`define OP_NOP   3'd0
`define OP_LOADA 3'd1
`define OP_LOADB 3'd2
`define OP_STORE 3'd3
`define OP_READ  3'd4
`define OP_LOADI 3'd5
`define OP_ROUTE 3'd6
`define OP_RUG   3'd7

`define DIRECTION_N  3'd0
`define DIRECTION_NE 3'd1
`define DIRECTION_E  3'd2
`define DIRECTION_SE 3'd3
`define DIRECTION_S  3'd4
`define DIRECTION_SW 3'd5
`define DIRECTION_W  3'd6
`define DIRECTION_NW 3'd7

module chip(input clk, input [2:0] op, input [15:0] I, input io_pin, input CS, output reg [15:0] mem_in, input [15:0] mem_out, output reg mem_write);

   // parity is unimplemented

   // OP_LOADA
   wire [3:0] flagr = I[3:0];
   wire 	  bsel = I[4];
   wire [0:7] aluc = I[12:5];

   // OP_LOADB
   wire [3:0] cond = I[3:0];
   wire 	  inv = I[4];
   wire [0:7] alus = I[12:5];

   // OP_STORE
   wire [3:0] flagw = I[3:0];
   wire 	  edge_ = I[7];
   wire [3:0] cube = I[11:8];

   // OP_ROUTE
   wire [5:0] cycle = I[5:0];
   wire [1:0] check = I[7:6];
   wire [3:0] xor_  = I[11:8];
   wire [2:0] snarf = I[14:12];
   wire 	  odd   = I[15];

   // OP_RUG
   wire 	  rw = I[0];
   wire 	  ac = I[1];
   wire 	  news = I[2];
   wire [4:0] reg_ = I[8:4];


   reg [15:0] A = 0;
   reg [15:0] B = 0;
   reg [15:0] C = 0;
   reg [15:0] F = 0;
   reg [15:0] Cond = 0;
   reg [15:0] R = 0;
   reg [7:0]  alu_sum = 0;
   reg [7:0]  alu_carry = 0;
   reg [15:0] cube_in;
   reg 		  io;

   // these are not really regs

   reg [15:0]  alu_sum_out;
   reg [15:0]  alu_carry_out;

   reg [2:0]  alu_index [15:0];

   reg [15:0]  idx;

   always @* begin
	  for(idx = 0; idx < 16; idx=idx+1) begin
		 alu_index[idx] = (A[idx] << 2) + (B[idx] << 1) + F[idx];
		 alu_sum_out[idx] <= alu_sum[alu_index[idx]];
		 alu_carry_out[idx] <= alu_carry[alu_index[idx]];
	  end
   end

   reg [3:0] newstable[0:15][0:7];

   initial begin
	  newstable[0][0] = 12;
	  newstable[0][1] = 13;
	  newstable[0][2] = 1;
	  newstable[0][3] = 5;
	  newstable[0][4] = 4;
	  newstable[0][5] = 7;
	  newstable[0][6] = 3;
	  newstable[0][7] = 15;
	  newstable[1][0] = 13;
	  newstable[1][1] = 14;
	  newstable[1][2] = 2;
	  newstable[1][3] = 6;
	  newstable[1][4] = 5;
	  newstable[1][5] = 4;
	  newstable[1][6] = 0;
	  newstable[1][7] = 12;
	  newstable[2][0] = 14;
	  newstable[2][1] = 15;
	  newstable[2][2] = 3;
	  newstable[2][3] = 7;
	  newstable[2][4] = 6;
	  newstable[2][5] = 5;
	  newstable[2][6] = 1;
	  newstable[2][7] = 13;
	  newstable[3][0] = 15;
	  newstable[3][1] = 12;
	  newstable[3][2] = 0;
	  newstable[3][3] = 4;
	  newstable[3][4] = 7;
	  newstable[3][5] = 6;
	  newstable[3][6] = 2;
	  newstable[3][7] = 14;
	  newstable[4][0] = 0;
	  newstable[4][1] = 1;
	  newstable[4][2] = 5;
	  newstable[4][3] = 9;
	  newstable[4][4] = 8;
	  newstable[4][5] = 11;
	  newstable[4][6] = 7;
	  newstable[4][7] = 3;
	  newstable[5][0] = 1;
	  newstable[5][1] = 2;
	  newstable[5][2] = 6;
	  newstable[5][3] = 10;
	  newstable[5][4] = 9;
	  newstable[5][5] = 8;
	  newstable[5][6] = 4;
	  newstable[5][7] = 0;
	  newstable[6][0] = 2;
	  newstable[6][1] = 3;
	  newstable[6][2] = 7;
	  newstable[6][3] = 11;
	  newstable[6][4] = 10;
	  newstable[6][5] = 9;
	  newstable[6][6] = 5;
	  newstable[6][7] = 1;
	  newstable[7][0] = 3;
	  newstable[7][1] = 0;
	  newstable[7][2] = 4;
	  newstable[7][3] = 8;
	  newstable[7][4] = 11;
	  newstable[7][5] = 10;
	  newstable[7][6] = 6;
	  newstable[7][7] = 2;
	  newstable[8][0] = 4;
	  newstable[8][1] = 5;
	  newstable[8][2] = 9;
	  newstable[8][3] = 13;
	  newstable[8][4] = 12;
	  newstable[8][5] = 15;
	  newstable[8][6] = 11;
	  newstable[8][7] = 7;
	  newstable[9][0] = 5;
	  newstable[9][1] = 6;
	  newstable[9][2] = 10;
	  newstable[9][3] = 14;
	  newstable[9][4] = 13;
	  newstable[9][5] = 12;
	  newstable[9][6] = 8;
	  newstable[9][7] = 4;
	  newstable[10][0] = 6;
	  newstable[10][1] = 7;
	  newstable[10][2] = 11;
	  newstable[10][3] = 15;
	  newstable[10][4] = 14;
	  newstable[10][5] = 13;
	  newstable[10][6] = 9;
	  newstable[10][7] = 5;
	  newstable[11][0] = 7;
	  newstable[11][1] = 4;
	  newstable[11][2] = 8;
	  newstable[11][3] = 12;
	  newstable[11][4] = 15;
	  newstable[11][5] = 14;
	  newstable[11][6] = 10;
	  newstable[11][7] = 6;
	  newstable[12][0] = 8;
	  newstable[12][1] = 9;
	  newstable[12][2] = 13;
	  newstable[12][3] = 1;
	  newstable[12][4] = 0;
	  newstable[12][5] = 3;
	  newstable[12][6] = 15;
	  newstable[12][7] = 11;
	  newstable[13][0] = 9;
	  newstable[13][1] = 10;
	  newstable[13][2] = 14;
	  newstable[13][3] = 2;
	  newstable[13][4] = 1;
	  newstable[13][5] = 0;
	  newstable[13][6] = 12;
	  newstable[13][7] = 8;
	  newstable[14][0] = 10;
	  newstable[14][1] = 11;
	  newstable[14][2] = 15;
	  newstable[14][3] = 3;
	  newstable[14][4] = 2;
	  newstable[14][5] = 1;
	  newstable[14][6] = 13;
	  newstable[14][7] = 9;
	  newstable[15][0] = 11;
	  newstable[15][1] = 8;
	  newstable[15][2] = 12;
	  newstable[15][3] = 0;
	  newstable[15][4] = 3;
	  newstable[15][5] = 2;
	  newstable[15][6] = 14;
	  newstable[15][7] = 10;
   end // initial begin

   reg [3:0] flags_addr_latch;
   reg [3:0] flags_addr;

   always @* begin
	  if(flags_addr_latch)
		flags_addr <= flags_addr_latch;
	  else
		case(op)
		  `OP_LOADA:
			flags_addr <= flagr;
		  `OP_LOADB:
			flags_addr <= cond;
		  `OP_STORE:
			flags_addr <= flagw;
		  default:
			flags_addr <= 0;
		endcase
   end // always @ *

   reg  [15:0] flags_in;
   wire [15:0] flags_out;
   reg 		   flags_write;

   reg [15:0]  latest_news;

   RAM #(.ADDRESS_BITS(3)) flags (.clk(clk), .write(flags_write), .addr(flags_addr[2:0]), .in(flags_in), .out(flags_out));

   reg [15:0]  flag_or_news;

   reg [15:0]  newsidx;

   always @* begin
	  if(flags_addr[3]) begin // read from news
		 for(idx = 0; idx < 16; idx++) begin
			newsidx = newstable[idx][flags_addr[2:0]];
			flag_or_news[idx] = latest_news[newsidx];
		 end
	  end else begin
		 flag_or_news = flags_out;
	  end
   end

   always @ (posedge clk) begin
	  if(mem_write)
		mem_write <= 0;
	  if(flags_write) begin
		 flags_write <= 0;
		 flags_addr_latch <= 0;
	  end

	  case (op)
		`OP_NOP: begin end

		`OP_LOADA:
		  begin
			 alu_carry <= aluc;
			 F <= flag_or_news;
			 A <= mem_out;
			 C <= mem_out;
			 io <= io_pin;
			 if (bsel)
			   B <= cube_in;
		  end

		`OP_LOADB:
		  begin
			 alu_sum <= alus;
			 Cond <= inv ? ~flag_or_news : flag_or_news;
			 B <= mem_out;
			 R <= mem_out;
		  end

		`OP_STORE:
		  begin
			 for(idx = 0; idx < 16; idx++) begin
				flags_in[idx] = Cond[idx] ? alu_carry_out[idx] : flags_out[idx];
				latest_news[idx] <= flags_in[idx];
			 end
			 if(flags_addr) begin // we do not write to flag 0
				flags_write <= 1;
				flags_addr_latch <= flags_addr;
			 end
			 mem_in <= alu_sum_out;
			 mem_write <= 1;
		  end

		`OP_READ:
		  begin
			 if (CS)
			   mem_in <= mem_out;
		  end

		`OP_LOADI:
		  begin
			 C <= mem_out;
			 A <= I;
			 alu_sum <= 8'b11110000; // out of A, B, F, select exactly A
		  end

/*		`OP_RUG:
		  begin
			 if(!rw && ac && !news)
			   begin
				  rug[reg_] <= A;
				  C <= mem_out;
			   end
			 if(!rw && !ac && !news)
			   begin
				  rug[reg_] <= C;
				  A <= mem_out;
			   end
			 if(rw && ac && !news)
			   begin
				  A <= rug[reg_];
				  mem_in <= C;
			   end
			 if(rw && !ac && !news)
			   begin
				  C <= rug[reg_];
				  mem_in <= A;
			   end
			 if(rw && !ac && news)
			   begin
				  R <= mem_out;
				  cube_in <= mem_out;
			   end
			 if(rw && ac && news)
			   begin
				  cube_in <= mem_out;
			   end
		  end
*/
	  endcase
   end
endmodule