export type Method = "GET" | "POST" | "PUT" | "DELETE" | "PATCH";

export interface BackendApiEndpoint<
    M extends Method,
    PP extends string[],
    T,
    R
> {
    method: M;
    endpoint: string;
    pathParams: PP;
    request?: T;
    response?: R;
}

function nestedUrlSearchParams(data: any, topLevel: boolean = true): string {
    switch (typeof data) {
        case "string":
        case "bigint":
        case "boolean":
        case "number":
        case "symbol":
            if (topLevel) return encodeURIComponent(data.toString()) + "=";

            return data.toString();
        case "object":
            if (data === null) return "null";

            if (Array.isArray(data))
                return data
                    .map((d) => nestedUrlSearchParams(d, true))
                    .map(encodeURIComponent)
                    .join("&");

            const inner = Object.entries(data).map(([k, v]) => [
                k,
                nestedUrlSearchParams(v, false),
            ]);

            return new URLSearchParams(inner).toString();

        default:
            return "";
    }
}

export type MagApiErrorCode = "Client:GenericApiError" | string;

export interface MagApiError {
    status: number;
    code: MagApiErrorCode;
    message: string;
}

export class MagApiClient {
    private readonly baseUrl: string;

    constructor(baseUrl: string) {
        this.baseUrl = baseUrl;
    }

    async call<
        T extends BackendApiEndpoint<
            T["method"] & Method,
            T["pathParams"] & string[],
            T["request"],
            T["response"]
        >
    >(
        { endpoint, method }: T,
        data: T["request"],
        pathParams: {
            [K in keyof T["pathParams"] as T["pathParams"][K] & string]:
                | string
                | number;
        },
        token?: string | null | undefined
    ): Promise<T["response"]> {
        type Response = T["response"];

        const authorizationToken = token ?? undefined;
        const authorization = authorizationToken
            ? `Bearer ${authorizationToken}`
            : undefined;

        for (const name in pathParams) {
            endpoint = endpoint.replace(`:${name}`, `${pathParams[name]}`);
        }

        const baseUrl = this.baseUrl.replace(/\/+$/, "");
        let url = `${baseUrl}${endpoint}`;

        if (method === "GET") {
            const query = nestedUrlSearchParams(data as any);
            if (query) {
                url += `?${query}`;
            }
        }

        return await fetch(url, {
            method,
            body: method !== "GET" ? JSON.stringify(data) : undefined,
            credentials: "omit",
            cache: "no-cache",
            headers: authorization ? { authorization } : {},
        })
            .then(async (res) => {
                const body = res.status === 204 ? null : await res.json();

                if (res.status === 200) {
                    return body as Response;
                } else if (res.status === 204) {
                    return null as any as Response;
                } else {
                    throw body as MagApiError;
                }
            })
            .catch((e) => {
                throw {
                    status: -1,
                    code: "Client:GenericApiError",
                    message: e,
                } as MagApiError;
            });
    }
}