1)"
  vm_running && state="RUNNING"
  echo
  printf '\033[1;36m== musicfs-server VM ==\033[0m\n'
  printf '  name:    %s\n' "$VM_NAME"
  printf '  state:   %s\n' "$state"
  printf '  ipv4:    %s\n' "${ip:-<none>}"
  printf '  image:   %s\n' "$IMAGE"
  printf '  listen:  0.0.0.0:%s (reach via VM bridge IP above)\n' "$LISTEN_PORT"
  local ro_actual="read-only"
  if vm_exists; then
    local ro_val
    ro_val="$(incus config device get "$VM_NAME" music readonly 2>/dev/null || true)"
    [[ "$ro_val" == "false" ]] && ro_actual="read-write"
  else
    [[ "$READONLY" == "0" ]] && ro_actual="read-write"
  fi
  printf '  music:   %s -> %s (%s)\n' "$MUSIC_SOURCE" "$MUSIC_MOUNT" "$ro_actual"
  printf '  server:  %s/server\n' "$SERVER_DIR"
  if [ -n "$ip" ]; then
    printf '\n  test:    grpcurl -plaintext %s:%s list\n\n' "$ip" "$LISTEN_PORT"
  else
    printf '\n  test:    grpcurl -plaintext <vm-ip>:%s list\n\n' "$LISTEN_PORT"
  fi
}

cmd_status() { require incus; print_status; incus exec "$VM_NAME" -- systemctl status "$UNIT_NAME" --no-pager 2>/dev/null || true; }

# ───────────────────────────────── main ────────────────────────────────
usage() {
  sed -n '3,/^$/p' "$0" | sed 's/^# \?//'
  exit 1
}

main() {
  local cmd="${1:-up}"
  shift || true
  while (( $# )); do
    case "$1" in
      --writable) [[ -z "${READONLY:-}" ]] && READONLY=0 ;;
      --readonly) [[ -z "${READONLY:-}" ]] && READONLY=1 ;;
      *) die "unknown flag '$1'. Try: $0 --help" ;;
    esac
    shift
  done
  READONLY="${READONLY:-1}"
  case "$cmd" in
    up)        cmd_up ;;
    redeploy)  cmd_redeploy ;;
    restart)   cmd_restart ;;
    logs)      cmd_logs ;;
    status)    cmd_status ;;
    shell)     cmd_shell ;;
    down)      cmd_down ;;
    destroy)   cmd_destroy ;;
    -h|--help|help) usage ;;
    *) die "unknown command '$cmd'. Try: $0 --help" ;;
  esac
}

main "$@"