enhance(frontend): improve forms usability

packages/frontend/src/scripts/use-form.ts

@@ -0,0 +1,55 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { computed, Reactive, reactive, watch } from 'vue';
+
+function copy<T>(v: T): T {
+	return JSON.parse(JSON.stringify(v));
+}
+
+function unwrapReactive<T>(v: Reactive<T>): T {
+	return JSON.parse(JSON.stringify(v));
+}
+
+export function useForm<T extends Record<string, any>>(initialState: T, save: (newState: T) => Promise<void>) {
+	const currentState = reactive<T>(copy(initialState));
+	const previousState = reactive<T>(copy(initialState));
+
+	const modifiedStates = reactive<Record<keyof T, boolean>>({} as any);
+	for (const key in currentState) {
+		modifiedStates[key] = false;
+	}
+	const modified = computed(() => Object.values(modifiedStates).some(v => v));
+	const modifiedCount = computed(() => Object.values(modifiedStates).filter(v => v).length);
+
+	watch([currentState, previousState], () => {
+		for (const key in modifiedStates) {
+			modifiedStates[key] = currentState[key] !== previousState[key];
+		}
+	}, { deep: true });
+
+	async function _save() {
+		await save(unwrapReactive(currentState));
+		for (const key in currentState) {
+			previousState[key] = copy(currentState[key]);
+		}
+	}
+
+	function discard() {
+		for (const key in currentState) {
+			currentState[key] = copy(previousState[key]);
+		}
+	}
+
+	return {
+		state: currentState,
+		savedState: previousState,
+		modifiedStates,
+		modified,
+		modifiedCount,
+		save: _save,
+		discard,
+	};
+}