module ppu_ioregs (
  input  logic clk,
  input  logic nreset,

  input  logic [15:0] cpu_addr_i,
  output logic [ 7:0] cpu_rdata_o,
  input  logic        cpu_we_i,
  input  logic [ 7:0] cpu_wdata_i,

  output logic        display_enable_o,
  output logic        tilemap_base_sel_o,
  output logic [ 8:0] ly_o,
  output logic [ 7:0] lx_o
);

`define IOREG_DECL(name)    \
  logic [ 7:0] name``_r;    \
  logic [ 7:0] name``_next; \
  logic        name``_we;   \
  logic        name``_sel;

`define IOREG_DEF(name, addr, rstval) \
  always_ff @(posedge clk or negedge nreset) begin \
    if (!nreset) \
      name``_r <= rstval; \
    else if (name``_we) \
      name``_r <= name``_next; \
  end \
  assign name``_sel = (cpu_addr_i == addr); \
  assign name``_we  = name``_sel & cpu_we_i;

typedef struct packed {
  logic lcd_en;
  logic win_tilemap_sel;
  logic win_en;
  logic tiledata_sel;
  logic bg_tilemap_sel;
  logic obj_size;
  logic obj_display;
  logic bgwin_display;
} lcdc_t;

lcdc_t            lcdc;
logic [3:0] [1:0] bgp;

`IOREG_DECL(lcdc);
`IOREG_DECL(ly);
`IOREG_DECL(sy);
`IOREG_DECL(bgp);

`IOREG_DEF    (lcdc, 16'hFF40, '0);
`IOREG_DEF    (  sy, 16'hFF42, '0);
`IOREG_DEF    ( bgp, 16'hFF47, '0);

assign lcdc_next = cpu_wdata_i;
assign   sy_next = cpu_wdata_i;
assign  bgp_next = cpu_wdata_i;

assign lcdc = lcdc_r;
assign bgp  = bgp_r;


assign cpu_rdata_o =
  {8{lcdc_sel}} & lcdc_r |
  {8{  sy_sel}} &   sy_r;

assign display_enable_o = lcdc.lcd_en;

assign tilemap_base_sel_o = lcdc.bg_tilemap_sel;

`ifdef SVA_ENABLE
  logic sva_sel;
  assign sva_sel = lcdc_sel | sy_sel;
`endif /* SVA_ENABLE */

endmodule : ppu_ioregs