//explicacion
//mas explicacion


module stop_light(north, south, east, west, clk, reset);

    input clk, reset;
    output reg [3:0] north, east, south, west;
    reg [3:0] clk_count = 4'b0000;

    // N/S
    parameter NS_LAR = 3'b001;      // state 001 => north/south light left arrow/red AND east/west light red
    parameter NS_G = 3'b010;        // state 010 => north/south light green AND east/west light red
    parameter NS_Y = 3'b011;        // state 011 => north/south light yellow AND east/west light red

    // E/W
    parameter EW_LAR = 3'b100;      // state 100 => north/south light red AND east/west light left arrow/red
    parameter EW_G = 3'b101;        // state 101 => north/south light red AND east/west light green
    parameter EW_Y = 3'b110;        // state 110 => north/south light red AND east/west light yellow

    // Reset / All lights to red
    parameter NSEW_red = 3'b111;    // state 111 => north/south light red AND east/west light red (RESET STATE)

    // Our current state value (intitally set to turn north/south left arrow/red light on and east/west light red)
    reg [3:0] state = NS_LAR;

    always @(posedge clk)
    begin

        // check to see if the reset switch has been set
        if (reset == 1)
        begin
            state = NSEW_red;
            clk_count = 4b'0000;
        end  //end if

        else
        begin
            if (state == NS_LAR)
                begin
                    if (clk_count = 4b'1010)  //once the clock has reached 10 seconds
                    begin
                        state = NS_G;
                        clk_count = 4'b0000;
                    end   //end if
                    else
                    begin
                        state = NS_LAR;
                        clk_count = clk_count + 1;
                    end  //end else
                end  //end NS_LAR case

            if (state == NS_G)
                begin
                    if (clk_count = 4b'1111)  //once the clock has reached 15 seconds
                    begin
                        state = NS_Y;
                        clk_count = 4'b0000;
                    end   //end if
                    else
                    begin
                        state = NS_G;
                        clk_count = clk_count + 1;
                    end  //end else
                end  //end NS_G case

            if (state == NS_Y)
                begin
                    if (clk_count = 4b'0101)  //once the clock has reached 5 seconds
                    begin
                        state = EW_LAR;
                        clk_count = 4'b0000;
                    end   //end if
                    else
                    begin
                        state = NS_Y;
                        clk_count = clk_count + 1;
                    end  //end else
                end  //end NS_Y case

            if (state == EW_LAR)
                begin
                    if (clk_count = 4b'1010)  //once the clock has reached 10 seconds
                    begin
                        state = EW_G;
                        clk_count = 4'b0000;
                    end   //end if
                    else
                    begin
                        state = EW_LAR;
                        clk_count = clk_count + 1;
                    end  //end else
                end  //end EW_LAR case

            if (state == EW_G)
                begin
                    if (clk_count = 4b'1111)  //once the clock has reached 15 seconds
                    begin
                        state = EW_Y;
                        clk_count = 4'b0000;
                    end   //end if
                    else
                    begin
                        state = EW_G;
                        clk_count = clk_count + 1;
                    end  //end else
                end  //end EW_G case

            if (state == EW_Y)
                begin
                    if (clk_count = 4b'0101)  //once the clock has reached 5 seconds
                    begin
                        state = NS_LAR;
                        clk_count = 4'b0000;
                    end   //end if
                    else
                    begin
                        state = EW_Y;
                        clk_count = clk_count + 1;
                    end  //end else
                end  //end EW_Y case

        end  //end else

    end  //end always posedge clk

    always @(state)
    begin

        if (state == NS_LAR)
            north = 4'b1001;
            south = 4'b1001;
            east = 4b'0001;
            west = 4b'0001;

        if (state == NS_G)
            north = 4b'0100;
            south = 4b'0100;
            east = 4b'0001;
            west = 4b'0001;

        if (state == NS_Y)
            north = 4b'0010;
            south = 4b'0010;;
            east = 4b'0001;
            west = 4b'0001;

        if (state == EW_LAR)
            north = 4b'0001;
            south = 4b'0001;
            east = 4'b1001;
            west = 4'b1001;

        if (state == EW_G)
            north = 4b'0001;
            south = 4b'0001;
            east = 4b'0100;
            west = 4b'0100;

        if (state == EW_Y)
            north = 4b'0001;
            south = 4b'0001;
            east = 4b'0010;;
            west = 4b'0010;;

        if (state == NSEW_red)
            north = 4b'0001;
            south = 4b'0001;
            east = 4b'0001;
            west = 4b'0001;

    end  //end always state


endmodule