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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 io.milton.http.fs;

import io.milton.http.*;
import io.milton.http.exceptions.NotAuthorizedException;
import io.milton.resource.LockableResource;

import java.io.File;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.UUID;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 *
 */
public class FsMemoryLockManager implements LockManager {

    private static final Logger log = LoggerFactory.getLogger(FsMemoryLockManager.class);
    /**
     * maps current locks by the file associated with the resource
     */
    final Map locksByFile;
    final Map locksByToken;

    public FsMemoryLockManager() {
        locksByFile = new HashMap<>();
        locksByToken = new HashMap<>();
    }

    @Override
    public synchronized LockResult lock(LockTimeout timeout, LockInfo lockInfo, LockableResource r) {
        FsResource resource = (FsResource) r;
        LockToken currentLock = currentLock(resource);
        if (currentLock != null) {
            return LockResult.failed(LockResult.FailureReason.ALREADY_LOCKED);
        }

        LockToken newToken = new LockToken(UUID.randomUUID().toString(), lockInfo, timeout);
        CurrentLock newLock = new CurrentLock(resource.getFile(), newToken, lockInfo.lockedByUser);
        locksByFile.put(resource.getFile(), newLock);
        locksByToken.put(newToken.tokenId, newLock);
        return LockResult.success(newToken);
    }

    @Override
    public synchronized LockResult refresh(String tokenId, LockTimeout timeout, LockableResource resource) {
        CurrentLock curLock = locksByToken.get(tokenId);
        if (curLock == null) {
            log.debug("can't refresh because no lock");
            return LockResult.failed(LockResult.FailureReason.PRECONDITION_FAILED);
        } else {
            curLock.token.setTimeout(timeout);
            curLock.token.setFrom(new Date());
            return LockResult.success(curLock.token);
        }
    }

    @Override
    public synchronized void unlock(String tokenId, LockableResource r) throws NotAuthorizedException {
        FsResource resource = (FsResource) r;
        LockToken lockToken = currentLock(resource);
        if (lockToken == null) {
            log.debug("not locked");
            return;
        }
        if (lockToken.tokenId.equals(tokenId)) {
            removeLock(lockToken);
        } else {
            throw new NotAuthorizedException(resource);
        }
    }

    private LockToken currentLock(FsResource resource) {
        CurrentLock curLock = locksByFile.get(resource.getFile());
        if (curLock == null) return null;
        LockToken token = curLock.token;
        if (token.isExpired()) {
            removeLock(token);
            return null;
        } else {
            return token;
        }
    }

    private void removeLock(LockToken token) {
        log.debug("removeLock: " + token.tokenId);
        CurrentLock currentLock = locksByToken.get(token.tokenId);
        if (currentLock != null) {
            locksByFile.remove(currentLock.file);
            locksByToken.remove(currentLock.token.tokenId);
        } else {
            log.warn("couldnt find lock: " + token.tokenId);
        }
    }

    @Override
    public LockToken getCurrentToken(LockableResource r) {
        FsResource resource = (FsResource) r;
        CurrentLock lock = locksByFile.get(resource.getFile());
        if (lock == null) return null;
        LockToken token = new LockToken();
        token.info = new LockInfo(LockInfo.LockScope.EXCLUSIVE, LockInfo.LockType.WRITE, lock.lockedByUser, LockInfo.LockDepth.ZERO);
        token.info.lockedByUser = lock.lockedByUser;
        token.timeout = lock.token.timeout;
        token.tokenId = lock.token.tokenId;
        return token;
    }

    static class CurrentLock {

        final File file;
        final LockToken token;
        final String lockedByUser;

        public CurrentLock(File file, LockToken token, String lockedByUser) {
            this.file = file;
            this.token = token;
            this.lockedByUser = lockedByUser;
        }
    }
}