{ pkgs, ... }:

let
  healthScript = pkgs.writeShellScriptBin "nixserve-health" ''
    R='\033[0;31m' G='\033[0;32m' Y='\033[1;33m' B='\033[0;34m' W='\033[1m' N='\033[0m'
    ok()     { echo -e "  ''${G}✓''${N} $*"; }
    warn()   { echo -e "  ''${Y}⚠''${N} $*"; }
    bad()    { echo -e "  ''${R}✗''${N} $*"; }
    section(){ echo -e "\n''${W}''${B}$*''${N}"; }

    echo -e "''${W}nixserve''${N} — $(date '+%Y-%m-%d %H:%M')  uptime: $(uptime -p | sed 's/up //')  load: $(cut -d' ' -f1-3 /proc/loadavg)"

    # ── ZFS ────────────────────────────────────────────────────────────────────
    section "ZFS"
    while IFS= read -r pool; do
      health=$(zpool list -H -o health "$pool" 2>/dev/null)
      errors=$(zpool status "$pool" 2>/dev/null | awk '/errors:/{$1=""; print substr($0,2)}')
      scrub=$(zpool status "$pool" 2>/dev/null | awk '/scan:/{$1=""; print substr($0,2)}' | head -1)
      if [[ "$health" == "ONLINE" ]]; then
        ok "$pool  $health  — $errors"
      else
        bad "$pool  $health  — $errors"
      fi
      [[ -n "$scrub" ]] && echo -e "       scrub: $scrub"
    done < <(zpool list -H -o name 2>/dev/null)

    # ── Systemd ─────────────────────────────────────────────────────────────────
    section "Systemd"
    failed=$(systemctl --failed --no-legend --no-pager 2>/dev/null | awk '{print $1}')
    if [[ -z "$failed" ]]; then
      ok "No failed units"
    else
      while IFS= read -r u; do bad "$u"; done <<< "$failed"
    fi

    # ── Docker ──────────────────────────────────────────────────────────────────
    section "Docker"
    if docker info &>/dev/null 2>&1; then
      while IFS=$'\t' read -r name status; do
        [[ -z "$name" ]] && continue
        if [[ "$status" == Up* ]]; then ok "$name  ($status)"
        else bad "$name  ($status)"; fi
      done < <(docker ps -a --format $'{{.Names}}\t{{.Status}}' 2>/dev/null)
    else
      warn "docker not reachable"
    fi

    # ── Disk ────────────────────────────────────────────────────────────────────
    section "Disk"
    df -h --output=target,pcent,used,size -x tmpfs -x devtmpfs -x efivarfs 2>/dev/null \
      | tail -n +2 \
      | while read -r mnt pct used size; do
          n=''${pct/\%/}
          if   (( n >= 90 )); then bad  "$mnt  $pct  ($used / $size)"
          elif (( n >= 75 )); then warn "$mnt  $pct  ($used / $size)"
          else                     ok   "$mnt  $pct  ($used / $size)"
          fi
        done

    # ── Memory ──────────────────────────────────────────────────────────────────
    section "Memory"
    free -h | awk '/^Mem:/{printf "  used: %s / %s   free: %s\n", $3, $2, $4}'

    # ── Recent errors ───────────────────────────────────────────────────────────
    section "Journal errors (last hour)"
    errs=$(journalctl -p err --since "1 hour ago" --no-pager -q 2>/dev/null \
           | grep -v "^$" | tail -8)
    if [[ -z "$errs" ]]; then
      ok "None"
    else
      while IFS= read -r line; do warn "$line"; done <<< "$errs"
    fi

    echo
  '';
in
{
  environment.systemPackages = [ healthScript ];

  programs.zsh.loginShellInit = ''
    [[ -n "$SSH_CONNECTION" ]] && nixserve-health
  '';
}