import type { AxiosError, AxiosInstance, RawAxiosRequestHeaders } from 'axios';
import axios from 'axios';

import { createSseClient } from '../core/serverSentEvents';
import type { HttpMethod } from '../core/types';
import { getValidRequestBody } from '../core/utils';
import type { Client, Config, RequestOptions } from './types';
import { buildUrl, createConfig, mergeConfigs, mergeHeaders, setAuthParams } from './utils';

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

  let instance: AxiosInstance;

  if (_config.axios && !('Axios' in _config.axios)) {
    instance = _config.axios;
  } else {
    // eslint-disable-next-line @typescript-eslint/no-unused-vars
    const { auth, ...configWithoutAuth } = _config;
    instance = axios.create(configWithoutAuth);
  }

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

  const setConfig = (config: Config): Config => {
    _config = mergeConfigs(_config, config);
    instance.defaults = {
      ...instance.defaults,
      ..._config,
      // @ts-expect-error
      headers: mergeHeaders(instance.defaults.headers, _config.headers),
    };
    return getConfig();
  };

  const beforeRequest = async <
    TData = unknown,
    ThrowOnError extends boolean = boolean,
    Url extends string = string,
  >(
    options: RequestOptions<TData, ThrowOnError, Url>,
  ) => {
    const opts = {
      ..._config,
      ...options,
      axios: options.axios ?? _config.axios ?? instance,
      headers: mergeHeaders(_config.headers, options.headers),
    };

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

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

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

    const url = buildUrl(opts);

    return { opts, url };
  };

  // @ts-expect-error
  const request: Client['request'] = async (options) => {
    const { opts, url } = await beforeRequest(options);
    try {
      // assign Axios here for consistency with fetch
      const _axios = opts.axios!;
      // eslint-disable-next-line @typescript-eslint/no-unused-vars
      const { auth, ...optsWithoutAuth } = opts;
      const response = await _axios({
        ...optsWithoutAuth,
        baseURL: '', // the baseURL is already included in `url`
        data: getValidRequestBody(opts),
        headers: opts.headers as RawAxiosRequestHeaders,
        // let `paramsSerializer()` handle query params if it exists
        params: opts.paramsSerializer ? opts.query : undefined,
        url,
      });

      let { data } = response;

      if (opts.responseType === 'json') {
        if (opts.responseValidator) {
          await opts.responseValidator(data);
        }

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

      return {
        ...response,
        data: data ?? {},
      };
    } catch (error) {
      const e = error as AxiosError;
      if (opts.throwOnError) {
        throw e;
      }
      // @ts-expect-error
      e.error = e.response?.data ?? {};
      return e;
    }
  };

  const makeMethodFn = (method: Uppercase<HttpMethod>) => (options: RequestOptions) =>
    request({ ...options, method });

  const makeSseFn = (method: Uppercase<HttpMethod>) => async (options: RequestOptions) => {
    const { opts, url } = await beforeRequest(options);
    return createSseClient({
      ...opts,
      body: opts.body as BodyInit | null | undefined,
      headers: opts.headers as Record<string, string>,
      method,
      serializedBody: getValidRequestBody(opts) as BodyInit | null | undefined,
      // @ts-expect-error
      signal: opts.signal,
      url,
    });
  };

  const _buildUrl: Client['buildUrl'] = (options) =>
    buildUrl({ axios: instance, ..._config, ...options });

  return {
    buildUrl: _buildUrl,
    connect: makeMethodFn('CONNECT'),
    delete: makeMethodFn('DELETE'),
    get: makeMethodFn('GET'),
    getConfig,
    head: makeMethodFn('HEAD'),
    instance,
    options: makeMethodFn('OPTIONS'),
    patch: makeMethodFn('PATCH'),
    post: makeMethodFn('POST'),
    put: makeMethodFn('PUT'),
    request,
    setConfig,
    sse: {
      connect: makeSseFn('CONNECT'),
      delete: makeSseFn('DELETE'),
      get: makeSseFn('GET'),
      head: makeSseFn('HEAD'),
      options: makeSseFn('OPTIONS'),
      patch: makeSseFn('PATCH'),
      post: makeSseFn('POST'),
      put: makeSseFn('PUT'),
      trace: makeSseFn('TRACE'),
    },
    trace: makeMethodFn('TRACE'),
  } as Client;
};