-- Data structures for SMG Communication Protocol
 -- S.MG, 2018

with Interfaces; -- for fixed-size types
with Raw_Types;  -- for protocol raw types
with System;     -- for Bit_Order
with Serpent;    -- for Serpent.Key type

package Data_Structs is
  Pragma Pure(Data_Structs);

  -- an object in the world, with record layout fully specified
  -- a storage element is 8-bit aka 1 octet
  -- "at" gives number of storage element
  -- "range" gives bits inside storage element

  type SMG_Object is
    record
      -- ID of the object
      ID         : Interfaces.Unsigned_32;

      -- Position of the object in the world.
      -- For a world with map coordinates (MC) between -500 and +500,
      -- the relationship with given figure (GF) is:
      -- MC = GF / 65.535 - 500
      -- where 65.535 comes from the mapping 65535 / (500 - - 500)
      X, Y, Z    : Interfaces.Integer_16;

      -- Rotation of the object (RO) linked to GF by:
      -- RO = GF / 128*pi
      RX, RY, RZ : Interfaces.Unsigned_8;
    end record;
  for SMG_Object'Size use 104; -- in bits!
  for SMG_Object'Bit_Order use System.Low_Order_First;
  for SMG_Object use
    record
      ID at 0  range 0 .. 31;
      X  at 4  range 0 .. 15;
      Y  at 6  range 0 .. 15;
      Z  at 8  range 0 .. 15;
      RX at 10 range 0 .. 7;
      RY at 11 range 0 .. 7;
      RZ at 12 range 0 .. 7;
    end record;

  -------------------------
  -- A set of Serpent Keys
  -- parametrized record for a Serpent Keyset 
  -- parameters: 
  --   N is number of Serpent Keys contained
  -- this can be the content of messages 4.1 or 5.2 in protocol spec.

  -- an array of Serpent Keys
  -- MAXIMUM 40 keys allowed in a message, hence subtype for key count
  subtype Keys_Count is Interfaces.Unsigned_8 range 1..40;
  type SKeys_Array is array( Keys_Count range <>) of Serpent.Key;

  type Serpent_Keyset( N : Keys_Count := Keys_Count'Last) is
    record
      -- actual Serpent Keys
      Keys      : SKeys_Array( 1..N );
      -- whether for talking to client (LSB set) or talking to server (MSB set)
      Flag      : Interfaces.Unsigned_8;
    end record;

  ------------------------------
  -- Serpent Keys Management
  type Keys_Mgm (N_Burnt: Interfaces.Unsigned_8) is
    record
      -- count of server keys requested
      N_Server: Interfaces.Unsigned_8; 
      -- count of client keys requested
      N_Client: Interfaces.Unsigned_8;
      -- ID of Serpent key preferred for further inbound Serpent msgs.
      Key_ID  : Interfaces.Unsigned_8;
      -- IDs of Serpent keys burnt by this message
      Burnt   : SKeys_Array( 1..N_Burnt );
    end record;

end Data_Structs;