export type ApiMethod = "GET" | "POST" | "PATCH" | "DELETE";

export interface ApiClientConfig {
  baseUrl: string;
  getAccessToken?: () => string | Promise<string | undefined> | undefined;
}

export class ApiError extends Error {
  status: number;
  body: unknown;

  constructor(status: number, message: string, body: unknown) {
    super(message);
    this.status = status;
    this.body = body;
  }
}

export class ApiClient {
  private baseUrl: string;
  private getAccessToken?: ApiClientConfig["getAccessToken"];

  constructor(config: ApiClientConfig) {
    this.baseUrl = config.baseUrl.replace(/\/+$/, "");
    this.getAccessToken = config.getAccessToken;
  }

  private async buildHeaders(extra?: HeadersInit): Promise<HeadersInit> {
    const token = this.getAccessToken ? await this.getAccessToken() : undefined;
    return {
      ...(token ? { Authorization: `Bearer ${token}` } : {}),
      ...extra,
    };
  }

  private buildUrl(path: string, query?: Record<string, string | number | boolean | undefined>) {
    const url = new URL(`${this.baseUrl}${path}`);
    if (query) {
      for (const [k, v] of Object.entries(query)) {
        if (v !== undefined && v !== null) url.searchParams.set(k, String(v));
      }
    }
    return url.toString();
  }

  async request<TResponse, TBody = undefined>(params: {
    method: ApiMethod;
    path: string;
    query?: Record<string, string | number | boolean | undefined>;
    body?: TBody;
    headers?: HeadersInit;
    isFormData?: boolean;
  }): Promise<TResponse> {
    const { method, path, query, body, headers, isFormData } = params;
    const finalHeaders = await this.buildHeaders(headers);

    const response = await fetch(this.buildUrl(path, query), {
      method,
      headers: isFormData ? finalHeaders : { "Content-Type": "application/json", ...finalHeaders },
      body: body
        ? isFormData
          ? (body as unknown as FormData)
          : JSON.stringify(body)
        : undefined,
    });

    const text = await response.text();
    const data = text ? safeJsonParse(text) : null;

    if (!response.ok) {
      throw new ApiError(response.status, response.statusText, data);
    }

    return data as TResponse;
  }

  get<TResponse>(path: string, query?: Record<string, string | number | boolean | undefined>) {
    return this.request<TResponse>({ method: "GET", path, query });
  }

  post<TResponse, TBody = undefined>(
    path: string,
    body?: TBody,
    options?: { headers?: HeadersInit; isFormData?: boolean }
  ) {
    return this.request<TResponse, TBody>({
      method: "POST",
      path,
      body,
      headers: options?.headers,
      isFormData: options?.isFormData,
    });
  }

  patch<TResponse, TBody = undefined>(path: string, body?: TBody) {
    return this.request<TResponse, TBody>({ method: "PATCH", path, body });
  }

  delete<TResponse>(path: string) {
    return this.request<TResponse>({ method: "DELETE", path });
  }
}

function safeJsonParse(text: string) {
  try {
    return JSON.parse(text);
  } catch {
    return text;
  }
}