/*
 * Copyright 2008 Google, Inc.
 *
 * 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 net.oauth;

import java.io.IOException;
import java.net.URISyntaxException;

import net.oauth.signature.OAuthSignatureMethod;

/**
 * A simple OAuthValidator, which checks the version, whether the timestamp
 * is close to now and the signature is valid. Each check may be overridden.
 *
 * @author Dirk Balfanz
 * @author John Kristian
 * @hide
 */
public class SimpleOAuthValidator implements OAuthValidator {

    // default window for timestamps is 5 minutes
    public static final long DEFAULT_TIMESTAMP_WINDOW = 5 * 60 * 1000L;

    /**
     * Construct a validator that rejects messages more than five minutes out
     * of date, or with a OAuth version other than 1.0, or with an invalid
     * signature.
     */
    public SimpleOAuthValidator() {
        this(DEFAULT_TIMESTAMP_WINDOW, Double.parseDouble(OAuth.VERSION_1_0));
    }

    /**
     * Public constructor.
     *
     * @param timestampWindowSec
     *            specifies, in seconds, the windows (into the past and
     *            into the future) in which we'll accept timestamps.
     * @param maxVersion
     *            the maximum acceptable oauth_version
     */
    public SimpleOAuthValidator(long timestampWindowMsec, double maxVersion) {
        this.timestampWindow = timestampWindowMsec;
        this.maxVersion = maxVersion;
    }

    protected final double minVersion = 1.0;
    protected final double maxVersion;
    protected final long timestampWindow;

    /** {@inherit} 
     * @throws URISyntaxException */
    public void validateMessage(OAuthMessage message, OAuthAccessor accessor)
    throws OAuthException, IOException, URISyntaxException {
        validateVersion(message);
        validateTimestampAndNonce(message);
        validateSignature(message, accessor);
    }

    protected void validateVersion(OAuthMessage message)
    throws OAuthException, IOException {
        String versionString = message.getParameter(OAuth.OAUTH_VERSION);
        if (versionString != null) {
            double version = Double.parseDouble(versionString);
            if (version < minVersion || maxVersion < version) {
                OAuthProblemException problem = new OAuthProblemException("version_rejected");
                problem.setParameter("oauth_acceptable_versions", minVersion + "-" + maxVersion);
                throw problem;
            }
        }
    }

    /** This implementation doesn't check the nonce value. */
    protected void validateTimestampAndNonce(OAuthMessage message)
    throws IOException, OAuthProblemException {
        message.requireParameters(OAuth.OAUTH_TIMESTAMP, OAuth.OAUTH_NONCE);
        long timestamp = Long.parseLong(message.getParameter(OAuth.OAUTH_TIMESTAMP)) * 1000L;
        long now = currentTimeMsec();
        long min = now - timestampWindow;
        long max = now + timestampWindow;
        if (timestamp < min || max < timestamp) {
            OAuthProblemException problem = new OAuthProblemException("timestamp_refused");
            problem.setParameter("oauth_acceptable_timestamps", min + "-" + max);
            throw problem;
        }
    }

    protected void validateSignature(OAuthMessage message, OAuthAccessor accessor)
    throws OAuthException, IOException, URISyntaxException {
        message.requireParameters(OAuth.OAUTH_CONSUMER_KEY,
                OAuth.OAUTH_SIGNATURE_METHOD, OAuth.OAUTH_SIGNATURE);
        OAuthSignatureMethod.newSigner(message, accessor).validate(message);
    }

    protected long currentTimeMsec() {
        return System.currentTimeMillis();
    }

}