Base PGPainlessCLI on new sop-java module

* Rename pgpainless-sop -> pgpainless-cli
* Introduce sop-java (implementation-independent SOP API)
* Introduce sop-java-picocli (CLI frontend for sop-java)
* Introduce pgpainless-sop (implementation of sop-java using PGPainless)
* Rework pgpainless-cli (plugs pgpainless-sop into sop-java-picocli)

sop-java/src/main/java/sop/operation/Decrypt.java

@@ -0,0 +1,94 @@
+/*
+ * Copyright 2021 Paul Schaub.
+ *
+ * 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 sop.operation;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Date;
+
+import sop.DecryptionResult;
+import sop.ReadyWithResult;
+import sop.SessionKey;
+import sop.exception.SOPGPException;
+
+public interface Decrypt {
+
+    /**
+     * Makes the SOP consider signatures before this date invalid.
+     *
+     * @param timestamp timestamp
+     * @return builder instance
+     */
+    Decrypt verifyNotBefore(Date timestamp)
+            throws SOPGPException.UnsupportedOption;
+
+    /**
+     * Makes the SOP consider signatures after this date invalid.
+     *
+     * @param timestamp timestamp
+     * @return builder instance
+     */
+    Decrypt verifyNotAfter(Date timestamp)
+            throws SOPGPException.UnsupportedOption;
+
+    /**
+     * Adds the verification cert.
+     *
+     * @param cert input stream containing the cert
+     * @return builder instance
+     */
+    Decrypt verifyWithCert(InputStream cert)
+            throws SOPGPException.BadData,
+            IOException;
+
+    /**
+     * Tries to decrypt with the given session key.
+     *
+     * @param sessionKey session key
+     * @return builder instance
+     */
+    Decrypt withSessionKey(SessionKey sessionKey)
+            throws SOPGPException.UnsupportedOption;
+
+    /**
+     * Tries to decrypt with the given password.
+     *
+     * @param password password
+     * @return builder instance
+     */
+    Decrypt withPassword(String password)
+            throws SOPGPException.PasswordNotHumanReadable,
+            SOPGPException.UnsupportedOption;
+
+    /**
+     * Adds the decryption key.
+     *
+     * @param key input stream containing the key
+     * @return builder instance
+     */
+    Decrypt withKey(InputStream key)
+            throws SOPGPException.KeyIsProtected,
+            SOPGPException.BadData,
+            SOPGPException.UnsupportedAsymmetricAlgo;
+
+    /**
+     * Decrypts the given ciphertext, returning verification results and plaintext.
+     * @param ciphertext ciphertext
+     * @return ready with result
+     */
+    ReadyWithResult<DecryptionResult> ciphertext(InputStream ciphertext)
+            throws SOPGPException.BadData, SOPGPException.MissingArg, SOPGPException.CannotDecrypt;
+}