---
- name: Test host layout
  hosts: localhost
  become: true

  vars:
    storage_node_count: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
    expected_masters:   [1, 1, 3, 3, 3, 3, 3, 5, 5,  5,  5,  7,  7,  7,  7,  9,  9,  9,  9, 11]

  tasks:

    # the elasticserch cluster elects one master from all those which are marked as master-eligible
    # 1 node cluster can only have one master
    # 2 node clusters have 1 master-eligable nodes to avoid split-brain
    # 3 node clusters have 3 master-eligable nodes
    # >3 node clusters have (nodes // 2) eligable masters rounded up to the next odd number
    - name: Master node count fact
      set_fact:
        master_node_count: |-
          {% set masters = 0 %}
          {% if (item | int) < 3 %}
          {%   set masters = 1 %}
          {% elif (item | int) == 3 %}
          {%   set masters = 3 %}
          {% else %}
          {%   set masters = (item | int ) // 2 %}
          {%   if ((masters | int) % 2 == 0) %}
          {%     set masters = (masters | int) + 1 %}
          {%   endif %}
          {% endif %}
          {{ masters }}
      with_items: "{{ storage_node_count }}"
      register: computed_masters

    - name: Gather results
      set_fact:
        masters: "{{ masters|default([]) + [ { 'nodes': item.item, 'masters': (item.ansible_facts.master_node_count|int) } ] }}"
      with_items: "{{ computed_masters.results }}"

    - name: Check results
      assert:
        that: item.0 == item.1.masters
      with_together:
        - "{{ expected_masters }}"
        - "{{ masters }}"