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Common utility classes for building cloud pools.

There is a newer version: 5.2.3

package com.elastisys.scale.cloudpool.commons.basepool;

import static com.google.common.base.Preconditions.checkArgument;

import java.io.File;
import java.util.Arrays;
import java.util.List;
import java.util.Set;

import com.elastisys.scale.cloudpool.commons.basepool.poolfetcher.impl.CachingPoolFetcher;
import com.google.common.collect.ImmutableSet;

/**
 * Declares where runtime state is stored during execution, and where runtime
 * state is recovered from when the {@link BaseCloudPool} process is restarted.
 */
public class StateStorage {
	public static final String DEFAULT_CACHED_MACHINE_POOL_FILENAME = "cached_machine_pool.json";

	/**
	 * File where the {@link CachingPoolFetcher} stores its machine pool cache.
	 */
	private final File cachedMachinePoolFile;

	/**
	 * Creates a {@link StateStorage} instance.
	 *
	 * @param cachedMachinePoolFile
	 *            File where the {@link CachingPoolFetcher} stores its machine
	 *            pool cache.
	 */
	private StateStorage(File cachedMachinePoolFile) {
		this.cachedMachinePoolFile = cachedMachinePoolFile;
	}

	/**
	 * File where the {@link CachingPoolFetcher} stores its machine pool cache.
	 *
	 * @return
	 */
	public File getCachedMachinePoolFile() {
		return this.cachedMachinePoolFile;
	}

	public static StateStorageBuilder builder(String storageDir) {
		return builder(new File(storageDir));
	}

	public static StateStorageBuilder builder(File storageDir) {
		return new StateStorageBuilder(storageDir);
	}

	/**
	 * Builds {@link StateStorage} instances with files relative to a given
	 * storage directory.
	 */
	public static class StateStorageBuilder {
		private final File storageDir;

		private String cachedMachinePoolFileName = DEFAULT_CACHED_MACHINE_POOL_FILENAME;

		public StateStorageBuilder(File storageDir) {
			checkArgument(storageDir != null, "storageDir cannot be null");
			this.storageDir = storageDir;
		}

		public StateStorage build() {
			List allFileNames = Arrays
					.asList(this.cachedMachinePoolFileName);
			Set uniqueFileNames = ImmutableSet.copyOf(allFileNames);
			checkArgument(allFileNames.size() == uniqueFileNames.size(),
					"all StateStorage file names need to be unique");

			File cachedMachinePoolFile = new File(this.storageDir,
					this.cachedMachinePoolFileName);
			return new StateStorage(cachedMachinePoolFile);
		}

		/**
		 * The name of the tile where the {@link CachingPoolFetcher} stores its
		 * machine pool cache.
		 *
		 * @param fileName
		 * @return
		 */
		public StateStorageBuilder withCachedMachinePoolFileName(
				String fileName) {
			checkArgument(fileName != null, "fileName cannot be null");
			this.cachedMachinePoolFileName = fileName;
			return this;
		}
	}
}