Rules Engine

window.lcards.core.rulesManager — Evaluates conditions and hot-patches card styles at runtime.

Overview

RulesEngine extends BaseService. It maintains a compiled index of rules, tracks which entities each rule depends on, and re-evaluates dirty rules on every HASS state push. Matched rules produce patches — plain style objects that are merged onto target overlays without those overlays needing to know the rule exists.

Key Classes

Class	File	Role
`RulesEngine`	`core/rules/RulesEngine.js`	Evaluation loop, dependency index, patch distribution
`compileConditions`	`core/rules/compileConditions.js`	Compiles rule `when` DSL to optimised predicate functions
`RuleTraceBuffer`	`core/rules/RuleTraceBuffer.js`	Ring buffer of evaluation events for the Debug Panel

Evaluation Flow

HASS state push
    → mark affected rules dirty  (dependency index O(1) lookup)
    → evaluate dirty rules only  (compiled predicates)
    → for each matched rule: compute patches
    → distribute patches to registered overlay listeners
    → overlays call requestUpdate()

Rule Schema

yaml

rules:
  - id: high_temp
    priority: 10
    when:
      entity: sensor.cpu_temp
      above: 75
    apply:
      style:
        color: var(--lcards-red)
      animations:
        - tag: temp_widget
          preset: alert_pulse
          loop: true

  - id: motion_active
    when:
      entity: binary_sensor.front_door
      state: "on"
    apply:
      style:
        background: var(--lcards-orange)

Condition Operators

Operator	Value type	Meaning
`state`	string	Exact state match
`above`	number	`numeric_state > value`
`below`	number	`numeric_state < value`
`attribute`	`{ key, value }`	Attribute equals value
`template`	JS string	`[[[code]]]` — truthy return
`all`	array of conditions	AND
`any`	array of conditions	OR

Targeting

Rules target overlays via:

Field	Matches
`id:`	Exact overlay ID
`tag:`	Any overlay with that tag
`type:`	All overlays of that card type
`*`	All registered overlays

Card Integration

javascript

// Register overlay (in _handleFirstUpdate)
this._registerOverlayForRules({ id: `btn-${this._cardGuid}`, type: 'button' });

// Receive patches
_onRulePatchesChanged(patches) {
  this._resolveStyle();   // merge config.style + patches, then requestUpdate()
}

Priority & Stop Processing

Higher priority (lower number) wins when multiple rules target the same overlay property. A rule can include stop_processing: true to prevent lower-priority rules from being evaluated for that overlay.

Rules Engine ​

Overview ​

Key Classes ​

Evaluation Flow ​

Rule Schema ​

Condition Operators ​

Targeting ​

Card Integration ​

Priority & Stop Processing ​

See Also ​