Feat: 外部サイトからテーマ・プラグインのインストールができるように (#12034)

* Feat: 外部サイトからテーマ・プラグインのインストールができるように

* Update Changelog

* Change Changelog

* Remove unnecessary imports

* Update fetch-external-resources.ts

* Update CHANGELOG.md

* Update CHANGELOG.md

packages/frontend/src/scripts/install-theme.ts

@@ -0,0 +1,37 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import JSON5 from 'json5';
+import { addTheme, getThemes } from '@/theme-store.js';
+import { Theme, applyTheme, validateTheme } from '@/scripts/theme.js';
+
+export function parseThemeCode(code: string): Theme {
+	let theme;
+
+	try {
+		theme = JSON5.parse(code);
+	} catch (err) {
+		throw new Error('Failed to parse theme json');
+	}
+	if (!validateTheme(theme)) {
+		throw new Error('This theme is invaild');
+	}
+	if (getThemes().some(t => t.id === theme.id)) {
+		throw new Error('This theme is already installed');
+	}
+
+	return theme;
+}
+
+export function previewTheme(code: string): void {
+	const theme = parseThemeCode(code);
+	if (theme) applyTheme(theme, false);
+}
+
+export async function installTheme(code: string): Promise<void> {
+	const theme = parseThemeCode(code);
+	if (!theme) return;
+	await addTheme(theme);
+}