#generate 16-bit code
.code16

#hint the assembler that here is the executable code located
.text
.globl _start;
#boot code entry
_start:
  jmp _boot
start: .asciz "Start.\n\r"
error: .asciz "Error.\n\r"
succes: .asciz "Succes.\n\r"
ffs: .asciz "F.\n\r"
end: .asciz "End.\n\r"
derpy2str: .asciz "This is from derpy2.\n\r"
cookies: .word derpy2

.macro mWriteString str              #macro which calls a function to print a string
  leaw  \str, %si
  call .writeStringIn
.endm

# function to print the string
.writeStringIn:
    lodsb
    orb  %al, %al
    jz   .writeStringOut
    movb $0x0e, %ah
    int  $0x10
    jmp  .writeStringIn
  .writeStringOut:
ret
  

_boot:
  mWriteString start
  
  movb $0x0e, %ah
  movb $'X', %al
  int $0x10
  
  movb $'\n', %al
  int $0x10
  
  movb $'\r', %al
  int $0x10
  
  lgdt gdtdesc
  
  #movb $42, %bl #NOT 'A'
  #movb %bl, 0x512
  
  #This goes first as to now overwrite %ah and %al.
  mov $0x00, %ax
  #mov $0x08, %ax
  mov %ax, %es #Section to write into
  
  mov $0x02, %ah # Read sectors from drive
  mov $0x01, %al # Number of sectors to read
  mov $0x00, %ch # Low 8 bits of cylinder
  mov $0x02, %cl # First sector to read (bits 0-5), upper bits of cylinder (bits 6-7)
  mov $0x00, %dh # Head number
  mov $0x00, %dl # Drive number
#  mov $0x00, %es
  #mov $0x7e00, %bx #Offset into section
  mov $(_start+0x200), %bx #Offset into section
  #mov $0x0, %bx #Offset into section
  int $0x13 # Low level disk services
  
  jnc notcarry
  #mWriteString error
  jmp endcarrycheck
  
  notcarry:
  #mWriteString succes
  
  #mov $0x7000, %ax
  #movb (%ax), %bl
  #movb %bl, ffs
  #movb 0x7000, %bl
  #movb %bl, ffs
  #mWriteString ffs
  #fallthrough
  
  endcarrycheck:
  
  #mWriteString mystr-block2_offset
  #mWriteString 0x513
  #mWriteString mystr
  
  #ljmp $0x0, $derpy
  #.byte 0, 0, 0, 0, 0, 0, 0, 0
  #ljmp $0x00, $0x7e00
  #ljmp $0x00, $derpy2
  ljmp $0x00, $code
  
#  movw $derpy, %ax
#  
#  cmp $0x7e00, %ax
#  je equal
#  mWriteString error
#  jmp after
#  
#  equal:
#  mWriteString succes
#  
#  after:
  /*
  movb $0x0e, %ah
  
  movw $derpy, %cx
  
  movb 0x0e, %ah
  movb $'I', %al
  int $0x10
  movb 0x0e, %ah
  movb $'J', %al
  int $0x10
  */
  
  #movw $0x7E00, %cx
  movw $derpy2, %cx
  
  movb $0x0e, %ah
  #movb $'Y', %al
  movb %ch, %al
  #movb $'H', %al
  #movb $0x7E, %al
  int $0x10
  
  movb $0x0e, %ah
  #movb $'Z', %al
  movb %cl, %al
  #add $0x7E, %al
  #sub $0x50, %al
  #movb $0x3C, %al
  int $0x10
  
  movb $0x0e, %ah
  movb $'\n', %al
  int $0x10
  
  movb $0x0e, %ah
  movb $'\r', %al
  int $0x10
  
  
  #mWriteString mystr
  
  #jmp derpy
  derpyret:
  
  mWriteString end
  
  #jmp 0x7008
  #endend:
  #mWriteString end
  
  cli
  hlt
  
  #

derpy:
  mWriteString ffs
  ljmp $0x00, $derpyret
  #jmp derpyret

.p2align	2	/* force 4-byte alignment */
gdt:
  .word	0, 0
  .byte	0, 0, 0, 0
  
  /* code segment */
  .word	0xFFFF, 0
  .byte	0, 0x9A, 0xCF, 0
  
  /* data segment */
  .word	0xFFFF, 0
  .byte	0, 0x92, 0xCF, 0
  
  /* 16 bit real mode CS */
  .word	0xFFFF, 0
  .byte	0, 0x9E, 0, 0
  
  /* 16 bit real mode DS */
  .word	0xFFFF, 0
  .byte	0, 0x92, 0, 0

/* this is the GDT descriptor */
gdtdesc:
  .word	0x27			/* limit */
  .long	gdt			/* addr */

#move to 510th byte from the start and append boot signature
. = _start + 510
.byte 0x55
.byte 0xaa
#block2_offset:
.byte 'A' #Byte 513
#mystr: .asciz "asdf\n\r"

#derpderp:
#  mwriteString 0x7001
#  jmp endend

derpy2:
  mWriteString derpy2str
  ljmp $0x00, $derpyret

code:
  mWriteString derpy2str
  movb $0x0e, %ah
  movb $'C', %al
  int $0x10
  movb $0x0e, %ah
  movb $'\n', %al
  int $0x10
  movb $0x0e, %ah
  movb $'\r', %al
  int $0x10
  ljmp $0x00, $derpyret

. = _start + 1021
.byte 0x00

.word derpy2