Add preview to Threshold config & option flow (#19845)

Co-authored-by: Franck Nijhof <git@frenck.dev>

src/data/threshold.ts

@@ -0,0 +1,21 @@
+import { UnsubscribeFunc } from "home-assistant-js-websocket";
+import { HomeAssistant } from "../types";
+
+export interface ThresholdPreview {
+  state: string;
+  attributes: Record<string, any>;
+}
+
+export const subscribePreviewThreshold = (
+  hass: HomeAssistant,
+  flow_id: string,
+  flow_type: "config_flow" | "options_flow",
+  user_input: Record<string, any>,
+  callback: (preview: ThresholdPreview) => void
+): Promise<UnsubscribeFunc> =>
+  hass.connection.subscribeMessage(callback, {
+    type: "threshold/start_preview",
+    flow_id,
+    flow_type,
+    user_input,
+  });

src/dialogs/config-flow/previews/flow-preview-threshold.ts

@@ -0,0 +1,108 @@
+import { HassEntity, UnsubscribeFunc } from "home-assistant-js-websocket";
+import { LitElement, html } from "lit";
+import { customElement, property, state } from "lit/decorators";
+import { FlowType } from "../../../data/data_entry_flow";
+import {
+  ThresholdPreview,
+  subscribePreviewThreshold,
+} from "../../../data/threshold";
+import { HomeAssistant } from "../../../types";
+import "./entity-preview-row";
+import { debounce } from "../../../common/util/debounce";
+import { fireEvent } from "../../../common/dom/fire_event";
+
+@customElement("flow-preview-threshold")
+class FlowPreviewThreshold extends LitElement {
+  @property({ attribute: false }) public hass!: HomeAssistant;
+
+  @property() public flowType!: FlowType;
+
+  public handler!: string;
+
+  @property() public stepId!: string;
+
+  @property() public flowId!: string;
+
+  @property() public stepData!: Record<string, any>;
+
+  @state() private _preview?: HassEntity;
+
+  @state() private _error?: string;
+
+  private _unsub?: Promise<UnsubscribeFunc>;
+
+  disconnectedCallback(): void {
+    super.disconnectedCallback();
+    if (this._unsub) {
+      this._unsub.then((unsub) => unsub());
+      this._unsub = undefined;
+    }
+  }
+
+  willUpdate(changedProps) {
+    if (changedProps.has("stepData")) {
+      this._debouncedSubscribePreview();
+    }
+  }
+
+  protected render() {
+    if (this._error) {
+      return html`<ha-alert alert-type="error">${this._error}</ha-alert>`;
+    }
+    return html`<entity-preview-row
+      .hass=${this.hass}
+      .stateObj=${this._preview}
+    ></entity-preview-row>`;
+  }
+
+  private _setPreview = (preview: ThresholdPreview) => {
+    const now = new Date().toISOString();
+    this._preview = {
+      entity_id: `${this.stepId}.___flow_preview___`,
+      last_changed: now,
+      last_updated: now,
+      context: { id: "", parent_id: null, user_id: null },
+      ...preview,
+    };
+  };
+
+  private _debouncedSubscribePreview = debounce(() => {
+    this._subscribePreview();
+  }, 250);
+
+  private async _subscribePreview() {
+    if (this._unsub) {
+      (await this._unsub)();
+      this._unsub = undefined;
+    }
+    if (this.flowType === "repair_flow") {
+      return;
+    }
+    try {
+      this._unsub = subscribePreviewThreshold(
+        this.hass,
+        this.flowId,
+        this.flowType,
+        this.stepData,
+        this._setPreview
+      );
+      await this._unsub;
+      fireEvent(this, "set-flow-errors", { errors: {} });
+    } catch (err: any) {
+      if (typeof err.message === "string") {
+        this._error = err.message;
+      } else {
+        this._error = undefined;
+        fireEvent(this, "set-flow-errors", err.message);
+      }
+      this._unsub = undefined;
+      this._preview = undefined;
+    }
+  }
+}
+
+declare global {
+  interface HTMLElementTagNameMap {
+    "flow-preview-threshold": FlowPreviewThreshold;
+  }
+}