`timescale 1ns / 1ps
module top(
		input wire clk, reset,
		input wire [1:0] btn1,
		input wire [1:0] btn2,
		output wire hsync, vsync,
		output wire [2:0] rgb
	);


	// define state
	localparam  [1:0]
	new	 = 2'b00,	// new game
	play	= 2'b01,	// playing
	over	= 2'b10;	// game over

	reg [1:0] state, state_next;
	wire [9:0] pixel_x, pixel_y;
	wire video_on, pixel_tick, graph_on, miss;
	wire [2:0] graph_rgb;
	reg [2:0] rgb_now, rgb_next;
	reg graph_still, timer_start;			// graph_still: graph still
	wire [1:0] btn1_out, btn2_out;
	wire hit_left, hit_right;
	wire [7:0] left_s, right_s;
	wire text_on;
	wire [2:0] text_rgb;
	
	initial begin
		state = 2'b00;		// state: new
		rgb_now = 0;
		graph_still = 1'b1;
	end

	debounce p0(clk, btn1[0], btn1_out[0]);		// debounce for btns
	debounce p1(clk, btn1[1], btn1_out[1]);
	debounce p2(clk, btn2[0], btn2_out[0]);
	debounce p3(clk, btn2[1], btn2_out[1]);

	text_graph text
		(.clk(clk), .left_high(left_s[7:4]), .left_low(left_s[3:0]),
		.right_high(right_s[7:4]), .right_low(right_s[3:0]), .pix_x(pixel_x),
		.pix_y(pixel_y), .text_on(text_on), .text_rgb(text_rgb));
	
	vga_sync vsync_unit
		(.clk(clk), .reset(reset), .hsync(hsync), .vsync(vsync),
		.video_on(video_on), .p_tick(pixel_tick),
		.pixel_x(pixel_x), .pixel_y(pixel_y));

	pong_graph graph_unit
	  (.clk(clk), .reset(reset), .btn1(btn1_out), .btn2(btn2_out),
	   .pix_x(pixel_x), .pix_y(pixel_y),
	   .graph_still(graph_still), .miss(miss),.hit_left(hit_left),.hit_right(hit_right),
	   .graph_on(graph_on), .graph_rgb(graph_rgb), .left_score(left_s),.right_score(right_s));


	always @(posedge clk)
	begin
		if (reset)
			begin
				state <= new;
				rgb_now <= 0;
			end
		else
			begin
				state <= state_next;
				if (pixel_tick)
					rgb_now <= rgb_next;
			end
	end

	always @*
	begin
		graph_still = 1'b1;
		state_next = state;
		case (state)
			new:
				begin
					// any button pressed the game start
					if ((btn1_out != 2'b00) || (btn2_out != 2'b00))
					begin
						state_next = play;
					end
				end
			play:
				begin
					graph_still = 1'b0;
					// if any ball is missed, your game is over.
					if (miss)
					begin
						state_next = over;
					end
				end
			over:
				begin
					// may add more features here
					state_next = new;
				end
		endcase
	end

	always @*
	begin
		if (~video_on)
			rgb_next = "000"; // blank the edge/retrace
		else
			// the priority is defined here
			if(graph_on)
			   rgb_next = graph_rgb;
			else if (text_on)  // display graph
				rgb_next = text_rgb;
			else 
				rgb_next = 3'b110; // yellow background
	end

	assign rgb = rgb_now;	// assign rgb register to output

endmodule