source: frontend/src/api/axiosInstance.ts@ 484dc3f

import axios from "axios";

export const baseURL = import.meta.env.VITE_API_BASE_URL;

export const axiosInstance = axios.create({
        baseURL,
        withCredentials: true,
});

// set content-type to application/json unless sending FormData
axiosInstance.interceptors.request.use((config) => {
        if (!(config.data instanceof FormData)) {
                config.headers["Content-Type"] = "application/json";
        }
        return config;
});

let refreshPromise: Promise<void> | null = null;
let refreshTimeout: number | null = null;

export const clearRefreshTimeout = () => {
        if (refreshTimeout) {
                clearTimeout(refreshTimeout);
                refreshTimeout = null;
        }
};

export const scheduleTokenRefresh = (expiryTimeSeconds: number) => {
        clearRefreshTimeout();

        if (!expiryTimeSeconds || expiryTimeSeconds <= 0) {
                return;
        }

        const refreshTime = (expiryTimeSeconds - 60) * 1000;
        if (refreshTime <= 0) {
                refreshTokenMethod();
        } else {
                refreshTimeout = setTimeout(refreshTokenMethod, refreshTime);
        }
};

export const refreshTokenMethod = async (): Promise<void | null> => {
        if (refreshPromise) {
                return refreshPromise;
        }

        refreshPromise = (async () => {
                try {
                        const refreshResponse = await axiosInstance.post<{
                                tokenExpiresIn: number;
                        }>("/auth/refresh");
                        scheduleTokenRefresh(refreshResponse.data.tokenExpiresIn);
                } catch (err) {
                        clearRefreshTimeout();
                        console.error(err);
                        throw err;
                } finally {
                        refreshPromise = null;
                }
        })();
        return refreshPromise;
};

axiosInstance.interceptors.response.use(
        (response) => response,
        async (error) => {
                const originalConfig = error.config;
                if (
                        [401, 403].includes(error.response?.status) &&
                        !originalConfig._retry &&
                        originalConfig.url !== "/auth/refresh"
                ) {
                        originalConfig._retry = true;

                        try {
                                await refreshTokenMethod();
                                return axiosInstance(originalConfig);
                        } catch (err) {
                                clearRefreshTimeout();
                                return Promise.reject(err);
                        }
                }
                return Promise.reject(error);
        },
);

export default axiosInstance;