synchronize_lights.yaml

# inspirations:
# https://community.home-assistant.io/t/synchronize-the-on-off-state-and-brightness-of-two-lights/525423/6
# which linked to those gists:
# https://gist.github.com/creedda/31d391e007b978aed3879fcc1d0fb22c
# https://github.com/iqubik/synclamp/blob/14bb88c8b92219b5243a6a31eae07c0b6ee11fc1/syncthelamp.yaml
# https://gist.github.com/creedda/31d391e007b978aed3879fcc1d0fb22c
blueprint:
  name: Slave lights
  description: |
    Mirror the first light onto other lights. In effect the on/off state, brightness, xy_color and color_temp are mirrored.
  domain: automation
  input:
    master_entity:
      name: Master light
      selector:
        entity:
          domain: light
          multiple: false
    secondary_entities:
      name: Slave lights
      selector:
        entity:
          domain: light
          multiple: true
  source_url: https://gist.github.com/thiswillbeyourgithub/5471d6a48648a8b83020150cad66b8b6
mode: queued
max_exceeded: warn  # silent/warn/error/skip
variables:
  master_entity: !input master_entity
  secondary_entities: !input secondary_entities
trigger:
  - platform: state
    entity_id: !input master_entity
  - platform: state
    entity_id: !input master_entity
    attribute: brightness
  - platform: state
    entity_id: !input master_entity
    attribute: color_temp
  - platform: state
    entity_id: !input master_entity
    attribute: xy_color
condition: []
action:
  - choose:
      - conditions:
          - condition: template
            value_template: '{{ is_state(trigger.to_state.entity_id, "on") }}'
        sequence:
          - service: light.turn_on
            data: >
              {
                {% if state_attr(trigger.to_state.entity_id, "brightness") is not none %}
                  "brightness": {{ state_attr(trigger.to_state.entity_id, "brightness") }},
                {% endif %}
                {% if state_attr(trigger.to_state.entity_id, "color_temp") is not none %}
                  "color_temp": {{ state_attr(trigger.to_state.entity_id, "color_temp") }}
                {% endif %}
                {% if state_attr(trigger.to_state.entity_id, "xy_color") is not none 
                   and not state_attr(trigger.to_state.entity_id, "color_temp") %}
                  "xy_color": {{ state_attr(trigger.to_state.entity_id, "xy_color") }}
                {% endif %}
              }
            target:
              entity_id: "{{ secondary_entities }}"
      - conditions:
          - condition: template
            value_template: '{{ is_state(trigger.to_state.entity_id, "off") }}'
        sequence:
          - service: light.turn_off
            target:
              entity_id: "{{ secondary_entities }}"