#!/usr/bin/env bash
# detect-memory.sh — Detect container memory and calculate tuning parameters.
# Must be sourced (not executed) so variables are available to the caller.

# --- Memory detection (cgroups v2 → v1 → /proc/meminfo → fallback) ---
CONTAINER_MEMORY_BYTES=""

# cgroups v2
if [ -f /sys/fs/cgroup/memory.max ]; then
  val=$(cat /sys/fs/cgroup/memory.max 2>/dev/null)
  if [ "$val" != "max" ] && [ -n "$val" ]; then
    CONTAINER_MEMORY_BYTES=$val
  fi
fi

# cgroups v1
if [ -z "$CONTAINER_MEMORY_BYTES" ] && [ -f /sys/fs/cgroup/memory/memory.limit_in_bytes ]; then
  val=$(cat /sys/fs/cgroup/memory/memory.limit_in_bytes 2>/dev/null)
  # Values near page-aligned max (like 9223372036854771712) mean "no limit"
  if [ -n "$val" ] && [ "$val" -lt 8589934592000 ] 2>/dev/null; then
    CONTAINER_MEMORY_BYTES=$val
  fi
fi

# /proc/meminfo (host memory — used when no cgroup limit is set)
if [ -z "$CONTAINER_MEMORY_BYTES" ] && [ -f /proc/meminfo ]; then
  mem_kb=$(awk '/^MemTotal:/ {print $2}' /proc/meminfo)
  if [ -n "$mem_kb" ]; then
    CONTAINER_MEMORY_BYTES=$((mem_kb * 1024))
  fi
fi

# Fallback
if [ -z "$CONTAINER_MEMORY_BYTES" ]; then
  CONTAINER_MEMORY_BYTES=$((512 * 1024 * 1024))
fi

CONTAINER_MEMORY_MB=$((CONTAINER_MEMORY_BYTES / 1024 / 1024))

# --- Budget calculation ---
OS_RESERVE_MB=50
FIXED_PROCESS_MB=50
DEV_OVERHEAD_MB=0
if [ "$environment" = "DEV" ]; then
  DEV_OVERHEAD_MB=125
fi

AVAILABLE_MB=$((CONTAINER_MEMORY_MB - OS_RESERVE_MB - FIXED_PROCESS_MB - DEV_OVERHEAD_MB))
if [ "$AVAILABLE_MB" -lt 60 ]; then
  AVAILABLE_MB=60
fi

PHP_BUDGET_MB=$((AVAILABLE_MB * 80 / 100))
APACHE_BUDGET_MB=$((AVAILABLE_MB * 20 / 100))

# --- PHP-FPM parameters ---
PHP_WORKER_ESTIMATE_MB=${PHP_WORKER_ESTIMATE_MB:-60}

calc_max_children=$((PHP_BUDGET_MB / PHP_WORKER_ESTIMATE_MB))
# Floor at 2, cap at 50
if [ "$calc_max_children" -lt 2 ]; then
  calc_max_children=2
fi
if [ "$calc_max_children" -gt 50 ]; then
  calc_max_children=50
fi

PHP_FPM_PM=${FPM_PM:-ondemand}
PHP_FPM_MAX_CHILDREN=${FPM_MAX_CHILDREN:-$calc_max_children}
PHP_FPM_PROCESS_IDLE_TIMEOUT=${FPM_PROCESS_IDLE_TIMEOUT:-10s}
PHP_FPM_MAX_REQUESTS=${FPM_MAX_REQUESTS:-500}

# Dynamic mode fallbacks (used if user overrides FPM_PM=dynamic)
PHP_FPM_START_SERVERS=${FPM_START_SERVERS:-2}
PHP_FPM_MIN_SPARE=${FPM_MIN_SPARE_SERVERS:-1}
PHP_FPM_MAX_SPARE=${FPM_MAX_SPARE_SERVERS:-3}

# --- Apache MPM parameters ---
# ServerLimit: roughly 1 process per ~25 workers, floor 2, cap 16
calc_server_limit=$((APACHE_BUDGET_MB / 30))
if [ "$calc_server_limit" -lt 2 ]; then
  calc_server_limit=2
fi
if [ "$calc_server_limit" -gt 16 ]; then
  calc_server_limit=16
fi

# MaxRequestWorkers: ServerLimit * ThreadsPerChild (25)
calc_max_request_workers=$((calc_server_limit * 25))
if [ "$calc_max_request_workers" -gt 400 ]; then
  calc_max_request_workers=400
fi

# StartServers: 1 for ≤1GB, 2 for larger
calc_start_servers=1
if [ "$CONTAINER_MEMORY_MB" -gt 1024 ]; then
  calc_start_servers=2
fi

APACHE_START_SERVERS=${APACHE_START_SERVERS:-$calc_start_servers}
APACHE_SERVER_LIMIT=${APACHE_SERVER_LIMIT:-$calc_server_limit}
APACHE_MAX_REQUEST_WORKERS=${APACHE_MAX_REQUEST_WORKERS:-$calc_max_request_workers}
APACHE_MIN_SPARE_THREADS=${APACHE_MIN_SPARE_THREADS:-5}
APACHE_MAX_SPARE_THREADS=${APACHE_MAX_SPARE_THREADS:-15}
APACHE_MAX_CONNECTIONS_PER_CHILD=${APACHE_MAX_CONNECTIONS_PER_CHILD:-3000}

# --- Export all variables ---
export CONTAINER_MEMORY_MB
export PHP_FPM_PM PHP_FPM_MAX_CHILDREN PHP_FPM_PROCESS_IDLE_TIMEOUT PHP_FPM_MAX_REQUESTS
export PHP_FPM_START_SERVERS PHP_FPM_MIN_SPARE PHP_FPM_MAX_SPARE
export APACHE_START_SERVERS APACHE_SERVER_LIMIT APACHE_MAX_REQUEST_WORKERS
export APACHE_MIN_SPARE_THREADS APACHE_MAX_SPARE_THREADS APACHE_MAX_CONNECTIONS_PER_CHILD