// Important specification: https://uefi.org/sites/default/files/resources/ACPI_6_2.pdf
// HPET: https://www.intel.com/content/dam/www/public/us/en/documents/technical-specifications/software-developers-hpet-spec-1-0a.pdf

#include <kernel/io/io.h>
#include <kernel/lib/lib.h>
#include <kernel/timer/timer.h>
#include <kernel/acpi/acpi.h>
#include <stddef.h>
#include <kernel/system.h>
#include <kernel/lib/stdio.h>

struct FADT *fadt;
uint32_t *SMI_CMD;
char ACPI_ENABLE;
char ACPI_DISABLE;
uint32_t *PM1a_CNT;
uint32_t *PM1b_CNT;
int SLP_TYPa;
int SLP_TYPb;
int SLP_EN;
int SCI_EN;
char PM1_CNT_LEN;

unsigned int *acpi_check_rsd_ptr(unsigned int *ptr)
{
	char *sig = "RSD PTR ";
	struct RSD_ptr *rsdp = (struct RSD_ptr *)ptr;
	char *bptr;
	char check = 0;
	unsigned int i;

	if (memcmp(sig, rsdp, 8) == 0) {
		bptr = (char *)ptr;
		for (i = 0; i < sizeof(struct RSD_ptr); i++) {
			check += *bptr;
			bptr++;
		}

		if (check == 0) {
			return (unsigned int *)rsdp->rsdt_address;
		}
	}

	return NULL;
}

unsigned int *acpi_get_rsd_ptr()
{
	unsigned int *addr;
	unsigned int *rsdp;

	for (addr = (unsigned int *)0x000E0000; (int)addr < 0x00100000;
	     addr += 0x10 / sizeof(addr)) {
		rsdp = acpi_check_rsd_ptr(addr);
		if (rsdp != NULL)
			return rsdp;
	}

	int ebda = *((short *)0x40E);
	ebda = ebda * 0x10 & 0x000FFFFF;

	for (addr = (unsigned int *)ebda; (int)addr < ebda + 1024; addr += 0x10 / sizeof(addr)) {
		rsdp = acpi_check_rsd_ptr(addr);
		if (rsdp != NULL)
			return rsdp;
	}

	return NULL;
}

int acpi_enable()
{
	if ((inw((uint16_t)(unsigned int)PM1a_CNT) & SCI_EN) == 0) {
		if (SMI_CMD != 0 && ACPI_ENABLE != 0) {
			outb((uint16_t)(unsigned int)SMI_CMD, (uint8_t)ACPI_ENABLE); // Enable ACPI
			// Try 3s until ACPI is enabled
			int i;
			for (i = 0; i < 300; i++) {
				if ((inw((uint16_t)(unsigned int)PM1a_CNT) & SCI_EN) == 1)
					break;
				timer_wait(1);
			}
			if (PM1b_CNT != 0)
				for (; i < 300; i++) {
					if ((inw((uint16_t)(unsigned int)PM1b_CNT) & SCI_EN) == 1)
						break;
					timer_wait(1);
				}
			if (i < 300) {
				return 0; // Successfully enabled ACPI
			} else {
				serial_printf("ACPI couldn't be enabled!");
				return -1; // ACPI couldn't be enabled
			}
		} else {
			serial_printf("ACPI is not supported!");
			return -1; // ACPI is not supported
		}
	} else {
		serial_printf("ACPI was already enabled!");
		return 0; // ACPI was already enabled
	}
}

int acpi_install()
{
	unsigned int *ptr = acpi_get_rsd_ptr();

	int success = 0;

	if (ptr != NULL && memcmp(ptr, "RSDT", 4) == 0) {
		int entries = *(ptr + 1);
		entries = (entries - 36) / 4;
		ptr += 36 / 4;

		while (0 < entries--) {
			if (memcmp((unsigned int *)*ptr, "FACP", 4) == 0) {
				fadt = (struct FADT
						*)*ptr; // TODO: Allocate ACPI tables after paging (page fault)!
				if (memcmp((unsigned int *)fadt->DSDT, "DSDT", 4) == 0) {
					char *S5Addr = (char *)fadt->DSDT + 36;
					int dsdt_length = (int)(*(fadt->DSDT + 1) - 36);
					while (0 < dsdt_length--) {
						if (memcmp(S5Addr, "_S5_", 4) == 0)
							break;
						S5Addr++;
					}
					if (dsdt_length > 0) {
						// TODO: Implement device detection via DSDT ACPI (p199 -> AML)
						if ((*(S5Addr - 1) == 0x08 ||
						     (*(S5Addr - 2) == 0x08 &&
						      *(S5Addr - 1) == '\\')) &&
						    *(S5Addr + 4) == 0x12) {
							S5Addr += 5;
							S5Addr += ((*S5Addr & 0xC0) >> 6) + 2;

							if (*S5Addr == 0x0A)
								S5Addr++;
							SLP_TYPa = *(S5Addr) << 10;
							S5Addr++;

							if (*S5Addr == 0x0A)
								S5Addr++;
							SLP_TYPb = *(S5Addr) << 10;

							SMI_CMD = fadt->SMI_CMD;

							ACPI_ENABLE = fadt->ACPI_ENABLE;
							ACPI_DISABLE = fadt->ACPI_DISABLE;

							PM1a_CNT = fadt->PM1a_CNT_BLK;
							PM1b_CNT = fadt->PM1b_CNT_BLK;

							PM1_CNT_LEN = fadt->PM1_CNT_LEN;

							SLP_EN = 1 << 13;
							SCI_EN = 1;

							acpi_enable();
							vga_log("Installed ACPI");

							success = 1;
						} // Else: \_S5 parse error
					} // Else: \_S5 not present
				} // Else: DSDT invalid
			}
			if (memcmp((unsigned int *)*ptr, "HPET", 4) == 0) {
				hpet = (struct HPET *)*ptr;
				serial_printf("%c%c%c%c", hpet->signature[0], hpet->signature[1],
					      hpet->signature[2], hpet->signature[3]);
				serial_printf("%d", hpet->legacy_replacement);
				serial_printf("%d", hpet->address.address);
			}
			ptr++;
		} // Else: no valid FADT present
	} else {
		serial_printf("ACPI is not supported!");
	}

	return success == 1 ? 0 : -1;
}

void acpi_poweroff()
{
	cli();
	if (SCI_EN == 0) {
		warn("ACPI shutdown is not supported\n");
		return;
	}

	// Send shutdown command
	outw((uint16_t)(unsigned int)PM1a_CNT, (uint16_t)(SLP_TYPa | SLP_EN));
	if (PM1b_CNT != 0)
		outw((uint16_t)(unsigned int)PM1b_CNT, (uint16_t)(SLP_TYPb | SLP_EN));
	else {
		outw(0xB004, 0x2000); // Bochs
		outw(0x604, 0x2000); // QEMU
		outw(0x4004, 0x3400); // VirtualBox
	}
}

void reboot()
{
	cli();
	uint8_t good = 0x02;
	while (good & 0x02)
		good = inb(0x64);
	outb(0x64, 0xFE);
	halt_loop();
}