#include <multiboot.h>
#include <acpi.h>
#include <vga.h>
#include <printf.h>
#include <strcmp.h>

struct kernel_context {
    struct rsdp *rsdp;
    struct xsdp *xsdp;

    struct rsdt *rsdt;
};

struct kernel_context ctx = {0};


void *acpi_find_sdt(void *RootSDT, const char sig[4]) {
    struct rsdt *rsdt = (struct rsdt *) RootSDT;
    int entries = (rsdt->h.Length - sizeof(rsdt->h)) / 4;
 
    for (int i = 0; i < entries; i++)
    {
        struct ACPISDTHeader *h = (struct ACPISDTHeader *) rsdt->other_sdt[i];
        if (!strncmp(h->Signature, sig, 4))
            return (void *) h;
    }
 
    return 0;
}

uint16_t readw(uint32_t addr, uint32_t offset, uint8_t bus, uint8_t slot, uint8_t func) {
    uint32_t lbus  = (uint32_t)bus;
    uint32_t lslot = (uint32_t)slot;
    uint32_t lfunc = (uint32_t)func;

    uint32_t address = addr + offset + ((lbus) << 20 | lslot << 15 | lfunc << 12);
 
    return *(uint16_t *)address;
}

uint8_t readb(uint32_t addr, uint32_t offset, uint8_t bus, uint8_t slot, uint8_t func) {
    uint32_t lbus  = (uint32_t)bus;
    uint32_t lslot = (uint32_t)slot;
    uint32_t lfunc = (uint32_t)func;

    uint32_t address = addr + offset + ((lbus) << 20 | lslot << 15 | lfunc << 12);
 
    return *(uint8_t *)address;
}

uint32_t readd(uint32_t addr, uint32_t offset, uint8_t bus, uint8_t slot, uint8_t func) {
    uint32_t lbus  = (uint32_t)bus;
    uint32_t lslot = (uint32_t)slot;
    uint32_t lfunc = (uint32_t)func;

    uint32_t address = addr + offset + ((lbus) << 20 | lslot << 15 | lfunc << 12);
 
    return *(uint32_t *)address;
}

void kmain(struct multiboot_info *info) {
    clear_screen();

    // Check if the bootloader gave us the upper and lower memory
    if (!(info->flags & 0x1)) goto halt;

    struct rsdp *found_rsdp = acpi_search_for_rsdp();
    if (!found_rsdp) {
        printf("Failed to find RSDP signature\n");
        goto halt;
    }

    printf("RSDP detected at 0x%X\n", found_rsdp);

    if (found_rsdp->Revision == ACPI_VER_1) {
        // ACPI v1.0 is being used
        if (!acpi_validate_rsdp_checksum(found_rsdp)) {
            printf("RSDP has an invalid checksum\n");
            goto halt;
        }
        ctx.rsdp = found_rsdp;
        ctx.xsdp = 0;

        if (!acpi_validate_sdt_checksum((struct ACPISDTHeader *)found_rsdp->RsdtAddress)) {
            printf("RSDT has an invalid checksum\n");
            goto halt;
        }

        ctx.rsdt = (struct rsdt*)found_rsdp->RsdtAddress;

        printf("RSDT detected at 0x%X\n", found_rsdp->RsdtAddress);

    } else if (found_rsdp->Revision == ACPI_VER_OTHER) {
        printf("ACPI versions higher than 1.0 are not supported\n");
        goto halt;
    } else {
        printf("Invalid RSDP\n");
        goto halt;
    }

    printf("Using ACPI v1.0\n");

    struct mcfg *mcfg = acpi_find_sdt(ctx.rsdt, "MCFG");
    if (!mcfg) {
        printf("Failed to find MCFG\n");
        goto halt;
    }

    printf("Detected MCFG at 0x%X\n", mcfg);
    int entries = (mcfg->h.Length - 44) / 16;
    for (int i = 0; i < entries; i++) {
        uint32_t addr = (uint32_t)mcfg->entries[i].base_addr;
        for (int j = 0; j < 256; j++) {
            for (int k = 0; k < 8; k++) {
                uint32_t word = readd(addr, 8, i, j, k);
                if (word != 0xFFFFFFFF && word) {
                    printf("%08X\n", word >> 8);
                }
            }
        }
    }

halt:
    for (;;) {}
}