DataSource System

window.lcards.core.dataSourceManager — Named entity data buffers with history and processing pipelines.

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Overview

DataSourceManager extends BaseService and manages a collection of named DataSource instances. Each source subscribes to a single HA entity, records a rolling value history, runs processor pipelines, and notifies subscribers on every update.

Cards never talk to HA entity state directly for data — they declare data sources in config and subscribe to the manager.

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Key Classes

Class	File	Role
DataSourceManager	core/data-sources/DataSourceManager.js	Lifecycle, card registration, entity index
DataSource	core/data-sources/DataSource.js	Single entity subscription, buffer, processor chain
RollingBuffer	core/data-sources/RollingBuffer.js	Fixed-size circular value history
ProcessorManager	core/data-sources/ProcessorManager.js	Runs processor chain; writes keyed output buffers

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Data Object Structure

Every subscriber callback receives:

{
  v: 72.5,             // Raw entity state value (main buffer)
  celsius: 22.5,       // Processor output keyed by processor's `key`
  rolling_avg: 71.8,   // Another processor output
  t: 1707580800000     // Timestamp (ms)
}

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Config Schema

data_sources:
  temp_sensor:
    entity_id: sensor.temperature
    update_interval: 5          # polling interval (seconds); 0 = push-only
    history_size: 100           # rolling buffer depth
    processors:
      - type: unit_conversion
        key: celsius
        from_unit: fahrenheit
        to_unit: celsius
      - type: smooth
        key: rolling_avg
        window: 10

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Processors Reference

Type	Key field	Output
unit_conversion	custom	Converted numeric value
smooth	custom	Moving average
rate	custom	Rate of change per second
delta	custom	Difference from previous value
round	custom	Rounded to N decimal places
scale	custom	Linear scale (min→max mapping)
clamp	custom	Value clamped to [min, max]
threshold	custom	Boolean: value above threshold
trend	custom	"rising" / "falling" / "stable"
statistics	custom	{ min, max, avg, stddev } object
duration	custom	Duration entity formatted string
expression	custom	Arbitrary JS expression result

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Card Usage

// In _handleFirstUpdate():
const dsm = window.lcards.core.dataSourceManager;
await dsm.initializeFromConfig(this.config.data_sources || {});

const source = dsm.getSource('temp_sensor');
this._unsubscribe = source.subscribe((data) => {
  this._temp = data.celsius;
  this.requestUpdate();
});

// In disconnectedCallback():
if (this._unsubscribe) this._unsubscribe();

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Template Access

text: "{ds:temp_sensor}"              # main buffer (.v)
text: "{ds:temp_sensor.celsius:.1f}"  # processor buffer with format
text: "{datasource:temp_sensor.rolling_avg}"  # explicit prefix

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See Also

• DataSource Buffer Reference
• Template System