#!/usr/bin/env bash
# Collects ZFS pool utilization and boot partition usage for Prometheus textfile collector
set -euo pipefail

TEXTFILE="${TEXTFILE:?TEXTFILE env required}"
TMP="${TEXTFILE}.$$"

{
  echo '# HELP zpool_size_bytes Total size of ZFS pool in bytes'
  echo '# TYPE zpool_size_bytes gauge'
  echo '# HELP zpool_used_bytes Used space in ZFS pool in bytes'
  echo '# TYPE zpool_used_bytes gauge'
  echo '# HELP zpool_free_bytes Free space in ZFS pool in bytes'
  echo '# TYPE zpool_free_bytes gauge'

  # -Hp: scripting mode, parseable, bytes
  zpool list -Hp -o name,size,alloc,free | while IFS=$'\t' read -r name size alloc free; do
    echo "zpool_size_bytes{pool=\"${name}\"} ${size}"
    echo "zpool_used_bytes{pool=\"${name}\"} ${alloc}"
    echo "zpool_free_bytes{pool=\"${name}\"} ${free}"
  done

  echo '# HELP partition_size_bytes Total size of partition in bytes'
  echo '# TYPE partition_size_bytes gauge'
  echo '# HELP partition_used_bytes Used space on partition in bytes'
  echo '# TYPE partition_used_bytes gauge'
  echo '# HELP partition_free_bytes Free space on partition in bytes'
  echo '# TYPE partition_free_bytes gauge'

  # Boot drive partitions: /boot (ESP), /persistent, /nix
  # Use df with 1K blocks and convert to bytes
  for mount in /boot /persistent /nix; do
    if mountpoint -q "$mount" 2>/dev/null; then
      read -r size used avail _ <<< "$(df -k --output=size,used,avail "$mount" | tail -1)"
      size_b=$((size * 1024))
      used_b=$((used * 1024))
      avail_b=$((avail * 1024))
      echo "partition_size_bytes{mount=\"${mount}\"} ${size_b}"
      echo "partition_used_bytes{mount=\"${mount}\"} ${used_b}"
      echo "partition_free_bytes{mount=\"${mount}\"} ${avail_b}"
    fi
  done
} > "$TMP"
mv "$TMP" "$TEXTFILE"