#include <string.h>
#include <vga/vga.h>

#include <tty.h>

static size_t terminal_row;
static size_t terminal_column;
static uint8_t terminal_color;
static uint16_t* terminal_buffer;

void terminal_initialize(void)
{
  terminal_initializec(0x00);
}

void terminal_initializec(uint8_t color)
{
  terminal_row = 0;
  terminal_column = 0;
  
  if (color == 0x00)
  {
    terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
  }
  else {
    terminal_color = color;
  }
  
  terminal_buffer = VGA_MEMORY;
  for (size_t y = 0; y < VGA_HEIGHT; y++)
  {
    for (size_t x = 0; x < VGA_WIDTH; x++)
    {
      const size_t index = y * VGA_WIDTH + x;
      terminal_buffer[index] = vga_entry(' ', terminal_color);
    }
  }
}

void terminal_setcolor(uint8_t color)
{
  terminal_color = color;
}

uint8_t terminal_getcolor(void)
{
  return terminal_color;
}

void terminal_putentryat(unsigned char c, uint8_t color, size_t x, size_t y)
{
  const size_t index = y * VGA_WIDTH + x;
  terminal_buffer[index] = vga_entry(c, color);
}

void terminal_putchar(const char c)
{
  unsigned char uc = c;
  
  if (uc == '\n')
  {
    terminal_column = 0;
    if (++terminal_row == VGA_HEIGHT)
    {
      terminal_scroll();
      terminal_row = VGA_HEIGHT - 1;
    }
    return;
  }
  else if (uc == '\t')
  {
    terminal_column += 4;
    
    if (terminal_column >= VGA_WIDTH)
    {
      terminal_putchar('\n');
    }
    
    return;
  }
  else if (uc == '\b')
  {
    if (terminal_column == 0)
    {
      terminal_row -= 1;
      
      if (terminal_row == (size_t)-1)
      {
        terminal_row = 0;
      }
      
      terminal_column = VGA_WIDTH;
      
      terminal_putentryat(' ', terminal_getcolor(), (size_t)terminal_column, (size_t)terminal_row);
    }
    else
    {
      terminal_putentryat(' ', terminal_getcolor(), (size_t)--terminal_column, (size_t)terminal_row);
    }

    return;
  }
	
  terminal_putentryat(uc, terminal_color, terminal_column, terminal_row);
  
  
  if (++terminal_column == VGA_WIDTH)
  {
    terminal_column = 0;
    if (++terminal_row == VGA_HEIGHT)
    {
      terminal_scroll();
      terminal_row = VGA_HEIGHT - 1;
    }
  }
}

void terminal_write(const char* data, size_t size)
{
  for (size_t i = 0; i < size; i++)
  {
    terminal_putchar(data[i]);
  }
}

void terminal_writestring(const char* data)
{
  terminal_write(data, strlen(data));
}

void terminal_debug_writestring(const char* data)
{
  terminal_writestring("[ DEBUG ] ");
  terminal_writestring(data);
}

void terminal_writeline(const char* data)
{
  terminal_column = 0;
  terminal_writestring(data);
}

void terminal_writechar_r(const char ch)
{
  unsigned char uch = ch;

  for (size_t i = 0; i < VGA_WIDTH; i++)
  {
    terminal_putchar(uch);
  }
}

void terminal_clear(void)
{
  terminal_clearl(-1);
}

void terminal_clearl(size_t num_lines)
{
  if (num_lines == (size_t)-1)
  {
    terminal_initializec(terminal_getcolor());
  }
  else
  {
    /* XXX note to self: VGA_HEIGHT is 25, and VGA_WIDTH is 80 XXX */
    /* static size_t terminal_row; static size_t terminal_column; */
    
    terminal_row = VGA_HEIGHT;
    terminal_column = 0;
    
    while (terminal_row < num_lines)
    {
      for (int32_t k = 0; k < (int32_t)VGA_WIDTH; k++)
      {
        terminal_putentryat((unsigned char)' ', terminal_getcolor(), (size_t)terminal_row, (size_t)k);
      }
      terminal_row -= 1;
    }
  }
}

void terminal_scroll(void)
{
  for (size_t y = 1; y < VGA_HEIGHT; y++)
  {
    for (size_t x = 0; x < VGA_WIDTH; x++)
    {
      const size_t src_index = y * VGA_WIDTH + x;
      const size_t dst_index = (y - 1) * VGA_WIDTH + x;
      terminal_buffer[dst_index] = terminal_buffer[src_index];
    }
  }

  for (size_t x = 0; x < VGA_WIDTH; x++)
  {
    const size_t index = (VGA_HEIGHT - 1) * VGA_WIDTH + x;
    terminal_buffer[index] = (terminal_color << 8) | ' ';
  }
}

unsigned char terminal_get_shifted(unsigned char uc)
{
  unsigned char lowerc[] = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '\0' };
  unsigned char upperc[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '\0' };
  unsigned char nums[]   = { '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '\0' };
  unsigned char nsyms[]  = { '!', '@', '#', '$', '%', '^', '&', '*', '(', ')', '\0' };
  unsigned char syms1[]  = { ',', '.', '/', ';', '\'', '[', ']', '`', '-', '=', '\\', '\0' };
  unsigned char syms2[]  = { '<', '>', '?', ':', '\"', '{', '}', '~', '_', '+', '|', '\0' };
  
  for (int32_t i = 0; i < (int32_t)(strlen((char*)lowerc)); ++i)
  {
    if (uc == lowerc[i])
    {
      return upperc[i];
    }
    else if (uc == upperc[i])
    {
      return lowerc[i];
    }
  }
  
  for (int32_t i = 0; i < (int32_t)(strlen((char*)nums)); ++i)
  {
    if (uc == nums[i])
    {
      return nsyms[i];
    }
    else if (uc == nsyms[i])
    {
      return nums[i];
    }
  }
  
  for (int32_t i = 0; i < (int32_t)(strlen((char*)syms1)); ++i)
  {
    if (uc == syms1[i])
    {
      return syms2[i];
    }
    else if (uc == syms2[i])
    {
      return syms1[i];
    }
  }
  
  return '\0';
}