From 3e79caafdd77d0070988548a291f564c90172976 Mon Sep 17 00:00:00 2001
From: Krzysztof Borowy <krizzu.dev@gmail.com>
Date: Sun, 11 Aug 2019 15:22:24 +0200
Subject: [PATCH 1/7] fix: better typing

---
 packages/core/src/AsyncStorage.ts             |  61 +++++-----
 packages/core/src/defaults.ts                 |   8 ++
 packages/core/src/index.ts                    |  18 ++-
 packages/core/types/index.d.ts                | 101 +++++++++++------
 packages/storage-legacy/src/index.ts          | 107 +++++++++++++-----
 packages/storage-legacy/types/index.d.ts      |  44 ++++---
 .../storage-legacy/types/nativeModule.d.ts    |  25 ++++
 7 files changed, 259 insertions(+), 105 deletions(-)
 create mode 100644 packages/storage-legacy/types/nativeModule.d.ts

diff --git a/packages/core/src/AsyncStorage.ts b/packages/core/src/AsyncStorage.ts
index 05a00ced..1f37454c 100644
--- a/packages/core/src/AsyncStorage.ts
+++ b/packages/core/src/AsyncStorage.ts
@@ -1,19 +1,26 @@
+/**
+ * Copyright (c) React Native Community.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
 import {simpleErrorHandler, simpleLogger, noop} from './defaults';
 import {
   FactoryOptions,
   IStorageBackend,
   LoggerAction,
-  StorageModel,
   StorageOptions,
 } from '../types';
 
-class AsyncStorage<STR extends IStorageBackend, VAL = StorageModel<STR>> {
-  private readonly _backend: STR;
+class AsyncStorage<M, T extends IStorageBackend<M>> {
+  private readonly _backend: T;
   private readonly _config: FactoryOptions;
   private readonly log: (action: LoggerAction) => void;
   private readonly error: (e: Error | string) => void;
 
-  constructor(storageBackend: STR, asOptions: FactoryOptions) {
+  constructor(storageBackend: T, asOptions: FactoryOptions) {
     this._backend = storageBackend;
     this._config = asOptions;
 
@@ -35,13 +42,15 @@ class AsyncStorage<STR extends IStorageBackend, VAL = StorageModel<STR>> {
           : simpleErrorHandler;
     }
   }
-
-  async get(key: string, opts: StorageOptions = null): Promise<VAL | null> {
-    let value = null;
+  async get<K extends keyof M>(
+    key: K,
+    opts: StorageOptions = null,
+  ): Promise<M[K] | null> {
+    let value = null as M[K] | null;
     try {
       this.log({
         action: 'read-single',
-        key: key,
+        key: key as string,
       });
       value = await this._backend.getSingle(key, opts);
     } catch (e) {
@@ -51,15 +60,15 @@ class AsyncStorage<STR extends IStorageBackend, VAL = StorageModel<STR>> {
     return value;
   }
 
-  async set(
-    key: string,
-    value: VAL,
+  async set<K extends keyof M>(
+    key: K,
+    value: M[K],
     opts: StorageOptions = null,
   ): Promise<void> {
     try {
       this.log({
         action: 'save-single',
-        key,
+        key: key as string,
         value,
       });
       await this._backend.setSingle(key, value, opts);
@@ -68,16 +77,16 @@ class AsyncStorage<STR extends IStorageBackend, VAL = StorageModel<STR>> {
     }
   }
 
-  async getMultiple(
-    keys: Array<string>,
+  async getMultiple<K extends keyof M>(
+    keys: Array<K>,
     opts: StorageOptions = null,
-  ): Promise<Array<VAL | null>> {
-    let values: Array<VAL | null> = [];
+  ): Promise<{[k in K]: M[k] | null}> {
+    let values = {} as {[k in K]: M[k] | null};
 
     try {
       this.log({
         action: 'read-many',
-        key: keys,
+        key: keys as string[],
       });
       values = await this._backend.getMany(keys, opts);
     } catch (e) {
@@ -87,8 +96,8 @@ class AsyncStorage<STR extends IStorageBackend, VAL = StorageModel<STR>> {
     return values;
   }
 
-  async setMultiple(
-    keyValues: Array<{[key: string]: VAL}>,
+  async setMultiple<K extends keyof M>(
+    keyValues: Array<{[k in K]: M[k]}>,
     opts: StorageOptions = null,
   ): Promise<void> {
     try {
@@ -102,11 +111,11 @@ class AsyncStorage<STR extends IStorageBackend, VAL = StorageModel<STR>> {
     }
   }
 
-  async remove(key: string, opts: StorageOptions = null): Promise<void> {
+  async remove(key: keyof M, opts: StorageOptions = null): Promise<void> {
     try {
       this.log({
         action: 'delete-single',
-        key,
+        key: key as string,
       });
       await this._backend.removeSingle(key, opts);
     } catch (e) {
@@ -115,13 +124,13 @@ class AsyncStorage<STR extends IStorageBackend, VAL = StorageModel<STR>> {
   }
 
   async removeMultiple(
-    keys: Array<string>,
+    keys: Array<keyof M>,
     opts: StorageOptions = null,
   ): Promise<void> {
     try {
       this.log({
         action: 'delete-many',
-        key: keys,
+        key: keys as string[],
       });
       await this._backend.removeMany(keys, opts);
     } catch (e) {
@@ -129,8 +138,8 @@ class AsyncStorage<STR extends IStorageBackend, VAL = StorageModel<STR>> {
     }
   }
 
-  async getKeys(opts: StorageOptions = null): Promise<Array<string>> {
-    let keys: Array<string> = [];
+  async getKeys(opts: StorageOptions = null): Promise<Array<keyof M>> {
+    let keys: Array<keyof M> = [];
 
     try {
       this.log({
@@ -157,7 +166,7 @@ class AsyncStorage<STR extends IStorageBackend, VAL = StorageModel<STR>> {
 
   // todo: think how we could provide additional functions through AS, without returning the instance
   // some kind of extension-like functionality
-  instance(): STR {
+  instance(): T {
     return this._backend;
   }
 }
diff --git a/packages/core/src/defaults.ts b/packages/core/src/defaults.ts
index a7c4ef4b..345ac170 100644
--- a/packages/core/src/defaults.ts
+++ b/packages/core/src/defaults.ts
@@ -1,3 +1,11 @@
+/**
+ * Copyright (c) React Native Community.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
 import {FactoryOptions, LoggerAction} from '../types';
 
 export const factoryOptions: FactoryOptions = {
diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index 0e1a4550..b96e17ec 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -1,6 +1,14 @@
+/**
+ * Copyright (c) React Native Community.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
 import AsyncStorage from './AsyncStorage';
 import {factoryOptions} from './defaults';
-import {IStorageBackend, FactoryOptions, StorageModel} from '../types';
+import {IStorageBackend, FactoryOptions, EmptyStorageModel} from '../types';
 
 class AsyncStorageFactory {
   constructor() {
@@ -9,11 +17,11 @@ class AsyncStorageFactory {
     );
   }
 
-  static create<STR extends IStorageBackend>(
-    storage: STR,
+  static create<M = EmptyStorageModel>(
+    storage: IStorageBackend,
     opts: FactoryOptions = factoryOptions,
-  ): AsyncStorage<STR, StorageModel<STR>> {
-    return new AsyncStorage(storage, opts);
+  ) {
+    return new AsyncStorage<M, IStorageBackend<M>>(storage, opts);
   }
 }
 
diff --git a/packages/core/types/index.d.ts b/packages/core/types/index.d.ts
index c384bc96..09700b3c 100644
--- a/packages/core/types/index.d.ts
+++ b/packages/core/types/index.d.ts
@@ -1,63 +1,94 @@
-export class AsyncStorage<
-  STR extends IStorageBackend,
-  VAL = StorageModel<STR>
-> {
-  get(key: string, opts?: StorageOptions): Promise<VAL | null>;
+/**
+ * Copyright (c) React Native Community.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
+/**
+ * Crates an Async Storage instance for given storage backend
+ * Enhanced by Factory Options, to, in example, enable logging
+ */
+export default class AsyncStorageFactory {
+  static create<M = EmptyStorageModel>(
+    storage: IStorageBackend,
+    opts: FactoryOptions,
+  ): AsyncStorage<M, IStorageBackend<M>>;
+}
+
+/**
+ * Do not instantiate. Create through AsyncStorageFactory.
+ * Main API that will be used to call underlying storage backend
+ */
+export class AsyncStorage<M, T extends IStorageBackend<M>> {
+  get<K extends keyof M>(key: K, opts?: StorageOptions): Promise<M[K] | null>;
 
-  set(key: string, value: VAL, opts?: StorageOptions): Promise<void>;
+  set<K extends keyof M>(
+    key: K,
+    value: M[K],
+    opts?: StorageOptions,
+  ): Promise<void>;
 
-  getMultiple(
-    keys: Array<string>,
+  getMultiple<K extends keyof M>(
+    keys: Array<K>,
     opts?: StorageOptions,
-  ): Promise<Array<VAL | null>>;
+  ): Promise<{[k in K]: M[k] | null}>;
 
-  setMultiple(
-    keyValues: Array<{[key: string]: VAL}>,
+  setMultiple<K extends keyof M>(
+    keyValues: Array<Partial<{[k in keyof M]: M[k]}>>,
     opts?: StorageOptions,
   ): Promise<void>;
 
-  remove(key: string, opts?: StorageOptions): Promise<void>;
+  remove(key: keyof M, opts?: StorageOptions): Promise<void>;
 
-  removeMultiple(keys: Array<string>, opts?: StorageOptions): Promise<void>;
+  removeMultiple(keys: Array<keyof M>, opts?: StorageOptions): Promise<void>;
 
-  getKeys(opts?: StorageOptions): Promise<Array<string>>;
+  getKeys(opts?: StorageOptions): Promise<Array<keyof M>>;
 
   clearStorage(opts?: StorageOptions): Promise<void>;
 
-  instance(): STR;
+  instance(): T;
 }
 
-export default class AsyncStorageFactory {
-  static create<STR extends IStorageBackend>(
-    storage: STR,
-    opts: FactoryOptions,
-  ): AsyncStorage<STR, StorageModel<STR>>;
-}
-
-export interface IStorageBackend<VAL = any> {
-  getSingle(key: string, opts?: StorageOptions): Promise<VAL | null>;
+/**
+ * Interface that must be implemented by any Storage Backend
+ * Provides basic API for reading/writing and deleting of data
+ */
+export interface IStorageBackend<T = EmptyStorageModel> {
+  getSingle<K extends keyof T>(
+    key: K,
+    opts?: StorageOptions,
+  ): Promise<T[K] | null>;
 
-  setSingle(key: string, value: VAL, opts?: StorageOptions): Promise<void>;
+  setSingle<K extends keyof T>(
+    key: K,
+    value: T[K],
+    opts?: StorageOptions,
+  ): Promise<void>;
 
-  getMany(
-    keys: Array<string>,
+  getMany<K extends keyof T>(
+    keys: Array<K>,
     opts?: StorageOptions,
-  ): Promise<Array<VAL | null>>;
+  ): Promise<{[k in K]: T[k] | null}>;
 
-  setMany(
-    values: Array<{[key: string]: VAL}>,
+  setMany<K extends keyof T>(
+    values: Array<{[k in K]: T[k]}>,
     opts?: StorageOptions,
   ): Promise<void>;
 
-  removeSingle(key: string, opts?: StorageOptions): Promise<void>;
+  removeSingle(key: keyof T, opts?: StorageOptions): Promise<void>;
 
-  removeMany(keys: Array<string>, opts?: StorageOptions): Promise<void>;
+  removeMany(keys: Array<keyof T>, opts?: StorageOptions): Promise<void>;
 
-  getKeys(opts?: StorageOptions): Promise<Array<string>>;
+  getKeys(opts?: StorageOptions): Promise<Array<keyof T>>;
 
   dropStorage(opts?: StorageOptions): Promise<void>;
 }
 
+/**
+ * Used by Factory to enhance calls
+ */
 export type FactoryOptions = {
   logger?: ((action: LoggerAction) => void) | boolean;
   errorHandler?: ((error: Error | string) => void) | boolean;
@@ -78,8 +109,12 @@ export type LoggerAction = {
   key?: string | Array<string>;
 };
 
+// Helper types
+
 export type StorageModel<T> = T extends IStorageBackend<infer V> ? V : any;
 
+export type EmptyStorageModel = {[key in symbol | number | string]: any};
+
 export type StorageOptions = {
   [key: string]: any;
 } | null;
diff --git a/packages/storage-legacy/src/index.ts b/packages/storage-legacy/src/index.ts
index 75425f1e..6ca81aa8 100644
--- a/packages/storage-legacy/src/index.ts
+++ b/packages/storage-legacy/src/index.ts
@@ -1,5 +1,5 @@
 /**
- * Copyright (c) Facebook, Inc. and its affiliates.
+ * Copyright (c) React Native Community.
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
@@ -8,9 +8,11 @@
 
 import {NativeModules} from 'react-native';
 import {
+  EmptyStorageModel,
   IStorageBackend,
   StorageOptions,
 } from '@react-native-community/async-storage';
+import {ILegacyNativeModule} from '../types/nativeModule';
 
 function convertErrors(errs?: Array<Error> | Error) {
   if (!errs) {
@@ -19,8 +21,10 @@ function convertErrors(errs?: Array<Error> | Error) {
   return Array.isArray(errs) ? errs.filter(e => !!e) : [errs];
 }
 
-export default class LegacyAsyncStorage<T = any> implements IStorageBackend<T> {
-  private readonly _asyncStorageNativeModule: any;
+export default class LegacyAsyncStorage<
+  T extends EmptyStorageModel = EmptyStorageModel
+> implements IStorageBackend<T> {
+  private readonly _asyncStorageNativeModule: ILegacyNativeModule;
 
   constructor() {
     this._asyncStorageNativeModule =
@@ -35,17 +39,20 @@ export default class LegacyAsyncStorage<T = any> implements IStorageBackend<T> {
     }
   }
 
-  async getSingle(key: string, opts?: StorageOptions): Promise<T | null> {
+  async getSingle<K extends keyof T>(
+    key: K,
+    opts?: StorageOptions,
+  ): Promise<T[K] | null> {
     if (opts) {
       // noop
     }
 
-    return new Promise<T | null>((resolve, reject) => {
+    return new Promise((resolve, reject) => {
       this._asyncStorageNativeModule.multiGet([key], function(
         errors: Array<Error>,
-        result: Array<[any, T | null]>,
+        result: Array<[any, T[K] | null]>,
       ) {
-        const value = result && result[0] && result[0][1] ? result[0][1] : null;
+        const value = (result && result[0] && result[0][1]) || null;
         const errs = convertErrors(errors);
         if (errs && errs.length) {
           reject(errs[0]);
@@ -56,12 +63,16 @@ export default class LegacyAsyncStorage<T = any> implements IStorageBackend<T> {
     });
   }
 
-  async setSingle(key: string, value: T, opts?: StorageOptions): Promise<void> {
+  async setSingle<K extends keyof T>(
+    key: K,
+    value: T[K],
+    opts?: StorageOptions,
+  ): Promise<void> {
     if (opts) {
       // noop
     }
 
-    return new Promise<void>((resolve, reject) => {
+    return new Promise((resolve, reject) => {
       this._asyncStorageNativeModule.multiSet([[key, value]], function(
         errors: Array<Error>,
       ) {
@@ -75,24 +86,30 @@ export default class LegacyAsyncStorage<T = any> implements IStorageBackend<T> {
     });
   }
 
-  async getMany(
-    keys: Array<string>,
+  async getMany<K extends keyof T>(
+    keys: Array<K>,
     opts?: StorageOptions,
-  ): Promise<Array<T | null>> {
+  ): Promise<{[k in K]: T[k] | null}> {
     if (opts) {
       // noop
     }
 
-    return new Promise<Array<T | null>>((resolve, reject) => {
+    return new Promise((resolve, reject) => {
       this._asyncStorageNativeModule.multiGet(keys, function(
         errors: Array<Error>,
-        result: any,
+        result: Array<[K, T[K]]>,
       ) {
-        const value =
-          result &&
-          result.reduce((acc: Array<any[]>, current: Array<any>) => {
-            return [...acc, current[1]];
-          }, []);
+        const value: {[k in K]: T[k]} = result.reduce<any>(
+          (acc, current: [K, T[K]]) => {
+            const key = current[0];
+            const val = current[1] || null;
+            return {
+              ...acc,
+              [key]: val,
+            };
+          },
+          {},
+        );
         const errs = convertErrors(errors);
         if (errs && errs.length) {
           reject(errs[0]);
@@ -103,17 +120,17 @@ export default class LegacyAsyncStorage<T = any> implements IStorageBackend<T> {
     });
   }
 
-  async setMany(
-    values: Array<{[key: string]: T}>,
+  async setMany<K extends keyof T>(
+    values: Array<Partial<{[k in K]: T[k]}>>,
     opts?: StorageOptions,
   ): Promise<void> {
     if (opts) {
       // noop
     }
 
-    return new Promise<void>((resolve, reject) => {
+    return new Promise((resolve, reject) => {
       const valuesArray = values.map(entry => {
-        return [Object.keys(entry)[0], entry];
+        return [Object.keys(entry)[0] as K, entry];
       });
       this._asyncStorageNativeModule.multiSet([valuesArray], function(
         errors: Array<Error>,
@@ -128,7 +145,7 @@ export default class LegacyAsyncStorage<T = any> implements IStorageBackend<T> {
     });
   }
 
-  async removeSingle(key: string, opts?: StorageOptions): Promise<void> {
+  async removeSingle(key: keyof T, opts?: StorageOptions): Promise<void> {
     if (opts) {
       // noop
     }
@@ -147,7 +164,7 @@ export default class LegacyAsyncStorage<T = any> implements IStorageBackend<T> {
     });
   }
 
-  async removeMany(keys: Array<string>, opts?: StorageOptions): Promise<void> {
+  async removeMany(keys: Array<keyof T>, opts?: StorageOptions): Promise<void> {
     if (opts) {
       // noop
     }
@@ -166,15 +183,15 @@ export default class LegacyAsyncStorage<T = any> implements IStorageBackend<T> {
     });
   }
 
-  async getKeys(opts?: StorageOptions): Promise<Array<string>> {
+  async getKeys(opts?: StorageOptions): Promise<Array<keyof T>> {
     if (opts) {
       // noop
     }
 
-    return new Promise<Array<string>>((resolve, reject) => {
+    return new Promise((resolve, reject) => {
       this._asyncStorageNativeModule.getAllKeys(function(
         errors: Array<Error>,
-        keys: Array<string>,
+        keys: Array<keyof T>,
       ) {
         const err = convertErrors(errors);
 
@@ -205,3 +222,37 @@ export default class LegacyAsyncStorage<T = any> implements IStorageBackend<T> {
     });
   }
 }
+
+// type MyModel = {
+//   user: {
+//     name: string;
+//   };
+//   preferences: {
+//     hour: boolean | null;
+//     hair: string;
+//   };
+//   isEnabled: boolean;
+// };
+
+// async function xxx() {
+//   const a = new LegacyAsyncStorage<MyModel>();
+//
+//   const x = await a.getSingle('preferences');
+//
+//   x.hour;
+//
+//   const all = await a.getMany(['user', 'isEnabled']);
+//
+//   all.user;
+//
+//   await a.setMany([
+//     {user: {name: 'Jerry'}},
+//     {isEnabled: false},
+//     {
+//       preferences: {
+//         hour: true,
+//         hair: 'streight',
+//       },
+//     },
+//   ]);
+// }
diff --git a/packages/storage-legacy/types/index.d.ts b/packages/storage-legacy/types/index.d.ts
index 336dc8cb..f0f0fffd 100644
--- a/packages/storage-legacy/types/index.d.ts
+++ b/packages/storage-legacy/types/index.d.ts
@@ -1,28 +1,46 @@
 /**
- * Copyright (c) Facebook, Inc. and its affiliates.
+ * Copyright (c) React Native Community.
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
  */
+
 import {
+  EmptyStorageModel,
   IStorageBackend,
   StorageOptions,
 } from '@react-native-community/async-storage';
-export default class LegacyAsyncStorage<T = any> implements IStorageBackend<T> {
+export default class LegacyAsyncStorage<T = EmptyStorageModel>
+  implements IStorageBackend<T> {
   private readonly _asyncStorageNativeModule;
-  constructor();
-  getSingle(key: string, opts?: StorageOptions): Promise<T | null>;
-  setSingle(key: string, value: T, opts?: StorageOptions): Promise<void>;
-  getMany(keys: Array<string>, opts?: StorageOptions): Promise<Array<T | null>>;
-  setMany(
-    values: Array<{
-      [key: string]: T;
-    }>,
+
+  getSingle<K extends keyof T>(
+    key: K,
+    opts?: StorageOptions,
+  ): Promise<T[K] | null>;
+
+  setSingle<K extends keyof T>(
+    key: K,
+    value: T[K],
+    opts?: StorageOptions,
+  ): Promise<void>;
+
+  getMany<K extends keyof T>(
+    keys: Array<K>,
+    opts?: StorageOptions,
+  ): Promise<{[k in K]: T[k] | null}>;
+
+  setMany<K extends keyof T>(
+    values: Array<{[k in K]: T[k]}>,
     opts?: StorageOptions,
   ): Promise<void>;
-  removeSingle(key: string, opts?: StorageOptions): Promise<void>;
-  removeMany(keys: Array<string>, opts?: StorageOptions): Promise<void>;
-  getKeys(opts?: StorageOptions): Promise<Array<string>>;
+
+  removeSingle(key: keyof T, opts?: StorageOptions): Promise<void>;
+
+  removeMany(keys: Array<keyof T>, opts?: StorageOptions): Promise<void>;
+
+  getKeys(opts?: StorageOptions): Promise<Array<keyof T>>;
+
   dropStorage(opts?: StorageOptions): Promise<void>;
 }
diff --git a/packages/storage-legacy/types/nativeModule.d.ts b/packages/storage-legacy/types/nativeModule.d.ts
new file mode 100644
index 00000000..2897b367
--- /dev/null
+++ b/packages/storage-legacy/types/nativeModule.d.ts
@@ -0,0 +1,25 @@
+/**
+ * Copyright (c) React Native Community.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
+export interface ILegacyNativeModule {
+  multiGet(
+    keys: Array<any>,
+    callback: (errors: Array<Error>, result: Array<[any, any]>) => void,
+  ): void;
+
+  multiSet(
+    values: Array<Array<any>>,
+    callback: (errors: Array<Error>) => void,
+  ): void;
+
+  multiRemove(keys: Array<any>, callback: (errors: Array<Error>) => void): void;
+
+  getAllKeys(callback: (errors: Array<Error>, keys: Array<any>) => void): void;
+
+  clear(callback: (errors: Array<Error>) => void): void;
+}

From 6b1fa9e4f410bafc6072bfcfd0dc07f39e914c04 Mon Sep 17 00:00:00 2001
From: Krzysztof Borowy <krizzu.dev@gmail.com>
Date: Sun, 11 Aug 2019 15:23:42 +0200
Subject: [PATCH 2/7] fix: types in tests

---
 packages/core/__tests__/AsyncStorage.test.ts | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/packages/core/__tests__/AsyncStorage.test.ts b/packages/core/__tests__/AsyncStorage.test.ts
index d55bc76f..642df7ae 100644
--- a/packages/core/__tests__/AsyncStorage.test.ts
+++ b/packages/core/__tests__/AsyncStorage.test.ts
@@ -20,13 +20,13 @@ describe('AsyncStorage', () => {
   });
 
   type testCases = [
-    Partial<keyof AsyncStorage<any>>,
+    Partial<keyof AsyncStorage<any, any>>,
     Partial<keyof StorageMock>,
     string
   ][];
 
   describe('main API', () => {
-    const asyncStorage = new AsyncStorage<any>(mockedStorage, {
+    const asyncStorage = new AsyncStorage<any, any>(mockedStorage, {
       logger: false,
       errorHandler: false,
     });
@@ -63,7 +63,7 @@ describe('AsyncStorage', () => {
     it('uses logger when provided', async () => {
       const loggerFunc = jest.fn();
 
-      const as = new AsyncStorage(mockedStorage, {
+      const as = new AsyncStorage<any, any>(mockedStorage, {
         logger: loggerFunc,
         errorHandler: false,
       });
@@ -81,7 +81,7 @@ describe('AsyncStorage', () => {
         throw error;
       });
 
-      const as = new AsyncStorage(mockedStorage, {
+      const as = new AsyncStorage<any, any>(mockedStorage, {
         errorHandler,
         logger: false,
       });

From d05ccdd948423d27d2124ab3830fc323d832ab2d Mon Sep 17 00:00:00 2001
From: Krzysztof Borowy <krizzu.dev@gmail.com>
Date: Sun, 11 Aug 2019 16:01:04 +0200
Subject: [PATCH 3/7] docs: core docs

---
 packages/core/README.md | 59 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 packages/core/README.md

diff --git a/packages/core/README.md b/packages/core/README.md
new file mode 100644
index 00000000..466cc66d
--- /dev/null
+++ b/packages/core/README.md
@@ -0,0 +1,59 @@
+# Async Storage Core
+
+Main Async Storage component. 
+
+## Installation
+
+```bash
+$ yarn install @react-native-community/async-storage
+```
+
+## Usage
+
+Use `AsyncStorageFactory` to create your Async Storage instance 
+
+
+```typescript
+
+// storage.js
+
+import ASFactory from '@react-native-community/async-storage'
+
+// use any available Storage Backend
+const storageBackend = new StorageBackend();
+
+const mobileStorage = ASFactory.create(storageBackend);
+
+export default mobileStorage;
+```
+
+## Providing a storage model
+
+You can provide a `Model` type when creating Async Storage, to have a fully typed storage. 
+
+
+```typescript
+import ASFactory from '@react-native-community/async-storage'
+
+type StorageModel = {
+  user: {
+    name: string;
+    age: number;
+  };
+  preferences: {
+    darkModeEnabled: boolean;
+  };
+  subscribedChannels: Array<Channel>;
+  onboardingCompleted: boolean;
+};
+
+// use any available Storage Backend
+const storageBackend = new StorageBackend();
+
+const storage = ASFactory.create<StorageModel>(storageBackend);
+
+```
+  
+## License
+
+MIT.

From 919189c16ae71de8ae1d53d9026e75657d5aebb9 Mon Sep 17 00:00:00 2001
From: Krzysztof Borowy <krizzu.dev@gmail.com>
Date: Thu, 22 Aug 2019 23:05:04 +0200
Subject: [PATCH 4/7] docs: core

---
 README.md                         | 20 +++++++++++--
 packages/core/README.md           | 50 ++++++++++++++++++++++++-------
 packages/core/types/index.d.ts    |  3 --
 packages/storage-legacy/README.md |  3 ++
 4 files changed, 60 insertions(+), 16 deletions(-)
 create mode 100644 packages/storage-legacy/README.md

diff --git a/README.md b/README.md
index a7d7874c..5ff96037 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # Async Storage
 
-A storage system for React Native.
+A persistent data storage solution for your next mobile, web or desktop application. 
 
 ## Work in progress
 
@@ -10,8 +10,22 @@ If you're looking for published and operational Async Storage version, please ch
 
 If you'd like to see the progress of v2, [please visit Project page.](https://github.com/react-native-community/async-storage/projects/1) 
 
-## Running Examples
+## Features
+
+todo
+
+## Documentation
+
+todo
+
+## Available storage backends
+
+- [Legacy](./packages/storage-legacy/README.md)
+
+
+## License
+
+MIT
 
-### React Native
 
 
diff --git a/packages/core/README.md b/packages/core/README.md
index 466cc66d..8b8c5484 100644
--- a/packages/core/README.md
+++ b/packages/core/README.md
@@ -1,20 +1,22 @@
 # Async Storage Core
 
-Main Async Storage component. 
+Public-facing API of Async Storage. 
 
-## Installation
+## Install
 
 ```bash
 $ yarn install @react-native-community/async-storage
 ```
 
-## Usage
+## API
 
-Use `AsyncStorageFactory` to create your Async Storage instance 
 
+### `AsyncStorageFactory`
+
+A factory module for `AsyncStorage` instance with selected storage backend attached. 
 
-```typescript
 
+```typescript
 // storage.js
 
 import ASFactory from '@react-native-community/async-storage'
@@ -22,14 +24,40 @@ import ASFactory from '@react-native-community/async-storage'
 // use any available Storage Backend
 const storageBackend = new StorageBackend();
 
-const mobileStorage = ASFactory.create(storageBackend);
+const mobileStorage = ASFactory.create(storageBackend, options);
 
 export default mobileStorage;
 ```
 
-## Providing a storage model
 
-You can provide a `Model` type when creating Async Storage, to have a fully typed storage. 
+**Factory options**
+
+`AsyncStorageFactory.create` accepts an options object, that enables additional features.
+
+
+- *logger*
+
+```typescript
+type logger = ((action: LoggerAction) => void) | boolean;
+``` 
+
+Used to log `AsyncStorage` method calls and used arguments.
+You can provide your own implementation or use provided default logger (enabled by default in DEV mode).
+
+
+- *errorHandler*
+
+```typescript
+type errorHandler = ((error: Error | string) => void) | boolean;
+````
+
+Used to report any errors thrown.
+You can provide your own implementation or use provided default error handler (enabled by default in DEV mode).
+
+
+**Providing a storage model**
+
+If you know the structure of the stored data upfront, you can use the full potential of the type system, by providing a type argument to  `AsyncStorageFactory.create<T>` method.
 
 
 ```typescript
@@ -43,17 +71,19 @@ type StorageModel = {
   preferences: {
     darkModeEnabled: boolean;
   };
-  subscribedChannels: Array<Channel>;
+  subscribedChannels: Array<string>;
   onboardingCompleted: boolean;
 };
 
 // use any available Storage Backend
 const storageBackend = new StorageBackend();
 
+
 const storage = ASFactory.create<StorageModel>(storageBackend);
 
 ```
   
 ## License
 
-MIT.
+MIT
+
diff --git a/packages/core/types/index.d.ts b/packages/core/types/index.d.ts
index 09700b3c..6f466bf0 100644
--- a/packages/core/types/index.d.ts
+++ b/packages/core/types/index.d.ts
@@ -110,9 +110,6 @@ export type LoggerAction = {
 };
 
 // Helper types
-
-export type StorageModel<T> = T extends IStorageBackend<infer V> ? V : any;
-
 export type EmptyStorageModel = {[key in symbol | number | string]: any};
 
 export type StorageOptions = {
diff --git a/packages/storage-legacy/README.md b/packages/storage-legacy/README.md
new file mode 100644
index 00000000..93e854a2
--- /dev/null
+++ b/packages/storage-legacy/README.md
@@ -0,0 +1,3 @@
+# Storage Backend: Legacy
+
+todo

From 9037a3a919ff2944fa52a662f28041f6adfe616f Mon Sep 17 00:00:00 2001
From: Krzysztof Borowy <krizzu.dev@gmail.com>
Date: Sun, 25 Aug 2019 21:49:29 +0200
Subject: [PATCH 5/7] docs: legacy docs

---
 examples/mobile/README.md         |  4 ++++
 packages/core/README.md           | 32 +++++++++++++++++++++++++++-
 packages/storage-legacy/README.md | 35 ++++++++++++++++++++++++++++++-
 3 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/examples/mobile/README.md b/examples/mobile/README.md
index 7a43b515..d1e3155b 100644
--- a/examples/mobile/README.md
+++ b/examples/mobile/README.md
@@ -28,3 +28,7 @@ $ yarn start
 
 Let me know about any issue found or feedback you have at [Async-Storage issue page](https://github.com/react-native-community/async-storage/issues). 
 Please mark it as `examples` label. 
+
+## License
+
+MIT
diff --git a/packages/core/README.md b/packages/core/README.md
index 8b8c5484..f23e990f 100644
--- a/packages/core/README.md
+++ b/packages/core/README.md
@@ -1,6 +1,7 @@
 # Async Storage Core
 
-Public-facing API of Async Storage. 
+Main, public-facing components of Async Storage. The core module contains a factory to create an `AsyncStorage` instance 
+and `IStorageBackend`, that needs to be implemented by any Backend Storage in order to be compatible.   
 
 ## Install
 
@@ -82,6 +83,35 @@ const storageBackend = new StorageBackend();
 const storage = ASFactory.create<StorageModel>(storageBackend);
 
 ```
+
+
+### `IStorageBackend`
+
+In order to let `AsyncStorage` use a storage backend, it has to implement this interface. 
+Contains basic set method of methods to get, set and remove data, return already used keys or drop the whole storage.
+
+
+```typescript
+
+import {
+  IStorageBackend,
+} from '@react-native-community/async-storage';
+
+type Model = {
+  count: number
+  user: {
+    name: string,
+    rating: number
+  }
+}
+
+class MyStorageSolution implements IStorageBackend<Model> {
+  // implement necessary methods
+}
+
+```
+
+
   
 ## License
 
diff --git a/packages/storage-legacy/README.md b/packages/storage-legacy/README.md
index 93e854a2..29703a68 100644
--- a/packages/storage-legacy/README.md
+++ b/packages/storage-legacy/README.md
@@ -1,3 +1,36 @@
 # Storage Backend: Legacy
 
-todo
+An `AsyncStorage` storage backend, fully compatible with former version.  
+
+## Installation
+
+
+// todo: check naming before relase
+```bash
+$ yarn add @react-native-community/async-storage-legacy
+```
+
+
+## Usage
+
+
+```typescript
+
+import LegacyStorage from '@react-native-community/async-storage-legacy';
+import AsyncStorageFactory from '@react-native-community/async-storage';
+
+type MyModel = {
+  // ...your storage model
+}
+
+const legacyStorage = new LegacyStorage();
+
+const storage = AsyncStorageFactory.create<MyModel>(legacyStorage);
+
+// ready to use
+export default storage;
+```
+
+## License
+
+MIT

From eae485a9e0e6558fd1402c7247bec58f17d180eb Mon Sep 17 00:00:00 2001
From: Krzysztof Borowy <krizzu.dev@gmail.com>
Date: Wed, 11 Sep 2019 08:15:39 +0200
Subject: [PATCH 6/7] fix: naming, ignoring publish files

---
 .npmignore                            | 85 ---------------------------
 examples/mobile/.babelrc              |  2 +-
 examples/mobile/src/legacy/storage.js |  2 +-
 lerna.json                            |  2 +-
 packages/core/.npmignore              | 30 ++++++++++
 packages/core/package.json            |  4 +-
 packages/storage-legacy/.npmignore    | 30 ++++++++++
 packages/storage-legacy/package.json  | 12 ++--
 8 files changed, 73 insertions(+), 94 deletions(-)
 delete mode 100644 .npmignore
 create mode 100644 packages/core/.npmignore
 create mode 100644 packages/storage-legacy/.npmignore

diff --git a/.npmignore b/.npmignore
deleted file mode 100644
index 9b128286..00000000
--- a/.npmignore
+++ /dev/null
@@ -1,85 +0,0 @@
-# JS
-node_modules
-yarn.lock
-
-# Project files
-CONTRIBUTING.md
-CODE_OF_CONDUCT.md
-README.md
-
-# Config files
-.babelrc
-babel.config.js
-.editorconfig
-.eslintrc
-.flowconfig
-.watchmanconfig
-jsconfig.json
-.npmrc
-.gitattributes
-.circleci
-*.coverage.json
-.opensource
-.circleci
-.eslintignore
-codecov.yml
-
-# Example
-example/
-
-# Android
-android/*/build/
-android/gradlew
-android/build
-android/gradlew.bat
-android/gradle/
-android/com_crashlytics_export_strings.xml
-android/local.properties
-android/.gradle/
-android/.signing/
-android/.idea/gradle.xml
-android/.idea/libraries/
-android/.idea/workspace.xml
-android/.idea/tasks.xml
-android/.idea/.name
-android/.idea/compiler.xml
-android/.idea/copyright/profiles_settings.xml
-android/.idea/encodings.xml
-android/.idea/misc.xml
-android/.idea/modules.xml
-android/.idea/scopes/scope_settings.xml
-android/.idea/vcs.xml
-android/*.iml
-android/.settings
-
-# iOS
-ios/*.xcodeproj/xcuserdata
-*.pbxuser
-*.mode1v3
-*.mode2v3
-*.perspectivev3
-*.xcuserstate
-project.xcworkspace/
-xcuserdata/
-
-# Misc
-.DS_Store
-.DS_Store?
-*.DS_Store
-coverage.android.json
-coverage.ios.json
-coverage
-npm-debug.log
-.github
-._*
-.Spotlight-V100
-.Trashes
-ehthumbs.db
-Thumbs.dbandroid/gradle
-docs
-.idea
-tests/
-bin/test.js
-codorials
-.vscode
-.nyc_output
\ No newline at end of file
diff --git a/examples/mobile/.babelrc b/examples/mobile/.babelrc
index 82ff5cf6..0dec7f52 100644
--- a/examples/mobile/.babelrc
+++ b/examples/mobile/.babelrc
@@ -5,7 +5,7 @@
       {
         "alias": {
           "@react-native-community/async-storage": "../../packages/core/build",
-          "@react-native-community/async-storage-legacy": "../../packages/storage-legacy/build"
+          "@react-native-community/async-storage-backend-legacy": "../../packages/storage-legacy/build"
         },
         "cwd": "babelrc"
       }
diff --git a/examples/mobile/src/legacy/storage.js b/examples/mobile/src/legacy/storage.js
index bb9b9007..e7a46d2f 100644
--- a/examples/mobile/src/legacy/storage.js
+++ b/examples/mobile/src/legacy/storage.js
@@ -1,4 +1,4 @@
-import LegacyStorage from '@react-native-community/async-storage-legacy';
+import LegacyStorage from '@react-native-community/async-storage-backend-legacy';
 import AsyncStorageFactory from '@react-native-community/async-storage';
 
 
diff --git a/lerna.json b/lerna.json
index 48642ca1..f784ae75 100644
--- a/lerna.json
+++ b/lerna.json
@@ -1,7 +1,7 @@
 {
   "packages": [
     "core",
-    "storages/*"
+    "storages-*"
   ],
   "version": "independent",
   "npmClient": "yarn",
diff --git a/packages/core/.npmignore b/packages/core/.npmignore
new file mode 100644
index 00000000..09e55784
--- /dev/null
+++ b/packages/core/.npmignore
@@ -0,0 +1,30 @@
+# Core
+node_modules
+yarn.lock
+src/
+__tests__/
+CONTRIBUTING.md
+CODE_OF_CONDUCT.md
+
+
+########## Trash ##########
+.DS_Store
+.DS_Store?
+*.DS_Store
+coverage.android.json
+coverage.ios.json
+coverage
+npm-debug.log
+.github
+._*
+.Spotlight-V100
+.Trashes
+ehthumbs.db
+Thumbs.dbandroid/gradle
+.idea
+bin/test.js
+codorials
+.vscode
+.nyc_output
+yarn-error.log
+
diff --git a/packages/core/package.json b/packages/core/package.json
index 0c6c07e5..afc2c512 100644
--- a/packages/core/package.json
+++ b/packages/core/package.json
@@ -2,13 +2,13 @@
   "name": "@react-native-community/async-storage",
   "version": "2.0.0",
   "main": "build/index.js",
-  "files": ["build/**/*"],
   "types": "types/index.d.ts",
   "author": "Krzysztof Borowy <dev@krizzu.dev>",
   "license": "MIT",
   "scripts": {
     "build": "babel src --root-mode upward --out-dir build/ --extensions .ts --ignore build/**/* --ignore types/* --source-maps inline",
     "clean": "rm build -rf",
-    "start": "yarn build:lib --watch"
+    "start": "yarn build:lib --watch",
+    "prepublish": "yarn clean && yarn build"
   }
 }
diff --git a/packages/storage-legacy/.npmignore b/packages/storage-legacy/.npmignore
new file mode 100644
index 00000000..dbf057c9
--- /dev/null
+++ b/packages/storage-legacy/.npmignore
@@ -0,0 +1,30 @@
+# Legacy storage backend
+node_modules
+yarn.lock
+# see https://github.com/yarnpkg/yarn/issues/7540
+./src/
+CONTRIBUTING.md
+CODE_OF_CONDUCT.md
+android/build/
+ios/*.xcodeproj/xcuserdata
+
+########## Trash ##########
+.DS_Store
+.DS_Store?
+*.DS_Store
+coverage.android.json
+coverage.ios.json
+coverage
+npm-debug.log
+.github
+._*
+.Spotlight-V100
+.Trashes
+ehthumbs.db
+Thumbs.dbandroid/gradle
+.idea
+bin/test.js
+codorials
+.vscode
+.nyc_output
+yarn-error.log
diff --git a/packages/storage-legacy/package.json b/packages/storage-legacy/package.json
index 99cef15f..a130da8b 100644
--- a/packages/storage-legacy/package.json
+++ b/packages/storage-legacy/package.json
@@ -1,14 +1,18 @@
 {
-  "name": "@react-native-community/async-storage-legacy",
+  "name": "@react-native-community/async-storage-backend-legacy",
   "version": "2.0.0",
-  "main": "build/LegacyAsyncStorage.js",
+  "main": "build/index.js",
   "types": "types/index.d.ts",
   "author": "Krzysztof Borowy <dev@krizzu.dev>",
   "license": "MIT",
   "scripts": {
-    "build": "babel src --root-mode upward --out-dir build/ --extensions .ts --ignore build/**/* --ignore types/* --source-maps inline",
+    "build": "babel src --root-mode upward --out-dir build/ --extensions .ts --ignore build/**/* --ignore types/**/* --source-maps inline",
     "clean": "rm build -rf",
-    "generate:types": "tsc src/index.ts --noEmit false --lib es2015 --declarationDir types/ -d true -emitDeclarationOnly true"
+    "generate:types": "tsc src/index.ts --noEmit false --lib es2015 --declarationDir types/ -d true -emitDeclarationOnly true",
+    "prepublish": "yarn clean && yarn build"
+  },
+  "dependencies": {
+    "@react-native-community/async-storage": "^2.0"
   },
   "peerDependencies": {
     "react": "^16.0",

From 5a110c3a112a254f877a47ebbac25d5b7a5a8468 Mon Sep 17 00:00:00 2001
From: Krzysztof Borowy <krizzu.dev@gmail.com>
Date: Thu, 12 Sep 2019 07:50:39 +0200
Subject: [PATCH 7/7] docs: writing storage backend

---
 README.md                                     |   2 +-
 packages/core/docs/Writing_Storage_Backend.md | 113 ++++++++++++++++++
 2 files changed, 114 insertions(+), 1 deletion(-)
 create mode 100644 packages/core/docs/Writing_Storage_Backend.md

diff --git a/README.md b/README.md
index 5ff96037..a8591870 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@ todo
 
 ## Documentation
 
-todo
+- [Creating a custom Storage backend](./packages/core/docs/Writing_Storage_Backend.md)
 
 ## Available storage backends
 
diff --git a/packages/core/docs/Writing_Storage_Backend.md b/packages/core/docs/Writing_Storage_Backend.md
new file mode 100644
index 00000000..e17f74f4
--- /dev/null
+++ b/packages/core/docs/Writing_Storage_Backend.md
@@ -0,0 +1,113 @@
+# Authoring Storage Backend
+
+To create custom storage, one must create a class that implements `IStorageBackend` interface. 
+This contract makes sure that Core knows how to use it.
+
+## Example
+
+Let's create a storage backend for web, using `LocalStorage` API. 
+
+Start by adding `AsyncStorage` to your dependencies.
+
+```bash
+$ yarn add @react-native-community/async-storage
+``` 
+
+Then, create a class and implement `IStorageBackend` interface;
+
+
+```typescript
+
+import { IStorageBackend, EmptyStorageModel, StorageOptions } from '@react-native-community/async-storage';
+
+class WebStorage<T extends EmptyStorageModel = EmptyStorageModel> implements IStorageBackend<T> {
+
+    storage = window.localStorage;
+ 
+    async getSingle<K extends keyof T>(
+      key: K,
+      opts?: StorageOptions,
+    ): Promise<T[K] | null> {
+      
+      return this.storage.getItem(key);
+    } 
+  
+    async setSingle<K extends keyof T>(
+      key: K,
+      value: T[K],
+      opts?: StorageOptions,
+    ): Promise<void> {
+      return this.storage.setItem(key, value);
+    } 
+  
+    async getMany<K extends keyof T>(
+      keys: Array<K>,
+      opts?: StorageOptions,
+    ): Promise<{[k in K]: T[k] | null}>{
+      
+      return Promise.all(keys.map(k => this.storage.getItem(k)))
+    }
+  
+    async setMany<K extends keyof T>(
+      values: Array<{[k in K]: T[k]}>,
+      opts?: StorageOptions,
+    ): Promise<void>{
+     
+      for(let keyValue of values){
+        const key = Object.getOwnPropertyNames(keyValue)[0];
+        if(!key) continue;
+        this.storage.setItem(key, keyValue[key])
+      }     
+    }
+  
+    async removeSingle(key: keyof T, opts?: StorageOptions): Promise<void> {
+      return this.storage.removeItem(key);
+    } 
+  
+    async removeMany(keys: Array<keyof T>, opts?: StorageOptions): Promise<void> {
+      for (let key in keys) {
+        this.storage.removeItem(key);
+      }
+    } 
+  
+    async getKeys(opts?: StorageOptions): Promise<Array<keyof T>> {
+      return Object.keys(this.storage);
+    }
+  
+    async dropStorage(opts?: StorageOptions): Promise<void> {
+      const keys = await this.getKeys();
+      await this.removeMany(keys);
+    }
+}
+
+export default WebStorage;
+```
+
+### Notes
+
+- Each function should be asynchronous - even if access to storage is not.
+- In `localStorage`, remember that __keys__ and __values__  are always `string` - it's up to you if you're going to stringify it or accept stringified arguments. 
+- `opts` argument can be used to 'enhance' each call, for example, one could use it to decide if the stored value should be replaced:
+
+```typescript
+
+// in a class
+
+async setSingle<K extends keyof T>(
+  key: K,
+  value: T[K],
+  opts?: StorageOptions,
+): Promise<void> {
+  
+  if(!opts.replaceCurrent) {
+    const current = this.storage.getItem(key);
+    if(!current){
+      this.storage.setItem(key, value);
+    } 
+    return;
+  } 
+
+  return this.storage.setItem(key, value);
+} 
+
+```