package me.impy.aegis;

import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;

import java.lang.reflect.UndeclaredThrowableException;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;

import me.impy.aegis.crypto.CryptoUtils;
import me.impy.aegis.crypto.MasterKey;
import me.impy.aegis.crypto.slots.FingerprintSlot;
import me.impy.aegis.crypto.slots.PasswordSlot;
import me.impy.aegis.crypto.slots.Slot;
import me.impy.aegis.crypto.slots.SlotCollection;
import me.impy.aegis.crypto.slots.SlotIntegrityException;

public class SlotCollectionTask<T extends Slot> extends AsyncTask<SlotCollectionTask.Params, Void, MasterKey> {
    private Callback _cb;
    private Class<T> _type;
    private ProgressDialog _dialog;

    public SlotCollectionTask(Class<T> type, Context context, Callback cb) {
        _cb = cb;
        _type = type;
        _dialog = new ProgressDialog(context);
        _dialog.setCancelable(false);
    }

    @Override
    protected MasterKey doInBackground(SlotCollectionTask.Params... args) {
        SlotCollectionTask.Params params = args[0];
        try {
            if (!params.Slots.has(_type)) {
                throw new RuntimeException();
            }

            MasterKey masterKey = null;
            for (Slot slot : params.Slots.findAll(_type)) {
                try {
                    if (slot instanceof PasswordSlot) {
                        char[] password = (char[])params.Obj;
                        SecretKey key = ((PasswordSlot)slot).deriveKey(password);
                        CryptoUtils.zero(password);
                        Cipher cipher = Slot.createCipher(key, Cipher.DECRYPT_MODE);
                        masterKey = params.Slots.decrypt(slot, cipher);
                    } else if (slot instanceof FingerprintSlot) {
                        masterKey = params.Slots.decrypt(slot, (Cipher)params.Obj);
                    } else {
                        throw new RuntimeException();
                    }
                    break;
                } catch (SlotIntegrityException e) { }
            }

            if (masterKey == null) {
                throw new SlotIntegrityException();
            }

            return masterKey;
        } catch (SlotIntegrityException e) {
            return null;
        } catch (Exception e) {
            throw new UndeclaredThrowableException(e);
        }
    }

    @Override
    protected void onPreExecute() {
        _dialog.setMessage("Decrypting database");
        _dialog.show();
    }

    @Override
    protected void onPostExecute(MasterKey masterKey) {
        if (_dialog.isShowing()) {
            _dialog.dismiss();
        }
        _cb.onTaskFinished(masterKey);
    }

    static class Params {
        public SlotCollection Slots;
        public Object Obj;
    }

    interface Callback {
        void onTaskFinished(MasterKey key);
    }
}