module Simon_Game (
  input i_Clk,

  input i_Switch_1,
  input i_Switch_2,
  input i_Switch_3,
  input i_Switch_4,

  output reg [3:0] o_Score,

  output o_LED_1,
  output o_LED_2,
  output o_LED_3,
  output o_LED_4
);
  parameter CLKS_PER_SECOND = 25000000;
  parameter GAME_LIMIT = 6;

  localparam START = 3'd0;
  localparam PATTERN_OFF = 3'd1;
  localparam PATTERN_SHOW = 3'd2;
  localparam WAIT_PLAYER = 3'd3;
  localparam INCREMENT_SCORE = 3'd4;
  localparam PLAYER_LOST = 3'd5;
  localparam PLAYER_WON = 3'd6;

  reg [2:0] r_currentState;

  // count and toggle results
  wire w_IncomingDelay;
  reg r_DelayCompleted;
  wire w_EnableCounter;

  // user input handling
  reg r_Switch_1, r_Switch_2, r_Switch_3, r_Switch_4;
  reg r_Button_notDown;
  reg [1:0] r_currentButtonDown;

  // game pattern & construction
  reg [1:0] r_LEDPattern [0:10];
  wire [21:0] w_LFSR_Data;
  reg [$clog2(GAME_LIMIT)-1:0] r_currentLEDPattern;

  always @(posedge i_Clk) begin
    if (i_Switch_1 & i_Switch_2) begin
      r_currentState <= START;
    end else begin
      case (r_currentState)
        START:
        begin
          if (!i_Switch_1 & !i_Switch_2 & r_Button_notDown) begin
            o_Score <= 0;
            r_currentLEDPattern <= 0;
            r_currentState <= PATTERN_OFF;
          end
        end

        PATTERN_OFF:
        begin
          if (!w_IncomingDelay & r_DelayCompleted) begin
            r_currentState <= PATTERN_SHOW;
          end
        end

        PATTERN_SHOW:
        begin
          if (!w_IncomingDelay & r_DelayCompleted) begin
            // this limits the number of 
            if (o_Score == r_currentLEDPattern) begin
              r_currentLEDPattern <= 0;
              r_currentState <= WAIT_PLAYER;
            end else begin
              r_currentLEDPattern <= r_currentLEDPattern + 1;
              r_currentState <= PATTERN_OFF;
            end
          end
        end

        WAIT_PLAYER:
        begin
          if (r_Button_notDown) begin
            if (
              r_LEDPattern[r_currentLEDPattern] == r_currentButtonDown &&
              o_Score == r_currentLEDPattern
            ) begin
              r_currentLEDPattern <= 0;
              r_currentState <= INCREMENT_SCORE;
            end else if (
              r_LEDPattern[r_currentLEDPattern] != r_currentButtonDown
            ) begin
              r_currentState <= PLAYER_LOST;
            end else begin
              r_currentLEDPattern <= r_currentLEDPattern + 1;
            end
          end
        end

        INCREMENT_SCORE:
        begin
          o_Score <= o_Score + 1;
          if (o_Score == GAME_LIMIT - 1) begin
            r_currentState <= PLAYER_WON;
          end else begin
            r_currentState <= PATTERN_OFF;
          end
        end

        PLAYER_WON:
        begin
          o_Score <= 4'hA;
        end

        PLAYER_LOST:
        begin
          o_Score <= 4'hF;
        end

        default:
        begin
          r_currentState <= START;
        end
      endcase
    end
  end

  always @(posedge i_Clk) begin
    if (r_currentState == START) begin
      r_LEDPattern[0] <= w_LFSR_Data[1:0];
      r_LEDPattern[1] <= w_LFSR_Data[3:2];
      r_LEDPattern[2] <= w_LFSR_Data[5:4];
      r_LEDPattern[3] <= w_LFSR_Data[7:6];
      r_LEDPattern[4] <= w_LFSR_Data[9:8];
      r_LEDPattern[5] <= w_LFSR_Data[11:10];
      r_LEDPattern[6] <= w_LFSR_Data[13:12];
      r_LEDPattern[7] <= w_LFSR_Data[15:14];
      r_LEDPattern[8] <= w_LFSR_Data[17:16];
      r_LEDPattern[9] <= w_LFSR_Data[19:18];
      r_LEDPattern[10] <= w_LFSR_Data[21:20];
    end
  end

  assign o_LED_1 = (
    (r_currentState == PATTERN_SHOW && r_LEDPattern[r_currentLEDPattern] == 0) ?
    1 :
    i_Switch_1
  );

  assign o_LED_2 = (
    (r_currentState == PATTERN_SHOW && r_LEDPattern[r_currentLEDPattern] == 1) ?
    1 :
    i_Switch_2
  );

  assign o_LED_3 = (
    (r_currentState == PATTERN_SHOW && r_LEDPattern[r_currentLEDPattern] == 2) ?
    1 :
    i_Switch_3
  );

  assign o_LED_4 = (
    (r_currentState == PATTERN_SHOW && r_LEDPattern[r_currentLEDPattern] == 3) ?
    1 :
    i_Switch_4
  );

  always @(posedge i_Clk) begin
    r_DelayCompleted <= w_IncomingDelay;
    r_Switch_1 <= i_Switch_1;
    r_Switch_2 <= i_Switch_2;
    r_Switch_3 <= i_Switch_3;
    r_Switch_4 <= i_Switch_4;

    if (r_Switch_1 && !i_Switch_1) begin
      r_Button_notDown <= 1;
      r_currentButtonDown <= 0;
    end else if (r_Switch_2 && !i_Switch_2) begin
      r_Button_notDown <= 1;
      r_currentButtonDown <= 1;
    end else if (r_Switch_3 && !i_Switch_3) begin
      r_Button_notDown <= 1;
      r_currentButtonDown <= 2;
    end else if (r_Switch_4 && !i_Switch_4) begin
      r_Button_notDown <= 1;
      r_currentButtonDown <= 3;
    end else begin
      r_Button_notDown <= 0;
      r_currentButtonDown <= 0;
    end
  end

  assign w_EnableCounter = (r_currentState == PATTERN_SHOW || r_currentState == PATTERN_OFF);

  Count_And_Toggle #(
    .COUNT_LIMIT(CLKS_PER_SECOND/4)
  ) Counter (
    .i_Clk(i_Clk),
    .i_Enable(w_EnableCounter),
    .o_Toggle(w_IncomingDelay)
  );

  LFSR #(
    .SIZE(22)
  ) MyLFSR (
    .i_Clk(i_Clk),
    .o_LFSR_Data(w_LFSR_Data),
    .o_LFSR_Done()
  );
endmodule