let instance;
const baseUrl = import.meta.env?.VITE_API_BASE_URL ?? "http://localhost:8080/api/v1";

class HttpClient {
    baseURL: string;
    commonHeaders: Headers;

    constructor(baseURL: string) {
        this.baseURL = baseURL;
        this.commonHeaders = new Headers({
            "Content-Type": "application/json"
        })
        if (instance) {
            throw new Error("New instance cannot be created!");
        }

        instance = this;
    }

    private getURL(endpoint: string): URL {
        return new URL(endpoint, this.baseURL);
    }

    private token(): string | null {
        return localStorage.getItem('token');
    }

    private async makeRequest(request: Request): Promise<Response> {
        return fetch(request)
    }

    async get({ endpoint, headers }: IHttpParameters): Promise<Response> {
        const url: URL = this.getURL(endpoint);
        headers = Object.assign<Headers, Headers>(headers, this.commonHeaders);
        const request: Request = new Request(url, {
            method: "GET",
            headers
        });

        return this.makeRequest(request);
    }

    async post({ endpoint, authenticated, body, headers }: IHttpParameters): Promise<Response> {
        const url = this.getURL(endpoint);

        if (authenticated) {
            const token: string | null = this.token();
            headers.append('Authorization', `Bearer ${token}`);
        }

        const request: Request = new Request(url, {
            method: "POST",
            body: JSON.stringify(body),
            headers
        })

        return this.makeRequest(request);
    }

    async patch({ endpoint, authenticated, headers }: IHttpParameters): Promise<Response> {
        const url = this.getURL(endpoint);
        if (authenticated) {

        }
        const response: Response = await fetch(url, {
            method: "PATCH",
            headers
        });
    }

    async delete({ endpoint, authenticated, headers }: IHttpParameters): Promise<Response> {
        const url = this.getURL(endpoint);
        if (authenticated) {

        }
        const response: Response = await fetch(url, {
            method: "DELETE",
            headers
        })
    }
}

interface IHttpParameters {
    endpoint: string;
    body: Record<string, any>;
    authenticated: boolean;
    headers: Headers;
}

let http: Readonly<HttpClient> = Object.freeze(new HttpClient(baseUrl));

export default http;