#include <arch/acpi.h>
#include <socks/vm.h>
#include <socks/printk.h>
#include <stddef.h>

static struct acpi_rsdp rsdp;

static struct acpi_rsdp_10 *search_for_rsdp(void)
{
	uint64_t *start = vm_phys_to_virt(0x80000);
	uint64_t *end = vm_phys_to_virt(0xFFFFF);
	
	for (uint64_t *i = start; i < end; i++) {
		if (*i == ACPI_SIG_RSDP) {
			return (struct acpi_rsdp_10 *)i;
		}
	}

	return NULL;
}

static int init_rsdt(void)
{
	struct acpi_rsdp_10 *x = search_for_rsdp();

	if (!x) {
		printk("acpi: not available");
		return -1;
	}

	uint8_t *b = (uint8_t *)x;
	size_t chksum = 0;
	for (unsigned int i = 0; i < sizeof *x; i++) {
		chksum += b[i];
	}
		
	if (chksum & 0xFF) {
		printk("acpi: not available");
		return -1;
	}

	if (x->r_revision == 2) {
		chksum = 0;
		
		for (unsigned int i = sizeof *x; i < sizeof(struct acpi_rsdp_20); i++) {
			chksum += b[i];
		}

		if (chksum & 0xFF) {
		    printk("acpi: not available");
		    return -1;
		}
	}
		
	memcpy(&rsdp.rsdp_20, x, sizeof rsdp.rsdp_20);
	return 0;
}

static struct acpi_sdt *find_via_rsdt(uint32_t sig)
{
	struct acpi_rsdt *rsdt = vm_phys_to_virt(rsdp.rsdp_10.r_rsdt_ptr);
	unsigned long nr_tables = (rsdt->r_header.s_length - sizeof(struct acpi_sdt)) / sizeof(uint32_t);

	for (unsigned long i = 0; i < nr_tables; i++) {
		struct acpi_sdt *table = vm_phys_to_virt(rsdt->r_tables[i]);
		if (*(uint32_t *)table == sig) {
			return table;
		}
	}

	return NULL;
}

static struct acpi_sdt *find_via_xsdt(uint32_t sig)
{
	struct acpi_xsdt *xsdt = vm_phys_to_virt(rsdp.rsdp_20.r_xsdt_ptr);
	unsigned long nr_tables = (xsdt->x_header.s_length - sizeof(struct acpi_sdt)) / sizeof(uint64_t);

	for (unsigned long i = 0; i < nr_tables; i++) {
		struct acpi_sdt *table = vm_phys_to_virt(xsdt->x_tables[i]);
		if (*(uint32_t *)table == sig) {
			return table;
		}
	}

	return NULL;
}

struct acpi_sdt *acpi_find_sdt(uint32_t sig)
{
	if (!rsdp.rsdp_10.r_sig[0]) {
		if (init_rsdt() != 0) {
			return NULL;
		}
	}

	if (rsdp.rsdp_10.r_revision == 0) {
		return find_via_rsdt(sig);
	} else {
		return find_via_xsdt(sig);
	}
}