ios: SimpleXChat framework to be shared by app/NSE (#714)

* ios: SimpleXChat framework to be shared by app/NSE

* remove bridging headers from pp/NSE

* embed & sign

apps/ios/SimpleXChat/API.swift

@@ -0,0 +1,66 @@
+//
+//  API.swift
+//  SimpleX NSE
+//
+//  Created by Evgeny on 26/04/2022.
+//  Copyright © 2022 SimpleX Chat. All rights reserved.
+//
+
+import Foundation
+
+private var chatController: chat_ctrl?
+
+public func getChatCtrl() -> chat_ctrl {
+    if let controller = chatController { return controller }
+    let dataDir = getDocumentsDirectory().path + "/mobile_v1"
+    logger.debug("documents directory \(dataDir)")
+    var cstr = dataDir.cString(using: .utf8)!
+    chatController = chat_init(&cstr)
+    logger.debug("getChatCtrl: chat_init")
+    return chatController!
+}
+
+public func sendSimpleXCmd(_ cmd: ChatCommand) -> ChatResponse {
+    var c = cmd.cmdString.cString(using: .utf8)!
+    return chatResponse(chat_send_cmd(getChatCtrl(), &c))
+}
+
+public func chatResponse(_ cjson: UnsafeMutablePointer<CChar>) -> ChatResponse {
+    let s = String.init(cString: cjson)
+    let d = s.data(using: .utf8)!
+// TODO is there a way to do it without copying the data? e.g:
+//    let p = UnsafeMutableRawPointer.init(mutating: UnsafeRawPointer(cjson))
+//    let d = Data.init(bytesNoCopy: p, count: strlen(cjson), deallocator: .free)
+    do {
+        let r = try jsonDecoder.decode(APIResponse.self, from: d)
+        return r.resp
+    } catch {
+        logger.error("chatResponse jsonDecoder.decode error: \(error.localizedDescription)")
+    }
+
+    var type: String?
+    var json: String?
+    if let j = try? JSONSerialization.jsonObject(with: d) as? NSDictionary {
+        if let j1 = j["resp"] as? NSDictionary, j1.count == 1 {
+            type = j1.allKeys[0] as? String
+        }
+        json = prettyJSON(j)
+    }
+    free(cjson)
+    return ChatResponse.response(type: type ?? "invalid", json: json ?? s)
+}
+
+func prettyJSON(_ obj: NSDictionary) -> String? {
+    if let d = try? JSONSerialization.data(withJSONObject: obj, options: .prettyPrinted) {
+        return String(decoding: d, as: UTF8.self)
+    }
+    return nil
+}
+
+public func responseError(_ err: Error) -> String {
+    if let r = err as? ChatResponse {
+        return String(describing: r)
+    } else {
+        return err.localizedDescription
+    }
+}