#if defined (bios)

#include <stddef.h>
#include <stdint.h>
#include <protos/chainload.h>
#include <lib/part.h>
#include <lib/config.h>
#include <lib/blib.h>
#include <drivers/disk.h>
#include <lib/term.h>
#include <mm/mtrr.h>
#include <sys/idt.h>
#include <drivers/vga_textmode.h>

__attribute__((noinline))
__attribute__((section(".realmode")))
static void spinup(uint8_t drive) {
    struct idtr real_mode_idt = { 0x3ff, 0x0 };

    asm volatile (
        "cli\n\t"
        "cld\n\t"

        "lidt [eax]\n\t"

        "jmp 0x08:1f\n\t"
        "1: .code16\n\t"
        "mov ax, 0x10\n\t"
        "mov ds, ax\n\t"
        "mov es, ax\n\t"
        "mov fs, ax\n\t"
        "mov gs, ax\n\t"
        "mov ss, ax\n\t"
        "mov eax, cr0\n\t"
        "and al, 0xfe\n\t"
        "mov cr0, eax\n\t"
        "mov eax, OFFSET 1f\n\t"
        "push 0\n\t"
        "push ax\n\t"
        "retf\n\t"
        "1:\n\t"
        "mov ax, 0\n\t"
        "mov ds, ax\n\t"
        "mov es, ax\n\t"
        "mov fs, ax\n\t"
        "mov gs, ax\n\t"
        "mov ss, ax\n\t"

        "sti\n\t"

        "push 0\n\t"
        "push 0x7c00\n\t"
        "retf\n\t"

        ".code32\n\t"
        :
        : "a" (&real_mode_idt), "d" (drive)
        : "memory"
    );
}

void chainload(char *config) {
    uint64_t val;

    int part; {
        char *part_config = config_get_value(config, 0, "PARTITION");
        if (part_config == NULL) {
            part = -1;
        } else {
            val = strtoui(part_config, NULL, 10);
            if (val < 1 || val > 256) {
                panic("BIOS partition number outside range 1-256");
            }
            part = val - 1;
        }
    }
    int drive; {
        char *drive_config = config_get_value(config, 0, "DRIVE");
        if (drive_config == NULL) {
            panic("DRIVE not specified");
        }
        val = strtoui(drive_config, NULL, 10);
        if (val < 1 || val > 16) {
            panic("BIOS drive number outside range 1-16");
        }
        drive = (val - 1) + 0x80;
    }

    int rows, cols;
    init_vga_textmode(&rows, &cols, false);

    struct volume *p = volume_get_by_coord(drive, part);

    volume_read(p, (void *)0x7c00, 0, 512);

    mtrr_restore();

    spinup(drive);
}

#endif