---
- name: Update Cluster Nodes
  hosts: all
  serial: 1  # CRITICAL: Processes one node entirely before moving to the next
  become: yes
  tasks:
    - name: Determine an available k3s control plane node
      set_fact:
        # Picks the first server node that is NOT the one currently being updated
        active_master: "{{ groups['k3s_servers'] | difference([inventory_hostname]) | first }}"
      delegate_to: localhost

    - name: Check if updates are needed (Debian/Raspbian)
      apt:
        upgrade: dist
        update_cache: yes
      register: apt_status
      when: inventory_hostname in groups['k3s_servers'] or inventory_hostname in groups['k3s_agents_raspbian']

    # For NixOS, we just run the upgrade and check if a reboot is flagged.
    - name: Run NixOS update command
      command: sudo nix flake update --flake $NIX_FLAKE_PATH && sudo nixos-rebuild switch --flake $NIX_FLAKE_PATH#{{ inventory_hostname_short }}
      register: nixos_status
      when: inventory_hostname in groups['k3s_agents_nixos']

    - name: Check for Raspbian reboot required flag
      stat:
        path: /var/run/reboot-required
      register: reboot_required
      when: inventory_hostname not in groups['k3s_agents_nixos']

    # --- THE KUBERNETES DRAIN PHASE ---
    - name: Drain the node safely
      command: >
        sudo k3s kubectl drain {{ inventory_hostname_short }}
        --ignore-daemonsets
        --delete-emptydir-data
        --force
        --grace-period=90
        --timeout=5m
      delegate_to: "{{ active_master }}"
      when: (reboot_required.stat.exists | default(false)) or ('changed' in nixos_status | default({}))
      ignore_errors: yes # Prevents a stubborn pod from halting the entire cluster update

    # --- THE REBOOT PHASE ---
    - name: Reboot the node
      reboot:
        post_reboot_delay: 180 # Give k3s and Longhorn time to initialize
      when: (reboot_required.stat.exists | default(false)) or ('changed' in nixos_status | default({}))

    # --- THE UNCORDON PHASE ---
    - name: Uncordon the node
      command: sudo k3s kubectl uncordon {{ inventory_hostname_short }}
      delegate_to: "{{ active_master }}"
      when: (reboot_required.stat.exists | default(false)) or ('changed' in nixos_status | default({}))