; Planned commands:
; i insert
; a append
; d delete
; l prints lines
; w save to disk
; q quit
ed:
	pusha
	call .determine_line_count
	.main_loop:
		mov ax, ed_prompt
		mov bx, 40
		call keyboard_display_input ; AX = string location, BX = max prompt length
		mov si, ed_prompt
		mov bx, 0 ; Keeps track of whether comma has passed
		jmp .get_token

	; Types of tokens:
	; Number: eg 123
	; Doller (refers to the last line) $
	; Comma ,
	; Command: eg i
	; eg 123,127i
	.get_token:
		lodsb

		; COMMA
		cmp al, ','
		je .comma

		; NUMBER
		call check_is_number
		jc .get_number_token

		; COMMAND
		call check_is_letter
		jc .get_letter_token

	.error: ; Output ?
		mov ah, 0Eh

		mov al, '?'
		int 10h
		mov al, 0Ah
		int 10h
		mov al, 0Dh
		int 10h
		
		jmp .main_loop

	; Assign a number to either the start or end int (start,end)
	.get_number_token:
		push si
		dec si
		call string_cast_to_int ; AX = integer
		cmp bx, 0
		je .assign_start_int
		jg .assign_end_int
	.assign_start_int:
		mov [ed_start_int], ax
		jmp .after_int_assign
	.assign_end_int:
		mov [ed_end_int], ax
	.after_int_assign:
		pop si
		jmp .get_token

	; Determines a command
	.get_letter_token:
		cmp al, 'd'
		je .delete
		cmp al, 'q'
		je .quit
		jmp .get_token

	; Changes the value from start int to end int
	.comma:
		mov bx, 1
		jmp .get_token

	.determine_line_count:
		mov si, file_buffer
		mov dx, file_length ; STORES THE LENGTH OF THE FILE IN BYTES
		xor cx,cx
		.line_count_loop:
			lodsb
			cmp al, 0Ah
			je .increment_line_count
			dec dx
			cmp dx, 0
			jg .line_count_loop
		mov [ed_line_count], cx
		jmp .main_loop
		.increment_line_count:
			inc cx
			jmp .line_count_loop

	; COMMANDS
	.delete:
		; set up registers to shift data left
		mov bx, ed_end_int
		inc bx
		call get_byte_of_line ; CX = byte of start of new line (relative to file buffer)
		mov [ed_shift_from], cx

		mov bx, ed_start_int
		call get_byte_of_line
		mov ax, ed_start_int
		sub ax, cx
		mov [ed_shift_by], ax

	.quit:
		popa
		ret

shift_data_left:
	mov si, ed_shift_from
	mov cx, ed_shift_by
	mov di, ed_shift_from
	sub di, cx
	mov dx, file_length ; STORES THE LENGTH OF THE FILE IN BYTES
	.shift_left_loop:
		lodsb
		stosb
		cmp al, 0
		jne .shift_left_loop
	jmp ed.main_loop

; BX = target line
get_byte_of_line:
	push dx
	mov si, file_buffer
	xor dx,dx
	xor cx,cx
	jmp .increment_line_count
	.line_loop:
		lodsb
		inc cx
		cmp al, 0Ah
		je .increment_line_count
	.increment_line_count:
		inc dx
		cmp dx, bx
		jne .line_loop
		inc cx
		pop dx
		ret

ed_data_start: db "ED IS COOL"
ed_prompt:	times 40 db 0
ed_start_int: dw 0
ed_end_int: dw 0

ed_line_count: dw 0

ed_shift_from: dw 0
ed_shift_by: dw 0