`include "pll.v"
`include "ram.v"
`include "chip.v"
`include "uart.v"

`ifdef SIM
 `define UART_DIVIDE 1
`else
 `define UART_DIVIDE 1024
`endif

module worker (input CLKin, output [4:0] led, output uart_tx, input uart_rx, output reg busy_out = 1, input busy_in, input is_worker);
   wire clk = CLKin;

`ifndef SIM
   // if [is_worker == 0], boot into master image
   SB_WARMBOOT wb (.BOOT (!is_worker), .S0(1'b1), .S1(1'b0));
`endif

`ifdef SIM
   wire dont_send = 0;
`else
   reg [25:0]  dont_send = 23'b11111111111111111111111;

   always @(posedge clk) begin
	  if(busy_in)
		dont_send <= 21'b111111111111111111111;
	  else if(dont_send)
		dont_send <= dont_send - 1;
   end
`endif

   wire [11:0] mem_addr;
   wire [15:0] mem_in;
   wire [15:0] mem_out;
   wire 	   mem_write;

   reg [31:0]  the_rom [0:100];
   reg [10:0]  rom_pc = 0;

   initial begin
	  the_rom[0] <= 32'hfC000005;
	  the_rom[1] <= 32'hfC010007;
	  the_rom[2] <= 32'hf9001d00;
	  the_rom[3] <= 32'hfA0112d0;
	  the_rom[4] <= 32'hfB000004;
	  the_rom[5] <= 32'hf9000004;
	  the_rom[6] <= 32'hfA001550;
	  the_rom[7] <= 32'hfB010000;
   end

   RAM #(.ADDRESS_BITS(8)) ram (.clk(clk), .write(mem_write), .addr(mem_addr), .in(mem_in), .out(mem_out));

   reg [7:0]   from_uart [3:0];
   reg [2:0]   uart_ptr = 0;

   wire [15:0] I  = {from_uart[1], from_uart[0]};
   assign mem_addr = from_uart[2];
   wire [2:0]  op_from_uart = from_uart[3][2:0];

   wire [3:0]  chip_select = from_uart[3][7:4];
   wire 	   is_virtual = from_uart[3][3];
   wire 	   dont_propagate = is_virtual || ~| chip_select;
   wire 	   not_for_us = !chip_select[0];

   wire [7:0]   to_uart [3:0];
   wire [3:0]   next_chip_select = {0, chip_select[3:1]};
   assign to_uart[0] = from_uart[0];
   assign to_uart[1] = from_uart[1];
   assign to_uart[2] = from_uart[2];
   assign to_uart[3] = {next_chip_select, from_uart[3][3:0]};

   /* to execute a ROUTE instruction, we send our neighbour a STOREI
   /* instruction with the correct address and value. This is the
   /* STOREI instruction. */
   wire [7:0]  route_storei [3:0];
   assign route_storei[0] = mem_out[7:0];
   assign route_storei[1] = mem_out[15:8];
   assign route_storei[2] = from_uart[0];
   assign route_storei[3] = 8'h1C; // chip_select = 1, is_virtual = 1, op = OP_STOREI

   reg [2:0]   op = 0;

   reg [2:0]   last_op = 0;

   reg [15:0]  I;

   reg [3:0]   led_out;

   chip chip (.clk(clk), .op(op), .I(I), .mem_in(mem_in), .mem_out(mem_out), .mem_write(mem_write), .led_out(led_out));

   wire 	   received;
   wire [7:0]  rx_byte;
   reg 		   transmit = 0;
   reg  [7:0]  tx_byte = 0;
   wire 	   is_receiving;
   wire 	   is_transmitting;
   wire 	   recv_error;

   uart #(.CLOCK_DIVIDE(`UART_DIVIDE)) uart (.clk(clk), .rx(uart_rx), .tx(uart_tx), .received(received), .transmit(transmit), .tx_byte(tx_byte), .rx_byte(rx_byte), .is_receiving(is_receiving), .is_transmitting(is_transmitting), .recv_error(recv_error));

`define STATE_IDLE 0
`define STATE_PROPAGATE 1
`define STATE_PREEXEC 2
`define STATE_EXECUTE 3
`define STATE_ROUTE 4

   reg [3:0]   state = `STATE_IDLE;

   assign led[3:0] = uart_ptr;
   assign led[4] = is_receiving;

   always @ (posedge clk) begin
	  case(state)
		`STATE_IDLE: begin
		   if(uart_ptr == 4) begin
			  last_op <= op_from_uart;
			  uart_ptr <= 0;
			  if(dont_propagate)
				state <= `STATE_PREEXEC;
			  else
				state <= `STATE_PROPAGATE;
			  busy_out <= 1;
		   end
		   else	if (received) begin
			  from_uart[uart_ptr] <= rx_byte;
			  uart_ptr <= uart_ptr + 1;
		   end else begin
`ifdef SIM
			  from_uart[0] <= the_rom[rom_pc][7:0];
			  from_uart[1] <= the_rom[rom_pc][15:8];
			  from_uart[2] <= the_rom[rom_pc][23:16];
			  from_uart[3] <= the_rom[rom_pc][31:24];
			  uart_ptr <= 4;
			  rom_pc <= rom_pc + 1;
`else
			  busy_out <= 0;
`endif
		   end
		end

		`STATE_PROPAGATE: begin
		   if(transmit)
			  transmit <= 0;
		   else if(uart_ptr == 4) begin
			  uart_ptr <= 0;
			  state <= `STATE_PREEXEC;
		   end else if(!is_transmitting && !dont_send) begin
			  tx_byte <= to_uart[uart_ptr];
			  transmit <= 1;
			  uart_ptr <= uart_ptr + 1;
		   end
		end // case: `STATE_PROPAGATE

		`STATE_PREEXEC: begin
		   if(not_for_us) begin
			  state <= `STATE_IDLE;
		   end else if(last_op == `OP_ROUTE) begin
			  state <= `STATE_ROUTE;
		   end else begin
			  op <= last_op;
			  state <= `STATE_EXECUTE;
		   end
		end

		`STATE_EXECUTE: begin
		   op <= 0;
		   state <= `STATE_IDLE;
		end

		`STATE_ROUTE: begin
		   if(transmit)
			  transmit <= 0;
		   else if(uart_ptr == 4) begin
			  uart_ptr <= 0;
			  state <= `STATE_IDLE;
		   end else if(!is_transmitting && !dont_send) begin
			  tx_byte <= route_storei[uart_ptr];
			  transmit <= 1;
			  uart_ptr <= uart_ptr + 1;
		   end
		end
	  endcase
   end
endmodule