#!/usr/bin/env bash
#
# Reaper's Sky - server mod updater.
#
# Brings the server's mods/ folder in line with a mods.json manifest:
#   1. gracefully stops the running server (tmux session "mc")
#   2. prunes jars that are not in the manifest, downloads + sha1-verifies
#      the ones that are missing
#   3. boots the server again and waits until it reports "Done"
#
# Usage (on the server):
#     bash update.sh [MANIFEST] [--no-start]
#
#   MANIFEST    path to mods.json  (default: /tmp/reaper-sky-mods.json)
#   --no-start  sync only, leave the server stopped
#
# You normally do NOT run this by hand. From your PC run:
#     python3 server/build_mods.py --push
# which regenerates mods.json from the client instance, uploads it to
# /tmp/reaper-sky-mods.json on the server and pipes this script over SSH.
set -euo pipefail

SERVER_DIR="${DIR:-$HOME/reaper-sky-server}"
SESSION="mc"
MANIFEST="/tmp/reaper-sky-mods.json"
START=true

for arg in "$@"; do
  case "$arg" in
    --no-start) START=false ;;
    -h|--help) sed -n '2,20p' "$0"; exit 0 ;;
    *) MANIFEST="$arg" ;;
  esac
done

[ -f "$MANIFEST" ] || { echo "[update] ERROR: manifest not found: $MANIFEST" >&2; exit 1; }
[ -d "$SERVER_DIR" ] || { echo "[update] ERROR: server dir not found: $SERVER_DIR" >&2; exit 1; }

log() { printf '\033[1;34m[update]\033[0m %s\n' "$*"; }
die() { printf '\033[1;31m[update] ERROR:\033[0m %s\n' "$*" >&2; exit 1; }

# "running" = the tmux session's pane is executing java right now.
running() {
  tmux has-session -t "$SESSION" 2>/dev/null || return 1
  [ "$(tmux list-panes -t "$SESSION" -F '#{pane_current_command}' 2>/dev/null)" = "java" ]
}

# --- 1. stop -------------------------------------------------------------------
if running; then
  log "Stopping server (session '$SESSION')..."
  tmux send-keys -t "$SESSION" "stop" C-m
  for _ in $(seq 1 90); do
    running || break
    sleep 1
  done
  running && die "Server still running after 90s -- refusing to continue."
  log "Server stopped."
else
  log "Server not running -- skipping stop."
fi

# --- 2. sync mods ----------------------------------------------------------------
log "Syncing mods against $(basename "$MANIFEST")..."
mkdir -p "$SERVER_DIR/mods"
cd "$SERVER_DIR/mods"
python3 - "$MANIFEST" <<'PY'
import hashlib, json, os, subprocess, sys

manifest = json.load(open(sys.argv[1]))
keep = set()
for m in manifest["mods"]:
    fname, url, want = m["file"], m["url"], m["sha1"]
    keep.add(fname)
    if os.path.exists(fname):
        h = hashlib.sha1()
        with open(fname, "rb") as fh:
            for b in iter(lambda: fh.read(65536), b""):
                h.update(b)
        if h.hexdigest() == want:
            continue  # already present & correct
        print(f"  ~ {fname} (hash mismatch -- re-downloading)")
    else:
        print(f"  + {fname}")
    if not url:
        raise SystemExit(f"no download URL for {fname}")
    tmp = fname + ".part"
    subprocess.run(["curl", "-fsSL", "--retry", "3", "-o", tmp, url], check=True)
    h = hashlib.sha1()
    with open(tmp, "rb") as fh:
        for b in iter(lambda: fh.read(65536), b""):
            h.update(b)
    if h.hexdigest() != want:
        os.unlink(tmp)
        raise SystemExit(f"sha1 mismatch for {fname}")
    os.rename(tmp, fname)

for f in sorted(os.listdir(".")):
    if f.endswith(".jar") and f not in keep:
        os.unlink(f)
        print(f"  - {f} (stale)")

on_disk = len([f for f in os.listdir(".") if f.endswith(".jar")])
print(f"[update] {len(keep)} mods in manifest, {on_disk} jars on disk")
PY
log "Mods synced."

# --- 3. start + wait for boot ------------------------------------------------------
start_server() {
  if ! tmux has-session -t "$SESSION" 2>/dev/null; then
    tmux new-session -d -s "$SESSION" -c "$SERVER_DIR"
  fi
  tmux send-keys -t "$SESSION" "cd '$SERVER_DIR' && ./run.sh" C-m
}

if [ "$START" = false ]; then
  log "--no-start given: leaving the server stopped."
  exit 0
fi

LOG="$SERVER_DIR/logs/latest.log"
OFFSET=$(wc -l < "$LOG" 2>/dev/null || echo 0)   # ignore pre-boot log content
log "Starting server (tmux session '$SESSION')..."
start_server

log "Waiting for boot (up to 4 min)..."
for i in $(seq 1 240); do
  cur=$(wc -l < "$LOG" 2>/dev/null || echo 0)
  [ "$cur" -lt "$OFFSET" ] && OFFSET=0            # log was rotated/truncated
  if [ "$cur" -gt "$OFFSET" ] && tail -n +"$((OFFSET + 1))" "$LOG" | grep -q "Done ("; then
    log "Server is UP after ~${i}s."
    log "Console:  tmux attach -t $SESSION    (detach: Ctrl-b d)"
    exit 0
  fi
  # pane exited or left java => boot failed / crashed
  if ! tmux has-session -t "$SESSION" 2>/dev/null || ! running; then
    sleep 5  # give the shell a moment to print any error
    die "Server process exited during boot -- check: tail -50 $LOG"
  fi
  sleep 1
done

die "Timed out waiting for 'Done' after 4 min -- check: tail -50 $LOG"