`timescale 1ns / 1ps

module beer_draft_top(
    input clk,
    input reset,
    input next,draft,
    input [1:0] beer_level,
    output reg beer,
    output reg [1:0] state_display);

      localparam    s0 = 2'b00,
                    s1 = 2'b01,
                    s2 = 2'b10;

    reg b;
    reg [1:0] cur_state;
    reg [1:0] next_state;
    reg prev_next;

    always @(posedge clk)
    begin
        cur_state<=next_state;
        prev_next<=next;
        state_display<=cur_state;
        beer<=b;
    end

    always @(*)
    begin
        if(reset)
        begin
            b=1'b0;
            next_state=s0;
        end
        else if(next&&prev_next!=next)
        begin
            case(cur_state)
                s0: begin
                        if(~draft || (draft&&beer_level==2'b00)) begin   next_state=s0;
                                                                        b=0;
                                                                end
                            else    begin   next_state=s1;
                                            b=0;
                                    end
                    end
                s1: begin
                        if(draft&&beer_level==2'b10)
                        begin
                            next_state = s2;
                            b=1;
                        end
                        else if(~draft || (draft&&beer_level==2'b00)) begin  next_state=s0;
                                                                            b=0;
                                                                     end
                        else    begin
                                    next_state=s1;
                                    b=0;
                                end
                    end
                s2: {next_state,b} = (draft&&beer_level==2'b10)?{s2,1'b1}:{s1,1'b0};
                default: {next_state,b} = {s0,1'b0};
            endcase
        end
    end


endmodule