feat(mobx): add drafts and state context

src/mobx/stores/Draft.ts

@@ -0,0 +1,80 @@
+import { action, computed, makeAutoObservable, ObservableMap } from "mobx";
+
+import Persistent from "../Persistent";
+
+interface Data {
+    drafts: Record<string, string>;
+}
+
+/**
+ * Handles storing draft (currently being written) messages.
+ */
+export default class Draft implements Persistent<Data> {
+    private drafts: ObservableMap<string, string>;
+
+    /**
+     * Construct new Draft store.
+     */
+    constructor() {
+        this.drafts = new ObservableMap();
+        makeAutoObservable(this);
+    }
+
+    // eslint-disable-next-line require-jsdoc
+    toJSON() {
+        return {
+            drafts: this.drafts,
+        };
+    }
+
+    // eslint-disable-next-line require-jsdoc
+    @action hydrate(data: Data) {
+        Object.keys(data.drafts).forEach((key) =>
+            this.drafts.set(key, data.drafts[key]),
+        );
+    }
+
+    /**
+     * Get draft for a channel.
+     * @param channel Channel ID
+     */
+    @computed get(channel: string) {
+        return this.drafts.get(channel);
+    }
+
+    /**
+     * Check whether a channel has a draft.
+     * @param channel Channel ID
+     */
+    @computed has(channel: string) {
+        return this.drafts.has(channel) && this.drafts.get(channel)!.length > 0;
+    }
+
+    /**
+     * Set draft for a channel.
+     * @param channel Channel ID
+     * @param content Draft content
+     */
+    @action set(channel: string, content?: string) {
+        if (typeof content === "undefined") {
+            return this.clear(channel);
+        }
+
+        this.drafts.set(channel, content);
+    }
+
+    /**
+     * Clear draft from a channel.
+     * @param channel Channel ID
+     */
+    @action clear(channel: string) {
+        this.drafts.delete(channel);
+    }
+
+    /**
+     * Reset and clear all drafts.
+     */
+    @action reset() {
+        this.drafts.clear();
+    }
+}