module Pong(
  input i_Clk,
  input i_HSync,
  input i_VSync,

  input i_GameStart,

  input i_Player1_Up,
  input i_Player1_Down,
  input i_Player2_Up,
  input i_Player2_Down,

  output reg o_HSync,
  output reg o_VSync,
  output [2:0] o_Red,
  output [2:0] o_Green,
  output [2:0] o_Blue
);
  parameter TOTAL_COLUMNS = 800;
  parameter TOTAL_ROWS = 525;

  parameter ACTIVE_COLUMNS = 640;
  parameter ACTIVE_ROWS = 480;

  localparam SCREEN_WIDTH_CELLS = 40;
  localparam SCREEN_HEIGHT_CELLS = 30;
  localparam SCORE_LIMIT = 9;
  localparam PADDLE_HEIGHT = 6;
  localparam PADDLE_PLAYER1_X = 0;
  localparam PADDLE_PLAYER2_X = SCREEN_WIDTH_CELLS - 1;

  localparam STATE_IDLE = 0;
  localparam STATE_RUNNING = 1;
  localparam STATE_P1_WINNER = 2;
  localparam STATE_P2_WINNER = 3;
  localparam STATE_CLEANUP = 4;

  reg [2:0] r_currentState = STATE_IDLE;

  wire w_HSync, w_VSync;
  wire [9:0] w_X, w_Y;

  wire w_P1_DoDrawPaddle, w_P2_DoDrawPaddle;
  wire [5:0] w_P1_PaddleY, w_P2_PaddleY;
  wire w_DoDrawBall, w_DrawAny;
  wire [5:0] w_BallX, w_BallY;
  wire w_IsGameActive;

  reg [3:0] r_P1_Score = 0;
  reg [3:0] r_P2_Score = 0;

  wire [5:0] w_CellX, w_CellY;

  VGA_Current_Beam_Position #(
    .TOTAL_COLUMNS(TOTAL_COLUMNS),
    .TOTAL_ROWS(TOTAL_ROWS)
  ) CurrentPosition (
    .i_Clk(i_Clk),
    .i_HSync(i_HSync),
    .i_VSync(i_VSync),
    .o_HSync(w_HSync),
    .o_VSync(w_VSync),
    .o_X(w_X),
    .o_Y(w_Y)
  );

  always @(posedge i_Clk) begin
    o_HSync <= w_HSync;
    o_VSync <= w_VSync;
  end

  // right shift 4
  assign w_CellX = w_X[9:4];
  assign w_CellY = w_Y[9:4];

  // paddles

  PongPaddle #(
    .X_POS_CELLS(PADDLE_PLAYER1_X),
    .SCREEN_HEIGHT_CELLS(SCREEN_HEIGHT_CELLS),
    .PADDLE_HEIGHT_CELLS(PADDLE_HEIGHT)
  ) P1_Paddle (
    .i_Clk(i_Clk),
    .i_CellX(w_CellX),
    .i_CellY(w_CellY),
    .i_PaddleUp(i_Player1_Up),
    .i_PaddleDown(i_Player1_Down),
    .o_DoDrawPaddle(w_P1_DoDrawPaddle),
    .o_PaddleY(w_P1_PaddleY)
  );

  PongPaddle #(
    .X_POS_CELLS(PADDLE_PLAYER2_X),
    .SCREEN_HEIGHT_CELLS(SCREEN_HEIGHT_CELLS),
    .PADDLE_HEIGHT_CELLS(PADDLE_HEIGHT)
  ) P2_Paddle (
    .i_Clk(i_Clk),
    .i_CellX(w_CellX),
    .i_CellY(w_CellY),
    .i_PaddleUp(i_Player2_Up),
    .i_PaddleDown(i_Player2_Down),
    .o_DoDrawPaddle(w_P2_DoDrawPaddle),
    .o_PaddleY(w_P2_PaddleY)
  );

  PongBall #(
    .SCREEN_WIDTH_CELLS(SCREEN_WIDTH_CELLS),
    .SCREEN_HEIGHT_CELLS(SCREEN_HEIGHT_CELLS)
  ) Ball (
    .i_Clk(i_Clk),
    .i_IsGameActive(w_IsGameActive),
    .i_CellX(w_CellX),
    .i_CellY(w_CellY),
    .o_DoDrawBall(w_DoDrawBall),
    .o_BallX(w_BallX),
    .o_BallY(w_BallY)
  );

  always @(posedge i_Clk) begin
    case (r_currentState)
      STATE_IDLE:
      begin
        if (i_GameStart) begin
          r_currentState <= STATE_RUNNING;
        end
      end

      STATE_RUNNING:
      begin
        if (
          w_BallX == 0 && (
            w_BallY < w_P1_PaddleY ||
            w_BallY > w_P1_PaddleY + PADDLE_HEIGHT
          )
        ) begin
          r_currentState <= STATE_P1_WINNER;
        end else if (
          w_BallX == SCREEN_WIDTH_CELLS - 1 && (
            w_BallY < w_P2_PaddleY ||
            w_BallY > w_P2_PaddleY + PADDLE_HEIGHT
          )
        ) begin
          r_currentState <= STATE_P2_WINNER;
        end
      end

      STATE_P1_WINNER:
      begin
        if (r_P1_Score == SCORE_LIMIT - 1) begin
          r_P1_Score <= 0;
        end else begin
          r_P1_Score <= r_P1_Score + 1;
          r_currentState <= STATE_CLEANUP;
        end
      end

      STATE_P2_WINNER:
      begin
        if (r_P2_Score == SCORE_LIMIT - 1) begin
          r_P2_Score <= 0;
        end else begin
          r_P2_Score <= r_P2_Score + 1;
          r_currentState <= STATE_CLEANUP;
        end
      end

      STATE_CLEANUP:
      begin
        r_currentState <= STATE_IDLE;
      end
    endcase
  end

  assign w_IsGameActive = (r_currentState == STATE_RUNNING) ? 1 : 0;

  assign w_DrawAny = w_DoDrawBall | w_P1_DoDrawPaddle | w_P2_DoDrawPaddle;

  assign o_Red = w_DrawAny ? 7 : 0;
  assign o_Green = w_DrawAny ? 7 : 0;
  assign o_Blue = w_DrawAny ? 7 : 0;
endmodule