%macro push_regs 0
	pusha
	push gs
	push fs
	push es
	push ds
%endmacro

%macro pop_regs 0
	pop ds
	pop es
	pop fs
	pop gs
	popa
%endmacro

SECTION .text

extern idt_p
global load_idt
load_idt:
	lidt [idt_p]
	
	ret

%macro kernel_stack 0
	mov eax, [cur_cx]
	mov [eax], esp
	mov esp, [kernel_cx]
%endmacro

%macro proc_stack 0
	mov [kernel_cx], esp
	mov eax, [cur_cx]
	mov esp, [eax]
%endmacro

%macro begin_isr 1
extern interrupt_%1
global isr%1
isr%1:
	cli
	push_regs
	mov eax, [cur_cx]
	mov [eax], esp
	mov esp, [kernel_cx]
%endmacro

extern cur_cx
extern kernel_cx

%macro end_isr 0
	mov [kernel_cx], esp
	mov eax, [cur_cx]
	mov esp, [eax]
	pop_regs
	sti
	iretd
%endmacro

%macro define_basic_isr 1
begin_isr %1
	call interrupt_%1
end_isr
%endmacro

; ISR DEFINITIONS

define_basic_isr 0 ; division by zero
;define_basic_isr 1
;define_basic_isr 2
;define_basic_isr 3
;define_basic_isr 4
;define_basic_isr 5
;define_basic_isr 6
;define_basic_isr 7
;define_basic_isr 8
;define_basic_isr 9
;define_basic_isr 10
;define_basic_isr 11
;define_basic_isr 12
define_basic_isr 13 ; general protection fault

begin_isr 14 ; page fault
	mov eax, cr2 ; page fault addr
	push eax
	call interrupt_14
	add esp, 4
end_isr

define_basic_isr 32 ; system timer
define_basic_isr 33 ; keyboard controller
define_basic_isr 38 ; floppy controller

; interrupt st00f x3
;%macro push_regs 0
;	pusha  ; EAX, ECX, EDX, EBX, ESP, EBP, ESI and EDI
;	push gs
;	push fs
;	push es
;	push ds
;endmacro

; [proc_esp + 15 *4]
; 15*4 = 60

extern syscall_table
begin_isr 128 ; system call
	mov ebx, [cur_cx] ; get the current context's stack pointer
	mov eax, [ebx]
	
	mov long ebx, [eax + 60] ; syscall number
	push long [eax + 76] ; param 4
	push long [eax + 72]
	push long [eax + 68] 
	push long [eax + 64] ; param 1
	
	mov eax, [syscall_table + ebx * 4] ; syscall address
	
	or eax, eax ; does the syscall exist?
	jz no_syscall ; nope
	
	call eax ; call the syscall

;	push eax
;	push mojmsg
;extern printf
;	call printf
;	cli
;	hlt
	
	add esp, 16 ; pop params off kernel stack
	
	mov [kernel_cx], esp ; restore current context's stack
	mov ebx, [cur_cx]
	mov esp, [ebx]
	
	; pop regs by hand; we want to return a value in eax
	pop ds
	pop es
	pop fs
	pop gs
	pop edi
	pop esi
	pop ebp
	add esp, 4 ; esp
	pop ebx
	pop edx
	pop ecx
	add esp, 4 ; eax
	
	sti
	iret

no_syscall:
	; stack is kinda dirty here >_>
	push ebx
	push syscallnummsg
extern printf
	call printf
	add esp, 8

	push nosyscall
extern panic
	call panic

; Don't use
; Is this incredibly stupid? o_O
global lowlevel_yield
lowlevel_yield:
	mov [kernel_cx], esp
	mov eax, [cur_cx]
	mov esp, [eax]
	
	; reverse of iretd
	pushfd
	push cs
;	push .return
;	push long 0x12
	push .return
	
	push_regs

	mov eax, [cur_cx]
	mov [eax], esp
	mov esp, [kernel_cx]
	; TODO: schedule next process here
extern next_process
	call next_process
	
	mov [kernel_cx], esp
	mov eax, [cur_cx]
	mov esp, [eax]

	pop_regs
	; if all processes are currently yielding, we need to sti
	; for a while to let interrupts come through
	push ecx
extern num_processes
extern num_yielding
	mov ecx, [num_processes]
	cmp ecx, [num_yielding]
;	push waste
;	extern printf
;	call printf
	jnz .nowait
	sti
;	hlt ; wait for an interrupt
	mov ecx, 10 ; waste some cycles
.loop
	nop
	loop .loop
.nowait
	pop ecx
	sti
	iretd
;global lowlevel_yield
.return
;	begin_isr
;	push ork
;	extern printf
;	call printf
	cli
	kernel_stack
	ret


;%macro end_isr 0
;	mov [kernel_cx], esp
;	mov eax, [cur_cx]
;	mov esp, [eax]
;	pop_regs
;	sti
;	iret
;%endmacro

SECTION .data
	
	waste db "%d %d\n", 10, 0
	ork db "Oerk 0x%x", 10, 0
	mojmsg db "Moi: 0x%x", 10, 0
	nosyscall db "Missing syscall", 10, 0
	syscallnummsg db "Syscall number is %d", 10, 0