use core::{
    alloc::Layout,
    ops::{Deref, DerefMut},
    ptr::addr_of,
    sync::atomic::{AtomicUsize, Ordering},
};

use kernel_arch_interface::{
    mem::{DeviceMemoryAttributes, KernelTableManager, RawDeviceMemoryMapping},
    split_spinlock,
};
use kernel_arch_x86::registers::CR3;
use libk_mm_interface::{
    address::PhysicalAddress,
    table::{page_index, EntryLevel, EntryLevelExt},
};
use static_assertions::{const_assert_eq, const_assert_ne};
use yggdrasil_abi::error::Error;

use crate::KERNEL_VIRT_OFFSET;

use self::table::{PageAttributes, PageEntry, PageTable, L0, L1, L2, L3};

pub mod process;
pub mod table;

#[derive(Debug)]
pub struct KernelTableManagerImpl;

const CANONICAL_ADDRESS_MASK: usize = 0xFFFF000000000000;
const KERNEL_PHYS_BASE: usize = 0x200000;

// Mapped at compile time
const KERNEL_MAPPING_BASE: usize = KERNEL_VIRT_OFFSET + KERNEL_PHYS_BASE;
const KERNEL_L0_INDEX: usize = page_index::<L0>(KERNEL_MAPPING_BASE);
const KERNEL_L1_INDEX: usize = page_index::<L1>(KERNEL_MAPPING_BASE);
const KERNEL_START_L2_INDEX: usize = page_index::<L2>(KERNEL_MAPPING_BASE);

// Must not be zero, should be at 4MiB
const_assert_ne!(KERNEL_START_L2_INDEX, 0);
// From static mapping
const_assert_eq!(KERNEL_L0_INDEX, 511);
const_assert_eq!(KERNEL_L1_INDEX, 0);

// Mapped at boot
const EARLY_MAPPING_L2I: usize = KERNEL_START_L2_INDEX - 1;
const DEVICE_MAPPING_L1I: usize = KERNEL_L1_INDEX + 2;
const RAM_MAPPING_L0I: usize = KERNEL_L0_INDEX - 1;

const DEVICE_MAPPING_L3_COUNT: usize = 4;

split_spinlock! {
    use libk_mm_interface::KernelImageObject;
    use memtables::x86_64::FixedTables;
    use crate::ArchitectureImpl;

    #[link_section = ".data.tables"]
    static KERNEL_TABLES: KernelImageObject<FixedTables> =
        unsafe { KernelImageObject::new(FixedTables::zeroed()) };
}

// 2MiB for early mappings
const EARLY_MAPPING_OFFSET: usize = CANONICAL_ADDRESS_MASK
    | (KERNEL_L0_INDEX * L0::SIZE)
    | (KERNEL_L1_INDEX * L1::SIZE)
    | (EARLY_MAPPING_L2I * L2::SIZE);
static mut EARLY_MAPPING_L3: PageTable<L3> = PageTable::zeroed();
// 1GiB for device MMIO mapping
const DEVICE_MAPPING_OFFSET: usize =
    CANONICAL_ADDRESS_MASK | (KERNEL_L0_INDEX * L0::SIZE) | (DEVICE_MAPPING_L1I * L1::SIZE);
static mut DEVICE_MAPPING_L2: PageTable<L2> = PageTable::zeroed();
static mut DEVICE_MAPPING_L3S: [PageTable<L3>; DEVICE_MAPPING_L3_COUNT] =
    [PageTable::zeroed(); DEVICE_MAPPING_L3_COUNT];
// 512GiB for whole RAM mapping
pub const RAM_MAPPING_OFFSET: usize = CANONICAL_ADDRESS_MASK | (RAM_MAPPING_L0I * L0::SIZE);
pub static MEMORY_LIMIT: AtomicUsize = AtomicUsize::new(0);
pub static mut RAM_MAPPING_L1: PageTable<L1> = PageTable::zeroed();

impl KernelTableManager for KernelTableManagerImpl {
    fn virtualize(address: u64) -> usize {
        let address = address as usize;
        if address < MEMORY_LIMIT.load(Ordering::Acquire) {
            address + RAM_MAPPING_OFFSET
        } else {
            panic!("Invalid physical address: {:#x}", address);
        }
    }

    fn physicalize(address: usize) -> u64 {
        if address < RAM_MAPPING_OFFSET
            || address - RAM_MAPPING_OFFSET >= MEMORY_LIMIT.load(Ordering::Acquire)
        {
            panic!("Not a virtualized physical address: {:#x}", address);
        }

        (address - RAM_MAPPING_OFFSET) as _
    }

    unsafe fn map_device_pages(
        base: u64,
        count: usize,
        attrs: DeviceMemoryAttributes,
    ) -> Result<RawDeviceMemoryMapping<Self>, Error> {
        map_device_memory(PhysicalAddress::from_u64(base), count, attrs)
    }

    unsafe fn unmap_device_pages(mapping: &RawDeviceMemoryMapping<Self>) {
        unmap_device_memory(mapping)
    }
}

// Early mappings
unsafe fn map_early_pages(physical: PhysicalAddress, count: usize) -> Result<usize, Error> {
    for l3i in 0..512 {
        let mut taken = false;
        for i in 0..count {
            if EARLY_MAPPING_L3[i + l3i].is_present() {
                taken = true;
                break;
            }
        }

        if taken {
            continue;
        }

        for i in 0..count {
            // TODO NX, NC
            EARLY_MAPPING_L3[i + l3i] =
                PageEntry::page(physical.add(i * L3::SIZE), PageAttributes::WRITABLE);
        }

        return Ok(EARLY_MAPPING_OFFSET + l3i * L3::SIZE);
    }

    Err(Error::OutOfMemory)
}

unsafe fn unmap_early_page(address: usize) {
    if !(EARLY_MAPPING_OFFSET..EARLY_MAPPING_OFFSET + L2::SIZE).contains(&address) {
        panic!("Tried to unmap invalid early mapping: {:#x}", address);
    }

    let l3i = (address - EARLY_MAPPING_OFFSET).page_index::<L3>();

    assert!(EARLY_MAPPING_L3[l3i].is_present());
    EARLY_MAPPING_L3[l3i] = PageEntry::INVALID;
}

// Device mappings
unsafe fn map_device_memory_l3(
    base: PhysicalAddress,
    count: usize,
    _attrs: DeviceMemoryAttributes,
) -> Result<usize, Error> {
    // TODO don't map pages if already mapped

    'l0: for i in 0..DEVICE_MAPPING_L3_COUNT * 512 {
        for j in 0..count {
            let l2i = (i + j) / 512;
            let l3i = (i + j) % 512;

            if DEVICE_MAPPING_L3S[l2i][l3i].is_present() {
                continue 'l0;
            }
        }

        for j in 0..count {
            let l2i = (i + j) / 512;
            let l3i = (i + j) % 512;

            // TODO NX, NC
            DEVICE_MAPPING_L3S[l2i][l3i] =
                PageEntry::page(base.add(j * L3::SIZE), PageAttributes::WRITABLE);
        }

        return Ok(DEVICE_MAPPING_OFFSET + i * L3::SIZE);
    }

    Err(Error::OutOfMemory)
}

unsafe fn map_device_memory_l2(
    base: PhysicalAddress,
    count: usize,
    _attrs: DeviceMemoryAttributes,
) -> Result<usize, Error> {
    'l0: for i in DEVICE_MAPPING_L3_COUNT..512 {
        for j in 0..count {
            if DEVICE_MAPPING_L2[i + j].is_present() {
                continue 'l0;
            }
        }

        for j in 0..count {
            DEVICE_MAPPING_L2[i + j] =
                PageEntry::<L2>::block(base.add(j * L2::SIZE), PageAttributes::WRITABLE);
        }

        return Ok(DEVICE_MAPPING_OFFSET + i * L2::SIZE);
    }

    Err(Error::OutOfMemory)
}

unsafe fn map_device_memory(
    base: PhysicalAddress,
    size: usize,
    attrs: DeviceMemoryAttributes,
) -> Result<RawDeviceMemoryMapping<KernelTableManagerImpl>, Error> {
    let l3_aligned = base.page_align_down::<L3>();
    let l3_offset = base.page_offset::<L3>();
    let page_count = (l3_offset + size).page_count::<L3>();

    if page_count > 256 {
        // Large mapping, use L2 mapping instead
        let l2_aligned = base.page_align_down::<L2>();
        let l2_offset = base.page_offset::<L2>();
        let page_count = (l2_offset + size).page_count::<L2>();

        let base_address = map_device_memory_l2(l2_aligned, page_count, attrs)?;
        let address = base_address + l2_offset;

        Ok(RawDeviceMemoryMapping::from_raw_parts(
            address,
            base_address,
            page_count,
            L2::SIZE,
        ))
    } else {
        // Just map the pages directly
        let base_address = map_device_memory_l3(l3_aligned, page_count, attrs)?;
        let address = base_address + l3_offset;

        Ok(RawDeviceMemoryMapping::from_raw_parts(
            address,
            base_address,
            page_count,
            L3::SIZE,
        ))
    }
}

unsafe fn unmap_device_memory(map: &RawDeviceMemoryMapping<KernelTableManagerImpl>) {
    match map.page_size {
        L3::SIZE => {
            for i in 0..map.page_count {
                let page = map.base_address + i * L3::SIZE;
                let l2i = page.page_index::<L2>();
                let l3i = page.page_index::<L3>();
                assert!(DEVICE_MAPPING_L3S[l2i][l3i].is_present());
                DEVICE_MAPPING_L3S[l2i][l3i] = PageEntry::INVALID;
                flush_tlb_entry(page);
            }
        }
        L2::SIZE => todo!(),
        _ => unimplemented!(),
    }
}

/// Memory mapping which may be used for performing early kernel initialization
pub struct EarlyMapping<'a, T: ?Sized> {
    value: &'a mut T,
    page_count: usize,
}

impl<'a, T: Sized> EarlyMapping<'a, T> {
    /// # Safety
    ///
    /// `physical` address provided must be a valid non-NULL address actually containing `T`.
    pub unsafe fn map(physical: PhysicalAddress) -> Result<EarlyMapping<'a, T>, Error> {
        let layout = Layout::new::<T>();
        let aligned = physical.page_align_down::<L3>();
        let offset = physical.page_offset::<L3>();
        let page_count = (offset + layout.size()).div_ceil(L3::SIZE);

        let virt = map_early_pages(aligned, page_count)?;
        let value = &mut *((virt + offset) as *mut T);

        Ok(EarlyMapping { value, page_count })
    }

    /// # Safety
    ///
    /// `physical` address provided must be a valid non-NULL address actually containing a `T`
    /// slice of given `len`.
    pub unsafe fn map_slice(
        physical: PhysicalAddress,
        len: usize,
    ) -> Result<EarlyMapping<'a, [T]>, Error> {
        let layout = Layout::array::<T>(len).unwrap();
        let aligned = physical.page_align_down::<L3>();
        let offset = physical.page_offset::<L3>();
        let page_count = (offset + layout.size()).div_ceil(L3::SIZE);

        let virt = map_early_pages(aligned, page_count)?;
        let value = core::slice::from_raw_parts_mut((virt + offset) as *mut T, len);

        Ok(EarlyMapping { value, page_count })
    }
}

impl<T: ?Sized> Deref for EarlyMapping<'_, T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        self.value
    }
}

impl<T: ?Sized> DerefMut for EarlyMapping<'_, T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        self.value
    }
}

impl<T: ?Sized> Drop for EarlyMapping<'_, T> {
    fn drop(&mut self) {
        let address = (self.value as *mut T).addr() & !(L3::SIZE - 1);

        for i in 0..self.page_count {
            let page = address + i * L3::SIZE;

            unsafe {
                unmap_early_page(page);
            }
        }
    }
}

pub fn clone_kernel_tables(dst: &mut PageTable<L0>) {
    let tables = KERNEL_TABLES.lock();
    unsafe {
        dst[KERNEL_L0_INDEX] = PageEntry::from_raw(tables.l0.data[KERNEL_L0_INDEX]);
        dst[RAM_MAPPING_L0I] = PageEntry::from_raw(tables.l0.data[RAM_MAPPING_L0I]);
    }
}

/// Sets up the following memory map:
/// ...: KERNEL_TABLES.l0:
///     * 0xFFFFFF0000000000 .. 0xFFFFFFFF8000000000        : RAM_MAPPING_L1
///     * 0xFFFFFF8000000000 .. ...                         : KERNEL_TABLES.kernel_l1:
///         * 0xFFFFFF8000000000 .. 0xFFFFFF8040000000      : KERNEL_TABLES.kernel_l2
///             * 0xFFFFFF8000000000 .. 0xFFFFFF8000200000  : ---
///             * 0xFFFFFF8000200000 .. 0xFFFFFF8000400000  : EARLY_MAPPING_L3
///             * 0xFFFFFF8000400000 .. ...                 : KERNEL_TABLES.kernel_l3s
///         * 0xFFFFFF8040000000 .. 0xFFFFFF8080000000      : ---
///         * 0xFFFFFF8080000000 .. 0xFFFFFF8100000000      : DEVICE_MAPPING_L2
///             * 0xFFFFFF8080000000 .. 0xFFFFFF8080800000  : DEVICE_MAPPING_L3S
///             * 0xFFFFFF8080800000 .. 0xFFFFFF8100000000  : ...
///
/// # Safety
///
/// Unsafe, must only be called by BSP during its early init, must already be in "higher-half"
pub unsafe fn init_fixed_tables() {
    let mut tables = KERNEL_TABLES.lock();
    // TODO this could be built in compile-time too?
    let early_mapping_l3_phys = addr_of!(EARLY_MAPPING_L3) as usize - KERNEL_VIRT_OFFSET;
    let device_mapping_l2_phys = addr_of!(DEVICE_MAPPING_L2) as usize - KERNEL_VIRT_OFFSET;
    let ram_mapping_l1_phys = addr_of!(RAM_MAPPING_L1) as usize - KERNEL_VIRT_OFFSET;

    for i in 0..DEVICE_MAPPING_L3_COUNT {
        let device_mapping_l3_phys = PhysicalAddress::from_usize(
            &DEVICE_MAPPING_L3S[i] as *const _ as usize - KERNEL_VIRT_OFFSET,
        );
        DEVICE_MAPPING_L2[i] = PageEntry::table(device_mapping_l3_phys, PageAttributes::WRITABLE);
    }

    assert_eq!(tables.kernel_l2.data[EARLY_MAPPING_L2I], 0);
    tables.kernel_l2.data[EARLY_MAPPING_L2I] = (early_mapping_l3_phys as u64)
        | (PageAttributes::WRITABLE | PageAttributes::PRESENT).bits();

    assert_eq!(tables.kernel_l1.data[DEVICE_MAPPING_L1I], 0);
    tables.kernel_l1.data[DEVICE_MAPPING_L1I] = (device_mapping_l2_phys as u64)
        | (PageAttributes::WRITABLE | PageAttributes::PRESENT).bits();

    assert_eq!(tables.l0.data[RAM_MAPPING_L0I], 0);
    tables.l0.data[RAM_MAPPING_L0I] =
        (ram_mapping_l1_phys as u64) | (PageAttributes::WRITABLE | PageAttributes::PRESENT).bits();

    // TODO ENABLE EFER.NXE
    let cr3 = (&raw const tables.l0).addr() - KERNEL_VIRT_OFFSET;
    CR3.set_address(cr3);
}

/// # Safety
///
/// `address` must be page-aligned.
#[inline]
pub unsafe fn flush_tlb_entry(address: usize) {
    core::arch::asm!("invlpg ({0})", in(reg) address, options(att_syntax));
}