LOAD_ADDR equ 0x00010000 ; address this program is loaded at

TOKEN_TABLE_ADDR equ 0x00060000 ; address the token table is loaded at
TOKEN_TABLE_SIZE equ 0x1000     ; max length of table

TEST_ARENA_ADDR equ 0x00060000 ; address to run tests at
TEST_ARENA_SIZE equ 0x1000     ; maximum size tests can use

OUTPUT_ADDR equ 0x00070000 ; address of outputed binary
OUTPUT_SIZE equ 0x1000     ; max length of outputed binary

[bits 64]
[org LOAD_ADDR]

start:
  mov rsi, msg_welcome
  call print

  call run_tests

  jmp halt

;
; tokenising
;

; copy_token 
;
; description:
; copies a token from one spot in memory to another
; and returns metadata about that token
;
; parameters:
; rdi -> start of asm command to be read
; rsi -> start of buffer to be written
;
; returned:
copy_token:
  mov rax, rdi
  .loop:
    cmp al, " "
    je .continue
    jne .break
    .continue:
      call copy_byte
  .break:
    inc rax
  ret
    
; copy_byte
;
; description:
; copies a byte from one spot in memory to another
;
; parameters:
; rdi -> word to be read
; rsi -> word to be written
;
; returned:
; al = byte that was read
copy_byte:
  mov al, [rdi]
  mov [rsi], al
  ret

; 
; utilities
; 

; print
;
; description:
; prints a null-terminated string
;
; parameters:
; rsi -> start of null-terminated string
; dx = port to output to
print:
  .loop:
    mov al, [rsi]
    test al, al
    jz .done
    out dx, al
    inc rsi
    jmp .loop
  .done:
    ret

; halt
;
; description:
; halts the program, silly :)
halt:
  mov rsi, msg_halt
  call print
  hlt
  jmp halt

;
; tests
;

; run_tests
;
; description:
; runs all tests
;
; parameters:
; dx = port to output to
run_tests:
  mov rsi, .msg
  call print

  call test_copy_byte

  ret
  .msg db "running test suite...", 0x0D, 0x0A, 0x00

; test_copy_byte
;
; description:
; makes sure copy_byte function works by testing the following
; - that it copies one byte to a specified memory address
; - that it returns the copied byte in al
;
; parameters:
; dx = port to output to
test_copy_byte:
  mov rsi, .msg
  call print

  mov rdi, test_byte       ; byte to be copied
  mov rsi, TEST_ARENA_ADDR ; location of test
  call copy_byte

  mov cx, [rsi]
  cmp ax, cx ; compare returned byte to copied byte
  jne .fail
  je .pass

  .pass:
    mov rsi, msg_pass
    call print
    ret
  .fail:
    mov rsi, msg_fail
    call print
    ret
  .msg db "test_copy_byte...", 0x00

;
; data
;

msg_welcome db "Welcome to Twasm", 0x0D, 0x0A, 0x00
msg_halt db "halted.", 0x0D, 0x0A, 0x00
msg_pass db "passed.", 0x0D, 0x0A, 0x00
msg_fail db "failed.", 0x0D, 0x0A, 0x00

test_byte db "T"
test_token db "Test Token" ; two tokens, one followed by a space and one by nothing