✨ UI Editor for media-control card (#2336)

* ✨ UI Editor for `media-control` card

* Address review comments

* Note on LL interface

src/panels/lovelace/cards/hui-media-control-card.js

@@ -2,7 +2,21 @@ import "../../../cards/ha-media_player-card";
 
 import LegacyWrapperCard from "./hui-legacy-wrapper-card";
 
+// should be interface when converted to TS
+export const Config = {
+  entity: "",
+};
+
 class HuiMediaControlCard extends LegacyWrapperCard {
+  static async getConfigElement() {
+    await import("../editor/config-elements/hui-media-control-card-editor");
+    return document.createElement("hui-media-control-card-editor");
+  }
+
+  static getStubConfig() {
+    return {};
+  }
+
   constructor() {
     super("ha-media_player-card", "media_player");
   }

src/panels/lovelace/editor/config-elements/hui-media-control-card-editor.ts

@@ -0,0 +1,83 @@
+import { html, LitElement, PropertyDeclarations } from "@polymer/lit-element";
+import { TemplateResult } from "lit-html";
+
+import { struct } from "../../common/structs/struct";
+import { EntitiesEditorEvent, EditorTarget } from "../types";
+import { hassLocalizeLitMixin } from "../../../../mixins/lit-localize-mixin";
+import { HomeAssistant } from "../../../../types";
+import { LovelaceCardEditor } from "../../types";
+import { fireEvent } from "../../../../common/dom/fire_event";
+import { Config } from "../../cards/hui-media-control-card";
+
+import "../../../../components/entity/ha-entity-picker";
+
+const cardConfigStruct = struct({
+  type: "string",
+  entity: "string?",
+});
+
+export class HuiMediaControlCardEditor extends hassLocalizeLitMixin(LitElement)
+  implements LovelaceCardEditor {
+  public hass?: HomeAssistant;
+  private _config?: Config;
+
+  public setConfig(config: Config): void {
+    config = cardConfigStruct(config);
+    this._config = config;
+  }
+
+  static get properties(): PropertyDeclarations {
+    return { hass: {}, _config: {} };
+  }
+
+  get _entity(): string {
+    return this._config!.entity || "";
+  }
+
+  protected render(): TemplateResult {
+    if (!this.hass) {
+      return html``;
+    }
+
+    return html`
+      <div class="card-config">
+        <ha-entity-picker
+          .hass="${this.hass}"
+          .value="${this._entity}"
+          .configValue=${"entity"}
+          domain-filter="media_player"
+          @change="${this._valueChanged}"
+          allow-custom-entity
+        ></ha-entity-picker>
+      </div>
+    `;
+  }
+
+  private _valueChanged(ev: EntitiesEditorEvent): void {
+    if (!this._config || !this.hass) {
+      return;
+    }
+    const target = ev.target! as EditorTarget;
+    if (this[`_${target.configValue}`] === target.value) {
+      return;
+    }
+    if (target.configValue) {
+      this._config = {
+        ...this._config,
+        [target.configValue!]: target.value,
+      };
+    }
+    fireEvent(this, "config-changed", { config: this._config });
+  }
+}
+
+declare global {
+  interface HTMLElementTagNameMap {
+    "hui-media-control-card-editor": HuiMediaControlCardEditor;
+  }
+}
+
+customElements.define(
+  "hui-media-control-card-editor",
+  HuiMediaControlCardEditor
+);