diff --git a/src/index.ts b/src/index.ts
index 0349cbc..3419d64 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1 +1,59 @@
-export const myPackage = (taco = ''): string => `${taco} from my package`;
+import {
+  getInterpolationFunctionKeys,
+  getFunctionParams,
+  getTranslationKeys,
+  t18Options,
+  Translations,
+  UnionOmit,
+  ValidValues,
+} from './typings';
+
+export class t18<T extends Translations> {
+  private translations: Translations;
+  constructor(options: t18Options<T>) {
+    this.translations = options.translations;
+  }
+
+  t<Key extends getInterpolationFunctionKeys<T>>(
+    key: Key,
+    args: getFunctionParams<T, Key>
+  ): string;
+  t(
+    key: UnionOmit<getTranslationKeys<T>, getInterpolationFunctionKeys<T>>
+  ): string;
+  t(key: any, args?: any): string {
+    if (typeof key !== 'string') {
+      return 'INVALID KEY';
+    }
+
+    const objects = key.split('.');
+
+    let currentValue: ValidValues | Translations = this.translations;
+    for (const object of objects) {
+      if (typeof currentValue !== 'object') {
+        return 'INVALID PATH';
+      }
+
+      currentValue = currentValue[object];
+    }
+
+    const translation = currentValue;
+
+    if (typeof currentValue === 'function') {
+      if (!args || !Array.isArray(args)) {
+        return 'INVALID INTERPOLATION FUNCTION ARGUMENTS';
+      }
+
+      const withInterpolationTranslation = currentValue(...args);
+      if (typeof withInterpolationTranslation !== 'string') {
+        return 'INVALID VALUE';
+      }
+    }
+
+    if (typeof currentValue === 'object') {
+      return 'INVALID PATH';
+    }
+
+    return currentValue;
+  }
+}
diff --git a/src/typings.d.ts b/src/typings.d.ts
new file mode 100644
index 0000000..00ddd9e
--- /dev/null
+++ b/src/typings.d.ts
@@ -0,0 +1,67 @@
+/*export interface LanguageFile<T> {
+	language: string;
+	translations: T;
+}*/
+
+export interface t18Options<T> {
+  translations: T;
+}
+
+export interface Translations {
+  [key: string]: translations | ValidValues;
+}
+
+type InterpolationFunction = (...args: any[]) => string;
+
+export type ValidValues = string | InterpolationFunction; //| ;
+
+export type getTranslationKeys<Translation extends Translation> = Id<
+  RecKeysOf<Translation, ValidValues, ''>
+>;
+
+export type getFunctionParams<
+  Translation extends Translation,
+  Key extends getTranslationKeys<Translation>
+> = Id<RecParamsOf<Translation, ValidValues, '', Key>>;
+
+type Id<T> = T extends T ? { [P in keyof T]: T[P] } : never;
+
+type RecKeysOf<Dir, FileType, Prefix extends string> = {
+  [P in keyof Dir & (string | number)]: Dir[P] extends FileType
+    ? `${Prefix}${P}`
+    : RecKeysOf<Dir[P], FileType, `${Prefix}${P}.`>;
+}[keyof Dir & (string | number)];
+
+type UnionOmit<Target, Props> = Target extends Props ? never : Target;
+
+export type getInterpolationFunctionKeys<T extends Translations> = UnionOmit<
+  getTranslationKeys<T>,
+  Id<RecKeysOf<T, string, ''>>
+>;
+
+export type getNotInterpolationFunctionKeys<T extends Translations> = UnionOmit<
+  getTranslationKeys<T>,
+  getInterpolationFunctionKeys<T>
+>;
+
+type getParameters<T> = T extends (...args: infer P) => any ? P : never;
+
+type RecParamsOf<
+  Dir,
+  FileType,
+  Prefix extends string = '',
+  Key extends string
+> = {
+  [P in keyof Dir & (string | number)]: Dir[P] extends FileType
+    ? `${Prefix}${P}` extends Key
+      ? getParameters<Dir[P]>
+      : never
+    : RecParamsOf<Dir[P], FileType, `${Prefix}${P}.`, Key>;
+}[keyof Dir & (string | number)];
+
+// for getFixedT :)
+type RecAllPathsOf<Dir, FileType, Prefix extends string> = {
+  [P in keyof Dir & (string | number)]: Dir[P] extends FileType
+    ? `${Prefix}${P}`
+    : RecAllPathsOf<Dir[P], FileType, `${Prefix}${P}.`> | `${Prefix}${P}`;
+}[keyof Dir & (string | number)];
diff --git a/test/index.spec.ts b/test/index.spec.ts
index d305240..a3e1966 100644
--- a/test/index.spec.ts
+++ b/test/index.spec.ts
@@ -1,13 +1,34 @@
-import { myPackage } from '../src';
+import { t18 } from '../src';
 
 describe('index', () => {
-  describe('myPackage', () => {
-    it('should return a string containing the message', () => {
-      const message = 'Hello';
+  describe('t18', () => {
+    it('should translate key to message', () => {
+      const message = 'Hello World!';
 
-      const result = myPackage(message);
+      const translations = new t18({
+        translations: {
+          general: {
+            hello_word: 'Hello World!',
+          },
+        },
+      });
 
-      expect(result).toMatch(message);
+      expect(translations.t('general.hello_word')).toMatch(message);
+    });
+
+    it('should return welcome message with name', () => {
+      const message = (name: string) => `Welcome ${name}!`;
+      const name = 'Bob';
+
+      const translations = new t18({
+        translations: {
+          messages: {
+            welcome: message,
+          },
+        },
+      });
+
+      expect(translations.t('messages.welcome', [name])).toMatch(message(name));
     });
   });
 });