#!/usr/bin/env bash
# Fail a client job before it starts when the runner cannot hold it.
#
# Every client job here compiles the frontend from cold: `ng build
# --configuration production` peaks at 3.8 GB resident on a 4 vCPU box
# (measured with no .angular/cache present, which is what a fresh runner
# has), and the Cypress and Lighthouse jobs add a dev server and a browser on
# top of that. On a 4 GB runner the kernel OOM killer takes the build part way
# through, which surfaces as `exitcode '137'` at `ng build`, or as Karma
# disconnecting mid-suite ("no message in 30000 ms"). Both read as a flaky
# test rather than as an undersized box, and both cost a whole CI slot.
#
# 8 GB is the minimum supported runner size: it leaves roughly 2x headroom
# over that peak. This check runs before the installs, so an undersized runner
# fails in seconds with the numbers in the log.
#
# The floor is 7 GB rather than 8192 MB because an 8 GB box does not report 8
# GB: the fleet's report 7751 MB total, the rest going to firmware and the
# kernel. A 4 GB box reports under 4000 MB, so 7 GB separates the two sizes
# with room for a box that reserves a little more than ours do.
#
# What this does not catch is oversubscription: two client jobs landing on one
# box. A box that passes the floor can still OOM a build when another job is
# resident, and MemAvailable at start is the only sign of it - that is reported
# as a warning, not a failure, because a busy box is transient where a small
# box is not. Keep one client job per runner.
#
# Usage: check-runner-memory.sh [min_total_mb]
#   or:  MIN_TOTAL_MB=4096 check-runner-memory.sh
set -euo pipefail

MIN_TOTAL_MB="${1:-${MIN_TOTAL_MB:-7000}}"

# A typo here (8GB, a stray flag, an empty variable) would otherwise reach the
# integer test under `set -e` and abort with "integer expression expected".
case "$MIN_TOTAL_MB" in
  ''|*[!0-9]*)
    echo "usage: check-runner-memory.sh [min_total_mb] - got '$MIN_TOTAL_MB'" >&2
    exit 2
    ;;
esac

meminfo_field() {
  awk -v key="$1:" '$1 == key { print $2 }' /proc/meminfo
}

total_kb=$(meminfo_field MemTotal || true)
avail_kb=$(meminfo_field MemAvailable || true)
cpus=$(nproc 2>/dev/null || echo '?')

if [ -z "$total_kb" ]; then
  echo "runner memory: /proc/meminfo has no MemTotal - cannot measure, continuing"
  exit 0
fi

total_mb=$(( total_kb / 1024 ))
avail_mb=$(( ${avail_kb:-0} / 1024 ))
# Older kernels have no MemAvailable; report that rather than 0, which would
# read as a permanently exhausted runner.
if [ -n "$avail_kb" ]; then
  avail_display="${avail_mb} MB available"
else
  avail_display="available unknown"
fi

# A container usually sees the host's RAM, but may carry its own lower ceiling
# (cgroup v2 memory.max, v1 memory.limit_in_bytes). That ceiling is what the
# build is actually killed against, so it counts as the runner's size.
limit_mb=""
for f in /sys/fs/cgroup/memory.max /sys/fs/cgroup/memory/memory.limit_in_bytes; do
  [ -r "$f" ] || continue
  v=$(cat "$f")
  case "$v" in
    ''|max|*[!0-9]*) continue ;;
  esac
  # An unlimited v1 cgroup reports a sentinel near 2^63 bytes.
  [ "$v" -lt 100000000000 ] || continue
  candidate=$(( v / 1024 / 1024 ))
  if [ -z "$limit_mb" ] || [ "$candidate" -lt "$limit_mb" ]; then
    limit_mb="$candidate"
  fi
done

echo "runner memory: ${total_mb} MB total, ${avail_display}, ${cpus} vCPU${limit_mb:+, ${limit_mb} MB cgroup limit}"

effective_mb=$total_mb
if [ -n "$limit_mb" ] && [ "$limit_mb" -lt "$effective_mb" ]; then
  effective_mb=$limit_mb
fi

if [ "$effective_mb" -lt "$MIN_TOTAL_MB" ]; then
  echo "::error::runner has ${effective_mb} MB of memory, a client job needs at least ${MIN_TOTAL_MB} MB (8 GB is the supported minimum; a cold production build alone peaks at about 3.8 GB, and the Cypress and Lighthouse jobs add a dev server and a browser to that)."
  exit 1
fi

# Not a gate - a second job landing on the same box shows up here first.
if [ -n "$avail_kb" ] && [ "$avail_mb" -lt 5000 ]; then
  echo "::warning::only ${avail_mb} MB is available on this runner; another job may be running on the same box"
fi