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
;
; parameters:
; rdi -> start of buffer to be read
; rsi -> start of buffer to be written
;
; returned:
; rax -> last byte read
; rdx -> last byte written
; ------------------------------------------------------------------------------

copy_token:
  .loop:
    mov al, [rdi] ; check if next char is a space
    cmp al, " "
    je .break

    call copy_byte ; copy the next byte if not

    inc rdi ; increment read- and write-pointers
    inc rsi
    jmp .loop ; and loop again

  .break:
    mov rax, rdi ; return values
    mov rdx, rsi
    ret
  .msg db "yo loop copy_token", 0x0D, 0x0A, 0x00
    
; ------------------------------------------------------------------------------
; 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:
; rax = byte that was read
; ------------------------------------------------------------------------------

copy_byte:
  xor rax, rax ; zero out so it returns fine
  mov al, [rdi]
  mov [rsi], al
  ret

; ------------------------------------------------------------------------------
; utilities
; ------------------------------------------------------------------------------

; ------------------------------------------------------------------------------
; print
;
; description:
; prints a null-terminated string
;
; parameters:
; rsi -> start of null-terminated string
; ------------------------------------------------------------------------------

print:
  push rdx
  mov rdx, 0x3F8
  .loop:
    mov al, [rsi]
    test al, al
    jz .done
    out dx, al
    inc rsi
    jmp .loop
  .done:
    pop rdx
    ret

; ------------------------------------------------------------------------------
; halt
;
; description:
; halts the program, silly :)
; ------------------------------------------------------------------------------

halt:
  mov rsi, msg_halt
  call print
  hlt
  jmp halt

; ------------------------------------------------------------------------------
; tests
; ------------------------------------------------------------------------------

; ------------------------------------------------------------------------------
; run_tests
;
; description:
; runs all tests
; ------------------------------------------------------------------------------

run_tests:
  mov rsi, .msg
  call print

  call test_copy_byte
  call test_copy_token

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

; ------------------------------------------------------------------------------
; test_copy_byte
;
; description:
; tests copy_byte's described functionality
; ------------------------------------------------------------------------------

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]
  and ax, 0xFF ; only compare bottom byte
  and cx, 0xFF
  cmp ax, cx ; compare returned byte to copied byte
  jne .fail
  cmp al, [test_byte] ; compare returned byte to expected byte
  jne .fail

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

; ------------------------------------------------------------------------------
; test_copy_token
;
; description:
; tests copy_token described functionality
; ------------------------------------------------------------------------------

test_copy_token:
  mov rsi, .msg
  call print

  mov rdi, test_token      ; read buffer
  mov rsi, TEST_ARENA_ADDR ; write buffer
  call copy_token

  ; check reported final indicies with the expected final indicies
  cmp rax, test_token + 8 ; last byte read
  jne .fail
  cmp rdx, TEST_ARENA_ADDR + 8 ; last byte written
  jne .fail

  mov rsi, TEST_ARENA_ADDR
  mov rcx, [rsi]
  cmp rcx, [test_token] ; compare copied token to expected token
  jne .fail

  .pass:
    mov rsi, msg_pass
    call print
    ret
  .fail:
    mov rsi, msg_fail
    call print
    ret
  .msg db "test_copy_token...", 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 "TestTokn " ; followed by space. Quad word