/* Bart's Drive Operating System(BDOS)
 * A relatively simple OS that allows for some basic features including:
 * - Running a single user program with full hardware control
 * - Some system calls
 * - A basic shell
 * - Network loaders for sending data and controlling the FPGC
 * - HID fifo including USB keyboard driver
 * - BRFS Filesystem
 */

/* List of reserved stuff:
- Timer2 is used for USB keyboard polling, even when a user program is running
- Socket 7 is used for netHID
*/

/*
 * Defines (also might be used by included libraries below)
 */

// As of writing, BCC assigns 4 memory addresses to ints, so we should use chars instead
// However, this is confusing, so we typedef it to word, since that is what it basically is
#define word char

#define SYSCALL_RETVAL_ADDR 0x200000  // Address for system call communication with user program
#define TEMP_ADDR 0x220000            // Address for (potentially) large temporary outputs/buffers
#define RUN_ADDR 0x400000             // Address of loaded user program

#define NETWORK_LOCAL_IP 213          // local IP address (last byte)

#define MAX_PATH_LENGTH 127           // Max length of a file path
#define BDOS_DEFAULT_BLOCKS 1024      // Default number of blocks for the BRFS filesystem
#define BDOS_DEFAULT_BLOCK_SIZE 128   // Default number of words per block for the BRFS filesystem

// Interrupt IDs for interrupt handler
#define INTID_TIMER1 0x1
#define INTID_TIMER2 0x2
#define INTID_UART0 0x3
#define INTID_GPU 0x4
#define INTID_TIMER3 0x5
#define INTID_PS2 0x6
#define INTID_UART1 0x7
#define INTID_UART2 0x8

// System call IDs
#define SYSCALL_FIFO_AVAILABLE 1
#define SYSCALL_FIFO_READ 2
#define SYSCALL_PRINT_C_CONSOLE 3
#define SYSCALL_GET_ARGS 4       // Get arguments for executed program
#define SYSCALL_GET_PATH 5       // Get OS path
#define SYSCALL_GET_USB_KB_BUF 6 // Get the 8 bytes of the USB keyboard buffer

/*
 * Global vars (also might be used by included libraries below)
 */

// Flag that indicates whether a user program is running
word bdos_userprogram_running = 0;

/*
 * Included libraries
 */

// Data includes
#include "data/ASCII_BW.c"
#include "data/PS2SCANCODES.c"
#include "data/USBSCANCODES.c"

// Code includes
#include "lib/stdlib.c"
#include "lib/math.c"
#include "lib/gfx.c"
#include "lib/hidfifo.c"
#include "lib/ps2.c"
#include "lib/brfs.c"
#include "lib/shell.c"
#include "lib/usbkeyboard.c"
#include "lib/wiz5500.c"
#include "lib/netloader.c"
#include "lib/nethid.c"
#include "lib/spiflash.c"


/*
 * Functions
 */

/**
 * Initialize the BRFS filesystem
 * Returns 1 if successful, 0 if not
 */
word bdos_init_brfs()
{
  // Initialize the SPI flash
  spiflash_init();

  // Try to read the filesystem from the SPI flash
  GFX_PrintConsole("Reading BRFS from SPI flash...\n");
  if (brfs_read_from_flash())
  {
    GFX_PrintConsole("BRFS read from flash\n");
  }
  else
  {
    GFX_PrintConsole("Could not read BRFS from flash!\n");
    return 0;
  }

  return 1;
}

// Clears all VRAM
//  and copies the default ASCII pattern table and palette table
// also resets the cursor
void bdos_init_vram()
{
  GFX_initVram();
  GFX_copyPaletteTable((word)DATA_PALETTE_DEFAULT);
  GFX_copyPatternTable((word)DATA_ASCII_DEFAULT);
  GFX_cursor = 0;
}

// Initialize the W5500
void bdos_init_network()
{
  word ip_addr[4] = {192, 168, 0, NETWORK_LOCAL_IP};

  word gateway_addr[4] = {192, 168, 0, 1};

  word mac_addr[6] = {0xDE, 0xAD, 0xBE, 0xEF, 0x24, 0x64};

  word sub_mask[4] = {255, 255, 255, 0};

  wiz_Init(ip_addr, gateway_addr, mac_addr, sub_mask);
}


// Restores certain things when returning from a user program
void bdos_restore()
{
  // restore graphics (trying to keep text in window plane)
  GFX_copyPaletteTable((word)DATA_PALETTE_DEFAULT);
  GFX_copyPatternTable((word)DATA_ASCII_DEFAULT);
  GFX_clearBGtileTable();
  GFX_clearBGpaletteTable();
  GFX_clearWindowpaletteTable();
  GFX_clearSprites();

  // restore netloader
  NETLOADER_init(NETLOADER_SOCKET);
}

// Main BDOS code
int main()
{
  uprintln("BDOS_INIT");

  bdos_userprogram_running = 0; // Indicate that no user program is running

  bdos_init_vram();
  GFX_PrintConsole("VRAM initialized\n"); // Print to console now VRAM is initialized
  GFX_PrintConsole("Starting BDOS\n");

  GFX_PrintConsole("Initalizing network\n");
  bdos_init_network();

  GFX_PrintConsole("Initalizing netloader\n");
  NETLOADER_init(NETLOADER_SOCKET);

  GFX_PrintConsole("Initalizing netHID\n");
  NETHID_init(NETHID_SOCKET);

  GFX_PrintConsole("Initalizing USB keyboard\n");
  USBkeyboard_init();

  GFX_PrintConsole("Initalizing filesystem\n");
  if (!bdos_init_brfs())
  {
    GFX_PrintConsole("Error initializing FS\n");
    return 0;
  }

  GFX_PrintConsole("Initalizing shell\n");
  shell_init();

  // Main loop
  while (1)
  {
    shell_loop();                     // Update shell state
    NETLOADER_loop(NETLOADER_SOCKET); // Update netloader state
  }

  return 1;
}

// System call handler
// Returns at the same address it reads the command from
void syscall()
{
  word *p = (word *)SYSCALL_RETVAL_ADDR;
  word ID = p[0];

  switch (ID)
  {
  case SYSCALL_FIFO_AVAILABLE:
    p[0] = HID_FifoAvailable();
    break;
  case SYSCALL_FIFO_READ:
    p[0] = HID_FifoRead();
    break;
  case SYSCALL_PRINT_C_CONSOLE:
    GFX_PrintcConsole(p[1]);
    p[0] = 0;
    break;
  case SYSCALL_GET_ARGS:
    p[0] = 0; // TODO: implement
    break;
  case SYSCALL_GET_PATH:
    p[0] = 0; // TODO: implement
    break;
  case SYSCALL_GET_USB_KB_BUF:
    p[0] = USBkeyboard_buffer_parsed;
    break;
  default:
    p[0] = 0;
    break;
  }
}

// Interrupt handler
void interrupt()
{
  // Handle BDOS interrupts
  int i = getIntID();
  switch (i)
  {
  case INTID_TIMER1:
    timer1Value = 1; // Notify ending of timer1
    break;

  case INTID_TIMER2:
    USBkeyboard_HandleInterrupt(); // Handle USB keyboard interrupt
    break;

  case INTID_UART0:
    break;

  case INTID_GPU:
    if (NETHID_isInitialized == 1)
    {
      // Check using CS if we are not interrupting any critical access to the W5500
      word *spi3ChipSelect = (word *)0xC02732; // TODO: use a define for this address
      if (*spi3ChipSelect == 1)
      {
        NETHID_loop(NETHID_SOCKET); // Look for an input sent to netHID
      }
    }
    break;

  case INTID_TIMER3:
    break;

  case INTID_PS2:
    PS2_HandleInterrupt(); // Handle PS2 interrupt
    break;

  case INTID_UART1:
    break;

  case INTID_UART2:
    break;
  }

  // Handle user program interrupts
  if (bdos_userprogram_running)
  {
    // Call interrupt() of user program
    asm(
        "; backup registers\n"
        "push r1\n"
        "push r2\n"
        "push r3\n"
        "push r4\n"
        "push r5\n"
        "push r6\n"
        "push r7\n"
        "push r8\n"
        "push r9\n"
        "push r10\n"
        "push r11\n"
        "push r12\n"
        "push r13\n"
        "push r14\n"
        "push r15\n"

        "savpc r1\n"
        "push r1\n"
        "jump 0x400001\n"

        "; restore registers\n"
        "pop r15\n"
        "pop r14\n"
        "pop r13\n"
        "pop r12\n"
        "pop r11\n"
        "pop r10\n"
        "pop r9\n"
        "pop r8\n"
        "pop r7\n"
        "pop r6\n"
        "pop r5\n"
        "pop r4\n"
        "pop r3\n"
        "pop r2\n"
        "pop r1\n");
    return;
  }
  else
  {
    // Code to only run when not running a user program
  }
}