#include "lnxboot.h"
#include "efi/types.h"
#include "efi/memmap.h"

extern void _start();

[[gnu::section(".lnxhead")]]
[[gnu::used]]
[[gnu::aligned(1)]]
[[gnu::unavailable("not present at runtime. use setup_info instead")]]
struct setup_info bzhead = {
	.setup_sects = 2, // 1 512-byte sector
	.boot_flag = 0xAA55,
	.syssize = 16,
	.jump_instruction = 0xEB,
	.jump_offset = sizeof(struct setup_info) - __builtin_offsetof(struct setup_info, signature),
	.signature = 0x53726448,
	.version = 0x020F,
	.loadflags = 0x01, // LOADED_HIGH,
	.kernel_alignment = 1,
	.relocatable_kernel = 0,
	.xloadflags = 0x13, // XLF_KERNEL_64 | XLF_CAN_BE_LOADED_ABOVE_4G | XLF_5LEVEL
	.cmdline_size = 255, // max command line size
	.init_size = 0x10000 // we dont need THAT much memory
};

struct setup_info*  setup_info;
struct boot_params* boot_params;

unsigned short serial_port;

void outb(unsigned short port, unsigned char value) {
	asm volatile (
		  "outb %b0, %1"
		::"a" (value)
		 ,"d" (port)
	);
}

void serial_putc(char c) {
	outb(serial_port, c);
}

void serial_puts(const char* s) {
	while (*s) serial_putc(*(s++));
}

void serial_put_formatted_u64(u64 v) {
	if (v == 0) {
		serial_putc('0');
	} else {
		u64 max = 1;

		while (v > max) max *= 10;

		while (v) {
			serial_putc('0' + (u8)(v / max));

			v   %= max;
			max /= 10;
		}
	}
}

/**
 * We can't do anything, just hang.
 */
[[noreturn, gnu::naked]]
void Hang() {
	// This should make us hang
	asm volatile (
		"   cli\n"
		"1: hlt\n"
		"   jmp 1b"
	);
}

/**
 * Congratulations, you panicked twice!
 */
[[noreturn]]
void Panic(const char* message) {
	// We don't even do anything with the message, but it's nice to have just in case.
	Hang();
}

[[gnu::section(".text._start"), gnu::naked, gnu::no_reorder]]
extern void _start() {
	asm ("jmp _start");
	asm ( // grab the setup_info and boot_params locations
	      	  "mov  %%rsi,  %1\n"
		  "mov  %%rsi,  %0\n"
		  "addq $0x1f1, %0"
		: "=m" (setup_info),
		  "=m" (boot_params)
	);
	asm ("jmp entry");
}

c16* FirmwareVendor = 0;

/**
 * we're in some kind of purgatory between booted and not booted, a lot of devices are currently initialized from the previous
 * kernel, but we have no idea where they are, what they are, or how to use them. all we have is the stuff in setup_info and
 * boot_params, and whatever we can salvage from the crashed kernel.
 */
[[gnu::section(".text._start"), gnu::no_reorder]]
void entry() {
	// get command line from kernel. we likely won't use it, but its nice to have.
	u8* cmdline_ptr = (u8*)((u64)setup_info->cmd_line_ptr | ((u64)boot_params->ext_cmd_line_ptr << 32));	
	
	// do we have efi?
	struct EfiSystemTable* systab_ptr = 0;
	if (boot_params) {
	       	systab_ptr = (struct EfiSystemTable*)(
			(u64)boot_params->efi_info.EfiSystemTable |
			((u64)boot_params->efi_info.EfiSystemTableHigh << 32)
		);

		EfiLoadStoredMemoryMap(
			(struct EfiMemoryDescription*)(
				(u64)boot_params->efi_info.EfiMemoryMap |
				((u64)boot_params->efi_info.EfiMemoryMapHigh << 32)
			), // this might be 0, we should probably check ---------------V
			boot_params->efi_info.EfiMemoryMapSize / boot_params->efi_info.EfiMemoryDescriptionSize,
			boot_params->efi_info.EfiMemoryDescriptionSize
		);

		FirmwareVendor = EfiTranslatePointer(systab_ptr->FirmwareVendor);
		while (1) {
			volatile char* a = FirmwareVendor;
		}
	}

	// -- find acpi --
	struct AcpiRSDP* AcpiRSDP = 0;

	// check bootparams
	if (boot_params->acpi_rsdp_addr) AcpiRSDP = boot_params->acpi_rsdp_addr;

	// check efi
	if (!AcpiRSDP && systab_ptr && systab_ptr->NumberOfTableEntries) {
		volatile void* ConfigurationTable = EfiTranslatePointer(systab_ptr->ConfigurationTable);
	}

	// we're playing where's waldo with this stupid fucking tableS
	if (!AcpiRSDP) {
		for (struct AcpiRSDP* addr = 0x00000000; addr < 0x000FFFFF; addr = (void*)addr + 16) {
			if (addr->Signature[0] == 'R' && addr->Signature[1] == 'S'
			 && addr->Signature[2] == 'D' && addr->Signature[3] == ' '
			 && addr->Signature[4] == 'P' && addr->Signature[5] == 'T'
			 && addr->Signature[6] == 'R' && addr->Signature[7] == ' ') {
				AcpiRSDP = addr;
				break;
			}
		}
	}

	if (!AcpiRSDP) Panic("Failed to find ACPI RSDP");

	// do we have acpi?
	asm volatile ("ljmp 0");
	
	// we dont have the privilege of getting a rodata segment. any reads off our stack cause a triple fault
	// for some fucking reason. allocate our strings and shit on the stack.
	//char s_you_fucked_up[] = "!!! YOU FUCKED UP !!!\n";
	//char s_vga_you_fucked_up[] = "YOU FUCKED UP.\n";
	//char s_description[] = "A SERIOUS ERROR HAS OCCURED AND LINDOWS HAS STOPPED TO PREVENT FURTHER DAMAGE.";
	//char s_registers[] = "REGISTERS:";
	//char s_call_trace[] = "CALL TRACE:";
	//char s_dumpcore[] = "[(D)UMP CORE]";
	//char s_poweroff[] = "[(P)OWER OFF]";
	//char s_reboot[]   = "[(R)EBOOT   ]";

	// You fucked up.
	//serial_puts(s_you_fucked_up);
	//serial_puts(s_description);
	//serial_putc('\n');

	// register dump
	//serial_puts(s_registers);
	//serial_putc('\n');
	//serial_putc('\n');

	// call trace
	//serial_puts(s_call_trace);
	//serial_putc('\n');
	//serial_putc('\n');

	// thing
	// serial_puts("test\n");
	// serial_puts(bzhead.cmd_line_ptr);
	
	// Die.
	Panic("Nothing left to do.");
}