diff --git a/.gitignore b/.gitignore
index d221f13..8884f08 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,4 +17,5 @@ lib/
 **/coverage/
 **/.coverage/
 **/jest-cache/
+**/.jest-cache/
 **/__data__/**
diff --git a/.npmignore b/.npmignore
index 79a3e4d..18e4e45 100644
--- a/.npmignore
+++ b/.npmignore
@@ -4,7 +4,7 @@
 **/coverage
 **/mochawesome-report
 **/mochawesome-reports
-**/jest-cache
+**/.jest-cache/
 **/.github/
 **/.workflow/
 .travis/
diff --git a/DEV/App.jsx b/DEV/App.jsx
new file mode 100644
index 0000000..ffe3def
--- /dev/null
+++ b/DEV/App.jsx
@@ -0,0 +1,48 @@
+import React, { useEffect, useMemo } from 'react'
+import I18nContext from './I18nContext'
+import I18nResolver from './I18nResolver'
+import transform from './transform'
+import useObservableState from './useObservableState'
+
+
+/**
+ * @typedef Props
+ * @property {import("@daniloster/i18n/lib/types").I18nState} i18n
+ */
+
+
+/**
+ * Application dev
+ * @param {Props} props 
+ */
+export default function App({ i18n }) {
+  const [language] = useObservableState(i18n.language)
+  const [t] = useObservableState(i18n.t)
+  const [status] = useObservableState(i18n.status)
+
+  useEffect(() => {
+    i18n.init()
+  }, [i18n])
+  const i18nContextValue = useMemo(() => [i18n, transform], [i18n])
+
+  return (
+    <I18nContext.Provider value={i18nContextValue}>
+      <div>
+        <div>
+          <button type="button" onClick={() => i18n.languageService.set('en').catch(() => null)}>EN</button>
+          <button type="button" onClick={() => i18n.languageService.set('pt').catch(() => null)}>PT</button>
+          <button type="button" onClick={() => i18n.languageService.set('es').catch(() => null)}>ES</button>
+        </div>
+        <p>{status}</p>
+        <p>{language}</p>
+        <p>{t('PageOne.hello')}</p>
+        <p><I18nResolver path="PageOne.hello" /></p>
+        <p><I18nResolver path="PageOne.interpolation.text" /></p>
+        <p><I18nResolver path="PageOne.interpolation.nodes" /></p>
+        <div>
+          <I18nResolver path="PageOne.interpolation.simple" modifiers={{ name: 'Guest' }} />
+        </div>
+      </div>
+    </I18nContext.Provider>
+  )
+}
\ No newline at end of file
diff --git a/DEV/AppForTest.jsx b/DEV/AppForTest.jsx
new file mode 100644
index 0000000..381e8bf
--- /dev/null
+++ b/DEV/AppForTest.jsx
@@ -0,0 +1,55 @@
+import React, { useCallback, useEffect, useMemo, useState } from 'react'
+import I18nContext from './I18nContext'
+import I18nResolver from './I18nResolver'
+import transform from './transform'
+import useObservableState from './useObservableState'
+
+/**
+ * @typedef Props
+ * @property {import("@daniloster/i18n/lib/types").I18nState} i18n
+ */
+
+/**
+ * Application test
+ * @param {Props} props 
+ */
+export default function AppForTest({ i18n }) {
+  const [language] = useObservableState(i18n.language)
+  const [t] = useObservableState(i18n.t)
+  const [status] = useObservableState(i18n.status)
+  const [asyncError, setAsyncError] = useState(null)
+  const handleDebounceError = useCallback((e) => {
+    if (e.debounced) {
+      return null
+    }
+ 
+    setAsyncError(e)
+  }, [])
+
+  useEffect(() => {
+    i18n.init()
+  }, [i18n])
+  const i18nContextValue = useMemo(() => [i18n, transform], [i18n])
+
+  return (
+    <I18nContext.Provider value={i18nContextValue}>
+      <div>
+        <div>
+          <button type="button" data-testid="EN" onClick={() => i18n.languageService.set('en').catch(handleDebounceError)}>EN</button>
+          <button type="button" data-testid="PT" onClick={() => i18n.languageService.set('pt').catch(handleDebounceError)}>PT</button>
+          <button type="button" data-testid="ES" onClick={() => i18n.languageService.set('es').catch(handleDebounceError)}>ES</button>
+        </div>
+        {!!asyncError && <p>error: {asyncError.message}</p>}
+        <p>status: {status}</p>
+        <p>language: {language}</p>
+        <p>{t('PageOne.hello')}</p>
+        <p><I18nResolver path="PageOne.hello" /></p>
+        <p><I18nResolver path="PageOne.interpolation.text" /></p>
+        <p><I18nResolver path="PageOne.interpolation.nodes" /></p>
+        <div>
+          <I18nResolver path="PageOne.interpolation.simple" modifiers={{ name: 'Guest' }} />
+        </div>
+      </div>
+    </I18nContext.Provider>
+  )
+}
\ No newline at end of file
diff --git a/DEV/I18nContext.js b/DEV/I18nContext.js
new file mode 100644
index 0000000..d29bdec
--- /dev/null
+++ b/DEV/I18nContext.js
@@ -0,0 +1,3 @@
+import { createContext } from 'react'
+
+export default createContext([null, null])
diff --git a/DEV/I18nResolver.jsx b/DEV/I18nResolver.jsx
new file mode 100644
index 0000000..bc5b9c1
--- /dev/null
+++ b/DEV/I18nResolver.jsx
@@ -0,0 +1,23 @@
+import React from 'react'
+import useI18nResolver from './useI18nResolver'
+
+
+/**
+ * @typedef Props
+ * @property {string} namespace
+ * @property {string} path 
+ * @property {{ [key: string]: any }} modifiers 
+ */
+
+/**
+ * 
+ * @param {Props} props 
+ */
+export default function I18nResolver(props) {
+  const { namespace, path, modifiers } = props
+  const t = useI18nResolver({ namespace })
+  
+  return (
+    <>{t(path, modifiers)}</>
+  )
+}
diff --git a/DEV/assets/locales/en.json b/DEV/assets/locales/en.json
new file mode 100644
index 0000000..4d3341b
--- /dev/null
+++ b/DEV/assets/locales/en.json
@@ -0,0 +1,10 @@
+{
+  "PageOne": {
+    "hello": "Hello World",
+    "interpolation": {
+      "text": "Hey {name}! It is good to have you here. Thanks {name} for coming.",
+      "nodes": "Hey {name}! It is good <decorator>to have you here</decorator>. Thanks {name} for coming.",
+      "simple": "Hey {name} (awesome)!"
+    }
+  }
+}
\ No newline at end of file
diff --git a/DEV/assets/locales/es.json b/DEV/assets/locales/es.json
new file mode 100644
index 0000000..5ab43ee
--- /dev/null
+++ b/DEV/assets/locales/es.json
@@ -0,0 +1,10 @@
+{
+  "PageOne": {
+    "hello": "Hola Mundo",
+    "interpolation": {
+      "text": "¡Hola, {name}! Es bueno tenerte aquí. Gracias, {name} por venir.",
+      "nodes": "¡Hola {name}! Es bueno <decorator> tenerte aquí </decorator>. Gracias {name} por venir.",
+      "simple": "¡Hola {name} (super fantástico)!"
+    }
+  }
+}
\ No newline at end of file
diff --git a/DEV/assets/locales/pt.json b/DEV/assets/locales/pt.json
new file mode 100644
index 0000000..91d4315
--- /dev/null
+++ b/DEV/assets/locales/pt.json
@@ -0,0 +1,10 @@
+{
+  "PageOne": {
+    "hello": "Ola Mundo",
+    "interpolation": {
+      "text": "Ei, {name}! É bom ter você aqui. Obrigado {name} por ter vindo.",
+      "nodes": "Ei, {name}! É bom <decorator> tê-lo aqui </decorator>. Obrigado {name} por ter vindo.",
+      "simple": "Ei {name} (super fantástico)!"
+    }
+  }
+}
\ No newline at end of file
diff --git a/DEV/dev.d.ts b/DEV/dev.d.ts
new file mode 100644
index 0000000..e69de29
diff --git a/DEV/factoryI18n.js b/DEV/factoryI18n.js
new file mode 100644
index 0000000..69ebbae
--- /dev/null
+++ b/DEV/factoryI18n.js
@@ -0,0 +1,24 @@
+import factoryI18n from '@daniloster/i18n'
+
+/**
+ * @returns {import('@daniloster/i18n/lib/types').I18nState}
+ */
+export default (props) => factoryI18n({
+  defaultLanguage: 'en',
+  languageService: {
+    get: async () => localStorage.getItem('language'),
+    set: async (language) => localStorage.setItem('language', language),
+  },
+  resourcesService: {
+    get: async (language) => {
+      const response = await fetch(`/assets/locales/${language}.json`)
+      if (response.ok) {
+        return await response.json()
+      }
+
+      throw new Error(`[ERROR]: ${response.status} | ${response.statusText}`)
+    },
+    set: async () => null
+  },
+  ...props,
+})
diff --git a/DEV/i18n.js b/DEV/i18n.js
new file mode 100644
index 0000000..2141b94
--- /dev/null
+++ b/DEV/i18n.js
@@ -0,0 +1,16 @@
+import factoryI18n from './factoryI18n'
+
+export default factoryI18n({
+  defaultLanguage: 'en',
+  languageService: {
+    get: async () => localStorage.getItem('language'),
+    set: async (language) => localStorage.setItem('language', language),
+  },
+  resourcesService: {
+    get: async (language) => {
+      const response = await fetch(`/assets/locales/${language}.json`)
+      return await response.json()
+    },
+    set: async () => Promise.resolve(null)
+  },
+})
diff --git a/DEV/index.jsx b/DEV/index.jsx
new file mode 100644
index 0000000..3c9488d
--- /dev/null
+++ b/DEV/index.jsx
@@ -0,0 +1,11 @@
+import '@babel/polyfill'
+import React from 'react'
+import { render } from 'react-dom'
+import App from './App'
+import i18n from './i18n'
+
+
+const root = document.createElement('div')
+document.body.appendChild(root)
+
+render(<App i18n={i18n} />, root)
diff --git a/DEV/transform.js b/DEV/transform.js
new file mode 100644
index 0000000..2a1caed
--- /dev/null
+++ b/DEV/transform.js
@@ -0,0 +1,9 @@
+function interpolate(resolution, [key, value]) {
+  return resolution.replace(new RegExp(`{${key}}`, 'g'), value)
+}
+
+export default function transform({ template, modifiers }) {
+  return Object
+  .entries(modifiers || {})
+  .reduce(interpolate, template)
+}
diff --git a/DEV/useI18nResolver.jsx b/DEV/useI18nResolver.jsx
new file mode 100644
index 0000000..2f70402
--- /dev/null
+++ b/DEV/useI18nResolver.jsx
@@ -0,0 +1,36 @@
+import { useCallback, useContext } from 'react'
+import I18nContext from './I18nContext'
+import useObservableState from "./useObservableState"
+
+
+/**
+ * @typedef Props
+ * @property {string} namespace
+ */
+
+/**
+ * 
+ * @param {Props} props 
+ */
+export default function useI18nResolver(props) {
+  const { namespace } = props
+  /** @type {[import('@daniloster/i18n/lib/types').I18nState, import('@daniloster/i18n/lib/types').ResolverTransformer]} */
+  const [i18n, transformer] = useContext(I18nContext)
+  const [t] = useObservableState(i18n.t)
+  
+  return useCallback((path, modifiers) => {
+    /** @type {import('@daniloster/i18n/lib/types').ResolverTransformer} */
+    const interpolate = (options) => {
+      if (transformer) {
+        return transformer({ ...options, modifiers })
+      }
+  
+      return options.template || options.path
+    }
+    
+    return t(
+      namespace ? namespace + '.' + path : path,
+      transformer ? interpolate : transformer,
+    )
+  }, [t, transformer])
+}
diff --git a/DEV/useObservableState.js b/DEV/useObservableState.js
new file mode 100644
index 0000000..2fe6fbd
--- /dev/null
+++ b/DEV/useObservableState.js
@@ -0,0 +1,26 @@
+import { useEffect, useMemo, useState } from 'react'
+
+/**
+ * Listen to an observable state converting into react hook
+ * @param {import('@daniloster/i18n/lib/types').ObservableState<S>} observableState
+ * @returns {[S, ((value: S) => S) => void]}
+ * @template S
+ */
+export default function useObservableState(observableState) {
+  /** @type {[S, React.Dispatch<React.SetStateAction<S>>]} */
+  const state = useState(() => observableState.get())
+  const [value, setValue] = state
+
+  useEffect(() => {
+    const subscription = observableState.subscribe({
+      next: (newValue) => {
+        setValue((oldValue) => oldValue !== newValue ? newValue : oldValue)
+      }
+    })
+
+    return subscription.unsubscribe
+  }, [observableState])
+
+  /** @type {[S, ((value: S) => S) => void]} */
+  return useMemo(() => [value, observableState.set], [value, observableState.set])
+}
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..0c30297
--- /dev/null
+++ b/README.md
@@ -0,0 +1,32 @@
+# @daniloster/i18n
+
+![Main workflow](https://github.com/daniloster/i18n/workflows/Main%20workflow/badge.svg)
+
+## Contents
+
+- [Getting Started](https://github.com/daniloster/i18n/blob/master/docs/GETTING_STARTED.md)
+- [Contributions](#Contributions)
+  - [Steps](#Steps)
+  - [Dev](#Dev)
+
+## IE Polyfills
+
+- [string.prototype.matchall](https://www.npmjs.com/package/string.prototype.matchall)
+
+## Contributions
+
+Feel free to reach out and help improving this library.
+
+### Steps
+
+- Pull the repository `git clone https://github.com/daniloster/i18n.git`
+- Creating your contribution
+- Add at least one commit with message containing either `[patch]`, `[minor]` or `[major]`
+- Add at least one commit with message containing `[release]`, otherwise, it won't be released.
+- Do not use `git pull`, go for `git fetch` and `git rebase`
+- Add tests as "the changes are intended to be used by dev"
+
+### Dev
+
+- **Testing**: `yarn test` or `yarn test --watch`
+- **Web Dev App**: `yarn dev`
diff --git a/docs/GETTING_STARTED.md b/docs/GETTING_STARTED.md
new file mode 100644
index 0000000..db10c29
--- /dev/null
+++ b/docs/GETTING_STARTED.md
@@ -0,0 +1,3 @@
+# Getting Started
+
+`@daniloster/i18n` provides a simple abstraction layer to manage internationalization.
diff --git a/jest.config.js b/jest.config.js
index 508c040..529d937 100644
--- a/jest.config.js
+++ b/jest.config.js
@@ -2,7 +2,7 @@ process.env.TZ = 'UTC'
 process.env.NODE_ICU_DATA = 'node_modules/full-icu'
 
 module.exports = {
-  cacheDirectory: './jest-cache',
+  cacheDirectory: './.jest-cache',
   coverageReporters: ['html', 'json', 'lcov', 'text'],
   coverageDirectory: '<rootDir>/coverage/',
   collectCoverage: true,
diff --git a/package.json b/package.json
index 1124785..6559b2d 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@daniloster/i18n",
-  "version": "0.0.1",
+  "version": "0.0.0",
   "description": "Library to apply internationalization for node or javascript projects",
   "main": "lib/index.js",
   "types": "lib/types.d.ts",
@@ -74,6 +74,7 @@
     "mutation-helper": "1.0.0"
   },
   "resolutions": {
-    "jsdom": "16.2.2"
+    "jsdom": "16.2.2",
+    "lodash": "4.17.19"
   }
 }
diff --git a/src/Application.test.jsx b/src/Application.test.jsx
new file mode 100644
index 0000000..e1e3d5b
--- /dev/null
+++ b/src/Application.test.jsx
@@ -0,0 +1,169 @@
+import { act, fireEvent, render } from '@testing-library/react'
+import { Response } from 'miragejs'
+import React from 'react'
+import AppForTest from '../DEV/AppForTest'
+import factoryI18n from '../DEV/factoryI18n'
+import delay from '../tools/helpers/tests/delay'
+
+/**
+ * 
+ * @param {any} props 
+ * @returns {[import('@testing-library/react').RenderResult, import('@daniloster/i18n/lib/types').I18nState]}
+ */
+function renderComponent(props = {}) {
+  const i18n = factoryI18n(props)
+  return [render(<AppForTest i18n={i18n} />), i18n]
+}
+
+describe('Application', () => {
+  test('if Application renders the default language (en)', async () => {
+    const [wrapper] = renderComponent()
+    expect(await wrapper.findByText('status: Success', {}, { timeout: 5000 })).toBeTruthy()
+    expect(await wrapper.findByText('language: en')).toBeTruthy()
+    const helloWorlds = await wrapper.findAllByText('Hello World')
+    expect(helloWorlds).toBeTruthy()
+    expect(helloWorlds).toHaveLength(2)
+
+    expect(await wrapper.findByText('Hey {name}! It is good to have you here. Thanks {name} for coming.')).toBeTruthy()
+    expect(await wrapper.findByText('Hey {name}! It is good <decorator>to have you here</decorator>. Thanks {name} for coming.')).toBeTruthy()
+  }, 10000)
+
+  test('if Application renders the stored language (pt)', async () => {
+    localStorage.setItem('language', 'pt')
+    const [wrapper] = renderComponent()
+    expect(await wrapper.findByText('status: Success', {}, { timeout: 5000 })).toBeTruthy()
+    expect(await wrapper.findByText('language: pt')).toBeTruthy()
+    const helloWorlds = await wrapper.findAllByText('Ola Mundo', {}, { timeout: 5000 })
+    expect(helloWorlds).toBeTruthy()
+    expect(helloWorlds).toHaveLength(2)
+
+    expect(await wrapper.findByText('Ei, {name}! É bom ter você aqui. Obrigado {name} por ter vindo.')).toBeTruthy()
+    expect(await wrapper.findByText('Ei, {name}! É bom <decorator> tê-lo aqui </decorator>. Obrigado {name} por ter vindo.')).toBeTruthy()
+  }, 10000)
+
+  test('if Application is notified when load language after initialization', async () => {
+    const [wrapper, i18n] = renderComponent()
+    expect(await wrapper.findByText('status: Success', {}, { timeout: 5000 })).toBeTruthy()
+    expect(await wrapper.findByText('language: en')).toBeTruthy()
+
+    localStorage.setItem('language', 'es')
+    const next = jest.fn()
+    i18n.language.subscribe({ next })
+    await act(async () => {
+      await i18n.languageService.get()
+    })
+
+    expect(next).toHaveBeenCalled()
+    expect(next).toHaveBeenCalledTimes(1)
+    expect(next).toHaveBeenCalledWith('es')
+
+    // request is made to not affect next test
+    await delay(1000)
+  }, 10000)
+
+  test('if Application is forced to not notify when load language', async () => {
+    const [wrapper, i18n] = renderComponent()
+    expect(await wrapper.findByText('status: Success', {}, { timeout: 5000 })).toBeTruthy()
+    expect(await wrapper.findByText('language: en')).toBeTruthy()
+
+    localStorage.setItem('language', 'es')
+    const next = jest.fn()
+    i18n.language.subscribe({ next })
+    await act(async () => {
+      await i18n.languageService.get(true)
+    })
+
+    expect(next).not.toHaveBeenCalled()
+
+    // request is made to not affect next test
+    await delay(1000)
+  }, 10000)
+
+  test('if Application do not fetch loaded resource', async () => {
+    /**
+     * For this test, we are going to try against the default language
+     */
+    localStorage.setItem('language', 'pt')
+    const [wrapper, i18n] = renderComponent()
+    expect(await wrapper.findByText('status: Success', {}, { timeout: 5000 })).toBeTruthy()
+    expect(await wrapper.findByText('language: pt')).toBeTruthy()
+
+    const helloWorlds = await wrapper.findAllByText('Hello World')
+    expect(helloWorlds).toBeTruthy()
+    expect(helloWorlds).toHaveLength(2)
+
+    const next = jest.fn()
+    i18n.resources.subscribe({ next })
+    const en = await wrapper.findByTestId('EN')
+    fireEvent.click(en)
+    await delay(1000)
+
+    expect(next).not.toHaveBeenCalled()
+  }, 10000)
+
+  test('if Application changes language with debounce', async () => {
+    const [wrapper] = renderComponent()
+    expect(await wrapper.findByText('status: Success', {}, { timeout: 5000 })).toBeTruthy()
+    expect(await wrapper.findByText('language: en')).toBeTruthy()
+    const helloWorlds = await wrapper.findAllByText('Hello World')
+    expect(helloWorlds).toBeTruthy()
+    expect(helloWorlds).toHaveLength(2)
+
+    const pt = await wrapper.findByTestId('PT')
+
+    fireEvent.click(pt)
+    await delay(100)
+    fireEvent.click(pt)
+    await delay(100)
+    fireEvent.click(pt)
+    await delay(100)
+
+    expect(global.server.pretender.handledRequests).toHaveLength(1)
+    await delay(1500)
+    const requests = global.server.pretender.handledRequests
+    expect(requests).toHaveLength(2)
+    expect(requests[0].responseURL).toEqual('/assets/locales/en.json')
+    expect(requests[1].responseURL).toEqual('/assets/locales/pt.json')
+  }, 10000)
+
+  test('if Application changes language', async () => {
+    const [wrapper] = renderComponent()
+    expect(await wrapper.findByText('status: Success', {}, { timeout: 5000 })).toBeTruthy()
+    expect(await wrapper.findByText('language: en')).toBeTruthy()
+    const helloWorlds = await wrapper.findAllByText('Hello World')
+    expect(helloWorlds).toBeTruthy()
+    expect(helloWorlds).toHaveLength(2)
+
+    const pt = await wrapper.findByTestId('PT')
+
+    fireEvent.click(pt)
+    await delay(1000)
+
+    expect(await wrapper.findByText('status: Success', {}, { timeout: 5000 })).toBeTruthy()
+    expect(await wrapper.findByText('language: pt')).toBeTruthy()
+    
+    await delay(3000)
+
+    const olaMundos = await wrapper.findAllByText('Ola Mundo', {}, { timeout: 5000 })
+    expect(olaMundos).toBeTruthy()
+    expect(olaMundos).toHaveLength(2)
+  }, 20000)
+
+  test('if Application handler error on changing language', async () => {
+    const [wrapper] = renderComponent()
+    expect(await wrapper.findByText('status: Success', {}, { timeout: 5000 })).toBeTruthy()
+    expect(await wrapper.findByText('language: en')).toBeTruthy()
+    const helloWorlds = await wrapper.findAllByText('Hello World')
+    expect(helloWorlds).toBeTruthy()
+    expect(helloWorlds).toHaveLength(2)
+
+    const pt = await wrapper.findByTestId('PT')
+
+    global.server.get('/:language', () => new Response(500))
+
+    fireEvent.click(pt)
+    await delay(1000)
+
+    expect(await wrapper.findByText('status: Error', {}, { timeout: 5000 })).toBeTruthy()
+  }, 10000)
+})
diff --git a/src/AsyncStatus.js b/src/AsyncStatus.js
new file mode 100644
index 0000000..4f7f282
--- /dev/null
+++ b/src/AsyncStatus.js
@@ -0,0 +1,6 @@
+export default {
+  Initial: 'Initial',
+  Loading: 'Loading',
+  Success: 'Success',
+  Error: 'Error',
+}
diff --git a/src/ObservableState.js b/src/ObservableState.js
new file mode 100644
index 0000000..77d5719
--- /dev/null
+++ b/src/ObservableState.js
@@ -0,0 +1,46 @@
+class Subject {
+  constructor() {
+    this.subscribers = []
+  }
+
+  next(value) {
+    this.subscribers.forEach((subscriber) => {
+      subscriber.next(value)
+    })
+  }
+
+  subscribe(subscriber) {
+    const self = this
+    self.subscribers.push(subscriber)
+
+    return {
+      unsubscribe: () => {
+        self.subscribers = self.subscribers.filter((s) => s !== subscriber)
+      },
+    }
+  }
+}
+
+export default {
+  /**
+   * @param {T} initialValue
+   * @returns {import('@daniloster/i18n/lib/types').ObservableState<T>}
+   * @template T
+   */
+  create: (initialValue) => {
+    let value = initialValue
+    const subject = new Subject()
+
+    return {
+      get: () => value,
+      set: (transformer) => {
+        const newValue = transformer(value)
+        if (value !== newValue) {
+          value = newValue
+          subject.next(value)
+        }
+      },
+      subscribe: (subscriber) => subject.subscribe(subscriber),
+    }
+  },
+}
diff --git a/src/ObservableState.test.js b/src/ObservableState.test.js
new file mode 100644
index 0000000..e49c28d
--- /dev/null
+++ b/src/ObservableState.test.js
@@ -0,0 +1,101 @@
+import { act, fireEvent, render } from '@testing-library/react'
+import PropTypes from 'prop-types'
+import React from 'react'
+import useObservableState from '../DEV/useObservableState'
+import ObservableState from './ObservableState'
+
+function factorySharedState() {
+  const calcState = ObservableState.create({
+    number: 1,
+  })
+  
+  function useCalcState() {
+    return useObservableState(calcState)
+  }
+
+  return [useCalcState, calcState]
+}
+
+function Number({ prefix, useShareState }) {
+  const [state, setState] = useShareState()
+  return (
+    <>
+      <span>
+        {prefix}: {state.number}
+      </span>
+      <button
+        data-testid={'id-' + prefix.replace(' ', '-')}
+        type="button"
+        onClick={() => {
+          setState(({ number }) => ({
+            number: (prefix.includes('1st') ? 10 : 20) + number,
+          }))
+        }}
+      >
+        Increment {prefix}
+      </button>
+    </>
+  )
+}
+Number.propTypes = {
+  prefix: PropTypes.string.isRequired,
+  useShareState: PropTypes.func.isRequired,
+}
+
+function Wrapper({ useShareState }) {
+  return (
+    <div>
+      <Number prefix="1st Number" useShareState={useShareState} />
+      <Number prefix="2nd Number" useShareState={useShareState} />
+    </div>
+  )
+}
+Wrapper.propTypes = {
+  useShareState: PropTypes.func.isRequired,
+}
+
+describe('useObservableState', () => {
+  test('if useObservableState share state', () => {
+    const [useShareState] = factorySharedState()
+    const wrapper = render(<Wrapper useShareState={useShareState} />)
+
+    expect(wrapper.getByText(/1st number: 1/i)).toBeInTheDocument()
+    expect(wrapper.getByText(/2nd number: 1/i)).toBeInTheDocument()
+  })
+
+  test('if useObservableState share state changed from outside', () => {
+    const [useShareState, sharedState] = factorySharedState()
+    const wrapper = render(<Wrapper useShareState={useShareState} />)
+
+    act(() => {
+      sharedState.set((state) => ({ number: state.number + 100 }))
+    })
+    expect(wrapper.getByText(/1st number: 101/i)).toBeInTheDocument()
+    expect(wrapper.getByText(/2nd number: 101/i)).toBeInTheDocument()
+  })
+
+  test('if useObservableState share state changed from first internal component', async () => {
+    const [useShareState] = factorySharedState()
+    const wrapper = render(<Wrapper useShareState={useShareState} />)
+
+    fireEvent.click(await wrapper.getByTestId('id-1st-Number'))
+    expect(await wrapper.findByText(/1st number: 11/i)).toBeInTheDocument()
+    expect(await wrapper.findByText(/2nd number: 11/i)).toBeInTheDocument()
+  })
+
+  test('if useObservableState share state changed from first internal component', async () => {
+    const [useShareState] = factorySharedState()
+    const wrapper = render(<Wrapper useShareState={useShareState} />)
+
+    fireEvent.click(await wrapper.getByTestId('id-2nd-Number'))
+    expect(await wrapper.findByText(/1st number: 21/i)).toBeInTheDocument()
+    expect(await wrapper.findByText(/2nd number: 21/i)).toBeInTheDocument()
+  })
+
+  test('if ObservableState does not change after return current state', async () => {
+    const initialState = { name: 'The Same' }
+    const state = ObservableState.create(initialState)
+    state.set((val) => val)
+    expect(state.get()).toBe(initialState)
+  })
+})
diff --git a/src/factoryAsyncDebounce.js b/src/factoryAsyncDebounce.js
new file mode 100644
index 0000000..c26581b
--- /dev/null
+++ b/src/factoryAsyncDebounce.js
@@ -0,0 +1,36 @@
+/**
+ * Creates a debounced async function
+ * @param {(...args) => Promise<T>} fn 
+ * @param {import('@daniloster/i18n/lib/types').AsyncDebounceHooks} statusHooks
+ * @param {number} debounce 
+ * @returns {import('@daniloster/i18n/lib/types').Debounced<Promise<T>>}
+ * @template T
+ */
+export default function factoryAsyncDebounce(fn, statusHooks) {
+  let ref = null
+  let lastReject = () => null
+  const debounced = (...args) => new Promise((resolve, reject) => {
+    clearTimeout(ref)
+    lastReject({ debounced: true })
+    lastReject = reject
+    statusHooks.onStart()
+    /** @type {boolean} */
+    const skip = statusHooks.skip(...args)
+    const debouncedExecutor = () => {
+      fn(...args)
+        .then((...response) => {
+          resolve(...response)
+          statusHooks.onSuccess()
+        }).catch((...error) => {
+          statusHooks.onError()
+          reject(...error)
+        })
+    }
+    
+    ref = setTimeout(debouncedExecutor, skip ? 0 : statusHooks.debounce)
+  })
+
+  debounced.bypass = fn
+
+  return debounced
+}
diff --git a/src/factoryI18n.js b/src/factoryI18n.js
new file mode 100644
index 0000000..6bfbdb6
--- /dev/null
+++ b/src/factoryI18n.js
@@ -0,0 +1,98 @@
+import AsyncStatus from "./AsyncStatus"
+import factoryLanguageService from "./factoryLanguageService"
+import factoryResolver from "./factoryResolver"
+import factoryResourcesService from "./factoryResourcesService"
+import ObservableState from "./ObservableState"
+import onInit from "./onInit"
+
+const DEFAULT_DEBOUNCE = 300
+/**
+ * Validates if a real number is passed as debounce otherwise returns
+ * a default debounce (300)
+ * @param {number} debounce the delay time in milliseconds (optional)
+ * @returns {number} the delay time in milliseconds
+ */
+function getDebounce(debounce) {
+  return typeof debounce === 'number' ? debounce : DEFAULT_DEBOUNCE
+}
+
+/**
+ * Creates i18n object which manages internationalization asynchronously.
+ * @param {import('@daniloster/i18n/lib/types').I18nConfig} config 
+ * @returns {import('@daniloster/i18n/lib/types').I18nState}
+ */
+export default function factoryI18n(config) {
+  const {
+    debounceLanguageService,
+    debounceResourcesService,
+    defaultLanguage,
+  } = config
+  /** @type {import('@daniloster/i18n/lib/types').ObservableState<string>} */
+  const language = ObservableState.create(defaultLanguage)
+  /** @type {import('@daniloster/i18n/lib/types').ObservableState<import('@daniloster/i18n/lib/types').Resource>} */
+  const resources = ObservableState.create({})
+
+  const languageService = factoryLanguageService(
+    config.languageService,
+    language,
+    resources,
+    getDebounce(debounceLanguageService)
+  )
+  const resourcesService = factoryResourcesService(
+    config.resourcesService,
+    resources,
+    getDebounce(debounceResourcesService)
+  )
+  language.subscribe({
+    next: (lng) => {
+      // Errors will be captured by statusObservableList listeners
+      resourcesService.get(lng).catch(() => null)
+    }
+  })
+  const status = ObservableState.create(AsyncStatus.Initial)
+  const statusObservableList = [
+    languageService.status.get,
+    languageService.status.set,
+    resourcesService.status.get,
+    resourcesService.status.set,
+  ]
+  statusObservableList.forEach(statusObservable => {
+    statusObservable.subscribe({
+      next: () => {
+        if (statusObservableList.some(currentStatus => currentStatus.get() === AsyncStatus.Loading)) {
+          status.set(() => AsyncStatus.Loading)
+        } else if (statusObservableList.some(currentStatus => currentStatus.get() === AsyncStatus.Error)) {
+          status.set(() => AsyncStatus.Error)
+        } else {
+          status.set(() => AsyncStatus.Success)
+        }
+      }
+    })
+  })
+
+  const t = factoryResolver({
+    defaultLanguage,
+    language,
+    resources,
+    status,
+  })
+
+  async function init() {
+    await onInit({
+      defaultLanguage,
+      languageService,
+      resourcesService,
+      status,
+    })
+  }
+
+  return {
+    init,
+    languageService,
+    resourcesService,
+    language,
+    resources,
+    status,
+    t,
+  }
+}
diff --git a/src/factoryLanguageService.js b/src/factoryLanguageService.js
new file mode 100644
index 0000000..312abc9
--- /dev/null
+++ b/src/factoryLanguageService.js
@@ -0,0 +1,43 @@
+import AsyncStatus from "./AsyncStatus"
+import factoryAsyncDebounce from "./factoryAsyncDebounce"
+import factoryStatusHooks from "./factoryStatusHooks"
+import ObservableState from "./ObservableState"
+
+/**
+ * 
+ * @param {import('@daniloster/i18n/lib/types').LanguageService} languageService 
+ * @param {import('@daniloster/i18n/lib/types').ObservableState<string>} languageState  
+ * @param {import('@daniloster/i18n/lib/types').ObservableState<import('@daniloster/i18n/lib/types').Resource>} resourceState  
+ * @param {number} debounce  
+ * @returns {import('@daniloster/i18n/lib/types').LanguageServiceObservable<string>}
+ */
+export default function factoryLanguageService(languageService, languageState, resourceState, debounce) {
+  const status = {
+    get: ObservableState.create(AsyncStatus.Initial),
+    set: ObservableState.create(AsyncStatus.Initial),
+  }
+
+  function isResourceLoaded(language) {
+    return !!resourceState.get()[language]
+  }
+
+  /** @type {import('@daniloster/i18n/lib/types').LanguageServiceObservable<string>} */
+  const service = {
+    status,
+    get: factoryAsyncDebounce(async (bypassNotification) => {
+      const language = await languageService.get()
+      if (!bypassNotification) {
+        languageState.set(() => language)
+      }
+
+      return language
+    }, factoryStatusHooks(status.get, () => false, debounce)),
+    set: factoryAsyncDebounce(async (language) => {
+      const response = await languageService.set(language)
+      languageState.set(() => language)
+
+      return response
+    }, factoryStatusHooks(status.set, isResourceLoaded, debounce)),
+  }
+  return Object.freeze(service)
+}
\ No newline at end of file
diff --git a/src/factoryResolver.js b/src/factoryResolver.js
new file mode 100644
index 0000000..7b5e927
--- /dev/null
+++ b/src/factoryResolver.js
@@ -0,0 +1,98 @@
+import { get as getPath } from 'mutation-helper'
+import ObservableState from './ObservableState'
+
+function get(obj, path) {
+  try {
+    return getPath(obj, path)
+  } catch {
+    return null
+  }
+}
+
+/**
+ * 
+ * @param {import('@daniloster/i18n/lib/types').Resource} resources 
+ * @param {string} language 
+ * @param {AsyncStatus} status
+ * @returns {(path: string, transform: (string) => string) => string}
+ */
+function factoryTemplateResolver(resources, language, status, defaultResolver) {
+  /**
+   * Resolves the json path into a string template that can be transformed
+   * before returning
+   * @param {string} path
+   * @param {(string) => string} transform
+   * @returns {string}
+   */
+  return (path, transform) => {
+    const dictionary = get(resources, language)
+    const template = get(dictionary, path)
+    if (template === null || template === undefined) {
+      if (defaultResolver) {
+        const defaultTemplate = defaultResolver(path, transform)
+        /**
+         * Fallback to the default language. In case no value is found,
+         * it will return the proper path, then, when defaultTemplate !== path
+         * it means it got resolved.
+         */
+        if (defaultTemplate !== path) {
+          return defaultTemplate
+        }
+      }
+
+      return path
+    }
+
+    if (transform) {
+      return transform({ path, template, status })
+    }
+
+    return template
+  }
+}
+
+/**
+ * Creates a resolver for i18n key
+ * @param {import('@daniloster/i18n/lib/types').ResolverConfig} props
+ */
+export default function factoryResolver(props) {
+  const {
+    defaultLanguage,
+    language,
+    resources,
+    status,
+  } = props
+
+  let [rs, lng, st] = [resources.get(), language.get(), status.get()]
+
+  const getDefaultResolver = () => factoryTemplateResolver(resources.get(), defaultLanguage, status.get())
+
+  const resolver = ObservableState.create(factoryTemplateResolver(rs, lng, st)) 
+  const factory = () => {
+    resolver.set(() => factoryTemplateResolver(rs, lng, st, getDefaultResolver()))
+  }
+
+  status.subscribe({
+    next: (_st) => {
+      st = _st
+      factory()
+    }
+  })
+  language.subscribe({
+    next: (_lng) => {
+      if (rs[_lng]) {
+        lng = _lng
+      }
+      factory()
+    }
+  })
+  resources.subscribe({
+    next: (_rs) => {
+      rs = _rs
+      lng = language.get()
+      factory()
+    }
+  })
+
+  return resolver
+}
\ No newline at end of file
diff --git a/src/factoryResourcesService.js b/src/factoryResourcesService.js
new file mode 100644
index 0000000..6f2589c
--- /dev/null
+++ b/src/factoryResourcesService.js
@@ -0,0 +1,70 @@
+import AsyncStatus from "./AsyncStatus"
+import factoryAsyncDebounce from "./factoryAsyncDebounce"
+import factoryStatusHooks from "./factoryStatusHooks"
+import ObservableState from "./ObservableState"
+
+/**
+ * 
+ * @param {import('@daniloster/i18n/lib/types').ResourcesService} resourcesService 
+ * @param {import('@daniloster/i18n/lib/types').ObservableState<import('@daniloster/i18n/lib/types').Resource>} resourceState  
+ * @param {number} debounce  
+ * @returns {import('@daniloster/i18n/lib/types').ResourcesServiceObservable<import('@daniloster/i18n/lib/types').Resource>}
+ */
+export default function factoryResourcesService(resourcesService, resourceState, debounce) {
+  /**
+   * @type {{
+   * get: import('@daniloster/i18n/lib/types').ObservableState<import('@daniloster/i18n/lib/types').AsyncStatus>,
+   * set: import('@daniloster/i18n/lib/types').ObservableState<import('@daniloster/i18n/lib/types').AsyncStatus>
+   * }}
+   * */
+  const status = {
+    get: ObservableState.create(AsyncStatus.Initial),
+    set: ObservableState.create(AsyncStatus.Initial),
+  }
+
+  function isResourceLoaded(language) {
+    return !!resourceState.get()[language]
+  }
+
+  /** @type {import('@daniloster/i18n/lib/types').ResourcesServiceObservable<import('@daniloster/i18n/lib/types').Resource>} */
+  const service = {
+    status,
+    get: factoryAsyncDebounce(async (language) => {
+      const loadedResource = resourceState.get()[language]
+      if (loadedResource) {
+        return loadedResource
+      }
+      
+      const resource = await resourcesService.get(language)
+      resourceState.set(oldResources => {
+        if (!oldResources[language]) {
+          return {
+            ...oldResources,
+            [language]: resource
+          }
+        }
+
+        return oldResources
+      })
+
+      return resource
+    }, factoryStatusHooks(status.get, isResourceLoaded, debounce)),
+    set: factoryAsyncDebounce(async (language, resource) => {
+      const response = await resourcesService.set(language, resource)
+      resourceState.set(oldResources => {
+        if (!oldResources[language]) {
+          return {
+            ...oldResources,
+            [language]: resource
+          }
+        }
+
+        return oldResources
+      })
+
+      return response
+    }, factoryStatusHooks(status.set, () => false, debounce)),
+  }
+
+  return Object.freeze(service)
+}
\ No newline at end of file
diff --git a/src/factoryStatusHooks.js b/src/factoryStatusHooks.js
new file mode 100644
index 0000000..a6dec1f
--- /dev/null
+++ b/src/factoryStatusHooks.js
@@ -0,0 +1,22 @@
+import AsyncStatus from "./AsyncStatus"
+
+/**
+ * Creates a status hook
+ * @param {import('@daniloster/i18n/lib/types').ObservableState<import('@daniloster/i18n/lib/types').AsyncStatus>} observable 
+ * @param {Function(args): boolean} skip
+ * @param {number} debounce 
+ * @returns {import('@daniloster/i18n/lib/types').AsyncDebounceHooks}
+ */
+export default function factoryStatusHooks(observable, skip, debounce) {
+  const onStart = () => observable.set(() => AsyncStatus.Loading)
+  const onError = () => observable.set(() => AsyncStatus.Error)
+  const onSuccess = () => observable.set(() => AsyncStatus.Success)
+
+  return {
+    debounce,
+    skip,
+    onStart,
+    onError,
+    onSuccess,
+  }
+}
diff --git a/src/index.js b/src/index.js
new file mode 100644
index 0000000..61c306e
--- /dev/null
+++ b/src/index.js
@@ -0,0 +1,3 @@
+import factoryI18n from './factoryI18n'
+
+export default factoryI18n
diff --git a/src/onInit.js b/src/onInit.js
new file mode 100644
index 0000000..727d6a5
--- /dev/null
+++ b/src/onInit.js
@@ -0,0 +1,51 @@
+import AsyncStatus from "./AsyncStatus"
+
+// make sure won't trigger notification by getting language
+const BypassNotification = true
+
+/**
+ * 
+ * @typedef InitConfig
+ * @property {string} defaultLanguage
+ * @property {import('@daniloster/i18n/lib/types').LanguageServiceObservable<string>} languageService
+ * @property {import('@daniloster/i18n/lib/types').ResourcesServiceObservable<import('@daniloster/i18n/lib/types').Resource>} resourcesService
+ * @property {import('@daniloster/i18n/lib/types').ObservableState<string>} status
+ */
+
+/**
+ * 
+ * @param {InitConfig} config 
+ */
+export default async function onInit(config) {
+  const {
+    defaultLanguage,
+    languageService,
+    resourcesService,
+    status,
+  } = config
+  // start on loading
+  status.set(() => AsyncStatus.Loading)
+  try {
+    const remoteLanguage = await languageService.get.bypass(BypassNotification)
+    // define initial language
+    const initialLanguage = remoteLanguage || defaultLanguage
+    /**
+     * set new language if initial different from default. This
+     * will trigger load on demand
+     */
+    if (initialLanguage !== defaultLanguage) {
+      await resourcesService.get.bypass(defaultLanguage)
+      await languageService.set.bypass(initialLanguage)
+      status.set(() => AsyncStatus.Success)
+    } else {
+      /**
+       * otherwise, force load of default language
+       */
+      await resourcesService.get.bypass(initialLanguage)
+      status.set(() => AsyncStatus.Success)
+    }
+  } catch (e) {
+    status.set(() => AsyncStatus.Error)
+    throw e
+  }
+}
\ No newline at end of file
diff --git a/src/types.d.ts b/src/types.d.ts
new file mode 100644
index 0000000..8962a38
--- /dev/null
+++ b/src/types.d.ts
@@ -0,0 +1,111 @@
+interface Debounced<R> {
+  (...args): R
+
+  bypass(...args): R
+}
+
+type Resource = { [key: string]: string | number | Date | boolean | Resource }
+
+export interface ResourcesService {
+  get(language: string): Promise<Resource>
+  set(language: string, resource: Resource): Promise<any>
+}
+
+export interface ResourcesServiceObservable<T> extends ResourcesService<T> {
+  status: {
+    get: ObservableState<AsyncStatus>
+    set: ObservableState<AsyncStatus>
+  }
+}
+
+export interface LanguageService<T> {
+  get(): Promise<T>
+  set(language: string): Promise<any|T>
+}
+
+export interface LanguageServiceObservable<T> extends LanguageService<T> {
+  status: {
+    get: ObservableState<AsyncStatus>
+    set: ObservableState<AsyncStatus>
+  }
+}
+
+export interface Init<T> {
+  (): Promise<T>
+}
+
+export interface I18nConfig {
+  defaultLanguage: string
+  debounceLanguageService?: number
+  debounceResourcesService?: number
+  languageService: LanguageService
+  resourcesService: ResourcesService
+}
+
+export type ResolverTransformerInput = { path: string; template: string; status: AsyncStatus }
+
+export interface ResolverTransformer {
+  (arg: ResolverTransformerInput): string
+}
+
+interface Resolver {
+  (path: string, transformer: ResolverTransformer): string
+}
+
+export interface I18nState {
+  init: Promise<any>
+  languageService: LanguageService
+  language: ObservableState<string>
+  resourcesService: ResourcesService
+  resources: ObservableState<Resource>
+  status: ObservableState<AsyncStatus>
+  t: ObservableState<Resolver>
+}
+
+export interface Subscriber<T> {
+  next(value: T): void
+}
+
+export interface Subscription {
+  unsubscribe(): void
+}
+
+export interface Subject extends Subscriber<T> {
+  private subscribers: Subscriber<T>[]
+  subscribe(subscriber: Subscriber<T>): Subscription
+}
+
+export interface TransformerState<T> {
+  (state: T): T
+}
+
+export interface ObservableState<T> {
+  get: () => T,
+  set: (transformer: TransformerState<T>) => void
+  subscribe: (subscriber: Subscriber<T>) => Subscription
+}
+
+export interface FactoryObservableState<T> {
+  create(initialValue: T): ObservableState<T>
+}
+
+export interface AsyncDebounceHooks {
+  debounce: number
+  onStart: Function
+  onError: Function
+  onSuccess: Function
+}
+
+enum AsyncStatus {
+  Initial = 'Initial',
+  Loading = 'Loading',
+  Success = 'Success',
+  Error = 'Error',
+}
+
+export interface ResolverConfig {
+  defaultLanguage: string
+  language: ObservableState<string>
+  resources: ObservableState<Resource>
+  status: ObservableState<AsyncStatus>
+}
diff --git a/tools/__mocks__/startMirage.js b/tools/__mocks__/startMirage.js
index dc0d8eb..c5f916c 100644
--- a/tools/__mocks__/startMirage.js
+++ b/tools/__mocks__/startMirage.js
@@ -1,9 +1,9 @@
 import { Server } from 'miragejs'
 import en from '../../DEV/assets/locales/en.json'
 import es from '../../DEV/assets/locales/es.json'
-import ptBR from '../../DEV/assets/locales/pt.json'
+import pt from '../../DEV/assets/locales/pt.json'
 
-const resources = { 'en.json': en, 'pt-BR.json': ptBR, 'es.json': es }
+const resources = { 'en.json': en, 'pt.json': pt, 'es.json': es }
 
 /**
  * Creates a mock api server which mimics the api service behaviour
@@ -34,7 +34,7 @@ export default function startMirage(environment = 'development') {
         (schema, request) => {
           const { language } = request.params
 
-          // console.log({ language, resources: !!resources[language] })
+          // console.log({ language, resources: resources[language] })
 
           return resources[language]
         },
diff --git a/tools/helpers/jest.setup.afterEnv.js b/tools/helpers/jest.setup.afterEnv.js
index 313e8fa..78d4eb9 100644
--- a/tools/helpers/jest.setup.afterEnv.js
+++ b/tools/helpers/jest.setup.afterEnv.js
@@ -36,7 +36,7 @@ beforeEach(() => {
   mockMutationObserver()
   mockNavigator()
   HTMLElement.prototype.scrollIntoView = noop
-  localStorage.setItem('language', 'en')
+  localStorage.setItem('language', '')
   jest.useRealTimers()
 })
 
diff --git a/yarn.lock b/yarn.lock
index bf89aff..86545a5 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -5338,10 +5338,10 @@ lodash.values@^4.3.0:
   resolved "https://registry.yarnpkg.com/lodash.values/-/lodash.values-4.3.0.tgz#a3a6c2b0ebecc5c2cba1c17e6e620fe81b53d347"
   integrity sha1-o6bCsOvsxcLLocF+bmIP6BtT00c=
 
-lodash@^4.17.11, lodash@^4.17.13, lodash@^4.17.14, lodash@^4.17.15:
-  version "4.17.15"
-  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.15.tgz#b447f6670a0455bbfeedd11392eff330ea097548"
-  integrity sha512-8xOcRHvCjnocdS5cpwXQXVzmmh5e5+saE2QGoeQmbKmRS6J3VQppPOIt0MnmE+4xlZoumy0GPG0D0MVIQbNA1A==
+lodash@4.17.19, lodash@^4.17.11, lodash@^4.17.13, lodash@^4.17.14, lodash@^4.17.15:
+  version "4.17.19"
+  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.19.tgz#e48ddedbe30b3321783c5b4301fbd353bc1e4a4b"
+  integrity sha512-JNvd8XER9GQX0v2qJgsaN/mzFCNA5BRe/j8JN9d+tWyGLSodKQHKFicdwNYzWwI3wjRnaKPsGj1XkBjx/F96DQ==
 
 loglevel@^1.6.6:
   version "1.6.8"