Refactoring for HomeKit client

pkg/hap/README.md

@@ -0,0 +1,33 @@
+# Home Accessory Protocol
+
+> PS. Character = Characteristic
+
+**Device** - HomeKit end device (swith, camera, etc)
+
+- mDNS name: `MyCamera._hap._tcp.local.`
+- DeviceID - mac-like: `0E:AA:CE:2B:35:71`
+- HomeKit device is described by:
+  - one or more `Accessories` - has `AID` and `Services`  
+  - `Services` - has `IID`, `Type` and `Characters`  
+  - `Characters` - has `IID`, `Type`, `Format` and `Value`
+
+**Client** - HomeKit client (iPhone, iPad, MacBook or opensource library)
+
+- ClientID - static random UUID
+- ClientPublic/ClientPrivate - static random 32 byte keypair
+- can pair with Device (exchange ClientID/ClientPublic, ServerID/ServerPublic using Pin)
+- can auth to Device using ClientPrivate
+- holding persistant Secure connection to device
+- can read device Accessories
+- can read and write device Characters
+- can subscribe on device Characters change (Event)
+
+**Server** - HomeKit server (soft on end device or opensource library)
+
+- ServerID - same as DeviceID (using for Client auth)
+- ServerPublic/ServerPrivate - static random 32 byte keypair
+
+## Useful links
+
+- [Extracting HomeKit Pairing Keys](https://pvieito.com/2019/12/extract-homekit-pairing-keys)
+- [HAP in AirPlay2 receiver](https://github.com/openairplay/airplay2-receiver/blob/master/ap2/pairing/hap.py)