module timecode_nextcode (
    input [63:0] timecode,
    input [7:0] frame_mum,
    input drop,
    output [63:0] timecode_next
);
  wire [7:0] now_frame_units;
  wire [7:0] frame10;
  wire [7:0] sec;
  wire [7:0] sec10;
  wire [7:0] min;
  wire [7:0] min10;
  wire [7:0] hour;
  wire [7:0] hour10;

  assign now_frame_units = timecode[7:0]  & 8'b0000_1111;
  assign frame10  = timecode[15:8] & 8'b0000_0011;
  assign sec   = timecode[23:16]& 8'b0000_1111;
  assign sec10    = timecode[31:24]& 8'b0000_0111;
  assign min   = timecode[39:32]& 8'b0000_1111;
  assign min10    = timecode[47:40]& 8'b0000_0111;
  assign hour  = timecode[55:48]& 8'b0000_1111;
  assign hour10   = timecode[63:56]& 8'b0000_0011;

  wire houris23 = (hour10 == 2) && (hour == 3);
  wire houris19 = (hour10 == 1) && (hour == 9);
  wire houris09 = (hour10 == 0) && (hour == 9);

  wire minis59 = (min10 == 5) && (min == 9);
  wire minis49 = (min10 == 4) && (min == 9);
  wire minis39 = (min10 == 3) && (min == 9);
  wire minis29 = (min10 == 2) && (min == 9);
  wire minis19 = (min10 == 1) && (min == 9);
  wire minis09 = (min10 == 0) && (min == 9);

  wire secis59 = (sec10 == 5) && (sec == 9);
  wire secis49 = (sec10 == 4) && (sec == 9);
  wire secis39 = (sec10 == 3) && (sec == 9);
  wire secis29 = (sec10 == 2) && (sec == 9);
  wire secis19 = (sec10 == 1) && (sec == 9);
  wire secis09 = (sec10 == 0) && (sec == 9);

  wire frameisfinal = (frame10 == 2) && (now_frame_units == (frame_mum - 20 - 1));
  wire frameis19 = (frame10 == 1) && (now_frame_units == 9);
  wire frameis09 = (frame10 == 0) && (now_frame_units == 9);

  //   reg [63:0] next_frame;

  reg [63:0] next_frame;
  wire [7:0] n_10hour;
  wire [7:0] n_hour;
  wire [7:0] n_10min;
  wire [7:0] n_min;
  wire [7:0] n_10sec;
  wire [7:0] n_sec;
  wire [7:0] n_10frame;
  wire [7:0] n_frame;
  assign n_10hour[7:0] = next_frame[63:56];
  assign n_hour[7:0] = next_frame[55:48];
  assign n_10min[7:0] = next_frame[47:40];
  assign n_min[7:0] = next_frame[39:32];
  assign n_10sec[7:0] = next_frame[31:24];
  assign n_sec[7:0] = next_frame[23:16];
  assign n_10frame[7:0] = next_frame[15:8];
  assign n_frame[7:0] = next_frame[7:0];



  function [63:0] assign_timecode;
    input [7:0] hour_tens;
    input [7:0] hour_units;
    input [7:0] min_tens;
    input [7:0] min_units;
    input [7:0] sec_tens;
    input [7:0] sec_units;
    input [7:0] frame_tens;
    input [7:0] frame_units;
    begin
      assign_timecode[7:0]   = frame_units;
      assign_timecode[15:8]  = frame_tens;
      assign_timecode[23:16] = sec_units;
      assign_timecode[31:24] = sec_tens;
      assign_timecode[39:32] = min_units;
      assign_timecode[47:40] = min_tens;
      assign_timecode[55:48] = hour_units;
      assign_timecode[63:56] = hour_tens;
    end

  endfunction




  always @(*) begin
    /*******************************************************************************
     *                                    HOUR                                     *
     *******************************************************************************/
    if (houris23 && minis59 && secis59 && frameisfinal) begin  //23:59:59:29
      next_frame <= assign_timecode(0, 0, 0, 0, 0, 0, 0, 0);
    end else if (houris19 && minis59 && secis59 && frameisfinal) begin  //19:59:59:29
      next_frame <= assign_timecode(2, 0, 0, 0, 0, 0, 0, 0);
    end else if (houris09 && minis59 && secis59 && frameisfinal) begin  //09:59:59:29
      next_frame <= assign_timecode(1, 0, 0, 0, 0, 0, 0, 0);
    end else if (minis59 && secis59 && frameisfinal) begin  //xx:59:59:29
      next_frame <= assign_timecode(hour10, hour + 1, 0, 0, 0, 0, 0, 0);
    end 
    /*******************************************************************************
     *                                     MIN                                     *
     *******************************************************************************/
    else if (minis49 && secis59 && frameisfinal) begin  // xx:49:59:29
      next_frame <= assign_timecode(hour10, hour, 5, 0, 0, 0, 0, 0);
    end else if (minis39 && secis59 && frameisfinal) begin  // xx:39:59:29
      next_frame <= assign_timecode(hour10, hour, 4, 0, 0, 0, 0, 0);
    end else if (minis29 && secis59 && frameisfinal) begin  // xx:29:59:29
      next_frame <= assign_timecode(hour10, hour, 3, 0, 0, 0, 0, 0);
    end else if (minis19 && secis59 && frameisfinal) begin  // xx:19:59:29
      next_frame <= assign_timecode(hour10, hour, 2, 0, 0, 0, 0, 0);
    end else if (minis09 && secis59 && frameisfinal) begin  // xx:09:59:29
      next_frame <= assign_timecode(hour10, hour, 1, 0, 0, 0, 0, 0);
    end else if (secis59 && frameisfinal) begin  // xx:xx:59:29
      if (drop) begin
        next_frame <= assign_timecode(hour10, hour, min10, min + 1, 0, 0, 0, 2);
      end else begin
        next_frame <= assign_timecode(hour10, hour, min10, min + 1, 0, 0, 0, 0);
      end
    end 
    /*******************************************************************************
     *                                   SECOND                                    *
     *******************************************************************************/
    else if (secis49 && frameisfinal) begin  // xx:xx:49:29
      next_frame <= assign_timecode(hour10, hour, min10, min, 5, 0, 0, 0);
    end else if (secis39 && frameisfinal) begin  // xx:xx:39:29
      next_frame <= assign_timecode(hour10, hour, min10, min, 4, 0, 0, 0);
    end else if (secis29 && frameisfinal) begin  // xx:xx:29:29
      next_frame <= assign_timecode(hour10, hour, min10, min, 3, 0, 0, 0);
    end else if (secis19 && frameisfinal) begin  // xx:xx:19:29
      next_frame <= assign_timecode(hour10, hour, min10, min, 2, 0, 0, 0);
    end else if (secis09 && frameisfinal) begin  // xx:xx:09:29
      next_frame <= assign_timecode(hour10, hour, min10, min, 1, 0, 0, 0);
    end else if (frameisfinal) begin  // xx:xx:xx:29
      next_frame <= assign_timecode(hour10, hour, min10, min, sec10, sec + 1, 0, 0);
    end 
    /*******************************************************************************
     *                                   FRAME                                     *
     *******************************************************************************/
    else if (frameis19) begin  // xx:xx:xx:19
      next_frame <= assign_timecode(hour10, hour, min10, min, sec10, sec, 2, 0);
    end else if (frameis09) begin  // xx:xx:xx:09
      next_frame <= assign_timecode(hour10, hour, min10, min, sec10, sec, 1, 0);
    end else begin
      next_frame <=
          assign_timecode(hour10, hour, min10, min, sec10, sec, frame10, now_frame_units + 1);
    end
  end
  assign timecode_next = next_frame;


  // always @(*) begin
  // /*******************************************************************************
  //  *                                    HOUR                                     *
  //  *******************************************************************************/
  // if (houris23 && minis59 && secis59 && frameisfinal) begin  //23:59:59:29
  //   n_10hour <= 0;
  //   n_hour <= 0;
  //   n_10min <= 0;
  //   n_min <= 0;
  //   n_10sec <= 0;
  //   n_sec <= 0;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end else if (houris19 && minis59 && secis59 && frameisfinal) begin  //19:59:59:29
  //   n_10hour <= 2;
  //   n_hour <= 0;
  //   n_10min <= 0;
  //   n_min <= 0;
  //   n_10sec <= 0;
  //   n_sec <= 0;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end else if (houris09 && minis59 && secis59 && frameisfinal) begin  //09:59:59:29
  //   n_10hour <= 1;
  //   n_hour <= 0;
  //   n_10min <= 0;
  //   n_min <= 0;
  //   n_10sec <= 0;
  //   n_sec <= 0;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end else if (minis59 && secis59 && frameisfinal) begin  //xx:59:59:29
  //   n_10hour <= hour10;
  //   n_hour <= hour + 1;
  //   n_10min <= 0;
  //   n_min <= 0;
  //   n_10sec <= 0;
  //   n_sec <= 0;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end /*******************************************************************************
  //  *                                     MIN                                     *
  //  *******************************************************************************/
  // else if (minis49 && secis59 && frameisfinal) begin  // xx:49:59:29
  //   n_10hour <= hour10;
  //   n_hour <= hour;
  //   n_10min <= 5;
  //   n_min <= 0;
  //   n_10sec <= 0;
  //   n_sec <= 0;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end else if (minis39 && secis59 && frameisfinal) begin  // xx:39:59:29
  //   n_10hour <= hour10;
  //   n_hour <= hour;
  //   n_10min <= 4;
  //   n_min <= 0;
  //   n_10sec <= 0;
  //   n_sec <= 0;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end else if (minis29 && secis59 && frameisfinal) begin  // xx:29:59:29
  //   n_10hour <= hour10;
  //   n_hour <= hour;
  //   n_10min <= 3;
  //   n_min <= 0;
  //   n_10sec <= 0;
  //   n_sec <= 0;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end else if (minis19 && secis59 && frameisfinal) begin  // xx:19:59:29
  //   n_10hour <= hour10;
  //   n_hour <= hour;
  //   n_10min <= 2;
  //   n_min <= 0;
  //   n_10sec <= 0;
  //   n_sec <= 0;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end else if (minis09 && secis59 && frameisfinal) begin  // xx:09:59:29
  //   n_10hour <= hour10;
  //   n_hour <= hour;
  //   n_10min <= 1;
  //   n_min <= 0;
  //   n_10sec <= 0;
  //   n_sec <= 0;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end        /*******************************************************************************
  //  *                                   SECOND                                    *
  //  *******************************************************************************/
  // else if (secis49 && frameisfinal) begin  // xx:xx:49:29
  //   n_10hour <= hour10;
  //   n_hour <= hour;
  //   n_10min <= min10;
  //   n_min <= min;
  //   n_10sec <= 5;
  //   n_sec <= 0;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end else if (secis39 && frameisfinal) begin  // xx:xx:39:29
  //   n_10hour <= hour10;
  //   n_hour <= hour;
  //   n_10min <= min10;
  //   n_min <= min;
  //   n_10sec <= 4;
  //   n_sec <= 0;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end else if (secis29 && frameisfinal) begin  // xx:xx:29:29
  //   n_10hour <= hour10;
  //   n_hour <= hour;
  //   n_10min <= min10;
  //   n_min <= min;
  //   n_10sec <= 3;
  //   n_sec <= 0;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end else if (secis19 && frameisfinal) begin  // xx:xx:19:29
  //   n_10hour <= hour10;
  //   n_hour <= hour;
  //   n_10min <= min10;
  //   n_min <= min;
  //   n_10sec <= 2;
  //   n_sec <= 0;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end else if (secis09 && frameisfinal) begin  // xx:xx:09:29
  //   n_10hour <= hour10;
  //   n_hour <= hour;
  //   n_10min <= min10;
  //   n_min <= min;
  //   n_10sec <= 1;
  //   n_sec <= 0;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end else if (frameisfinal) begin  // xx:xx:xx:29
  //   n_10hour <= hour10;
  //   n_hour <= hour;
  //   n_10min <= min10;
  //   n_min <= min;
  //   n_10sec <= sec10;
  //   n_sec <= sec;
  //   n_10frame <= 0;
  //   n_frame <= 0;
  // end        /*******************************************************************************
  //  *                                   FRAME                                     *
  //  *******************************************************************************/
  // else if (frameis19) begin  // xx:xx:xx:19
  //   n_10hour <= hour10;
  //   n_hour <= hour;
  //   n_10min <= min10;
  //   n_min <= min;
  //   n_10sec <= sec10;
  //   n_sec <= sec;
  //   n_10frame <= 2;
  //   n_frame <= 0;
  // end else 
  // if (frameis09) begin  // xx:xx:xx:09
  //   n_10hour <= hour10;
  //   n_hour <= hour;
  //   n_10min <= min10;
  //   n_min <= min;
  //   n_10sec <= sec10;
  //   n_sec <= sec;
  //   n_10frame <= 1;
  //   n_frame <= 0;
  // end else begin
  //   n_10hour <= hour10;
  //   n_hour <= hour;
  //   n_10min <= min10;
  //   n_min <= min;
  //   n_10sec <= sec10;
  //   n_sec <= sec;
  //   n_10frame <= frame10;
  //   n_frame <= now_frame_units + 1;
  // end
  // end
  // assign timecode_next = next_frame;

  // assign timecode_next[7:0]   = n_frame;
  // assign timecode_next[15:8]  = n_10frame;
  // assign timecode_next[23:16] = n_sec;
  // assign timecode_next[31:24] = n_10sec;
  // assign timecode_next[39:32] = n_min;
  // assign timecode_next[47:40] = n_10min;
  // assign timecode_next[55:48] = n_hour;
  // assign timecode_next[63:56] = n_10hour;


  // wire [63:0] tmp_timecode_next;
  // assign tmp_timecode_next = timecode + 1;
  // assign timecode_next = tmp_timecode_next;


endmodule