From 7baa942d2902bcf58d7b95fd249bf17c236af9ce Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Adrian=20Truszczy=C5=84ski?=
 <TruszczynskiA@users.noreply.github.com>
Date: Tue, 27 Jun 2023 17:34:46 +0200
Subject: [PATCH] BLE - Communication with Android devices improvements (#948)

- Peripheral manager will now can return data with offset in BLE read requests.
---
 .../Common/Managers/BLE/BLEConstants.swift    |  2 +-
 .../Managers/BLE/BLEPeripheralManager.swift   | 50 ++++++++++++++-----
 2 files changed, 38 insertions(+), 14 deletions(-)

diff --git a/MobileWallet/Common/Managers/BLE/BLEConstants.swift b/MobileWallet/Common/Managers/BLE/BLEConstants.swift
index 1bfc02f4..2eb256ca 100644
--- a/MobileWallet/Common/Managers/BLE/BLEConstants.swift
+++ b/MobileWallet/Common/Managers/BLE/BLEConstants.swift
@@ -41,7 +41,7 @@
 import CoreBluetooth
 
 enum BLEConstants {
-    static var chunkSize = 200
+    static var chunkSize = 150
     static var contactBookService: BLEContactBookService.Type { BLEContactBookService.self }
 }
 
diff --git a/MobileWallet/Common/Managers/BLE/BLEPeripheralManager.swift b/MobileWallet/Common/Managers/BLE/BLEPeripheralManager.swift
index 91cdc621..7a79ae1f 100644
--- a/MobileWallet/Common/Managers/BLE/BLEPeripheralManager.swift
+++ b/MobileWallet/Common/Managers/BLE/BLEPeripheralManager.swift
@@ -157,20 +157,22 @@ final class BLEPeripheralManager: NSObject {
 
     private func handle(readRequest: CBATTRequest) {
 
-        var chunks: [Data] = cache[readRequest.characteristic.uuid] ?? []
-
-        if chunks.isEmpty {
-            chunks = makeUserProfileDeeplinkChunks()
-        }
-
-        guard !chunks.isEmpty else {
-            manager.respond(to: readRequest, withResult: .invalidHandle)
-            return
+        let chunk: Data
+
+        if readRequest.offset == 0 {
+            guard let nextChunk = nextChunk(characteristicUUID: readRequest.characteristic.uuid) else {
+                manager.respond(to: readRequest, withResult: .invalidHandle)
+                return
+            }
+            chunk = nextChunk
+        } else {
+            guard let currentChunk = currentChunk(characteristicUUID: readRequest.characteristic.uuid, offset: readRequest.offset) else {
+                manager.respond(to: readRequest, withResult: .invalidHandle)
+                return
+            }
+            chunk = currentChunk
         }
 
-        let chunk = chunks.removeFirst()
-
-        cache[readRequest.characteristic.uuid] = chunks
         readRequest.value = chunk
         manager.respond(to: readRequest, withResult: .success)
     }
@@ -250,7 +252,7 @@ final class BLEPeripheralManager: NSObject {
         }
     }
 
-    // MARK: - Factories
+    // MARK: - Helpers
 
     private func makeUserProfileDeeplinkChunks() -> [Data] {
         guard let alias = UserSettingsManager.name, let address = try? Tari.shared.walletAddress.byteVector.hex else { return [] }
@@ -258,6 +260,28 @@ final class BLEPeripheralManager: NSObject {
         guard let url = try? DeepLinkFormatter.deeplink(model: model) else { return [] }
         return url.absoluteString.data(using: .utf8)?.bleDataChunks ?? []
     }
+
+    private func nextChunk(characteristicUUID: CBUUID) -> Data? {
+
+        var chunks: [Data] = cache[characteristicUUID] ?? []
+
+        if !chunks.isEmpty {
+            chunks.removeFirst()
+        }
+
+        if chunks.isEmpty {
+            chunks = makeUserProfileDeeplinkChunks()
+        }
+
+        cache[characteristicUUID] = chunks
+        return chunks.first
+    }
+
+    private func currentChunk(characteristicUUID: CBUUID, offset: Int) -> Data? {
+        var chunks: [Data] = cache[characteristicUUID] ?? []
+        guard let chunk = chunks.first, chunk.count > offset else { return nil }
+        return chunk.subdata(in: offset..<chunk.count)
+    }
 }
 
 extension BLEPeripheralManager: CBPeripheralManagerDelegate {