`timescale 1ns / 1ps


module bullet_control(
    input clk,
    input reset_n,
    input start,

    input [10:0] tank_H,
    input [10:0] tank_V,
    input tank_en,
    input [1:0] tank_dir,
    input tank_fire,
    input [10:0] vgaH,
    input [10:0] vgaV,
    input ready,
    
    output [11:0] bulletData,
    output reg [10:0] bullet_H_feedback,
    output reg [10:0] bullet_V_feedback,
    output reg [2:0] bullet_direction
    );

    parameter BULLET_LONGER = 10;
    parameter BULLET_SHORTER = 5;
    parameter BULLET_LONGER_CENTER = 5;
    parameter BULLET_SHORTER_CENTER = 2;
    parameter HEIGHT = 480;
    parameter WIDTH = 640;
    parameter TANK_V_CENTER = 16;
    parameter TANK_H_CENTER = 16;
    parameter TANK_HEIGHT = 32, TANK_WIDTH = 32;

    localparam 
        UP = 3'd0,
        DOWN = 3'd1,
        LEFT = 3'd2,
        RIGHT = 3'd3,
        WAIT = 3'd4,
        READY = 3'd5;

    reg counter_en;
    reg [31:0] counter;
    reg [2:0] current_state, next_state;

    always @(posedge clk) begin:state_flip_flop
        if(!reset_n) current_state <= WAIT;
//        else if(!tank_en) current_state <= WAIT;
        else current_state <= next_state;
    end

    always @(*) begin: state_table
        case(current_state)
            WAIT: next_state = start ? READY : WAIT;
            READY: begin
                if(!tank_fire)
                    next_state = READY;
                else begin
                    case(tank_dir)
                        2'b00: next_state = UP;
                        2'b01: next_state = DOWN;
                        2'b10: next_state = LEFT;
                        2'b11: next_state = RIGHT;
                    endcase
                end
            end
            UP: next_state = ready ? READY : UP;
            DOWN: next_state = ready ? READY : DOWN;
            LEFT: next_state = ready ? READY : LEFT;
            RIGHT: next_state = ready ? READY : RIGHT;
            default: next_state = READY;
        endcase
    end

    always @(*) begin: bullet_logic
        counter_en = 0;
        bullet_direction = 3'b111;
        case(current_state)
            READY: begin
                counter_en = 0;
                bullet_direction = 3'b111;
            end
            UP: begin
                counter_en = 1;
                bullet_direction = 3'b000;
            end
            DOWN: begin
                counter_en = 1;
                bullet_direction = 3'b001;
            end
            LEFT: begin
                counter_en = 1;
                bullet_direction = 3'b010;
            end
            RIGHT: begin
                counter_en = 1;
                bullet_direction = 3'b011;
            end
        endcase
    end

    reg bullet_move_en;
    always @(posedge clk) begin: counter_logic
        if(!reset_n) begin
            counter <= 0;
            bullet_move_en <= 0;
        end
        else if(counter == 1_000_000) begin
            counter <= 0;
            bullet_move_en <= 1;
        end
        else if(counter_en == 0) begin
            counter <= 0;
            bullet_move_en <= 0;
        end
        else begin
            counter <= counter + 1;
            bullet_move_en <= 0;
        end
    end

    always @(posedge clk) begin: bullet_move
        if(bullet_direction[2]) begin   //if no direction
            case(tank_dir)
            2'b00: begin
                bullet_H_feedback <= tank_H + TANK_H_CENTER - BULLET_SHORTER_CENTER;
                bullet_V_feedback <= ( (tank_V >= BULLET_LONGER) ? (tank_V - BULLET_LONGER) : 0);
            end
            2'b01: begin
                bullet_H_feedback <= tank_H + TANK_H_CENTER - BULLET_SHORTER_CENTER;
                bullet_V_feedback <= ( (tank_V + TANK_HEIGHT + BULLET_LONGER <= HEIGHT) ? (tank_V + TANK_HEIGHT + BULLET_LONGER) : HEIGHT);
            end
            2'b10: begin
                bullet_H_feedback <= ( (tank_H >= BULLET_LONGER) ? (tank_H - BULLET_LONGER) : 0);
                bullet_V_feedback <= tank_V + TANK_V_CENTER - BULLET_SHORTER_CENTER;
            end
            2'b11: begin
                bullet_H_feedback <= ( (tank_H + BULLET_LONGER + TANK_WIDTH <= WIDTH) ? (tank_H + BULLET_LONGER + TANK_WIDTH) : WIDTH ) ;
                bullet_V_feedback <= tank_V + TANK_V_CENTER - BULLET_SHORTER_CENTER;
            end
            endcase
        end 
        else if(bullet_move_en) begin
            case(bullet_direction[1:0])
                2'b00:begin
                    bullet_V_feedback <= bullet_V_feedback - 1;
                    bullet_H_feedback <= bullet_H_feedback;
                end
                    
                2'b01: begin
                    bullet_V_feedback <= bullet_V_feedback + 1;
                    bullet_H_feedback <= bullet_H_feedback;
                end
                2'b10: begin
                    bullet_H_feedback <= bullet_H_feedback - 1;
                    bullet_V_feedback <= bullet_V_feedback;
                end
                2'b11: begin
                    bullet_H_feedback <= bullet_H_feedback + 1;
                    bullet_V_feedback <= bullet_V_feedback; 
                end
            endcase
        end
        else begin
            bullet_H_feedback <= bullet_H_feedback;
            bullet_V_feedback <= bullet_V_feedback;
        end
    end

    wire [11:0] UP_data, DOWN_data, LEFT_data, RIGHT_data;
    wire [7:0] bulletAddr;
    reg bullet_bound;

    always @(*) begin
        case(bullet_direction[1:0])
            2'b00: begin
                bullet_bound <= (bullet_H_feedback <= vgaH && bullet_H_feedback > vgaH - BULLET_SHORTER && bullet_V_feedback <= vgaV && bullet_V_feedback > vgaV - BULLET_LONGER) ? 1 : 0;
            end
            2'b01: begin
                bullet_bound <= (bullet_H_feedback <= vgaH && bullet_H_feedback > vgaH - BULLET_SHORTER && bullet_V_feedback <= vgaV && bullet_V_feedback > vgaV - BULLET_LONGER) ? 1 : 0;
            end
            2'b10: begin
                bullet_bound <= (bullet_H_feedback <= vgaH && bullet_H_feedback > vgaH - BULLET_LONGER && bullet_V_feedback > vgaV - BULLET_SHORTER) ? 1 : 0;
            end
            2'b11: begin
               bullet_bound <= (bullet_H_feedback <= vgaH && bullet_H_feedback > vgaH - BULLET_LONGER && bullet_V_feedback <= vgaV && bullet_V_feedback > vgaV - BULLET_SHORTER) ? 1 : 0;
            end 
        endcase
    end
    reg [5:0] bullet_addr;
    always @(*) begin
        case(bullet_direction[1:0])
            2'b00: begin
                bullet_addr <= bullet_bound ? ( (vgaV - bullet_V_feedback) * BULLET_SHORTER + (vgaH - bullet_H_feedback) ) : 15;
            end 
            2'b01: begin
                bullet_addr <= bullet_bound ? ( (vgaV - bullet_V_feedback) * BULLET_SHORTER + (vgaH - bullet_H_feedback) ) : 15;
            end
            2'b10: begin
                bullet_addr <= bullet_bound ? ( (vgaV - bullet_V_feedback) * BULLET_LONGER + (vgaH - bullet_H_feedback) ) : 15;
            end
            2'b11: begin
                bullet_addr <= bullet_bound ? ( (vgaV - bullet_V_feedback) * BULLET_LONGER + (vgaH - bullet_H_feedback) ): 15;
            end
        endcase

    end

    wire [11:0] outData;

    bullet_left_img left(.addra(bullet_addr), .clka(clk), .douta(LEFT_data), .ena(1'b1));
    bullet_right_img right(.addra(bullet_addr), .clka(clk), .douta(RIGHT_data), .ena(1'b1));
    bullet_up_img up(.addra(bullet_addr), .clka(clk), .douta(UP_data), .ena(1'b1));
    bullet_down_img down(.addra(bullet_addr), .clka(clk), .douta(DOWN_data), .ena(1'b1));

    tank_data_selector bullet_selector(.clk(clk), .UP(UP_data), .DOWN(DOWN_data), .LEFT(LEFT_data), 
                            .RIGHT(RIGHT_data), .Dir(bullet_dir_feedback), .tankData(outData));
    
    assign bulletData = (~ready & bullet_bound) ? outData : 0;

endmodule