nextstagelogic.sv



module memory (input logic [15:0] set,
				   input logic clk,
					input logic enable,
					output logic [15:0] get);
	always_ff @(posedge clk, posedge enable)
	begin
		if (enable) begin
			get <= set;
		end
	end
endmodule


module verifyinput (input logic [3:0] a, input logic [3:0] b,
						  output logic valid);
	assign valid = ~(a[0] ^ b[0]) & ~(a[1] ^ b[1]) & ~(a[2] ^ b[2]) & ~(a[3] ^ b[3]);
endmodule

module nextstatelogic (input logic [3:0] currentstate,
							  input logic [4:0] buttons,
							  input logic [15:0] comboin,
							  input clk,
					   	  output logic [3:0] nextstate,
							  output logic [15:0] comboout);
	always_comb begin
	   if (buttons[4]) begin
		    nextstate = 4'b1111;
			 comboout = comboin;
	   end else begin

		case (buttons)
			5'b00000 : begin
										  if (currentstate == 4'b1111) begin
										     nextstate = 4'b0000;
										  end else begin
			                          nextstate = currentstate;
										  end
										  comboout = comboin;
							end
		   5'b00001 : begin
						  nextstate = 4'b0000;
						  comboout = comboin;
						  end
			default : begin
						 logic pass;
						 logic [15:0] nextmem;
						 case (currentstate)
						    4'b0000 : begin
								        if (buttons[4:1] == comboin[3:0]) begin
								           nextstate = 4'b0001;
								        end else begin
										     nextstate = 4'b1001;
							           end
										  comboout = comboin;
										  end
							 4'b0001 : begin
					          		  if (buttons[4:1] == comboin[3:0]) begin
								           nextstate = 4'b0010;
								        end else begin
										     nextstate = 4'b1010;
							           end
										  comboout = comboin;
										  end
							 4'b0010 : begin
										  if (buttons[4:1] == comboin[3:0]) begin
										     nextstate = 4'b0011;
										  end else begin
										     nextstate = 4'b1011;
										  end
										  comboout = comboin;
										  end
							 4'b0011 : begin
										  if (buttons[4:1] == comboin[3:0]) begin
										     nextstate = 4'b0100;
										  end else begin
										     nextstate = 4'b1100;
										  end
										  comboout = comboin;
										  end
							 4'b1000: begin
										 nextstate = 4'b1001;
										 comboout = comboin;
										 end
							 4'b1001: begin
										 nextstate = 4'b1010;
										 comboout = comboin;
										 end
							 4'b1010: begin
										 nextstate = 4'b1011;
										 comboout = comboin;
										 end
							 4'b1011: begin
										 nextstate = 4'b1100;
										 comboout = comboin;
										 end
							 4'b1100: begin
										 nextstate = 4'b0000;
										 comboout = comboin;
										 end
							 4'b0100: begin
							          nextstate = 4'b0101;
										 comboout = {comboin[15:4], buttons[4:1]};
										 end
							 4'b0101: begin
							          nextstate = 4'b0110;
										 comboout = {comboin[15:8], buttons[4:1], comboin[3:0]};
										 end
							 4'b0110: begin
							          nextstate = 4'b0111;
										 comboout = {comboin[15:12], buttons[4:1], comboin[3:0]};
										 end
							 4'b0111: begin
							          nextstate = 4'b0000;
										 comboout = {buttons[4:1], comboin[11:0]};
										 end
							 default: begin
										 nextstate = currentstate;
										 comboout = comboin;
										 end

						 endcase
						 end
      endcase
	   end
	end
endmodule