package com.fsck.k9.activity.setup;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.DialogFragment;
import android.app.FragmentTransaction;
import android.content.DialogInterface;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
import android.os.Process;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;

import com.fsck.k9.*;
import com.fsck.k9.activity.K9Activity;
import com.fsck.k9.controller.MessagingController;
import com.fsck.k9.fragment.ConfirmationDialogFragment;
import com.fsck.k9.fragment.ConfirmationDialogFragment.ConfirmationDialogFragmentListener;
import com.fsck.k9.mail.AuthenticationFailedException;
import com.fsck.k9.mail.CertificateValidationException;
import com.fsck.k9.mail.ClientCertificateRequiredException;
import com.fsck.k9.mail.ServerSettings;
import com.fsck.k9.mail.Store;
import com.fsck.k9.mail.Transport;
import com.fsck.k9.mail.store.WebDavStore;
import com.fsck.k9.mail.filter.Hex;
import com.fsck.k9.net.ssl.SslHelper;
import com.fsck.k9.security.KeyChainKeyManager;

import java.security.cert.CertificateException;
import java.security.cert.CertificateEncodingException;
import java.security.cert.X509Certificate;
import java.security.NoSuchAlgorithmException;
import java.security.MessageDigest;
import java.util.Collection;
import java.util.List;
import java.util.Locale;

/**
 * Checks the given settings to make sure that they can be used to send and
 * receive mail.
 * 
 * XXX NOTE: The manifest for this app has it ignore config changes, because
 * it doesn't correctly deal with restarting while its thread is running.
 */
public class AccountSetupCheckSettings extends K9Activity implements OnClickListener,
        ConfirmationDialogFragmentListener{

    public static final int ACTIVITY_REQUEST_CODE = 1;

    private static final String EXTRA_ACCOUNT = "account";

    private static final String EXTRA_CHECK_DIRECTION ="checkDirection";

    public enum CheckDirection {
        INCOMING,
        OUTGOING
    }

    private Handler mHandler = new Handler();

    private ProgressBar mProgressBar;

    private TextView mMessageView;

    private Account mAccount;

    private boolean mIsClientCertSet;

    private CheckDirection mDirection;

    private boolean mCanceled;

    private boolean mDestroyed;

    public static void actionCheckSettings(Activity context, Account account,
            CheckDirection direction) {
        Intent i = new Intent(context, AccountSetupCheckSettings.class);
        i.putExtra(EXTRA_ACCOUNT, account.getUuid());
        i.putExtra(EXTRA_CHECK_DIRECTION, direction);
        context.startActivityForResult(i, ACTIVITY_REQUEST_CODE);
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.account_setup_check_settings);
        mMessageView = (TextView)findViewById(R.id.message);
        mProgressBar = (ProgressBar)findViewById(R.id.progress);
        ((Button)findViewById(R.id.cancel)).setOnClickListener(this);

        setMessage(R.string.account_setup_check_settings_retr_info_msg);
        mProgressBar.setIndeterminate(true);

        String accountUuid = getIntent().getStringExtra(EXTRA_ACCOUNT);
        mAccount = Preferences.getPreferences(this).getAccount(accountUuid);
        mDirection = (CheckDirection) getIntent().getSerializableExtra(EXTRA_CHECK_DIRECTION);

        new Thread() {
            @Override
            public void run() {
                Store store = null;
                Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
                try {
                    if (mDestroyed) {
                        return;
                    }
                    if (mCanceled) {
                        finish();
                        return;
                    }

                    final MessagingController ctrl = MessagingController.getInstance(getApplication());
                    ctrl.clearCertificateErrorNotifications(AccountSetupCheckSettings.this,
                            mAccount, mDirection);

                    if (mDirection.equals(CheckDirection.INCOMING)) {
                        // refresh URI that stores settings in order to include
                        // client certificate set by user
                        store = mAccount.getRemoteStore(mIsClientCertSet);

                        if (store instanceof WebDavStore) {
                            setMessage(R.string.account_setup_check_settings_authenticate);
                        } else {
                            setMessage(R.string.account_setup_check_settings_check_incoming_msg);
                        }
                        store.checkSettings();

                        if (store instanceof WebDavStore) {
                            setMessage(R.string.account_setup_check_settings_fetch);
                        }
                        MessagingController.getInstance(getApplication()).listFoldersSynchronous(mAccount, true, null);
                        MessagingController.getInstance(getApplication()).synchronizeMailbox(mAccount, mAccount.getInboxFolderName(), null, null);
                    }
                    if (mDestroyed) {
                        return;
                    }
                    if (mCanceled) {
                        finish();
                        return;
                    }
                    if (mDirection.equals(CheckDirection.OUTGOING)) {
                        if (!(mAccount.getRemoteStore() instanceof WebDavStore)) {
                            setMessage(R.string.account_setup_check_settings_check_outgoing_msg);
                        }
                        Transport transport = Transport.getInstance(mAccount);
                        transport.close();
                        transport.open();
                        transport.close();
                    }
                    if (mDestroyed) {
                        return;
                    }
                    if (mCanceled) {
                        finish();
                        return;
                    }
                    setResult(RESULT_OK);
                    finish();
                } catch (final AuthenticationFailedException afe) {
                    Log.e(K9.LOG_TAG, "Error while testing settings", afe);
                    showErrorDialog(
                        R.string.account_setup_failed_dlg_auth_message_fmt,
                        afe.getMessage() == null ? "" : afe.getMessage());
                } catch (final CertificateValidationException cve) {
                    handleCertificateValidationException(cve);
                } catch (final ClientCertificateRequiredException ccr) {
                    handleClientCertificateRequiredException(ccr);
                } catch (final Throwable t) {
                    Log.e(K9.LOG_TAG, "Error while testing settings", t);
                    showErrorDialog(
                        R.string.account_setup_failed_dlg_server_message_fmt,
                        (t.getMessage() == null ? "" : t.getMessage()));
                }
            }

        }
        .start();
    }

    private void handleCertificateValidationException(CertificateValidationException cve) {
        Log.e(K9.LOG_TAG, "Error while testing settings", cve);

        X509Certificate[] chain = cve.getCertChain();
        // Avoid NullPointerException in acceptKeyDialog()
        if (chain != null) {
            acceptKeyDialog(
                    R.string.account_setup_failed_dlg_certificate_message_fmt,
                    cve);
        } else {
            showErrorDialog(
                    R.string.account_setup_failed_dlg_server_message_fmt,
                    (cve.getMessage() == null ? "" : cve.getMessage()));
        }
    }

    private void handleClientCertificateRequiredException(ClientCertificateRequiredException ccr) {
        if (K9.DEBUG)
            Log.d(K9.LOG_TAG, "Client certificate alias required: " + ccr.getMessage());

        /* 
         * If the KeyChain API is not available on this Android
         * version, inform user and abort
         */
        if (!SslHelper.isClientCertificateSupportAvailable()) {
            mHandler.post(new Runnable() {
                public void run() {
                    showDialogFragment(R.id.dialog_client_certificate_not_supported);
                }
            });

            // abort
            return;
        }

        String alias = null;
        if (CheckDirection.INCOMING.equals(mDirection)) {
            ServerSettings storeSettings = Store.decodeStoreUri(mAccount.getStoreUri());
            alias = storeSettings.clientCertificateAlias;
        } else if (CheckDirection.OUTGOING.equals(mDirection)) {
            ServerSettings transportSettings = Transport.decodeTransportUri(mAccount.getTransportUri());
            alias = transportSettings.clientCertificateAlias;
        }

        if (K9.DEBUG)
            Log.d(K9.LOG_TAG, "Client certificate alias is: " + alias);

        alias = KeyChainKeyManager.interactivelyChooseClientCertificateAlias(
                AccountSetupCheckSettings.this,
                ccr.getKeyTypes(),
                ccr.getIssuers(),
                ccr.getHostName(),
                ccr.getPort(),
                alias);

        // Note: KeyChainKeyManager gives back "" on cancel
        if (alias != null && alias.equals("")) {
            alias = null;
        }

        // save client certificate alias
        if (alias != null) {
            if (CheckDirection.INCOMING.equals(mDirection)) {
                if (K9.DEBUG)
                    Log.d(K9.LOG_TAG, "Setting store client certificate alias to: " + alias);

                // Set incoming server client certificate alias
                String storeUri = mAccount.getStoreUri();
                ServerSettings incoming = Store.decodeStoreUri(storeUri);
                ServerSettings newIncoming = incoming.newClientCertificateAlias(alias);
                String newStoreUri = Store.createStoreUri(newIncoming);
                mAccount.setStoreUri(newStoreUri);
            } else if (CheckDirection.OUTGOING.equals(mDirection)) {
                if (K9.DEBUG)
                    Log.d(K9.LOG_TAG, "Setting transport client certificate alias to: " + alias);

                // Set outgoing server client certificate alias
                String transportUri = mAccount.getTransportUri();
                ServerSettings outgoing = Transport.decodeTransportUri(transportUri);
                ServerSettings newOutgoing = outgoing.newClientCertificateAlias(alias);
                String newTransportUri = Transport.createTransportUri(newOutgoing);
                mAccount.setTransportUri(newTransportUri);
            }

            // Save the account settings
            mAccount.save(Preferences.getPreferences(AccountSetupCheckSettings.this));

            // try again
            AccountSetupCheckSettings.actionCheckSettings(AccountSetupCheckSettings.this, mAccount,
                    mDirection);
        } else {
            showErrorDialog(R.string.dialog_client_certificate_required);
        }
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        mDestroyed = true;
        mCanceled = true;
    }

    private void setMessage(final int resId) {
        mHandler.post(new Runnable() {
            public void run() {
                if (mDestroyed) {
                    return;
                }
                mMessageView.setText(getString(resId));
            }
        });
    }

    private void acceptKeyDialog(final int msgResId, final CertificateValidationException ex) {
        mHandler.post(new Runnable() {
            public void run() {
                if (mDestroyed) {
                    return;
                }
                String exMessage = "Unknown Error";

                if (ex != null) {
                    if (ex.getCause() != null) {
                        if (ex.getCause().getCause() != null) {
                            exMessage = ex.getCause().getCause().getMessage();

                        } else {
                            exMessage = ex.getCause().getMessage();
                        }
                    } else {
                        exMessage = ex.getMessage();
                    }
                }

                mProgressBar.setIndeterminate(false);
                StringBuilder chainInfo = new StringBuilder(100);
                MessageDigest sha1 = null;
                try {
                    sha1 = MessageDigest.getInstance("SHA-1");
                } catch (NoSuchAlgorithmException e) {
                    Log.e(K9.LOG_TAG, "Error while initializing MessageDigest", e);
                }

                final X509Certificate[] chain = ex.getCertChain();
                // We already know chain != null (tested before calling this method)
                for (int i = 0; i < chain.length; i++) {
                    // display certificate chain information
                    //TODO: localize this strings
                    chainInfo.append("Certificate chain[").append(i).append("]:\n");
                    chainInfo.append("Subject: ").append(chain[i].getSubjectDN().toString()).append("\n");

                    // display SubjectAltNames too
                    // (the user may be mislead into mistrusting a certificate
                    //  by a subjectDN not matching the server even though a
                    //  SubjectAltName matches)
                    try {
                        final Collection < List<? >> subjectAlternativeNames = chain[i].getSubjectAlternativeNames();
                        if (subjectAlternativeNames != null) {
                            // The list of SubjectAltNames may be very long
                            //TODO: localize this string
                            StringBuilder altNamesText = new StringBuilder();
                            altNamesText.append("Subject has ").append(subjectAlternativeNames.size()).append(" alternative names\n");

                            // we need these for matching
                            String storeURIHost = (Uri.parse(mAccount.getStoreUri())).getHost();
                            String transportURIHost = (Uri.parse(mAccount.getTransportUri())).getHost();

                            for (List<?> subjectAlternativeName : subjectAlternativeNames) {
                                Integer type = (Integer)subjectAlternativeName.get(0);
                                Object value = subjectAlternativeName.get(1);
                                String name = "";
                                switch (type.intValue()) {
                                case 0:
                                    Log.w(K9.LOG_TAG, "SubjectAltName of type OtherName not supported.");
                                    continue;
                                case 1: // RFC822Name
                                    name = (String)value;
                                    break;
                                case 2:  // DNSName
                                    name = (String)value;
                                    break;
                                case 3:
                                    Log.w(K9.LOG_TAG, "unsupported SubjectAltName of type x400Address");
                                    continue;
                                case 4:
                                    Log.w(K9.LOG_TAG, "unsupported SubjectAltName of type directoryName");
                                    continue;
                                case 5:
                                    Log.w(K9.LOG_TAG, "unsupported SubjectAltName of type ediPartyName");
                                    continue;
                                case 6:  // Uri
                                    name = (String)value;
                                    break;
                                case 7: // ip-address
                                    name = (String)value;
                                    break;
                                default:
                                    Log.w(K9.LOG_TAG, "unsupported SubjectAltName of unknown type");
                                    continue;
                                }

                                // if some of the SubjectAltNames match the store or transport -host,
                                // display them
                                if (name.equalsIgnoreCase(storeURIHost) || name.equalsIgnoreCase(transportURIHost)) {
                                    //TODO: localize this string
                                    altNamesText.append("Subject(alt): ").append(name).append(",...\n");
                                } else if (name.startsWith("*.") && (
                                            storeURIHost.endsWith(name.substring(2)) ||
                                            transportURIHost.endsWith(name.substring(2)))) {
                                    //TODO: localize this string
                                    altNamesText.append("Subject(alt): ").append(name).append(",...\n");
                                }
                            }
                            chainInfo.append(altNamesText);
                        }
                    } catch (Exception e1) {
                        // don't fail just because of subjectAltNames
                        Log.w(K9.LOG_TAG, "cannot display SubjectAltNames in dialog", e1);
                    }

                    chainInfo.append("Issuer: ").append(chain[i].getIssuerDN().toString()).append("\n");
                    if (sha1 != null) {
                        sha1.reset();
                        try {
                            char[] sha1sum = Hex.encodeHex(sha1.digest(chain[i].getEncoded()));
                            chainInfo.append("Fingerprint (SHA-1): ").append(new String(sha1sum)).append("\n");
                        } catch (CertificateEncodingException e) {
                            Log.e(K9.LOG_TAG, "Error while encoding certificate", e);
                        }
                    }
                }

                // TODO: refactor with DialogFragment.
                // This is difficult because we need to pass through chain[0] for onClick()
                new AlertDialog.Builder(AccountSetupCheckSettings.this)
                .setTitle(getString(R.string.account_setup_failed_dlg_invalid_certificate_title))
                //.setMessage(getString(R.string.account_setup_failed_dlg_invalid_certificate)
                .setMessage(getString(msgResId, exMessage)
                            + " " + chainInfo.toString()
                           )
                .setCancelable(true)
                .setPositiveButton(
                    getString(R.string.account_setup_failed_dlg_invalid_certificate_accept),
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        acceptCertificate(chain[0]);
                    }
                })
                .setNegativeButton(
                    getString(R.string.account_setup_failed_dlg_invalid_certificate_reject),
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        finish();
                    }
                })
                .show();
            }
        });
    }

    /**
     * Permanently accepts a certificate for the INCOMING or OUTGOING direction
     * by adding it to the local key store.
     * 
     * @param certificate
     */
    private void acceptCertificate(X509Certificate certificate) {
        try {
            mAccount.addCertificate(mDirection, certificate);
        } catch (CertificateException e) {
            showErrorDialog(
                    R.string.account_setup_failed_dlg_certificate_message_fmt,
                    e.getMessage() == null ? "" : e.getMessage());
        }
        AccountSetupCheckSettings.actionCheckSettings(AccountSetupCheckSettings.this, mAccount,
                mDirection);
    }

    @Override
    public void onActivityResult(int reqCode, int resCode, Intent data) {
        setResult(resCode);
        finish();
    }

    private void onCancel() {
        mCanceled = true;
        setMessage(R.string.account_setup_check_settings_canceling_msg);
    }

    public void onClick(View v) {
        switch (v.getId()) {
        case R.id.cancel:
            onCancel();
            break;
        }
    }

    private void showErrorDialog(final int msgResId, final Object... args) {
        mHandler.post(new Runnable() {
            public void run() {
                showDialogFragment(R.id.dialog_account_setup_error, getString(msgResId, args));
            }
        });
    }

    private void showDialogFragment(int dialogId) {
        showDialogFragment(dialogId, null);
    }

    private void showDialogFragment(int dialogId, String customMessage) {
        if (mDestroyed) {
            return;
        }
        mProgressBar.setIndeterminate(false);

        DialogFragment fragment;
        switch (dialogId) {
            case R.id.dialog_account_setup_error: {
                fragment = ConfirmationDialogFragment.newInstance(dialogId,
                        getString(R.string.account_setup_failed_dlg_title),
                        customMessage,
                        getString(R.string.account_setup_failed_dlg_edit_details_action),
                        getString(R.string.account_setup_failed_dlg_continue_action)
                );
                break;
            }
            case R.id.dialog_client_certificate_not_supported: {
                fragment = ConfirmationDialogFragment.newInstance(dialogId,
                        getString(R.string.dialog_client_certificate_title),
                        getString(R.string.dialog_client_certificate_not_supported),
                        getString(android.R.string.ok)
                );
                break;
            }
            default: {
                throw new RuntimeException("Called showDialog(int) with unknown dialog id.");
            }
        }

        FragmentTransaction ta = getFragmentManager().beginTransaction();
        ta.add(fragment, getDialogTag(dialogId));
        ta.commitAllowingStateLoss();

        // TODO: commitAllowingStateLoss() is used to prevent https://code.google.com/p/android/issues/detail?id=23761
        // but is a bad...
        //fragment.show(ta, getDialogTag(dialogId));
    }

    private String getDialogTag(int dialogId) {
        return String.format(Locale.US, "dialog-%d", dialogId);
    }

    @Override
    public void doPositiveClick(int dialogId) {
        switch (dialogId) {
            case R.id.dialog_account_setup_error: {
                finish();
                break;
            }
        }
    }

    @Override
    public void doNegativeClick(int dialogId) {
        switch (dialogId) {
            case R.id.dialog_account_setup_error:
            case R.id.dialog_client_certificate_not_supported: {
                mCanceled = false;
                setResult(RESULT_OK);
                finish();
                break;
            }
        }
    }

    @Override
    public void dialogCancelled(int dialogId) {
        // nothing to do here...
    }
}