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The Microsoft Azure IoT Device SDK for Java

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// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

package com.microsoft.azure.iothub.auth;

/** Grants device access to an IoT Hub for the specified amount of time. */
public final class IotHubSasToken
{
    /**
     * The SAS token format. The parameters to be interpolated are, in order:
     * the signature, the expiry time, the key name (device ID), and the
     * resource URI.
     */
    public static final String TOKEN_FORMAT = "SharedAccessSignature sig=%s&se=%s&sr=%s";

    /** Components of the SAS token. */
    protected final String signature;
    /** The time, as a UNIX timestamp, before which the token is valid. */
    protected final long expiryTime;
    /**
     * The URI for a connection from a device to an IoT Hub. Does not include a
     * protocol.
     */
    protected final String scope;

    /**
     * Constructor. Generates a SAS token that grants access to an IoT Hub for
     * the specified amount of time.
     *
     * @param scope the resource URI.
     * @param key the device key.
     * @param expiryTime the time, as a UNIX timestamp, after which the token
     * will become invalid.
     */
    public IotHubSasToken(String scope, String key, long expiryTime)
    {
        // Tests_SRS_IOTHUBSASTOKEN_11_002: [**The constructor shall save all input parameters to member variables.**]
        this.scope = scope;
        this.expiryTime = expiryTime;

        // Codes_SRS_IOTHUBSASTOKEN_11_005: [The signature shall be correctly computed and set.]
        Signature sig = new Signature(this.scope, this.expiryTime, key);
        this.signature = sig.toString();
    }

    /**
     * Returns the string representation of the SAS token.
     *
     * @return the string representation of the SAS token.
     */
    @Override
    public String toString()
    {
        // Tests_SRS_IOTHUBSASTOKEN_11_006: [The function shall return the string representation of the SAS token.]
        return buildSasToken();
    }

    protected String buildSasToken() {
        // Codes_SRS_IOTHUBSASTOKEN_11_001: [The SAS token shall have the format "SharedAccessSignature sig=&se=&sr=". The params can be in any order.]
        return String.format(TOKEN_FORMAT, this.signature, this.expiryTime, this.scope);
    }

    protected IotHubSasToken()
    {
        this.signature = null;
        this.expiryTime = 0l;
        this.scope = null;
    }
}