package ve.gob.cenditel.tibisaymovil;

import java.io.Serializable;
import java.security.PrivateKey;
import java.security.cert.X509Certificate;

import android.os.Build;
import android.os.Build.VERSION_CODES;

/**
 * Accesses the KeyChain in a unified way both in Android versions post and pre 4.0. Android 4.0 and later has an
 * operating system level keychain. This keychain is shared across the operating system and all applications. In prior
 * versions a custom, application private keychain will be used.
 *
 * @author José M. Prieto (jmprieto@emergya.com)
 */
public abstract class KeyChainStrategy implements Serializable {

    private static final long serialVersionUID = -5156264665372692833L;
    protected static KeyChainStrategy theInstance = null;

    protected static KeyChainClientActivity activity;

    public static KeyChainStrategy getInstance() {

        if (theInstance == null) {
            if (Build.VERSION.SDK_INT < VERSION_CODES.ICE_CREAM_SANDWICH) {
                // < Android 4.0. Does not have KeyChain API
                return CustomKeyChain.getInstance();
            } else {
                // >= Android 4.0. KeyChain available!
                return AndroidKeyChain.getInstance();
            }
        }
        return theInstance;
    }

    /**
     * Set the KeyChainClientActivity that will be notified of the alias selected by the user. The notification is done
     * via the {@link KeyChainClientActivity#setAlias(String)} callback.
     *
     * @param activity the receiver of notifications
     */
    public void setClientActivity(KeyChainClientActivity activity) {
        KeyChainStrategy.activity = activity;
    }

    /**
     * Launches an Activity for the user to select the alias for a private key and certificate pair for authentication.
     * The selected alias or null will be returned to the {@link KeyChainClientActivity} passed to the previous call to
     * {@link #setClientActivity(KeyChainClientActivity)} via the
     * {@link KeyChainClientActivity#setAlias(String)} callback.
     */
    public abstract void choosePrivateKeyAlias();
    
    
    /**
     * Same as before, but only to modify alias list.
     */
    public abstract void choosePrivateKeyList();
    

    /**
     * Get a certificate chain from the keystore.
     * This method requires the caller to hold the permission USE_CREDENTIALS on Android >= 4.0.
     *
     * @param alias The alias of the desired certificate chain
     * @return the X509Certificate chain for the requested alias, or null if no there is no result
     * @throws InterruptedException if the operation has been interrupted before completion
     * @throws KeystoreException when there is some error accessing the keystore
     */
    public abstract X509Certificate[] getCertificateChain(String alias)
    throws InterruptedException, KeystoreException;

    /**
     * Get a private key from the keystore.
     *
     * @param alias the alias of the desired private key
     * @return the PrivateKey for the requested alias, or null if no there is no result
     * @throws InterruptedException if the operation has been interrupted before completion
     * @throws KeystoreException when there is some error accessing the keystore
     */
    public abstract PrivateKey getPrivateKey(String alias)
    throws InterruptedException, KeystoreException;
    
    
    
    
    /**
     * Delete a certificate from the keystore.
     *
     * @param alias the alias of the certificate chain to delete
     * @throws InterruptedException if the operation has been interrupted before completion
     * @throws KeystoreException when there is some error accessing the keystore
     */
    public abstract int deleteCertificate(String alias) 
    		throws InterruptedException, KeystoreException;
    
    
    
}