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An OAuth2 client implementation based on http-client-essentials.
There is a newer version: 0.22.1
/*
 * Copyright (C) 2016 Marten Gajda 
 *
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.dmfs.oauth2.client.grants;

import java.io.IOException;
import java.net.URI;

import org.dmfs.httpessentials.client.HttpRequestExecutor;
import org.dmfs.httpessentials.exceptions.ProtocolError;
import org.dmfs.httpessentials.exceptions.ProtocolException;
import org.dmfs.oauth2.client.BasicOAuth2AuthorizationRequest;
import org.dmfs.oauth2.client.OAuth2AccessToken;
import org.dmfs.oauth2.client.OAuth2Client;
import org.dmfs.oauth2.client.OAuth2InteractiveGrant;
import org.dmfs.oauth2.client.OAuth2Scope;
import org.dmfs.oauth2.client.scope.StringScope;
import org.dmfs.oauth2.client.tokens.ImplicitGrantAccessToken;


/**
 * Implements the OAuth2 Implicit Grant as specified in RFC 6749, Section 4.2.
 * 
 * @author Marten Gajda 
 */
public final class ImplicitGrant implements OAuth2InteractiveGrant
{

	private final OAuth2Client mClient;
	private final OAuth2Scope mScope;
	private final String mState;


	/**
	 * Creates a new {@link ImplicitGrant} for the given {@link OAuth2Client} and {@link OAuth2Scope}.
	 * 
	 * @param client
	 *            The {@link OAuth2Client} that requests access.
	 * @param scope
	 *            The {@link OAuth2Scope} to request access to.
	 */
	public ImplicitGrant(OAuth2Client client, OAuth2Scope scope)
	{
		this(client, scope, client.generatedRandomState());
	}


	private ImplicitGrant(OAuth2Client client, OAuth2Scope scope, String state)
	{
		mClient = client;
		mScope = scope;
		mState = state;
	}


	@Override
	public URI authorizationUrl()
	{
		if (mScope.isEmpty())
		{
			return mClient.authorizationUrl(new BasicOAuth2AuthorizationRequest("token", mState));
		}
		else
		{
			return mClient.authorizationUrl(new BasicOAuth2AuthorizationRequest("token", mScope, mState));
		}
	}


	@Override
	public OAuth2InteractiveGrant withRedirect(final URI redirectUri)
	{
		return new AuthorizedImplicitGrant(mClient, redirectUri, mScope, mState);
	}


	@Override
	public OAuth2AccessToken accessToken(HttpRequestExecutor executor) throws IOException, ProtocolError, ProtocolException
	{
		throw new IllegalStateException("first use withRedirectUri(URI) to pass the redirect URI returned by the authorization endpoint.");
	}


	@Override
	public OAuth2InteractiveGrant.OAuth2GrantState state()
	{
		return new InitialImplicitGrantState(mScope, mState);
	}

	/**
	 * An {@link OAuth2InteractiveGrant} that represents the authorized state of an Implicit Grant. That means, the user has granted access and an access token
	 * was issued by the server.
	 * 
	 * The next step is to retrieve the {@link OAuth2AccessToken}.
	 */
	private final static class AuthorizedImplicitGrant implements OAuth2InteractiveGrant
	{
		private final OAuth2Client mClient;
		private final URI mRedirectUri;
		private final OAuth2Scope mScope;
		private final String mState;


		private AuthorizedImplicitGrant(OAuth2Client client, URI redirectUri, OAuth2Scope scope, String state)
		{
			mClient = client;
			mRedirectUri = redirectUri;
			mScope = scope;
			mState = state;
		}


		@Override
		public OAuth2AccessToken accessToken(HttpRequestExecutor executor) throws IOException, ProtocolError, ProtocolException
		{
			return new ImplicitGrantAccessToken(mRedirectUri, mScope, mState, mClient.defaultTokenTtl());
		}


		@Override
		public URI authorizationUrl()
		{
			throw new IllegalStateException("This grant has already been completed. You can't start it again.");
		}


		@Override
		public OAuth2InteractiveGrant withRedirect(URI redirectUri)
		{
			throw new IllegalStateException("This grant has already been completed. You can't feed another redirect URI.");
		}


		@Override
		public OAuth2GrantState state()
		{
			throw new UnsupportedOperationException(
				"There is no need to store the state of an Implicit grant that was already authorized. Just get the access token.");
		}
	}

	/**
	 * An {@link OAuth2GrantState} that represents the state of an Implicit Grant that was not confirmed by the user so far.
	 */
	private final static class InitialImplicitGrantState implements OAuth2InteractiveGrant.OAuth2GrantState
	{

		private static final long serialVersionUID = 1L;

		private final String mScopeString;
		private final String mState;


		public InitialImplicitGrantState(OAuth2Scope scope, String state)
		{
			mScopeString = scope.toString();
			mState = state;
		}


		@Override
		public ImplicitGrant grant(OAuth2Client client)
		{
			return new ImplicitGrant(client, new StringScope(mScopeString), mState);
		}

	}
}