Replaced the sqlcipher database with a custom one

Still a WIP. This change was made to allow us to use Android's SecretKey API.
Which in turn allows us to store our secret keys in the Android KeyStore.

You can read about the database file format here: doc/db.md

app/src/main/java/me/impy/aegis/db/Database.java

@@ -1,99 +1,94 @@
 package me.impy.aegis.db;
 
-import android.content.Context;
-
-import net.sqlcipher.Cursor;
-import net.sqlcipher.database.SQLiteDatabase;
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
 
+import java.io.UnsupportedEncodingException;
 import java.util.ArrayList;
-import java.util.Collections;
-import java.util.Comparator;
 import java.util.List;
 
 import me.impy.aegis.KeyProfile;
 import me.impy.aegis.crypto.KeyInfo;
 
 public class Database {
-    private static Database instance;
-    private static Boolean libsLoaded = false;
-    private SQLiteDatabase db;
+    private static final int version = 1;
+    private List<DatabaseEntry> entries = new ArrayList<>();
 
-    private Database(Context context, String filename, char[] password) {
-        DatabaseHelper helper = new DatabaseHelper(context, filename);
-        db = helper.getWritableDatabase(password);
-    }
-
-    public static Database createInstance(Context context, String filename, char[] password) {
-        // load the sqlcipher library, once
-        if (!libsLoaded) {
-            SQLiteDatabase.loadLibs(context);
-            libsLoaded = true;
+    public byte[] serialize() throws JSONException, UnsupportedEncodingException {
+        JSONArray array = new JSONArray();
+        for (DatabaseEntry e : entries) {
+            array.put(e.serialize());
         }
 
-        if (instance == null) {
-            instance = new Database(context, filename, password);
-        }
+        JSONObject obj = new JSONObject();
+        obj.put("version", version);
+        obj.put("entries", array);
 
-        return instance;
+        return obj.toString().getBytes("UTF-8");
+    }
+
+    public void deserialize(byte[] data) throws Exception {
+        JSONObject obj = new JSONObject(new String(data, "UTF-8"));
+
+        // TODO: support different version deserialization providers
+        int ver = obj.getInt("version");
+        if (ver != version) {
+            throw new Exception("Unsupported version");
+        }
+
+        JSONArray array = obj.getJSONArray("entries");
+        for (int i = 0; i < array.length(); i++) {
+            DatabaseEntry e = new DatabaseEntry();
+            e.deserialize(array.getJSONObject(i));
+            entries.add(e);
+        }
     }
 
-    // adds a key to the database and returns it's ID
     public void addKey(KeyProfile profile) throws Exception {
-        db.execSQL("insert into otp (name, url) values (?, ?)",
-                new Object[]{ profile.Name, profile.Info.getURL() });
-        profile.ID = getLastID(db, "otp");
+        DatabaseEntry e = new DatabaseEntry();
+        e.Name = profile.Name;
+        e.URL = profile.Info.getURL();
+        e.Order = profile.Order;
+        e.ID = entries.size() + 1;
+        profile.ID = e.ID;
+        entries.add(e);
     }
 
     public void updateKey(KeyProfile profile) throws Exception {
-        db.execSQL("update otp set name=?, url=?, 'order'=? where id=?",
-                new Object[]{ profile.Name, profile.Info.getURL(), profile.Order, profile.ID });
+        DatabaseEntry e = findEntry(profile);
+        e.Name = profile.Name;
+        e.URL = profile.Info.getURL();
+        e.Order = profile.Order;
     }
 
-    public void removeKey(KeyProfile profile) {
-        db.execSQL("delete from otp where id=?", new Object[]{ profile.ID });
+    public void removeKey(KeyProfile profile) throws Exception {
+        DatabaseEntry e = findEntry(profile);
+        entries.remove(e);
     }
 
     public List<KeyProfile> getKeys() throws Exception {
         List<KeyProfile> list = new ArrayList<>();
-        Cursor cursor = db.rawQuery("select * from otp order by 'order' desc", null);
 
-        try {
-            while (cursor.moveToNext()) {
-                KeyProfile profile = new KeyProfile();
-                profile.ID = cursor.getInt(cursor.getColumnIndexOrThrow("id"));
-                profile.Name = cursor.getString(cursor.getColumnIndexOrThrow("name"));
-                profile.Order = cursor.getInt(cursor.getColumnIndexOrThrow("order"));
-                String url = cursor.getString(cursor.getColumnIndexOrThrow("url"));
-                profile.Info = KeyInfo.FromURL(url);
-
-                list.add(profile);
-            }
-            Collections.sort(list, new Comparator<KeyProfile>() {
-                @Override
-                public int compare(KeyProfile a, KeyProfile b) {
-                    return b.compareTo(a);
-                }
-            });
-            return list;
-        } finally {
-            cursor.close();
+        for (DatabaseEntry e : entries) {
+            KeyProfile profile = new KeyProfile();
+            profile.Name = e.Name;
+            profile.Info = KeyInfo.FromURL(e.URL);
+            profile.Order = e.Order;
+            profile.ID = e.ID;
+            list.add(profile);
         }
+
+        return list;
     }
 
-    public void close() {
-        db.close();
-    }
-
-    private int getLastID(SQLiteDatabase db, String table) throws Exception {
-        Cursor cursor = db.rawQuery(String.format("select id from %s order by id desc limit 1", table), null);
-        try {
-            if (!cursor.moveToFirst()) {
-                throw new Exception("no items in the table, this should not happen here");
+    private DatabaseEntry findEntry(KeyProfile profile) throws Exception {
+        for (DatabaseEntry e : entries) {
+            if (e.ID == profile.ID) {
+                return e;
             }
-
-            return cursor.getInt(cursor.getColumnIndexOrThrow("id"));
-        } finally {
-            cursor.close();
         }
+
+        throw new Exception("Key doesn't exist");
     }
-}
+}