import { addAzureParams, AZURE_BASE_URL } from '../../../client-side-encryption/providers/azure';
import { MongoAzureError } from '../../../error';
import { get } from '../../../utils';
import type { MongoCredentials } from '../mongo_credentials';
import { type AccessToken, MachineWorkflow } from './machine_workflow';
import { type TokenCache } from './token_cache';

/** Azure request headers. */
const AZURE_HEADERS = Object.freeze({ Metadata: 'true', Accept: 'application/json' });

/** Invalid endpoint result error. */
const ENDPOINT_RESULT_ERROR =
  'Azure endpoint did not return a value with only access_token and expires_in properties';

/** Error for when the token audience is missing in the environment. */
const TOKEN_RESOURCE_MISSING_ERROR =
  'TOKEN_RESOURCE must be set in the auth mechanism properties when ENVIRONMENT is azure.';

/**
 * Device workflow implementation for Azure.
 *
 * @internal
 */
export class AzureMachineWorkflow extends MachineWorkflow {
  /**
   * Instantiate the machine workflow.
   */
  constructor(cache: TokenCache) {
    super(cache);
  }

  /**
   * Get the token from the environment.
   */
  async getToken(credentials?: MongoCredentials): Promise<AccessToken> {
    const tokenAudience = credentials?.mechanismProperties.TOKEN_RESOURCE;
    const username = credentials?.username;
    if (!tokenAudience) {
      throw new MongoAzureError(TOKEN_RESOURCE_MISSING_ERROR);
    }
    const response = await getAzureTokenData(tokenAudience, username);
    if (!isEndpointResultValid(response)) {
      throw new MongoAzureError(ENDPOINT_RESULT_ERROR);
    }
    return response;
  }
}

/**
 * Hit the Azure endpoint to get the token data.
 */
async function getAzureTokenData(tokenAudience: string, username?: string): Promise<AccessToken> {
  const url = new URL(AZURE_BASE_URL);
  addAzureParams(url, tokenAudience, username);
  const response = await get(url, {
    headers: AZURE_HEADERS
  });
  if (response.status !== 200) {
    throw new MongoAzureError(
      `Status code ${response.status} returned from the Azure endpoint. Response body: ${response.body}`
    );
  }
  const result = JSON.parse(response.body);
  return {
    access_token: result.access_token,
    expires_in: Number(result.expires_in)
  };
}

/**
 * Determines if a result returned from the endpoint is valid.
 * This means the result is not nullish, contains the access_token required field
 * and the expires_in required field.
 */
function isEndpointResultValid(
  token: unknown
): token is { access_token: unknown; expires_in: unknown } {
  if (token == null || typeof token !== 'object') return false;
  return (
    'access_token' in token &&
    typeof token.access_token === 'string' &&
    'expires_in' in token &&
    typeof token.expires_in === 'number'
  );
}