Add template support

README.md

@@ -25,6 +25,7 @@ entities:
   - <entity>
   - <entity>
 filter:
+  template: <template>
   include:
     - <filter>
     - <filter>
@@ -42,14 +43,15 @@ sort: <sort_method>
 - `card:` **Required.** The card to display. Specify this as you would specify any normal lovelace card, but ommit the `entities:` parameter.
 - `entities:` Any entities added here will be added to the card before any filters are applied.
 - `filter:`
-  - `include:` **Required.** A list of filters specifying which entities to add to the card
+  - `template:` A jinja2 template evaluating to a whitespace- or comma-separated list of entity ids to include
+  - `include:` A list of filters specifying which entities to add to the card
   - `exclude:` A list of filters specifying which entities to remove from the card
 - `show_empty:` Whether to display the card if it has no entities. Default: `true`.
 - `unique:` Whether to remove duplicate values after filtering and sorting. Default: `false`.
 - `sort:` How to sort the entities of the card. Default: `none`. See [Sorting entities for details](#sorting-entities)
 
 ### Filters
-The two filter sections `include` and `exclude` each takes a list of filters.
+The two main filter sections `include` and `exclude` each takes a list of filters.
 
 Filters have the following options, and will match any entity fulfilling **ALL** options:
 
@@ -70,11 +72,17 @@ Special options:
 - `not:` Specifies a filter that entities must *not* match.
 - `sort:` Specifies a method to sort entities matched by *this filter only*.
 
+### Template filter
+The filter section `template` takes a jinja2 template which evaluates to a list of comma- or whitespace separated `entity_id`s which are included.
+
+> Note: Due to how the templating engine of Home Assistant works, this may or may not be as useful as it sounds. See note at templating example below.
+
 ## How it works
 `auto-entities` creates a list of entities by:
 1. Including every entitiy given in `entities:` (this allow nesting of `auto-entities`if you'd want to do that for some reason...)
-2. Include all entities that matches **ALL** options of **ANY** filter in the `filter.include` section. The same entity may be included several times by different filters.
-3. Remove all entities that matches **ALL** options on **ANY** filter in the `filter.exclude` section.
+2. Include every entity listed in a `filter.template` evaluation
+3. Include all entities that matches **ALL** options of **ANY** filter in the `filter.include` section. The same entity may be included several times by different filters.
+4. Remove all entities that matches **ALL** options on **ANY** filter in the `filter.exclude` section.
 
 It then creates a card based on the configuration given in `card:`, and fills in `entities:` of that card with the entities from above.
 
@@ -296,5 +304,42 @@ filter:
             entity_id: this.entity_id
 ```
 
+Example using templates:
+```yaml
+type: custom:auto-entities
+card:
+  type: entities
+filter:
+  template: |
+    {% for light in states.light %}
+      {% if light.state == "on" %}
+        {{ light.entity_id}},
+      {% endif %}
+    {% endfor %}
+```
+> Note: templates won't update automatically on state changes unless they contain the literal entity id of the entity whose state changes.
+> I.e. the example above will not update when a light is turned on or off, unless the view is reloaded.
+>
+> This is a limitation of the Home Assistant template engine, and nothing I can do anything about. There are, however two mitigations you could make.
+>
+> One is to redefine the template, e.g.:
+> ```yaml
+>      template: |
+>        {%if is_state('light.bed_light','on')%}light.bed_light{%endif%}
+>        {%if is_state('light.kitchen_lights','on')%}light.kitchen_lights{%endif%}
+>        {%if is_state('light.ceiling_lights','on')%}light.ceiling_lights{%endif%}
+> ```
+>
+> The other option is to add a list of entities to monitor:
+> ```yaml
+>   filter:
+>     template: |
+>       ...etc...
+>     entity_ids:
+>       - light.bed_light
+>       - light.kitchen_lights
+>       - light.ceiling_lights
+> ```
+
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