diff --git a/src/core/client.ts b/src/core/client.ts
new file mode 100644
index 0000000..451fdc1
--- /dev/null
+++ b/src/core/client.ts
@@ -0,0 +1,48 @@
+import _fetch from "node-fetch";
+import { API_ENDPOINT } from "../lib";
+import { Config } from "./dicorc";
+
+export const fetch = async <R>(
+	endpoint: string,
+	token: string,
+	options?: { [key: string]: unknown }
+): Promise<{ status: number; msg: string; data: R }> => {
+	const headers: { [key: string]: string } = {
+		authorization: `Bearer ${token}`
+	};
+
+	if (options && options.headers && typeof options.headers === "object") {
+		Object.entries(options.headers).map(([k, v]) => {
+			if (typeof v === "string") {
+				headers[k] = v;
+			}
+		});
+	}
+
+	const response = await _fetch(`${API_ENDPOINT}${endpoint}`, {
+		...options,
+		headers
+	});
+
+	const json = await response.json();
+
+	if (!response.ok) {
+		throw json || response;
+	}
+
+	return json;
+};
+
+export const whoami = async (
+	token: string
+): Promise<Required<Config>["user"]> => {
+	const {
+		data: { fullname, email }
+	} = await fetch<Required<Config>["user"]>("/whoami", token);
+
+	return {
+		token,
+		fullname,
+		email
+	};
+};
diff --git a/src/core/dicorc.ts b/src/core/dicorc.ts
new file mode 100644
index 0000000..a79a13e
--- /dev/null
+++ b/src/core/dicorc.ts
@@ -0,0 +1,84 @@
+import * as rc from "rc9";
+import { RC_FILE } from "../lib";
+import * as client from "./client";
+
+export interface Config {
+	user?: {
+		token: string;
+		fullname: string;
+		email: string;
+	};
+}
+
+/**
+ * Read config file
+ */
+export const read = (): Config => {
+	return rc.readUser(RC_FILE);
+};
+
+/**
+ * Write config file
+ */
+export const write = (config: Config): void => {
+	rc.writeUser(config, RC_FILE);
+};
+
+/**
+ * Update config file
+ */
+export const update = (config: Config): void => {
+	rc.updateUser(config, RC_FILE);
+};
+
+/**
+ * Sign in used
+ */
+export const signin = async (
+	token: string
+): Promise<Required<Config>["user"]> => {
+	const user = await client.whoami(token);
+
+	update({ user });
+
+	return user;
+};
+
+/**
+ * Sign out user
+ */
+export const signout = (): void => {
+	const config = read();
+
+	delete config.user;
+
+	write(config);
+};
+
+/**
+ * Check if user is signed in
+ */
+export const isSignedIn = async (): Promise<boolean> => {
+	const config = read();
+
+	if (!config.user) {
+		return false;
+	}
+
+	// Invalid token
+	if (config.user.token.length !== 64) {
+		signout();
+
+		return false;
+	}
+
+	try {
+		await client.whoami(config.user.token);
+	} catch (error) {
+		signout();
+
+		console.log(error);
+	}
+
+	return true;
+};