// Copyright (C) 2020-2021  The SymbiFlow Authors.
//
// Use of this source code is governed by a ISC-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/ISC
//
// SPDX-License-Identifier:ISC

module fsm (
    clock,
    reset,
    req_0,
    req_1,
    gnt_0,
    gnt_1
);
  input clock, reset, req_0, req_1;
  output gnt_0, gnt_1;
  wire clock, reset, req_0, req_1;
  reg gnt_0, gnt_1;

  parameter SIZE = 3;
  parameter IDLE = 3'b001;
  parameter GNT0 = 3'b010;
  parameter GNT1 = 3'b100;
  parameter GNT2 = 3'b101;

  reg [SIZE-1:0] state;
  reg [SIZE-1:0] next_state;

  always @(posedge clock) begin : FSM
    if (reset == 1'b1) begin
      state <= #1 IDLE;
      gnt_0 <= 0;
      gnt_1 <= 0;
    end else
      case (state)
        IDLE:
        if (req_0 == 1'b1) begin
          state <= #1 GNT0;
          gnt_0 <= 1;
        end else if (req_1 == 1'b1) begin
          gnt_1 <= 1;
          state <= #1 GNT0;
        end else begin
          state <= #1 IDLE;
        end
        GNT0:
        if (req_0 == 1'b1) begin
          state <= #1 GNT0;
        end else begin
          gnt_0 <= 0;
          state <= #1 IDLE;
        end
        GNT1:
        if (req_1 == 1'b1) begin
          state <= #1 GNT2;
          gnt_1 <= req_0;
        end
        GNT2:
        if (req_0 == 1'b1) begin
          state <= #1 GNT1;
          gnt_1 <= req_1;
        end
        default: state <= #1 IDLE;
      endcase
  end
endmodule