package com.atlassian.refapp.trustedapps.internal;
   
   import com.atlassian.sal.api.pluginsettings.PluginSettings;
   import com.atlassian.sal.api.pluginsettings.PluginSettingsFactory;
   import com.atlassian.security.auth.trustedapps.EncryptionProvider;
   
   import java.security.KeyPair;
   import java.security.NoSuchAlgorithmException;
   import java.security.NoSuchProviderException;
  import java.security.PrivateKey;
  import java.security.PublicKey;
  import java.util.Random;
  
  /**
   * Factory for getting key pairs to use in net applications.  Stores keys in the com.atlassian.refapp.sal.pluginsettings for possible
   * persistence between restarts.
   */
  public class KeyFactory {
      private static final String PRIVATE_KEY = "trustedapps.private-key";
      private static final String PUBLIC_KEY = "trustedapps.public-key";
      private static final String APPLICTAION_ID = "trustedapps.application-id";
  
      private EncryptionProvider encryptionProvider;
      private PluginSettings pluginSettings;
  
      public KeyFactory(EncryptionProvider encryptionProvider, PluginSettingsFactory pluginSettingsFactory) {
          this.encryptionProvider = encryptionProvider;
          pluginSettings = pluginSettingsFactory.createGlobalSettings();
      }
  
      public KeyPair getKeyPair() {
          KeyPair keyPair;
          if (pluginSettings.get(PRIVATE_KEY) != null) {
              keyPair = fetchKeyPair();
          } else {
              keyPair = createKeyPair();
              storeKeyPair(keyPair);
          }
          return keyPair;
      }
  
      public String getApplicationId() {
          return (String) pluginSettings.get(APPLICTAION_ID);
      }
  
      private KeyPair createKeyPair() {
          try {
              return encryptionProvider.generateNewKeyPair();
          } catch (NoSuchAlgorithmException e) {
              throw new IllegalArgumentException("No such algorithm", e);
          } catch (NoSuchProviderException e) {
              throw new IllegalArgumentException("No such provider", e);
          }
      }
  
      private void storeKeyPair(KeyPair keyPair) {
          pluginSettings.put(PUBLIC_KEY, KeyUtils.encode(keyPair.getPublic()));
          pluginSettings.put(PRIVATE_KEY, KeyUtils.encode(keyPair.getPrivate()));
          pluginSettings.put(APPLICTAION_ID, "refapp:" + Integer.toString(new Random().nextInt(90000) + 10000));
      }
  
      private KeyPair fetchKeyPair() {
          return new KeyPair(fetchPublicKey(), fetchPrivateKey());
      }
  
      private PrivateKey fetchPrivateKey() {
          String keyStr = (String) pluginSettings.get(PRIVATE_KEY);
          return KeyUtils.decodePrivateKey(encryptionProvider, keyStr);
      }
  
      private PublicKey fetchPublicKey() {
          String keyStr = (String) pluginSettings.get(PUBLIC_KEY);
          return KeyUtils.decodePublicKey(encryptionProvider, keyStr);
      }
  
  }