alcedo/kernel/arch/i386/tty.nim

import vga

const
  vgaWidth = 80
  vgaHeight = 25
  terminalBufferBaseAddress = 0xB8000
  bufferWidthSkip = vgaWidth * 2

var
  terminalRow, terminalColumn = 0
  terminalColour: int

proc terminalWriteAtPoint(writeChar: char, colour: int, xPos: int, yPos: int) =
  let index = terminalBufferBaseAddress + (yPos * bufferWidthSkip + (xPos * 2))
  cast[ptr int16](index)[] = vga.vgaEntry(writeChar, terminalColour) # Write directly to display memory

proc terminalInitialize*() =
  terminalColour = vgaEntryColour(VGA_Colour.lightGreen, VGA_Colour.red)
  for x in 0..<vgaWidth:
    for y in 0..<vgaHeight:
      terminalWriteAtPoint(' ', terminalColour, x, y)

proc setTerminalColour(newColour: int) =
  terminalColour = newColour

proc terminalWriteChar(writeChar: char) =
  if(writeChar == '\L'):
    inc(terminalRow)
    terminalColumn = 0
    if(terminalRow == vgaHeight): terminalRow = 0
    return
  terminalWriteAtPoint(writeChar, terminalColour, terminalColumn, terminalRow)
  inc(terminalColumn)
  if(terminalColumn == vgaWidth):
    terminalColumn = 0
    inc(terminalRow)
    if(terminalRow == vgaHeight): terminalRow = 0

proc terminalWrite*(data: string) =
  for character in data:
    terminalWriteChar(character)