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

package com.microsoft.azure.credentials;

import com.microsoft.azure.AzureEnvironment;
import com.microsoft.azure.management.apigeneration.Beta;
import com.microsoft.azure.serializer.AzureJacksonAdapter;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

Managed Service Identity token based credentials for use with a REST Service Client.
/**
 * Managed Service Identity token based credentials for use with a REST Service Client.
 */
@Beta
public class AppServiceMSICredentials extends AzureTokenCredentials {
    private final String endpoint;
    private final String secret;
    private final AzureJacksonAdapter adapter;
    private String clientId;

    
Creates an MSI credential for app services.
Params:
environment – the environment this application is running in/**
     * Creates an MSI credential for app services.
     * @param environment the environment this application is running in
     */
    public AppServiceMSICredentials(AzureEnvironment environment) {
        this(environment, System.getenv("MSI_ENDPOINT"), System.getenv("MSI_SECRET"));
    }

    
Creates an MSI credential for app services.
Params:
environment – the environment this application is running in
endpoint – the MSI endpoint
secret – the MSI secret/**
     * Creates an MSI credential for app services.
     * @param environment the environment this application is running in
     * @param endpoint the MSI endpoint
     * @param secret the MSI secret
     */
    public AppServiceMSICredentials(AzureEnvironment environment, String endpoint, String secret) {
        super(environment, null);
        if (endpoint == null) {
            throw new IllegalArgumentException("endpoint == null");
        }
        if (secret == null) {
            throw new IllegalArgumentException("secret == null");
        }
        this.endpoint = endpoint;
        this.secret = secret;
        this.adapter = new AzureJacksonAdapter();
    }

    
Specifies the application id (client id) associated with a user assigned managed service identity
resource that should be used to retrieve the access token.
Params:
clientId – application id (client id) of the identity to use when authenticating to Azure AD.
Returns:
AppServiceMSICredentials/**
     * Specifies the application id (client id) associated with a user assigned managed service identity
     * resource that should be used to retrieve the access token.
     *
     * @param clientId application id (client id) of the identity to use when authenticating to Azure AD.
     * @return AppServiceMSICredentials
     */
    public AppServiceMSICredentials withClientId(String clientId) {
        this.clientId = clientId;
        return this;
    }

    @Override
    public String getToken(String resource) throws IOException {
        String urlString = null;

        if (this.clientId != null && !this.clientId.isEmpty()) {
            urlString = String.format("%s?resource=%s&clientid=%s&api-version=2017-09-01", this.endpoint,
                    resource, this.clientId);
        } else {
            urlString = String.format("%s?resource=%s&api-version=2017-09-01", this.endpoint,
                    resource);
        }

        URL url = new URL(urlString);
        HttpURLConnection connection = null;

        try {
            connection = (HttpURLConnection) url.openConnection();

            connection.setRequestMethod("GET");
            connection.setRequestProperty("Secret", this.secret);
            connection.setRequestProperty("Metadata", "true");

            connection.connect();

            InputStream stream = connection.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(stream, "UTF-8"), 100);
            String result = reader.readLine();

            MSIToken msiToken = adapter.deserialize(result, MSIToken.class);
            return msiToken.accessToken();
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
        }
    }
}