Add "iOS SDK" doc

docusaurus-site/docs/mobile docs/ios-sdk.md

+sidebar_position: 3
+---
+
+# iOS SDK
+
+## Installation
+The Elixxir SDK requires the use of the [Swift Package Manager](https://swift.org/package-manager/)—a tool for managing the distribution of Swift code. To use the SDK, add it to dependencies in your `Package.swift` file.
+
+```swift
+dependencies: [
+    .package(url: "https://git.xx.network/elixxir/elixxir-dapps-sdk-swift")
+]
+```
+
+## Initialization
+The instructions below describe how to initialize the client and connect to the network.
+
+1. First, you will need to create a secure area to store client data. You can do this by creating a `PasswordStorage` for saving and loading your client storage. For example purposes we will use UserDefaults, but really encourage you to not use it and use `Keychain`  instead. 
+
+```swift
+let demoPasswordStorage = PasswordStorage(
+  save: { password in
+    UserDefaults.standard.set(password, forKey: "SDKPassword")
+  },
+  load: {
+    UserDefaults.standard.value(forKey: "SDKPassword") as! Data
+  })
+```
+
+2. Next, create a client storage to manage client data stored on disk.
+
+```swift
+let clientStorage = ClientStorage.live(passwordStorage: demoPasswordStorage)
+```
+
+3. If a client storage already exists, load it instead of creating a new one.
+
+```swift
+let client = Client
+
+/*
+//loadClient is a blocking call, do it on the background thread
+//createClient is a blocking call, do it on the background thread
+*/
+
+if clientStorage.hasStoredClient() {
+   client = try? clientStorage.loadClient()
+} else {
+   client = try? clientStorage.createClient()
+}
+```
+
+4. Next, create an identity. You will need to create a connection later.
+
+```swift
+/*
+//Blocking call, do it on the background thread
+*/
+let myIdentity = try client.makeIdentity()
+```
+
+5. Start the network follower.
+
+```swift
+let networkFollower = client.networkFollower
+
+/*
+//Blocking call, do it on the background thread
+//Time is in millisecond
+*/
+try networkFollower.start(timeoutMS: 30_000) 
+```
+
+6. Finally, wait for the network to be connected.       
+
+```swift
+/*
+//Blocking call, do it on the background thread
+//Time is in millisecond
+*/
+let isConnected = client.waitForNetwork(30_000)  
+guard isConnected else { /* try again */ }
+```
+
+## Send Rest-like message
+The instructions below describe how to use the restlike API to send requests and receive messages like a rest API.
+
+1. First, to initiate a connection with the remote, use an unauthenticated connection. (To get remote identity, please refer to [this](https://git.xx.network/elixxir/client/-/blob/release/restlike/README.md) )
+
+```swift
+/*
+//Blocking call, do it on the background thread
+// You need your remote identity.
+*/
+let connection = try client.connect(withAuthentication: false, recipientContact: REMOTE_IDENTITY, myIdentity: myIdentity)
+```
+
+2. Next, create a RequestSender.
+
+```swift
+let restLikeRequestSender = RestlikeRequestSender.live(authenticated: false)
+```
+
+3. Create your request that you will send.
+
+```swift
+/*
+//All fields are customizable to meet your remote configuration
+//Content accepts any json encoded object, this is where you include your request body
+//Method number is used to refer to get, post, put, etc.
+*/
+let request = RestlikeMessage(
+   version: Int,
+   headers: YOUR_HEADERS,
+   content: YOUR_JSON_ENCODED_MODEL,
+   method: Int,
+   Uri: String,
+   error: String)
+```
+
+4. Send your request and wait for a response.
+
+```swift
+/*
+//Blocking call, do it on the background thread
+//Response is RestLikeMessage object
+*/
+
+let response = try? restLikeRequestSender.send(
+   client.getId(),
+   connection!.getId(),
+   request)
+
+/* 
+//Jumping to the main thread to update any UI with the response
+*/
+DispatchQueue.main.async {
+   let message = response 
+//Use the response message here to update UI
+}
+```
+
+## Send E2E message
+1. Initiate a connection with the remote. We will use an unauthenticated connection.  (To get remote identity, please refer to [this](https://git.xx.network/elixxir/client/-/blob/release/restlike/README.md) )
+
+```swift
+/*
+//Blocking call, do it on the background thread
+// You need your remote identity.
+*/
+let connection = try client.connect(
+  withAuthentication: false,
+  recipientContact: REMOTE_IDENTITY,
+  myIdentity: myIdentity)
+```
+
+2. Setup your messages listener.
+
+```swift
+/*
+//Blocking call, do it on the background thread
+//messageType value must be same as the value you will use to send a message
+*/
+connection.listen(messageType: Int) { message in
+/* 
+//Jumping to the main thread to update any UI with the message
+*/
+  DispatchQueue.main.async {
+    let msg = message
+    //Use the received message here to update UI
+  }
+}
+```
+
+3. Send the message and wait to get the send report, which contains the delivery status.
+
+```swift
+/*
+//Blocking call, do it on the background thread
+//messageType value must be same as the value you used to setup your messages listener
+*/
+let sendReport = try connection?.send(
+  messageType: Int,
+  payload: YOUR_JSON_ENCODED_MODEL)
+```
+
+4. Wait for the message to be delivered and update the UI if needed.
+
+```swift
+/*
+//Blocking call, do it on the background thread
+//Time is in millisecond
+*/
+
+client.waitForDelivery(report: sendReport, timeoutMS: 30_000) { result in
+/* 
+//Jumping to the main thread to update any UI
+*/
+  DispatchQueue.main.async {
+    switch result {
+      case .delivered(let roundResults):
+      // You can stop loading indicator here for example
+      case .notDelivered:
+      //Show error popup here for example
+    }
+  }
+}
+```
+
+