#!/usr/bin/env bash
# Lifecycle for the Rust redirector host.
#
#   redirector.sh start | stop | status | verify
#
# Mirrors sidecar.sh: refuses to start with an orphan present or the port busy,
# and stop PROVES the process is gone and the port free rather than assuming a
# signal worked.
#
# Additionally REFUSES TO START unless the binary's stamped commit equals HEAD
# and the migration crates are clean — evidence from an unidentifiable binary is
# not evidence.
set -uo pipefail

HERE="$(cd "$(dirname "$(readlink -f "$0")")" && pwd)"
ROOT="$(cd "$HERE/.." && pwd)"
RUNDIR="${OPENFUT_REDIRECTOR_RUNDIR:-${TMPDIR:-/tmp}/openfut-redirector}"
PIDFILE="$RUNDIR/redirector.pid"
PORTFILE="$RUNDIR/redirector.port"
# Commit the RUNNING process was started from. `verify` alone inspects the
# on-disk binary, which a rebuild (even `cargo test`, which re-runs build.rs
# when the branch ref moves) can silently advance past the live process.
STAMPFILE="$RUNDIR/redirector.commit"
LOGFILE="${OPENFUT_REDIRECTOR_LOG:-$RUNDIR/redirector.log}"
# Which artifact is under test must never be ambiguous. Preferring debug and
# falling back to release meant `cargo build --release` could produce a fresh
# binary while this kept launching a stale debug one — the guard then compared
# the WRONG artifact against HEAD and refused with a message naming a commit
# nobody was trying to run. Both present and disagreeing is an error, not a
# preference. Set OPENFUT_REDIRECTOR_BIN to choose deliberately.
DEBUG_BIN="$ROOT/target/debug/openfut-redirector-host"
RELEASE_BIN="$ROOT/target/release/openfut-redirector-host"
BIN_ERR=""
if [[ -n "${OPENFUT_REDIRECTOR_BIN:-}" ]]; then
  BIN="$OPENFUT_REDIRECTOR_BIN"
  [[ -x "$BIN" ]] || { echo "redirector: OPENFUT_REDIRECTOR_BIN is not executable: $BIN" >&2; exit 1; }
elif [[ -x "$DEBUG_BIN" && -x "$RELEASE_BIN" ]]; then
  d="$("$DEBUG_BIN" --identity 2>&1 | sed -nE 's/.*commit=([0-9a-f]+).*/\1/p' | head -1)"
  r="$("$RELEASE_BIN" --identity 2>&1 | sed -nE 's/.*commit=([0-9a-f]+).*/\1/p' | head -1)"
  if [[ "$d" != "$r" ]]; then
    # Recorded, NOT fatal here: `stop` and `status` must keep working no matter
    # what state the build tree is in. Rolling back can never be blocked by a
    # question about which artifact would have been started.
    BIN_ERR="REFUSING — two binaries exist and disagree.
  debug   $DEBUG_BIN  commit=$d
  release $RELEASE_BIN  commit=$r
  Rebuild both, delete one, or set OPENFUT_REDIRECTOR_BIN."
  fi
  BIN="$RELEASE_BIN"
elif [[ -x "$DEBUG_BIN" ]]; then
  BIN="$DEBUG_BIN"
else
  BIN="$RELEASE_BIN"
fi

die() { echo "redirector: $*" >&2; exit 1; }
pid_alive() { kill -0 "$1" 2>/dev/null; }
port_listening() { ss -ltn 2>/dev/null | grep -qE "[:.]${1}[[:space:]]"; }

# Match the resolved executable, not the command line: `pgrep -f` matches any
# shell whose arguments merely mention the name.
list_procs() {
  local self=$$ pid exe
  for d in /proc/[0-9]*; do
    pid="${d#/proc/}"; [[ "$pid" == "$self" ]] && continue
    # readlink, NOT readlink -f: once the binary is rebuilt the link reads
    # "<path> (deleted)", and -f resolves that to something that matches
    # nothing. The orphan check would then be blind to exactly the long-lived
    # processes it exists to find — verified: two orphans (a stale-cert
    # redirector and a Blaze sidecar) were both invisible to this until the
    # suffix was stripped.
    exe="$(readlink "$d/exe" 2>/dev/null)" || continue
    exe="${exe% (deleted)}"
    [[ "${exe##*/}" == "openfut-redirector-host" ]] && echo "$pid"
  done
  return 0
}

# Only the commands that actually run a binary care which one it is.
need_bin() { [[ -z "$BIN_ERR" ]] || die "$BIN_ERR"; }

# The binary prints `commit=<sha>` in its banner; ask it rather than guessing.
stamped_commit() { "$BIN" --identity 2>&1 | sed -nE 's/.*commit=([0-9a-f]+).*/\1/p' | head -1; }

cmd_verify() {
  need_bin
  local c; c="$(stamped_commit)"
  [[ -n "$c" ]] || die "could not read the binary's commit stamp"
  "$ROOT/scripts/verify-build-identity.sh" "$c"
}

cmd_start() {
  need_bin
  [[ -x "$BIN" ]] || die "not built: cargo build -p openfut-redirector-host"
  : "${OPENFUT_REDIRECTOR_HOST_PORT:?set OPENFUT_REDIRECTOR_HOST_PORT (no default: runs beside Python)}"
  local strays; strays="$(list_procs)"
  [[ -z "$strays" ]] || die "orphan redirector process(es): $strays"
  port_listening "$OPENFUT_REDIRECTOR_HOST_PORT" && die "port $OPENFUT_REDIRECTOR_HOST_PORT in use"

  cmd_verify || die "build identity check failed — refusing to start"

  mkdir -p "$RUNDIR"; echo "$OPENFUT_REDIRECTOR_HOST_PORT" > "$PORTFILE"
  stamped_commit > "$STAMPFILE"
  "$BIN" >"$LOGFILE" 2>&1 &
  local pid=$!; echo "$pid" > "$PIDFILE"
  local w=0
  while (( w < 100 )); do
    pid_alive "$pid" || { echo "died during startup:" >&2; tail -20 "$LOGFILE" >&2; rm -f "$PIDFILE"; return 1; }
    if port_listening "$OPENFUT_REDIRECTOR_HOST_PORT"; then
      echo "redirector started: pid $pid, port $OPENFUT_REDIRECTOR_HOST_PORT"
      grep -E 'SELF-TEST|openfut-redirector-host v' "$LOGFILE" | sed 's/^/  /'
      return 0
    fi
    sleep 0.1; w=$((w+1))
  done
  echo "did not listen within 10s:" >&2; tail -20 "$LOGFILE" >&2
  kill "$pid" 2>/dev/null; rm -f "$PIDFILE"; return 1
}

cmd_stop() {
  local rc=0 pid="" port=""
  [[ -f "$PIDFILE"  ]] && pid="$(cat "$PIDFILE")"
  [[ -f "$PORTFILE" ]] && port="$(cat "$PORTFILE")"
  if [[ -n "$pid" ]] && pid_alive "$pid"; then
    kill "$pid" 2>/dev/null
    local w=0; while pid_alive "$pid" && (( w < 50 )); do sleep 0.1; w=$((w+1)); done
    pid_alive "$pid" && kill -9 "$pid" 2>/dev/null
    sleep 0.2
  fi
  [[ -n "$pid"  ]] && pid_alive "$pid" && { echo "FAILED to stop $pid" >&2; rc=1; }
  [[ -n "$port" ]] && port_listening "$port" && { echo "FAILED: port $port still listening" >&2; rc=1; }
  local strays; strays="$(list_procs)"
  [[ -n "$strays" ]] && { echo "FAILED: still running: $strays" >&2; rc=1; }
  rm -f "$PIDFILE" "$PORTFILE"
  [[ $rc -eq 0 ]] && echo "redirector stopped and verified gone${pid:+ (pid $pid)}"
  return $rc
}

cmd_status() {
  if [[ -f "$PIDFILE" ]] && pid_alive "$(cat "$PIDFILE")"; then
    echo "running: pid $(cat "$PIDFILE"), port $(cat "$PORTFILE" 2>/dev/null || echo '?')"
  else
    echo "not running"
  fi
  local strays; strays="$(list_procs)"
  [[ -n "$strays" ]] && echo "redirector processes: $strays"
  return 0
}

cmd_verify_running() {
  # The stamp outlives the process it describes. Without this check the command
  # happily reports on a corpse — either "OK" or a REFUSAL naming a commit,
  # both implying something is running when nothing is.
  local pid=""
  [[ -f "$PIDFILE" ]] && pid="$(cat "$PIDFILE" 2>/dev/null)"
  if [[ -z "$pid" ]] || ! pid_alive "$pid"; then
    echo "REFUSING: nothing is running — the stamp describes a process that has exited." >&2
    return 1
  fi
  [[ -f "$STAMPFILE" ]] || die "no running-process stamp — was it started by this script?"
  local running head
  running="$(cat "$STAMPFILE")"; head="$(git -C "$ROOT" rev-parse --short=7 HEAD 2>/dev/null)"
  if [[ "$running" != "$head" ]]; then
    echo "REFUSING: the RUNNING process was started from $running but HEAD is $head" >&2
    echo "  Restart before treating this run as evidence." >&2
    return 1
  fi
  echo "running-process identity OK: started from $running == HEAD"
}

case "${1:-}" in
  start)  cmd_start ;;
  stop)   cmd_stop ;;
  status) cmd_status ;;
  verify) cmd_verify ;;
  verify-running) cmd_verify_running ;;
  *) sed -n '2,6p' "$0" | sed 's/^# \?//'; exit 2 ;;
esac