#pragma once

#include <stdint.h>

// The channel takes the lower 4 bits; the data pointer the upper 28. So a mail
// must be aligned to a 16-byte boundary.
#define MAIL_ALIGN 16

enum
{
  PROPERTY_CHANNEL = 8,
};

enum
{
  MAILBOX_REQUEST  = 0,
  MAILBOX_RESPONSE = 1,
};

enum
{
  MAILBOX_DELIVERY_ERROR = 0,
  MAILBOX_ERROR          = 0x80000001,
  MAILBOX_SUCCESS        = 0x80000000,
};

enum
{
  TAG_END                                  = 0,
  TAG_FRAMEBUFFER_ALLOCATE                 = 0x00040001,
  TAG_FRAMEBUFFER_RELEASE                  = 0x00048001,
  TAG_FRAMEBUFFER_SET_PHYSICAL_SCREEN_SIZE = 0x00048003,
  TAG_FRAMEBUFFER_SET_VIRTUAL_SCREEN_SIZE  = 0x00048004,
  TAG_FRAMEBUFFER_SET_DEPTH                = 0x00048005,
};

typedef struct Tag {
  union {
    uint32_t all;
    struct {
      uint16_t command : 12; // Command.
      uint8_t  type    :  4; // Command type.
      uint8_t  device  :  4; // Hardware device.
      uint16_t zeroes  : 12; // Reserved.
    } id;
  };
  uint32_t size;    // Buffer size.
  uint32_t code;    // Request/response code.
  uint32_t data[];  // Buffer data.
} Tag;

typedef struct __attribute__((aligned(MAIL_ALIGN))) Mail {
  uint32_t size;    // Buffer size.
  uint32_t code;    // Request/response code.
  Tag      tags[];  // Variable quantity.
} Mail;

#define MAIL_SIZE(TYPE) (sizeof(TYPE) + (2 * sizeof(uint32_t)))

void        mbox_init();
const Mail* mbox_read(uint8_t channel);
void        mbox_write(uint8_t channel, volatile const void* mail);