import { IParamsProvider, ResponseContext, ResponseHandlerFunction, IHttpClient, ClientCredentialsGrant } from '../models';
import { isBrowser } from '../utils';

export class HttpClient implements IHttpClient {

	constructor(
		private paramsProvider: IParamsProvider,
		private fetchFn: (input: RequestInfo, init?: RequestInit) => Promise<Response>) {
	}

	request<T>(url: string, request: RequestInit = {}): Promise<T> {
		let params = this.paramsProvider.getParams();

		const isRelativeRequestUrl = !params.rootUrl || params.rootUrl === '/';
		if (!isBrowser() && isRelativeRequestUrl) {
			throw new Error('You cannot specify a relative root url if not in a browser context.');
		}

		request.method = request.method || (!!request.body ? 'POST' : 'GET');
		if (!isRelativeRequestUrl) {
			request.mode = 'cors';
		}

		request.headers = request.headers || {};
		let headers = request.headers as any;
		if (!headers.accessToken && !!params.accessToken) {
			headers.accessToken = params.accessToken;
		}

		if (params.clientType === 'none' && !headers.accessToken) {
			throw new Error(`If the property clientType is set to "${params.clientType}" then the property accessToken must be provided.`);
		}

		if (params.clientType === 'client_credentials' && !(params.clientDetails as ClientCredentialsGrant)) {
			throw new Error(`If the property client type is set to "${params.clientType}" then the property clientDetails must be set to a ClientCredentialsGrant value.`);
		}

		if (!!params.defaultHeaders) {
			const keys = Object.keys(params.defaultHeaders);
			keys.forEach(key => {
				if (!headers[key] && !!params.defaultHeaders[key]) {
					headers[key] = params.defaultHeaders[key];
				}
			});
		}

		const requestUrl = isRelativeRequestUrl ? `${url}` : `${params.rootUrl}${url}`;
		return this.fetchFn(requestUrl, request)
			.then((response) => {
				let responseHandlerFunction: ResponseHandlerFunction = null;
				if (!!params.responseHandler) {
					if (!!params.responseHandler['*']) {
						responseHandlerFunction = params.responseHandler['*'];
					}

					if (!!params.responseHandler[response.status]) {
						responseHandlerFunction = params.responseHandler[response.status];
					}
				}

				let responseContext: ResponseContext = {
					status: response.status,
					statusText: response.statusText,
					url: response.url,
					data: null
				};

				return response
					.text()
					.then(text => {
						return !!text && text.length && text.length > 0 ? JSON.parse(text) : {};
					})
					.then(
						result => {
							responseContext.data = result;
							if (response.ok) {
								if (!!responseHandlerFunction) {
									responseHandlerFunction(response, responseContext);
								}

								return result;
							}

							return !!responseHandlerFunction ?
								responseHandlerFunction(response, responseContext)
								: Promise.reject(responseContext);
						},
						reason => {
							responseContext.data = reason;

							return !!responseHandlerFunction ?
								responseHandlerFunction(response, responseContext)
								: Promise.reject(responseContext);
						}
					);
			})
			.then(result => result as any);
	}
}