/*
 * ConnectBot: simple, powerful, open-source SSH client for Android
 * Copyright 2007 Kenny Root, Jeffrey Sharkey
 *
 * 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 com.five_ten_sg.connectbot;

import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;

import com.five_ten_sg.connectbot.bean.PubkeyBean;
import com.five_ten_sg.connectbot.util.EntropyDialog;
import com.five_ten_sg.connectbot.util.EntropyView;
import com.five_ten_sg.connectbot.util.OnEntropyGatheredListener;
import com.five_ten_sg.connectbot.util.PubkeyDatabase;
import com.five_ten_sg.connectbot.util.PubkeyUtils;
import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnFocusChangeListener;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.RadioGroup;
import android.widget.RadioGroup.OnCheckedChangeListener;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;

import ch.ethz.ssh2.signature.ECDSASHA2Verify;

public class GeneratePubkeyActivity extends Activity implements OnEntropyGatheredListener {
    public final static String TAG = "ConnectBot.GeneratePubkeyActivity";

    private static final int RSA_MINIMUM_BITS = 768;
    final static int DEFAULT_BITS = 2048;
    final static int DSA_BITS = 1024;
    final static int[] ECDSA_SIZES = ECDSASHA2Verify.getCurveSizes();
    final static int ECDSA_DEFAULT_BITS = ECDSA_SIZES[0];

    private LayoutInflater inflater = null;

    private EditText nickname;
    private RadioGroup keyTypeGroup;
    private SeekBar bitsSlider;
    private EditText bitsText;
    private CheckBox unlockAtStartup;
    private CheckBox confirmUse;
    private Button save;
    private Dialog entropyDialog;
    private ProgressDialog progress;

    private EditText password1, password2;

    private String keyType = PubkeyDatabase.KEY_TYPE_RSA;
    private int minBits = RSA_MINIMUM_BITS;
    private int bits = DEFAULT_BITS;

    private byte[] entropy;

    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        setContentView(R.layout.act_generatepubkey);
        nickname = (EditText) findViewById(R.id.nickname);
        keyTypeGroup = (RadioGroup) findViewById(R.id.key_type);
        bitsText = (EditText) findViewById(R.id.bits);
        bitsSlider = (SeekBar) findViewById(R.id.bits_slider);
        password1 = (EditText) findViewById(R.id.password1);
        password2 = (EditText) findViewById(R.id.password2);
        unlockAtStartup = (CheckBox) findViewById(R.id.unlock_at_startup);
        confirmUse = (CheckBox) findViewById(R.id.confirm_use);
        save = (Button) findViewById(R.id.save);
        inflater = LayoutInflater.from(this);
        nickname.addTextChangedListener(textChecker);
        password1.addTextChangedListener(textChecker);
        password2.addTextChangedListener(textChecker);
        keyTypeGroup.setOnCheckedChangeListener(new OnCheckedChangeListener() {
            public void onCheckedChanged(RadioGroup group, int checkedId) {
                if (checkedId == R.id.rsa) {
                    minBits = RSA_MINIMUM_BITS;
                    bitsSlider.setEnabled(true);
                    bitsSlider.setProgress(DEFAULT_BITS - minBits);
                    bitsText.setText(String.valueOf(DEFAULT_BITS));
                    bitsText.setEnabled(true);
                    keyType = PubkeyDatabase.KEY_TYPE_RSA;
                }
                else if (checkedId == R.id.dsa) {
                    // DSA keys can only be 1024 bits
                    bitsSlider.setEnabled(false);
                    bitsSlider.setProgress(DSA_BITS - minBits);
                    bitsText.setText(String.valueOf(DSA_BITS));
                    bitsText.setEnabled(false);
                    keyType = PubkeyDatabase.KEY_TYPE_DSA;
                }
                else if (checkedId == R.id.ec) {
                    minBits = ECDSA_DEFAULT_BITS;
                    bitsSlider.setEnabled(true);
                    bitsSlider.setProgress(ECDSA_DEFAULT_BITS - minBits);
                    bitsText.setText(String.valueOf(ECDSA_DEFAULT_BITS));
                    bitsText.setEnabled(true);
                    keyType = PubkeyDatabase.KEY_TYPE_EC;
                }
            }
        });
        bitsSlider.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
            public void onProgressChanged(SeekBar seekBar, int progress,
                                          boolean fromTouch) {
                if (PubkeyDatabase.KEY_TYPE_EC.equals(keyType)) {
                    bits = getClosestFieldSize(progress + minBits);
                    seekBar.setProgress(bits - minBits);
                }
                else {
                    // Stay evenly divisible by 8 because it looks nicer to have
                    // 2048 than 2043 bits.
                    final int ourProgress = progress - (progress % 8);
                    bits = minBits + ourProgress;
                }

                bitsText.setText(String.valueOf(bits));
            }
            public void onStartTrackingTouch(SeekBar seekBar) {
                // We don't care about the start.
            }
            public void onStopTrackingTouch(SeekBar seekBar) {
                // We don't care about the stop.
            }
        });
        bitsText.setOnFocusChangeListener(new OnFocusChangeListener() {
            public void onFocusChange(View v, boolean hasFocus) {
                if (!hasFocus) {
                    final boolean isEc = PubkeyDatabase.KEY_TYPE_EC.equals(keyType);

                    try {
                        bits = Integer.parseInt(bitsText.getText().toString());

                        if (bits < minBits) {
                            bits = minBits;
                            bitsText.setText(String.valueOf(bits));
                        }

                        if (isEc) {
                            bits = getClosestFieldSize(bits);
                        }
                    }
                    catch (NumberFormatException nfe) {
                        bits = isEc ? ECDSA_DEFAULT_BITS : DEFAULT_BITS;
                        bitsText.setText(String.valueOf(bits));
                    }

                    bitsSlider.setProgress(bits - minBits);
                }
            }
        });
        save.setOnClickListener(new OnClickListener() {
            public void onClick(View view) {
                GeneratePubkeyActivity.this.save.setEnabled(false);
                GeneratePubkeyActivity.this.startEntropyGather();
            }
        });
    }

    private void checkEntries() {
        boolean allowSave = true;

        if (!password1.getText().toString().equals(password2.getText().toString()))
            allowSave = false;

        if (nickname.getText().length() == 0)
            allowSave = false;

        save.setEnabled(allowSave);
    }

    private void startEntropyGather() {
        final View entropyView = inflater.inflate(R.layout.dia_gatherentropy, null, false);
        ((EntropyView)entropyView.findViewById(R.id.entropy)).addOnEntropyGatheredListener(GeneratePubkeyActivity.this);
        entropyDialog = new EntropyDialog(GeneratePubkeyActivity.this, entropyView);
        entropyDialog.show();
    }

    public void onEntropyGathered(byte[] entropy) {
        // For some reason the entropy dialog was aborted, exit activity
        if (entropy == null) {
            finish();
            return;
        }

        this.entropy = entropy.clone();
        int numSetBits = 0;

        for (int i = 0; i < 20; i++)
            numSetBits += measureNumberOfSetBits(this.entropy[i]);

        Log.d(TAG, "Entropy distribution=" + (int)(100.0 * numSetBits / 160.0) + "%");
        Log.d(TAG, "entropy gathered; attemping to generate key...");
        startKeyGen();
    }

    private void startKeyGen() {
        progress = new ProgressDialog(GeneratePubkeyActivity.this);
        progress.setMessage(GeneratePubkeyActivity.this.getResources().getText(R.string.pubkey_generating));
        progress.setIndeterminate(true);
        progress.setCancelable(false);
        progress.show();
        Thread keyGenThread = new Thread(mKeyGen);
        keyGenThread.setName("KeyGen");
        keyGenThread.start();
    }

    final private Runnable mKeyGen = new Runnable() {
        public void run() {
            try {
                boolean encrypted = false;
                int tmpbits = bits;

                if (keyType == PubkeyDatabase.KEY_TYPE_DSA)
                    tmpbits = DSA_BITS;

                SecureRandom random = new SecureRandom();
                // Work around JVM bug
                random.nextInt();
                random.setSeed(entropy);
                KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(keyType);
                keyPairGen.initialize(tmpbits, random);
                KeyPair pair = keyPairGen.generateKeyPair();
                PrivateKey priv = pair.getPrivate();
                PublicKey pub = pair.getPublic();
                String secret = password1.getText().toString();

                if (secret.length() > 0)
                    encrypted = true;

                Log.d(TAG, "private: " + PubkeyUtils.formatKey(priv));
                Log.d(TAG, "public: " + PubkeyUtils.formatKey(pub));
                PubkeyBean pubkey = new PubkeyBean();
                pubkey.setNickname(nickname.getText().toString());
                pubkey.setType(keyType);
                pubkey.setPrivateKey(PubkeyUtils.getEncodedPrivate(priv, secret));
                pubkey.setPublicKey(pub.getEncoded());
                pubkey.setEncrypted(encrypted);
                pubkey.setStartup(unlockAtStartup.isChecked());
                pubkey.setConfirmUse(confirmUse.isChecked());
                PubkeyDatabase pubkeydb = new PubkeyDatabase(GeneratePubkeyActivity.this);
                pubkeydb.savePubkey(pubkey);
                pubkeydb.close();
            }
            catch (Exception e) {
                Log.e(TAG, "Could not generate key pair");
                e.printStackTrace();
            }

            GeneratePubkeyActivity.this.runOnUiThread(new Runnable() {
                public void run() {
                    progress.dismiss();
                    GeneratePubkeyActivity.this.finish();
                }
            });
        }
    };

    final private TextWatcher textChecker = new TextWatcher() {
        public void afterTextChanged(Editable s) {}
        public void beforeTextChanged(CharSequence s, int start, int count,
                                      int after) {}
        public void onTextChanged(CharSequence s, int start, int before,
                                  int count) {
            checkEntries();
        }
    };

    private int measureNumberOfSetBits(byte b) {
        int numSetBits = 0;

        for (int i = 0; i < 8; i++) {
            if ((b & 1) == 1)
                numSetBits++;

            b >>= 1;
        }

        return numSetBits;
    }

    private int getClosestFieldSize(int bits) {
        int outBits = ECDSA_DEFAULT_BITS;
        int distance = Math.abs(bits - ECDSA_DEFAULT_BITS);

        for (int i = 1; i < ECDSA_SIZES.length; i++) {
            int thisDistance = Math.abs(bits - ECDSA_SIZES[i]);

            if (thisDistance < distance) {
                distance = thisDistance;
                outBits = ECDSA_SIZES[i];
            }
        }

        return outBits;
    }
}