#include <syscall.h>
#include <kernel.h>
#include <string.h>
#include <system.h>
#include <idt.h>
#include <isr.h>

isr_handler_ptr irq_handlers[16];

const char* exceptions[] = {
	"Division By Zero",
	"Debug",
	"Non Maskable Interrupt",
	"Breakpoint",
	"Into Detected Overflow",
	"Out of Bounds",
	"Invalid Opcode",
	"No Coprocessor",
	"Double Fault",
	"Coprocessor Segment Overrun",
	"Bad TSS",
	"Segment Not Present",
	"Stack Fault",
	"General Protection Fault",
	"Page Fault",
	"Unknown Interrupt",
	"Coprocessor Fault",
	"Alignment Check",
	"Machine Check",
	"Reserved",
	"Reserved",
	"Reserved",
	"Reserved",
	"Reserved",
	"Reserved",
	"Reserved",
	"Reserved",
	"Reserved",
	"Reserved",
	"Reserved",
	"Reserved",
	"Reserved"
};

// I have no clue how this works or what it does, but it doesn't work without it
void isr_remap_pic(void) {
	outb(0x20, 0x11); iowait();
	outb(0xa0, 0x11); iowait();
	outb(0x21, 0x20); iowait();
	outb(0xa1, 0x28); iowait();
	outb(0x21, 0x04); iowait();
	outb(0xa1, 0x02); iowait();
	outb(0x21, 0x01); iowait();
	outb(0xa1, 0x01); iowait();
	outb(0x21, 0x00); iowait();
	outb(0xa1, 0x00); iowait();
}

int isr_init(void) {
	idt_init();
	isr_remap_pic();

	for (int i = 0; i < 48; i++) {
		// First 32 IRSs are exceptions (traps) and the next 16 are hardware interrupts
		idt_set_gate(i, isr_redirect_table[i], (i < 32) ? IDT_FLAG_TRAP : IDT_FLAG_INT);
	}

	// System call (should be callable from userspace)
	idt_set_gate(0x80, (void*)(uint32_t)isr128, IDT_FLAG_USER);

	// Let interrupts interrupt
	__asm__ volatile ("sti");

	debugf("[isr] ISR initialized.\n");
	return 0;
}

void isr_register(uint8_t i, isr_handler_ptr handler) {
	if (i > 16) return; // Security 
	irq_handlers[i] = handler;
}

void isr_send_eoi(uint8_t irq) {
	if (irq >= 8) outb(0xA0, 0x20);
	outb(0x20, 0x20);
}

// TODO: Write fault handlers and make this more robust 
int isr_handle_interrupt(struct isr_int_frame iframe) {
	if (iframe.interrupt < 32) { 
		// ISRs 0-31 - Exceptions
		panic(exceptions[iframe.interrupt]);
	} else if (iframe.interrupt >= 32 && iframe.interrupt < 48) {
		// ISRs 32-47 - Hardware interrupts
		uint8_t irq = iframe.interrupt - 32;
		if (irq_handlers[irq]) irq_handlers[irq](&iframe);
		isr_send_eoi(irq);
	} else if (iframe.interrupt == 128) { 
		// ISR 128 - System call
		return syscall_handler(&iframe);
	}

	return 0;
}