/*
    * Copyright (C) 2007-2012 Argeo GmbH
    *
    * 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.argeo.cms.security;
  
  import java.io.ByteArrayInputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.CharArrayWriter;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.OutputStreamWriter;
  import java.io.Reader;
  import java.io.Writer;
  import java.security.AccessController;
  import java.security.Provider;
  import java.security.Security;
  import java.util.Arrays;
  import java.util.Iterator;
  
  import javax.crypto.SecretKey;
  import javax.security.auth.Subject;
  import javax.security.auth.callback.Callback;
  import javax.security.auth.callback.CallbackHandler;
  import javax.security.auth.callback.PasswordCallback;
  import javax.security.auth.callback.TextOutputCallback;
  import javax.security.auth.callback.UnsupportedCallbackException;
  import javax.security.auth.login.LoginContext;
  import javax.security.auth.login.LoginException;
  
  import org.apache.commons.io.IOUtils;
  import org.argeo.api.NodeConstants;
  import org.argeo.api.security.CryptoKeyring;
  import org.argeo.api.security.Keyring;
  import org.argeo.api.security.PBEKeySpecCallback;
  import org.argeo.cms.CmsException;
  
  /** username / password based keyring. TODO internationalize */
  public abstract class AbstractKeyring implements Keyring, CryptoKeyring {
  	// public final static String DEFAULT_KEYRING_LOGIN_CONTEXT = "KEYRING";
  
  	// private String loginContextName = DEFAULT_KEYRING_LOGIN_CONTEXT;
  	private CallbackHandler defaultCallbackHandler;
  
  	private String charset = "UTF-8";
  
  	/**
  	 * Default provider is bouncy castle, in order to have consistent behaviour
  	 * across implementations
  	 */
  	private String securityProviderName = "BC";
  
  	/**
  	 * Whether the keyring has already been created in the past with a master
  	 * password
  	 */
  	protected abstract Boolean isSetup();
  
  	/**
  	 * Setup the keyring persistently, {@link #isSetup()} must return true
  	 * afterwards
  	 */
  	protected abstract void setup(char[] password);
  
  	/** Populates the key spec callback */
  	protected abstract void handleKeySpecCallback(PBEKeySpecCallback pbeCallback);
  
  	protected abstract void encrypt(String path, InputStream unencrypted);
  
  	protected abstract InputStream decrypt(String path);
  
  	/** Triggers lazy initialization */
  	protected SecretKey getSecretKey(char[] password) {
  		Subject subject = Subject.getSubject(AccessController.getContext());
  		// we assume only one secrete key is available
  		Iterator<SecretKey> iterator = subject.getPrivateCredentials(SecretKey.class).iterator();
  		if (!iterator.hasNext() || password!=null) {// not initialized
  			CallbackHandler callbackHandler = password == null ? new KeyringCallbackHandler()
  					: new PasswordProvidedCallBackHandler(password);
  			ClassLoader currentContextClassLoader = Thread.currentThread().getContextClassLoader();
  			Thread.currentThread().setContextClassLoader(getClass().getClassLoader());
  			try {
  				LoginContext loginContext = new LoginContext(NodeConstants.LOGIN_CONTEXT_KEYRING, subject,
  						callbackHandler);
  				loginContext.login();
  				// FIXME will login even if password is wrong
  				iterator = subject.getPrivateCredentials(SecretKey.class).iterator();
 				return iterator.next();
 			} catch (LoginException e) {
 				throw new CmsException("Keyring login failed", e);
 			} finally {
 				Thread.currentThread().setContextClassLoader(currentContextClassLoader);
 			}
 
 		} else {
 			SecretKey secretKey = iterator.next();
 			if (iterator.hasNext())
 				throw new CmsException("More than one secret key in private credentials");
 			return secretKey;
 		}
 	}
 
 	public InputStream getAsStream(String path) {
 		return decrypt(path);
 	}
 
 	public void set(String path, InputStream in) {
 		encrypt(path, in);
 	}
 
 	public char[] getAsChars(String path) {
 		// InputStream in = getAsStream(path);
 		// CharArrayWriter writer = null;
 		// Reader reader = null;
 		try (InputStream in = getAsStream(path);
 				CharArrayWriter writer = new CharArrayWriter();
 				Reader reader = new InputStreamReader(in, charset);) {
 			IOUtils.copy(reader, writer);
 			return writer.toCharArray();
 		} catch (IOException e) {
 			throw new CmsException("Cannot decrypt to char array", e);
 		} finally {
 			// IOUtils.closeQuietly(reader);
 			// IOUtils.closeQuietly(in);
 			// IOUtils.closeQuietly(writer);
 		}
 	}
 
 	public void set(String path, char[] arr) {
 		// ByteArrayOutputStream out = new ByteArrayOutputStream();
 		// ByteArrayInputStream in = null;
 		// Writer writer = null;
 		try (ByteArrayOutputStream out = new ByteArrayOutputStream();
 				Writer writer = new OutputStreamWriter(out, charset);) {
 			// writer = new OutputStreamWriter(out, charset);
 			writer.write(arr);
 			writer.flush();
 			// in = new ByteArrayInputStream(out.toByteArray());
 			try (ByteArrayInputStream in = new ByteArrayInputStream(out.toByteArray());) {
 				set(path, in);
 			}
 		} catch (IOException e) {
 			throw new CmsException("Cannot encrypt to char array", e);
 		} finally {
 			// IOUtils.closeQuietly(writer);
 			// IOUtils.closeQuietly(out);
 			// IOUtils.closeQuietly(in);
 		}
 	}
 
 	public void unlock(char[] password) {
 		if (!isSetup())
 			setup(password);
 		SecretKey secretKey = getSecretKey(password);
 		if (secretKey == null)
 			throw new CmsException("Could not unlock keyring");
 	}
 
 	protected Provider getSecurityProvider() {
 		return Security.getProvider(securityProviderName);
 	}
 
 	public void setDefaultCallbackHandler(CallbackHandler defaultCallbackHandler) {
 		this.defaultCallbackHandler = defaultCallbackHandler;
 	}
 
 	public void setCharset(String charset) {
 		this.charset = charset;
 	}
 
 	public void setSecurityProviderName(String securityProviderName) {
 		this.securityProviderName = securityProviderName;
 	}
 
 	// @Deprecated
 	// protected static byte[] hash(char[] password, byte[] salt, Integer
 	// iterationCount) {
 	// ByteArrayOutputStream out = null;
 	// OutputStreamWriter writer = null;
 	// try {
 	// out = new ByteArrayOutputStream();
 	// writer = new OutputStreamWriter(out, "UTF-8");
 	// writer.write(password);
 	// MessageDigest pwDigest = MessageDigest.getInstance("SHA-256");
 	// pwDigest.reset();
 	// pwDigest.update(salt);
 	// byte[] btPass = pwDigest.digest(out.toByteArray());
 	// for (int i = 0; i < iterationCount; i++) {
 	// pwDigest.reset();
 	// btPass = pwDigest.digest(btPass);
 	// }
 	// return btPass;
 	// } catch (Exception e) {
 	// throw new CmsException("Cannot hash", e);
 	// } finally {
 	// IOUtils.closeQuietly(out);
 	// IOUtils.closeQuietly(writer);
 	// }
 	//
 	// }
 
 	/**
 	 * Convenience method using the underlying callback to ask for a password
 	 * (typically used when the password is not saved in the keyring)
 	 */
 	protected char[] ask() {
 		PasswordCallback passwordCb = new PasswordCallback("Password", false);
 		Callback[] dialogCbs = new Callback[] { passwordCb };
 		try {
 			defaultCallbackHandler.handle(dialogCbs);
 			char[] password = passwordCb.getPassword();
 			return password;
 		} catch (Exception e) {
 			throw new CmsException("Cannot ask for a password", e);
 		}
 
 	}
 
 	class KeyringCallbackHandler implements CallbackHandler {
 		public void handle(Callback[] callbacks) throws IOException, UnsupportedCallbackException {
 			// checks
 			if (callbacks.length != 2)
 				throw new IllegalArgumentException(
 						"Keyring requires 2 and only 2 callbacks: {PasswordCallback,PBEKeySpecCallback}");
 			if (!(callbacks[0] instanceof PasswordCallback))
 				throw new UnsupportedCallbackException(callbacks[0]);
 			if (!(callbacks[1] instanceof PBEKeySpecCallback))
 				throw new UnsupportedCallbackException(callbacks[0]);
 
 			PasswordCallback passwordCb = (PasswordCallback) callbacks[0];
 			PBEKeySpecCallback pbeCb = (PBEKeySpecCallback) callbacks[1];
 
 			if (isSetup()) {
 				Callback[] dialogCbs = new Callback[] { passwordCb };
 				defaultCallbackHandler.handle(dialogCbs);
 			} else {// setup keyring
 				TextOutputCallback textCb1 = new TextOutputCallback(TextOutputCallback.INFORMATION,
 						"Enter a master password which will protect your private data");
 				TextOutputCallback textCb2 = new TextOutputCallback(TextOutputCallback.INFORMATION,
 						"(for example your credentials to third-party services)");
 				TextOutputCallback textCb3 = new TextOutputCallback(TextOutputCallback.INFORMATION,
 						"Don't forget this password since the data cannot be read without it");
 				PasswordCallback confirmPasswordCb = new PasswordCallback("Confirm password", false);
 				// first try
 				Callback[] dialogCbs = new Callback[] { textCb1, textCb2, textCb3, passwordCb, confirmPasswordCb };
 				defaultCallbackHandler.handle(dialogCbs);
 
 				// if passwords different, retry (except if cancelled)
 				while (passwordCb.getPassword() != null
 						&& !Arrays.equals(passwordCb.getPassword(), confirmPasswordCb.getPassword())) {
 					TextOutputCallback textCb = new TextOutputCallback(TextOutputCallback.ERROR,
 							"The passwords do not match");
 					dialogCbs = new Callback[] { textCb, passwordCb, confirmPasswordCb };
 					defaultCallbackHandler.handle(dialogCbs);
 				}
 
 				if (passwordCb.getPassword() != null) {// not cancelled
 					setup(passwordCb.getPassword());
 				}
 			}
 
 			if (passwordCb.getPassword() != null)
 				handleKeySpecCallback(pbeCb);
 		}
 
 	}
 
 	class PasswordProvidedCallBackHandler implements CallbackHandler {
 		private final char[] password;
 
 		public PasswordProvidedCallBackHandler(char[] password) {
 			this.password = password;
 		}
 
 		@Override
 		public void handle(Callback[] callbacks) throws IOException, UnsupportedCallbackException {
 			// checks
 			if (callbacks.length != 2)
 				throw new IllegalArgumentException(
 						"Keyring requires 2 and only 2 callbacks: {PasswordCallback,PBEKeySpecCallback}");
 			if (!(callbacks[0] instanceof PasswordCallback))
 				throw new UnsupportedCallbackException(callbacks[0]);
 			if (!(callbacks[1] instanceof PBEKeySpecCallback))
 				throw new UnsupportedCallbackException(callbacks[0]);
 
 			PasswordCallback passwordCb = (PasswordCallback) callbacks[0];
 			passwordCb.setPassword(password);
 			PBEKeySpecCallback pbeCb = (PBEKeySpecCallback) callbacks[1];
 			handleKeySpecCallback(pbeCb);
 		}
 
 	}
 }