Rename "Database" to "Vault"

We decided on calling the state file the "vault" a while back. This patch makes
the naming consistent across the codebase. I left "DatabaseImporter" classes
alone, because I'm not sure what a better name for those would be.

app/src/main/java/com/beemdevelopment/aegis/vault/VaultFile.java

@@ -0,0 +1,167 @@
+package com.beemdevelopment.aegis.vault;
+
+import com.beemdevelopment.aegis.crypto.CryptParameters;
+import com.beemdevelopment.aegis.crypto.CryptResult;
+import com.beemdevelopment.aegis.crypto.MasterKeyException;
+import com.beemdevelopment.aegis.vault.slots.SlotList;
+import com.beemdevelopment.aegis.vault.slots.SlotListException;
+import com.beemdevelopment.aegis.encoding.Base64;
+import com.beemdevelopment.aegis.encoding.Base64Exception;
+import com.beemdevelopment.aegis.encoding.HexException;
+
+import org.json.JSONException;
+import org.json.JSONObject;
+
+import java.nio.charset.StandardCharsets;
+
+public class VaultFile {
+    public static final byte VERSION = 1;
+
+    private Object _content;
+    private Header _header;
+
+    public VaultFile() {
+
+    }
+
+    private VaultFile(Object content, Header header) {
+        _content = content;
+        _header = header;
+    }
+
+    public Header getHeader() {
+        return _header;
+    }
+
+    public boolean isEncrypted() {
+        return !_header.isEmpty();
+    }
+
+    public JSONObject toJson() {
+        try {
+            JSONObject obj = new JSONObject();
+            obj.put("version", VERSION);
+            obj.put("header", _header.toJson());
+            obj.put("db", _content);
+            return obj;
+        } catch (JSONException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public byte[] toBytes() {
+        JSONObject obj = toJson();
+
+        try {
+            String string = obj.toString(4);
+            return string.getBytes(StandardCharsets.UTF_8);
+        } catch (JSONException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public static VaultFile fromJson(JSONObject obj) throws VaultFileException {
+        try {
+            if (obj.getInt("version") > VERSION) {
+                throw new VaultFileException("unsupported version");
+            }
+
+            Header header = Header.fromJson(obj.getJSONObject("header"));
+            if (!header.isEmpty()) {
+                return new VaultFile(obj.getString("db"), header);
+            }
+
+            return new VaultFile(obj.getJSONObject("db"), header);
+        } catch (JSONException e) {
+            throw new VaultFileException(e);
+        }
+    }
+
+    public static VaultFile fromBytes(byte[] data) throws VaultFileException {
+        try {
+            JSONObject obj = new JSONObject(new String(data, StandardCharsets.UTF_8));
+            return VaultFile.fromJson(obj);
+        } catch (JSONException e) {
+            throw new VaultFileException(e);
+        }
+    }
+
+    public JSONObject getContent() {
+        return (JSONObject) _content;
+    }
+
+    public JSONObject getContent(VaultFileCredentials creds) throws VaultFileException {
+        try {
+            byte[] bytes = Base64.decode((String) _content);
+            CryptResult result = creds.decrypt(bytes, _header.getParams());
+            return new JSONObject(new String(result.getData(), StandardCharsets.UTF_8));
+        } catch (MasterKeyException | JSONException | Base64Exception e) {
+            throw new VaultFileException(e);
+        }
+    }
+
+    public void setContent(JSONObject obj) {
+        _content = obj;
+        _header = new Header(null, null);
+    }
+
+    public void setContent(JSONObject obj, VaultFileCredentials creds) throws VaultFileException {
+        try {
+            String string = obj.toString(4);
+            byte[] vaultBytes = string.getBytes(StandardCharsets.UTF_8);
+
+            CryptResult result = creds.encrypt(vaultBytes);
+            _content = Base64.encode(result.getData());
+            _header = new Header(creds.getSlots(), result.getParams());
+        } catch (MasterKeyException | JSONException e) {
+            throw new VaultFileException(e);
+        }
+    }
+
+    public static class Header {
+        private SlotList _slots;
+        private CryptParameters _params;
+
+        public Header(SlotList slots, CryptParameters params) {
+            _slots = slots;
+            _params = params;
+        }
+
+        public static Header fromJson(JSONObject obj) throws VaultFileException {
+            if (obj.isNull("slots") && obj.isNull("params")) {
+                return new Header(null, null);
+            }
+
+            try {
+                SlotList slots = SlotList.fromJson(obj.getJSONArray("slots"));
+                CryptParameters params = CryptParameters.fromJson(obj.getJSONObject("params"));
+                return new Header(slots, params);
+            } catch (SlotListException | JSONException | HexException e) {
+                throw new VaultFileException(e);
+            }
+        }
+
+        public JSONObject toJson() {
+            try {
+                JSONObject obj = new JSONObject();
+                obj.put("slots", _slots != null ? _slots.toJson() : JSONObject.NULL);
+                obj.put("params", _params != null ? _params.toJson() : JSONObject.NULL);
+                return obj;
+            } catch (JSONException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        public SlotList getSlots() {
+            return _slots;
+        }
+
+        public CryptParameters getParams() {
+            return _params;
+        }
+
+        public boolean isEmpty() {
+            return _slots == null && _params == null;
+        }
+    }
+}