// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License. See License.txt in the project root for license information.

import { HttpHeaders } from "../httpHeaders";
import { HttpOperationResponse } from "../httpOperationResponse";
import { Constants } from "../util/constants";
import { WebResource } from "../webResource";
import { getDefaultUserAgentKey, getPlatformSpecificData } from "./msRestUserAgentPolicy";
import { BaseRequestPolicy, RequestPolicy, RequestPolicyFactory, RequestPolicyOptions } from "./requestPolicy";

export type TelemetryInfo = { key?: string; value?: string };

function getRuntimeInfo(): TelemetryInfo[] {
  const msRestRuntime = {
    key: "ms-rest-js",
    value: Constants.msRestVersion
  };

  return [msRestRuntime];
}

function getUserAgentString(telemetryInfo: TelemetryInfo[], keySeparator = " ", valueSeparator = "/"): string {
  return telemetryInfo.map(info => {
    const value = info.value ? `${valueSeparator}${info.value}` : "";
    return `${info.key}${value}`;
  }).join(keySeparator);
}

export const getDefaultUserAgentHeaderName = getDefaultUserAgentKey;

export function getDefaultUserAgentValue(): string {
  const runtimeInfo = getRuntimeInfo();
  const platformSpecificData = getPlatformSpecificData();
  const userAgent = getUserAgentString(runtimeInfo.concat(platformSpecificData));
  return userAgent;
}

export function userAgentPolicy(userAgentData?: TelemetryInfo): RequestPolicyFactory {
  const key: string = (!userAgentData || userAgentData.key == undefined) ? getDefaultUserAgentKey() : userAgentData.key;
  const value: string = (!userAgentData || userAgentData.value == undefined) ?  getDefaultUserAgentValue() : userAgentData.value;

  return {
    create: (nextPolicy: RequestPolicy, options: RequestPolicyOptions) => {
      return new UserAgentPolicy(nextPolicy, options, key, value);
    }
  };
}

export class UserAgentPolicy extends BaseRequestPolicy {
  constructor(readonly _nextPolicy: RequestPolicy, readonly _options: RequestPolicyOptions, protected headerKey: string, protected headerValue: string) {
    super(_nextPolicy, _options);
  }

  sendRequest(request: WebResource): Promise<HttpOperationResponse> {
    this.addUserAgentHeader(request);
    return this._nextPolicy.sendRequest(request);
  }

  addUserAgentHeader(request: WebResource): void {
    if (!request.headers) {
      request.headers = new HttpHeaders();
    }

    if (!request.headers.get(this.headerKey) && this.headerValue) {
      request.headers.set(this.headerKey, this.headerValue);
    }
  }
}