#!/usr/bin/env bash

set -euo pipefail

usage() {
  cat <<'EOF'
Usage: profile-daily-loop.sh --pid PID [--seconds N] [--output-dir DIR] [--flamegraph-dir DIR]

Attaches perf to an existing FIDC runner process. It never starts, stops, or
restarts a service. The allocation report is a CPU-sample proxy for allocator
pressure; it is not an allocation count or byte-accurate heap profile.
EOF
}

pid=""
seconds=15
output_dir=""
flamegraph_dir=""

while [[ $# -gt 0 ]]; do
  case "$1" in
    --pid)
      pid="${2:-}"
      shift 2
      ;;
    --seconds)
      seconds="${2:-}"
      shift 2
      ;;
    --output-dir)
      output_dir="${2:-}"
      shift 2
      ;;
    --flamegraph-dir)
      flamegraph_dir="${2:-}"
      shift 2
      ;;
    -h|--help)
      usage
      exit 0
      ;;
    *)
      echo "unknown argument: $1" >&2
      usage >&2
      exit 2
      ;;
  esac
done

if [[ "${EUID}" -ne 0 ]]; then
  echo "run as root so perf can attach to the runner" >&2
  exit 2
fi
if [[ ! "${pid}" =~ ^[1-9][0-9]*$ ]]; then
  echo "--pid must be a positive process id" >&2
  exit 2
fi
if [[ ! "${seconds}" =~ ^[1-9][0-9]*$ ]]; then
  echo "--seconds must be a positive integer" >&2
  exit 2
fi
if ! kill -0 "${pid}" 2>/dev/null; then
  echo "process is not running: ${pid}" >&2
  exit 1
fi
if ! command -v perf >/dev/null 2>&1; then
  echo "perf is required" >&2
  exit 2
fi

if [[ -z "${output_dir}" ]]; then
  output_dir="$(pwd)/profile-$(date +%Y%m%d-%H%M%S)-${pid}"
fi
mkdir -p "${output_dir}"

perf record --quiet --call-graph dwarf -g -e cycles:P -p "${pid}" \
  -o "${output_dir}/perf.data" -- sleep "${seconds}"
perf report --stdio --no-children --sort symbol --percent-limit 0.5 \
  -i "${output_dir}/perf.data" > "${output_dir}/perf-report.txt"

grep -E 'malloc|calloc|realloc|free|cfree|drop_glue' "${output_dir}/perf-report.txt" \
  > "${output_dir}/allocation-samples.txt" || true

if [[ -n "${flamegraph_dir}" ]]; then
  if [[ ! -x "${flamegraph_dir}/stackcollapse-perf.pl" || ! -x "${flamegraph_dir}/flamegraph.pl" ]]; then
    echo "flamegraph tools not found under ${flamegraph_dir}" >&2
    exit 2
  fi
  perf script -i "${output_dir}/perf.data" > "${output_dir}/perf.script"
  "${flamegraph_dir}/stackcollapse-perf.pl" "${output_dir}/perf.script" \
    > "${output_dir}/daily-loop.folded"
  "${flamegraph_dir}/flamegraph.pl" \
    --title="FIDC engine daily loop CPU samples" \
    "${output_dir}/daily-loop.folded" > "${output_dir}/daily-loop-flamegraph.svg"
fi

printf '%s\n' "profile complete: ${output_dir}"