import type { Client, Config, RequestOptions } from "./types";
import {
  buildUrl,
  createConfig,
  createInterceptors,
  getParseAs,
  mergeConfigs,
  mergeHeaders,
  setAuthParams,
} from "./utils";

type ReqInit = Omit<RequestInit, "body" | "headers"> & {
  body?: any;
  headers: ReturnType<typeof mergeHeaders>;
};

export const createClient = (config: Config = {}): Client => {
  let _config = mergeConfigs(createConfig(), config);

  const getConfig = (): Config => ({ ..._config });

  const setConfig = (config: Config): Config => {
    _config = mergeConfigs(_config, config);
    return getConfig();
  };

  const interceptors = createInterceptors<
    Request,
    Response,
    unknown,
    RequestOptions
  >();

  const request: Client["request"] = async (options) => {
    const opts = {
      ..._config,
      ...options,
      fetch: options.fetch ?? _config.fetch ?? globalThis.fetch,
      headers: mergeHeaders(_config.headers, options.headers),
    };

    if (opts.security) {
      await setAuthParams({
        ...opts,
        security: opts.security,
      });
    }

    if (opts.requestValidator) {
      await opts.requestValidator(opts);
    }

    if (opts.body && opts.bodySerializer) {
      opts.body = opts.bodySerializer(opts.body);
    }

    // remove Content-Type header if body is empty to avoid sending invalid requests
    if (opts.body === undefined || opts.body === "") {
      opts.headers.delete("Content-Type");
    }

    const url = buildUrl(opts);
    const requestInit: ReqInit = {
      redirect: "follow",
      ...opts,
    };

    let request = new Request(url, requestInit);

    for (const fn of interceptors.request._fns) {
      if (fn) {
        request = await fn(request, opts);
      }
    }

    // fetch must be assigned here, otherwise it would throw the error:
    // TypeError: Failed to execute 'fetch' on 'Window': Illegal invocation
    const _fetch = opts.fetch!;
    let response = await _fetch(request);

    for (const fn of interceptors.response._fns) {
      if (fn) {
        response = await fn(response, request, opts);
      }
    }

    const result = {
      request,
      response,
    };

    if (response.ok) {
      if (
        response.status === 204 ||
        response.headers.get("Content-Length") === "0"
      ) {
        return opts.responseStyle === "data"
          ? {}
          : {
              data: {},
              ...result,
            };
      }

      const parseAs =
        (opts.parseAs === "auto"
          ? getParseAs(response.headers.get("Content-Type"))
          : opts.parseAs) ?? "json";

      let data: any;
      switch (parseAs) {
        case "arrayBuffer":
        case "blob":
        case "formData":
        case "json":
        case "text":
          data = await response[parseAs]();
          break;
        case "stream":
          return opts.responseStyle === "data"
            ? response.body
            : {
                data: response.body,
                ...result,
              };
      }

      if (parseAs === "json") {
        if (opts.responseValidator) {
          await opts.responseValidator(data);
        }

        if (opts.responseTransformer) {
          data = await opts.responseTransformer(data);
        }
      }

      return opts.responseStyle === "data"
        ? data
        : {
            data,
            ...result,
          };
    }

    const textError = await response.text();
    let jsonError: unknown;

    try {
      jsonError = JSON.parse(textError);
    } catch {
      // noop
    }

    const error = jsonError ?? textError;
    let finalError = error;

    for (const fn of interceptors.error._fns) {
      if (fn) {
        finalError = (await fn(error, response, request, opts)) as string;
      }
    }

    finalError = finalError || ({} as string);

    if (opts.throwOnError) {
      throw finalError;
    }

    // TODO: we probably want to return error and improve types
    return opts.responseStyle === "data"
      ? undefined
      : {
          error: finalError,
          ...result,
        };
  };

  return {
    buildUrl,
    connect: (options) => request({ ...options, method: "CONNECT" }),
    delete: (options) => request({ ...options, method: "DELETE" }),
    get: (options) => request({ ...options, method: "GET" }),
    getConfig,
    head: (options) => request({ ...options, method: "HEAD" }),
    interceptors,
    options: (options) => request({ ...options, method: "OPTIONS" }),
    patch: (options) => request({ ...options, method: "PATCH" }),
    post: (options) => request({ ...options, method: "POST" }),
    put: (options) => request({ ...options, method: "PUT" }),
    request,
    setConfig,
    trace: (options) => request({ ...options, method: "TRACE" }),
  };
};