const std = @import("std");
const BootParams = @import("params.zig").BootParams;
pub const MULTIBOOT_TAG_ALIGN: usize = 8;
pub const MultibootTagType = enum(u32) {
    end,
	cmdline,
	boot_loader_name,
	module,
	basic_meminfo,
	bootdev,
	mmap,
	vbe,
	framebuffer,
	elf_sections,
	apm,
	efi32,
	efi64,
	smbios,
	acpi_old,
	acpi_new,
	network,
	efi_mmap,
	efi_bs,
	efi32_ih,
	efi64_ih,
	load_base_addr,
};

pub const MultibootTag = extern struct {
    type: u32 align(1),
    size: u32 align(1),
};

pub const MultibootTagCmdline = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    string: [0]u8 align(1),
};

pub const MultibootTagModule = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    mod_start: u32 align(1),
    mod_end: u32 align(1),
    cmdline: [0]u8 align(1),
};

pub const MultibootTagBasicMeminfo = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    mem_lower: u32 align(1),
    mem_upper: u32 align(1),
};

pub const MultibootTagBootdev = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    biosdev: u32 align(1),
    slice: u32 align(1),
    part: u32 align(1),
};

pub const MultibootMmapEntry = extern struct {
    addr: u64 align(1),
    len: u64 align(1),
    type: u32 align(1),
    zero: u32 align(1),
};

pub const MultibootTagMmap = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    entry_size: u32 align(1),
    entry_version: u32 align(1),
    entries: [0]MultibootMmapEntry align(1),
};

pub const MultibootVbeInfoBlock = extern struct {
    external_specification: [512]u8 align(1),
};

pub const MultibootVbeModeInfoBlock = extern struct {
    external_specification: [256]u8 align(1),
};

pub const MultibootTagVbe = extern struct {
    type: u32 align(1),
    size: u32 align(1),

    vbe_mode: u16 align(1),
    vbe_interface_seg: u16 align(1),
    vbe_interface_off: u16 align(1),
    vbe_interface_len: u16 align(1),

    vbe_control_info: MultibootVbeInfoBlock align(1),
    vbe_mode_info: MultibootVbeModeInfoBlock align(1),
};

pub const MULTIBOOT_FRAMEBUFFER_TYPE_INDEXED = 0;
pub const MULTIBOOT_FRAMEBUFFER_TYPE_RGB = 1;
pub const MULTIBOOT_FRAMEBUFFER_TYPE_EGA_TEXT = 2;

pub const MultibootColor = extern struct {
    red: u8 align(1),
    green: u8 align(1),
    blue: u8 align(1),
};

pub const MultibootTagFramebufferCommon = extern struct {
    type: u32 align(1),
    size: u32 align(1),

    framebuffer_addr: u64 align(1),
    framebuffer_pitch: u32 align(1),
    framebuffer_width: u32 align(1),
    framebuffer_height: u32 align(1),
    framebuffer_bpp: u8 align(1),
    framebuffer_type: u8 align(1),
    reserved: u16 align(1),
};

pub const MultibootTagFramebuffer = extern struct {
    common: MultibootTagFramebufferCommon align(1),

    details: extern union {
        indexed: extern struct {
            framebuffer_palette_num_colors: u16 align(1),
            framebuffer_palette: [*]MultibootColor align(1),
        } align(1),
        rgb: extern struct {
            framebuffer_red_field_position: u8 align(1),
            framebuffer_red_mask_size: u8 align(1),
            framebuffer_green_field_position: u8 align(1),
            framebuffer_green_mask_size: u8 align(1),
            framebuffer_blue_field_position: u8 align(1),
            framebuffer_blue_mask_size: u8 align(1),
        } align(1),
    } align(1),
};

pub const MultibootTagElfSections = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    num: u32 align(1),
    entsize: u32 align(1),
    shndx: u32 align(1),
    sections: [*]u8 align(1),
};

pub const MultibootTagApm = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    version: u16 align(1),
    cseg: u16 align(1),
    offset: u32 align(1),
    cseg_16: u16 align(1),
    dseg: u16 align(1),
    flags: u16 align(1),
    cseg_len: u16 align(1),
    cseg_16_len: u16 align(1),
    dseg_len: u16 align(1),
};

pub const MultibootTagEfi32 = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    pointer: u32 align(1),
};

pub const MultibootTagEfi64 = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    pointer: u64 align(1),
};

pub const MultibootTagSmbios = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    major: u8 align(1),
    minor: u8 align(1),
    reserved: [6]u8 align(1),
    tables: [*]u8 align(1),
};

pub const MultibootTagOldAcpi = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    rsdp: [*]u8 align(1),
};

pub const MultibootTagNewAcpi = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    rsdp: [*]u8 align(1),
};

pub const MultibootTagNetwork = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    dhcpack: [*]u8 align(1),
};

pub const MultibootTagEfiMmap = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    descr_size: u32 align(1),
    descr_vers: u32 align(1),
    efi_mmap: [*]u8 align(1),
};

pub const MultibootTagEfi32Ih = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    pointer: u32 align(1),
};

pub const MultibootTagEfi64Ih = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    pointer: u64 align(1),
};

pub const MultibootTagLoadBaseAddr = extern struct {
    type: u32 align(1),
    size: u32 align(1),
    load_base_addr: u32 align(1),
};

pub fn parseMultibootInfo(multiboot_info: *u8) BootParams {
    var params = BootParams{
        .cmdline = &[_]u8{},
    };
    var offset: usize = @sizeOf(MultibootTag);
    while (true) {
        const tag: *MultibootTag = @ptrFromInt(@intFromPtr(multiboot_info) + offset);
        if (tag.type == @intFromEnum(MultibootTagType.end)) {
            break;
        }
        switch (@as(MultibootTagType, @enumFromInt(tag.type))) {
            MultibootTagType.cmdline => {
                const cmdline_tag: *MultibootTagCmdline = @ptrCast(tag);
                const sentinel_cmdline = @as([*:0]u8, @ptrCast(&cmdline_tag.string));
                params.cmdline = sentinel_cmdline[0..std.mem.len(sentinel_cmdline)];
            },
            else => {},
        }
        offset += (tag.size + MULTIBOOT_TAG_ALIGN - 1) & ~(MULTIBOOT_TAG_ALIGN - 1);
    }
    return params;
}