;NXOS shell
;----------
;Written by: Alberto Venturini (Alb‚) - 2001
;Email address: -albe-@libero.it

	org 0h

	cld
Main1:
	mov si,offset Prompt	;shows the prompt
	mov ah,01h
	mov bl,07h
	int 24h

	mov di,offset Command
	xor cx,cx

GetCommand:		;Get a string from the keyboard
	mov si,offset Command
	mov ah,07h
	int 25h
	dec si

ToUpCase:		;Turns everything upcase
	inc si
	mov al,ds:[si]
	cmp al,13
	je EndCommand
	cmp al,90
	jbe ToUpCase
	sub al,32
	mov ds:[si],al
	jmp ToUpCase

EndCommand:
	test cx,cx	;If only CR was pressed, just re-write the prompt
	jz Main1

	push cx
	mov di,offset Command

Test4Extension:			;tests if file extension is available
	mov al,es:[di]
	cmp al,'.'
	je ExtensionOk
	inc di
	dec cx
	jnz Test4Extension

NoExtension:			;there's no extension...assume it's an internal
				;shell command

	pop cx

	mov di,offset Command

	mov cx,3
	mov si,offset ClsCmd
	push di
	rep cmpsb
	pop di
	je ShellCommand_Cls

	mov cx,4
	mov si,offset HelpCmd
	push di
	rep cmpsb
	pop di
	je ShellCommand_Help

	mov ah,01h
	mov si,offset Error3
	mov bl,7
	int 24h

	jmp ClearCommandBuffer

ShellCommand_Cls:		;executes the "CLS" command
	mov ah,04h
	int 24h
	jmp ClearCommandBuffer

ShellCommand_Help:
	mov si,offset HelpTxt
	mov ah,01h
	mov bl,7
	int 24h
	jmp ClearCommandBuffer


ExtensionOk:	;there's the extension
	pop cx

StoreExtension:	;store the extension in a buffer ("Extension")
	push di
	inc di
	mov si,di
	mov di,offset Extension

	movsb
	movsb
	movsb

	pop di

	push di
	sub di,offset Command

	cmp di,8
	jb StoreExtension2

	pop di		;file name must be <= 8
	mov di,offset Command
	add di,8
	jmp StoreExtension3

StoreExtension2:
	mov cx,8
	sub cx,di
	mov al,' '

	pop di

	rep stosb

StoreExtension3:
	mov si,offset Extension
	movsb
	movsb
	movsb

ExecuteProgram:
	mov di,offset Extension
	mov si,offset BinExtension

	mov cx,3

	push di
	rep cmpsb	;tests if the extension is "BIN"
	pop di
	je ExecuteBinProgram

	mov si,offset ComExtension
	mov cx,3

	push di
	rep cmpsb
	pop di
	je ExecuteComProgram

	mov ah,01h
	mov si,offset Error2
	mov bl,7
	int 24h

	jmp Main1

ExecuteBinProgram:
	push es

	mov si,offset Command
	mov ah,00h
	int 20h
	test dx,dx
	jz FileNotFound
	mov bl,0
	mov ah,01h
	int 20h

	pop es

	jmp ClearCommandBuffer

ExecuteComProgram:
	push es

	mov si,offset Command
	mov ah,07h
	int 20h
	test dx,dx
	jz FileNotFound
	mov bl,0
	mov ah,01h
	int 20h

	pop es

	jmp ClearCommandBuffer

FileNotFound:
	pop es
	mov si,offset Error1
	mov ah,01h
	mov bl,7
	int 24h

ClearCommandBuffer:
	mov di,offset Command
	mov al,' '
	mov cx,95

ClearCommandBuffer2:
	mov byte ptr cs:[di],al
	inc di
	loop ClearCommandBuffer2

	jmp Main1


;------------------------------------------------------------------------------

Command db 100 dup (32)
Prompt	db 13,10,'Ready:',0
Error1	db 13,10,'File not found',13,10,0
Error2	db 13,10,'Invalid file name',13,10,0
Error3	db 13,10,'Invalid command',13,10,0
NextLine db 13,10,0
Extension db 3 dup (?)
BinExtension db 'BIN',0
ComExtension db 'COM',0

ClsCmd	db 'CLS'
HelpCmd	db 'HELP'

;------------------------------------------------------------------------------

;Help text

HelpTxt db 13,10,'NXOS shell',13,10
	db '-------------',13,10
	db 13,10
	db 'How to use this shell:',13,10
	db 'if you want to execute an external program, just type the',13,10
	db 'file name, with his extension.',13,10
	db 13,10
	db 'Available shell commands:',13,10
	db '  CLS: clears the screen',13,10
	db '  HELP: shows this screen',13,10,0