feat: add ability to configure the agent (also theme switcher) (#3)

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### Tests

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Reviewed-on: #3
Co-authored-by: Naomi Carrigan <commits@nhcarrigan.com>
Co-committed-by: Naomi Carrigan <commits@nhcarrigan.com>

src/lib/stores/config.ts

@@ -0,0 +1,114 @@
+import { writable, derived } from "svelte/store";
+import { invoke } from "@tauri-apps/api/core";
+
+export type Theme = "dark" | "light";
+
+export interface HikariConfig {
+  model: string | null;
+  api_key: string | null;
+  custom_instructions: string | null;
+  mcp_servers_json: string | null;
+  auto_granted_tools: string[];
+  theme: Theme;
+}
+
+const defaultConfig: HikariConfig = {
+  model: null,
+  api_key: null,
+  custom_instructions: null,
+  mcp_servers_json: null,
+  auto_granted_tools: [],
+  theme: "dark",
+};
+
+function createConfigStore() {
+  const config = writable<HikariConfig>(defaultConfig);
+  const isLoading = writable<boolean>(true);
+  const isSidebarOpen = writable<boolean>(false);
+  const saveError = writable<string | null>(null);
+
+  async function loadConfig() {
+    isLoading.set(true);
+    try {
+      const savedConfig = await invoke<HikariConfig>("get_config");
+      config.set(savedConfig);
+    } catch (error) {
+      console.error("Failed to load config:", error);
+      config.set(defaultConfig);
+    } finally {
+      isLoading.set(false);
+    }
+  }
+
+  async function saveConfig(newConfig: HikariConfig) {
+    saveError.set(null);
+    try {
+      await invoke("save_config", { config: newConfig });
+      config.set(newConfig);
+    } catch (error) {
+      const errorMessage = error instanceof Error ? error.message : String(error);
+      saveError.set(errorMessage);
+      console.error("Failed to save config:", error);
+      throw error;
+    }
+  }
+
+  async function updateConfig(updates: Partial<HikariConfig>) {
+    let currentConfig: HikariConfig = defaultConfig;
+    config.subscribe((c) => (currentConfig = c))();
+    const newConfig = { ...currentConfig, ...updates };
+    await saveConfig(newConfig);
+  }
+
+  return {
+    config: { subscribe: config.subscribe },
+    isLoading: { subscribe: isLoading.subscribe },
+    isSidebarOpen: { subscribe: isSidebarOpen.subscribe },
+    saveError: { subscribe: saveError.subscribe },
+
+    loadConfig,
+    saveConfig,
+    updateConfig,
+
+    openSidebar: () => isSidebarOpen.set(true),
+    closeSidebar: () => isSidebarOpen.set(false),
+    toggleSidebar: () => isSidebarOpen.update((open) => !open),
+
+    setTheme: async (theme: Theme) => {
+      await updateConfig({ theme });
+      applyTheme(theme);
+    },
+
+    addAutoGrantedTool: async (tool: string) => {
+      let currentConfig: HikariConfig = defaultConfig;
+      config.subscribe((c) => (currentConfig = c))();
+      if (!currentConfig.auto_granted_tools.includes(tool)) {
+        const newTools = [...currentConfig.auto_granted_tools, tool];
+        await updateConfig({ auto_granted_tools: newTools });
+      }
+    },
+
+    removeAutoGrantedTool: async (tool: string) => {
+      let currentConfig: HikariConfig = defaultConfig;
+      config.subscribe((c) => (currentConfig = c))();
+      const newTools = currentConfig.auto_granted_tools.filter((t) => t !== tool);
+      await updateConfig({ auto_granted_tools: newTools });
+    },
+
+    getConfig: (): HikariConfig => {
+      let currentConfig: HikariConfig = defaultConfig;
+      config.subscribe((c) => (currentConfig = c))();
+      return currentConfig;
+    },
+  };
+}
+
+export function applyTheme(theme: Theme) {
+  if (typeof document !== "undefined") {
+    document.documentElement.setAttribute("data-theme", theme);
+  }
+}
+
+export const configStore = createConfigStore();
+
+export const isDarkTheme = derived(configStore.config, ($config) => $config.theme === "dark");