`timescale 1ns / 1ps
`define space 2'b00
`define caseBegin 2'b01
`define caseEnd 2'b10
`define caseNo 2'b11

`define ini 3'b000
`define B 3'b001
`define BE 3'b010
`define BEG 3'b011
`define BEGI 3'b100
`define BEGIN 3'b101
`define E 3'b001
`define EN 3'b010
`define END 3'b011
`define NO 3'b111


module BlockChecker(
    input clk,
    input reset,
    input [7:0] in,
    output result
    );
	 reg [2:0]tem1;	//judge begin
	 reg [2:0]tem2;	//judge end
	 reg [1:0]control;
	 reg [31:0]stack;
	 reg judge;
	 assign result = stack == 32'd0 ? 1'b1 : 1'b0;
	always@(posedge clk or posedge reset)begin
		if(reset == 1)begin
			control <= `space;
			tem1 <= `ini;
			tem2 <= `ini;
			judge <= 1'b0;
			stack <= 32'd0;
		end
		else begin
			if(in == " ")begin
				if(control == `caseEnd && tem2 == `END && $signed(stack) < 0)begin
					judge <= 1'b1;
					control <= `caseNo;
				end
				else begin
					control <= `space;
				end
			end
			else if(judge == 1'b1)begin
				control <= `caseNo;
			end
			else if(control == `space)begin
				if(in == "B" || in == "b")begin
					control <= `caseBegin;
					tem1 <= `B;
				end
				if(in == "E" || in == "e")begin 
					control <= `caseEnd;
					tem2 <= `E;
				end
			end
			else if(control == `caseBegin)begin
				case(tem1)
						`B:begin
							if(in == "E" || in == "e")begin
								tem1 <= `BE;
							end
							else begin
								tem1 <= `NO;
								control <= `caseNo;
							end
						end
						`BE:begin
							if(in == "G" || in == "g")begin
								tem1 <= `BEG;
							end
							else begin
								tem1 <= `NO;
								control <= `caseNo;
							end
						end
						`BEG:begin
							if(in == "I" || in == "i")begin
								tem1 <= `BEGI;
							end
							else begin
								tem1 <= `NO;
								control <= `caseNo;
							end
						end
						`BEGI:begin
							if(in == "N" || in == "n")begin
								tem1 <= `BEGIN;
								if(judge == 1'b0)
									stack <= stack + 1;
							end
							else begin
								tem1 <= `NO;
								control <= `caseNo;
							end
						end
						`BEGIN:begin
							if(in != " ")begin
								stack <= stack - 1;
								tem1 <= `NO;
								control <= `caseNo;
							end
						end
						`NO:begin
							tem1 <= `NO;
							control <= `caseNo;
						end
				endcase
			end
			else if (control == `caseEnd)begin
				case(tem2)
					`E:begin
						if(in == "N" || in == "n")begin
							tem2 <= `EN;
						end
						else begin
							tem2 <= `NO;
							control <= `caseNo;
						end
					end
					`EN:begin
						if(in == "D" || in == "d")begin
							tem2 <= `END;
							stack <= stack - 1;
						end
						else begin
							tem2 <= `NO;
							control <= `caseNo;
						end
					end
					`END:begin
						if(in != " ")begin
							stack <= stack + 1;
							tem2 <= `NO;
							control <= `caseNo;
						end
					end
					`NO:begin
						tem2 <= `NO; 
						control <= `caseNo;
					end
				endcase
			end
			else if(control == `caseNo)begin
			
			end
		end
	end

endmodule