const console = @import("console.zig");

const ALIGN = 1 << 0;
const MEMINFO = 1 << 1;
const MAGIC = 0x1BADB002;
const FLAGS = ALIGN | MEMINFO;

const MultibootHeader = extern struct {
    magic: i32,
    flags: i32,
    checksum: i32,
};

export const multiboot align(4) linksection(".multiboot") = MultibootHeader{
    .magic = MAGIC,
    .flags = FLAGS,
    .checksum = -(MAGIC + FLAGS),
};

export var stack: [16 * 1024]u8 align(16) linksection(".bss") = undefined;
const stack_bytes_slice = stack[0..];

inline fn inb(port: u16) u8 {
    return asm volatile ("inb %[port], %[result]"
        : [result] "={al}" (-> u8),
        : [port] "N{dx}" (port),
    );
}

inline fn outb(port: u16, data: u8) void {
    asm volatile ("outb %[data], %[port]"
        :
        : [data] "{al}" (data),
          [port] "N{dx}" (port),
    );
}

fn write(data: []const u8) void {
    const len: u8 = @intCast(data.len & 0xFF);
    outb(0xe9, 0x30 + len);
    for (0..len) |i| {
        outb(0xe9, 0x30);
        outb(0xe9, data[i]);
    }
}

export fn _start() callconv(.C) noreturn {
    write("test\n");
    outb(0xe9, 'H');
    outb(0xe9, 'i');
    outb(0xe9, '!');
    outb(0xe9, '\n');

    asm volatile (
        \\ mov %[stk], %rsp
        \\ mov %rsp, %rbp
        :
        : [stk] "{rcx}" (@intFromPtr(&stack) + @sizeOf(@TypeOf(stack))),
    );
    asm volatile ("call kmain");

    while (true) {}
}

export fn kmain() void {
    outb(0xe9, '^');
    console.initialize();
    console.puts("Hello world!");
    outb(0xe9, '$');
    outb(0xe9, '\n');
}