use super::common::GearId;

use std::{

    any::TypeId,

    fmt::{Debug, Error, Formatter},

    marker::PhantomData,

    mem::{align_of, size_of, MaybeUninit},

    num::NonZeroU16,

    ptr::{copy_nonoverlapping, null_mut, NonNull},

    slice,

};

pub trait TypeTuple: Sized {

}

impl TypeTuple for () {

}

impl<T: 'static> TypeTuple for &T {

    }

}

pub trait TypeIter: TypeTuple {

    unsafe fn iter<F: FnMut(GearId, Self)>(slices: &[*mut u8], count: usize, f: F);

}

macro_rules! type_tuple_impl {

    ($($n: literal: $t: ident),+) => {

        impl<$($t: 'static),+> TypeTuple for ($(&$t),+,) {

            }

        }

        impl<$($t: 'static),+> TypeIter for ($(&$t),+,) {

                for i in 0..count {

                    f(*(*slices.get_unchecked(0) as *const GearId).add(i),

                      ($(&*(*slices.get_unchecked($n + 1) as *mut $t).add(i)),+,));

                }

            }

        }

        impl<$($t: 'static),+> TypeTuple for ($(&mut $t),+,) {

            }

        }

        impl<$($t: 'static),+> TypeIter for ($(&mut $t),+,) {

                for i in 0..count {

                    f(*(*slices.get_unchecked(0) as *const GearId).add(i),

                      ($(&mut *(*slices.get_unchecked($n + 1) as *mut $t).add(i)),+,));

                }

            }

        }

    }

}

type_tuple_impl!(0: A);

type_tuple_impl!(0: A, 1: B);

type_tuple_impl!(0: A, 1: B, 2: C);

type_tuple_impl!(0: A, 1: B, 2: C, 3: D);

type_tuple_impl!(0: A, 1: B, 2: C, 3: D, 4: E);

const BLOCK_SIZE: usize = 32768;

struct DataBlock {

    max_elements: u16,

    elements_count: u16,

    data: Box<[u8; BLOCK_SIZE]>,

    component_blocks: [Option<NonNull<u8>>; 64],

    element_sizes: Box<[u16]>,

}

impl Unpin for DataBlock {}

impl Debug for DataBlock {

    fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {

        write!(

            f,

            "Block ({}/{}) {{\n",

            self.elements_count, self.max_elements

        )?;

        write!(f, "\tIDs: [")?;

        let id_slice = unsafe {

            slice::from_raw_parts(

                self.data.as_ptr() as *const GearId,

                self.elements_count as usize,

            )

        };

        for gear_id in id_slice {

            write!(f, "{}, ", gear_id)?;

        }

        write!(f, "]\n")?;

        for type_index in 0..self.element_sizes.len() {

            if let Some(ptr) = self.component_blocks[type_index] {

                write!(f, "\tC{}: [", type_index)?;

                let slice = unsafe {

                    slice::from_raw_parts(

                        ptr.as_ptr(),

                        (self.elements_count * self.element_sizes[type_index]) as usize,

                    )

                };

                for byte in slice {

                    write!(f, "{}, ", byte)?;

                }

                write!(f, "]\n")?;

            }

        }

        write!(f, "}}\n")

    }

}

impl DataBlock {

    fn new(mask: u64, element_sizes: &[u16], element_alignments: &[u8]) -> Self {

        let total_padding: usize = element_alignments.iter().map(|x| *x as usize).sum();

        let total_size: u16 = element_sizes

            .iter()

            .enumerate()

            .filter(|(i, _)| mask & (1 << *i as u64) != 0)

            .map(|(_, size)| *size)

            .sum();

        let max_elements =

            ((BLOCK_SIZE - total_padding) / (total_size as usize + size_of::<GearId>())) as u16;

        //ensure the block memory is aligned to GearId

        let tmp_data: Box<[GearId; BLOCK_SIZE / size_of::<GearId>()]> =

            Box::new(unsafe { MaybeUninit::uninit().assume_init() });

        let mut data: Box<[u8; BLOCK_SIZE]> =

            unsafe { Box::from_raw(Box::into_raw(tmp_data) as *mut [u8; BLOCK_SIZE]) };

        let mut blocks = [None; 64];

        let mut address = unsafe {

            data.as_mut_ptr()

                .add(size_of::<GearId>() * max_elements as usize)

        };

        let mut mask_bits = mask;

        while mask_bits != 0 {

            let i = mask_bits.trailing_zeros() as usize;

            unsafe {

                address = address.add(address.align_offset(element_alignments[i] as usize));

                blocks[i] = Some(NonNull::new_unchecked(address));

                address = address.add(element_sizes[i] as usize * max_elements as usize)

            };

            mask_bits &= mask_bits - 1;

        }

        Self {

            elements_count: 0,

            max_elements,

            data,

            component_blocks: blocks,

            element_sizes: Box::from(element_sizes),

        }

    }

    #[inline]

    fn gear_ids(&self) -> &[GearId] {

        unsafe {

            slice::from_raw_parts(

                self.data.as_ptr() as *const GearId,

                self.max_elements as usize,

            )

        }

    }

    #[inline]

    fn gear_ids_mut(&mut self) -> &mut [GearId] {

        unsafe {

            slice::from_raw_parts_mut(

                self.data.as_mut_ptr() as *mut GearId,

                self.max_elements as usize,

            )

        }

    }

    #[inline]

    fn is_full(&self) -> bool {

        self.elements_count == self.max_elements

    }

}

#[derive(Clone, Copy, Debug, Default)]

struct LookupEntry {

    index: Option<NonZeroU16>,

    block_index: u16,

}

impl LookupEntry {

    fn new(block_index: u16, index: u16) -> Self {

        Self {

            index: unsafe { Some(NonZeroU16::new_unchecked(index + 1)) },

            block_index,

        }

    }

}

#[derive(Copy, Clone, Eq, PartialEq, Debug)]

struct BlockMask {

    type_mask: u64,

    tag_mask: u64,

}

impl BlockMask {

    #[inline]

    fn new(type_mask: u64, tag_mask: u64) -> Self {

        Self {

            type_mask,

            tag_mask,

        }

    }

    #[inline]

    fn with_type(&self, type_bit: u64) -> Self {

        Self::new(self.type_mask | type_bit, self.tag_mask)

    }

    #[inline]

    fn without_type(&self, type_bit: u64) -> Self {

        Self::new(self.type_mask & !type_bit, self.tag_mask)

    }

    #[inline]

    fn with_tag(&self, tag_bit: u64) -> Self {

        Self::new(self.type_mask, self.tag_mask | tag_bit)

    }

}

pub struct GearDataManager {

    types: Vec<TypeId>,

    tags: Vec<TypeId>,

    blocks: Vec<DataBlock>,

    block_masks: Vec<BlockMask>,

    element_sizes: Box<[u16; 64]>,

    element_alignments: Box<[u8; 64]>,

    lookup: Box<[LookupEntry]>,

}

impl GearDataManager {

    pub fn new() -> Self {

        Self {

            types: Vec::with_capacity(64),

            tags: Vec::with_capacity(64),

            blocks: vec![],

            block_masks: vec![],

            element_sizes: Box::new([0; 64]),

            element_alignments: Box::new([0; 64]),

            lookup: vec![LookupEntry::default(); u16::MAX as usize].into_boxed_slice(),

        }

    }

    #[inline]

    fn get_type_index<T: 'static>(&self) -> Option<usize> {

        let type_id = TypeId::of::<T>();

        self.types.iter().position(|id| *id == type_id)

    }

    #[inline]

    fn get_tag_index<T: 'static>(&self) -> Option<usize> {

        let type_id = TypeId::of::<T>();

        self.tags.iter().position(|id| *id == type_id)

    }

    fn move_between_blocks(

        &mut self,

        src_block_index: u16,

        src_index: u16,

        dest_block_index: u16,

    ) -> u16 {

        debug_assert!(src_block_index != dest_block_index);

        let src_mask = self.block_masks[src_block_index as usize];

        let dest_mask = self.block_masks[dest_block_index as usize];

        debug_assert!(src_mask.type_mask & dest_mask.type_mask != 0);

        let src_block = &self.blocks[src_block_index as usize];

        let dest_block = &self.blocks[dest_block_index as usize];

        debug_assert!(src_index < src_block.elements_count);

        debug_assert!(!dest_block.is_full());

        let dest_index = dest_block.elements_count;

        let mut type_mask = src_mask.type_mask;

        while type_mask != 0 {

            let i = type_mask.trailing_zeros() as usize;

            let size = self.element_sizes[i];

            let src_ptr = src_block.component_blocks[i].unwrap().as_ptr();

            if let Some(dest_ptr) = dest_block.component_blocks[i] {

                let dest_ptr = dest_ptr.as_ptr();

                unsafe {

                    copy_nonoverlapping(

                        src_ptr.add((src_index * size) as usize),

                        dest_ptr.add((dest_index * size) as usize),

                        size as usize,

                    );

                }

            }

            unsafe {

                if src_index < src_block.elements_count - 1 {

                    copy_nonoverlapping(

                        src_ptr.add((size * (src_block.elements_count - 1)) as usize),

                        src_ptr.add((size * src_index) as usize),

                        size as usize,

                    );

                }

            }

            type_mask &= type_mask - 1;

        }

        let src_block = &mut self.blocks[src_block_index as usize];

        let gear_id = src_block.gear_ids()[src_index as usize];

        if src_index + 1 < src_block.elements_count {

            let relocated_index = src_block.elements_count as usize - 1;

            let gear_ids = src_block.gear_ids_mut();

            let relocated_id = gear_ids[relocated_index];

            gear_ids[src_index as usize] = relocated_id;

            self.lookup[relocated_id.get() as usize - 1] =

                LookupEntry::new(src_block_index, src_index);

        }

        src_block.elements_count -= 1;

        let dest_block = &mut self.blocks[dest_block_index as usize];

        let dest_index = dest_block.elements_count;

        dest_block.gear_ids_mut()[dest_index as usize] = gear_id;

        self.lookup[gear_id.get() as usize - 1] = LookupEntry::new(dest_block_index, dest_index);

        dest_block.elements_count += 1;

        dest_block.elements_count - 1

    }

    fn add_to_block<T: Clone>(&mut self, gear_id: GearId, block_index: u16, value: &T) {

        debug_assert!(

            self.block_masks[block_index as usize]

                .type_mask

                .count_ones()

                == 1

        );

        let block = &mut self.blocks[block_index as usize];

        debug_assert!(block.elements_count < block.max_elements);

        unsafe {

            *(block.component_blocks[0].unwrap().as_ptr() as *mut T)

                .add(block.elements_count as usize) = value.clone();

        };

        let index = block.elements_count;

        self.lookup[gear_id.get() as usize - 1] = LookupEntry::new(block_index, index);

        block.gear_ids_mut()[index as usize] = gear_id;

        block.elements_count += 1;

    }

    fn remove_from_block(&mut self, block_index: u16, index: u16) {

        let block = &mut self.blocks[block_index as usize];

        debug_assert!(index < block.elements_count);

        for (i, size) in self.element_sizes.iter().cloned().enumerate() {

            if index < block.elements_count - 1 {

                if let Some(ptr) = block.component_blocks[i] {

                    unsafe {

                        copy_nonoverlapping(

                            ptr.as_ptr()

                                .add((size * (block.elements_count - 1)) as usize),

                            ptr.as_ptr().add((size * index) as usize),

                            size as usize,

                        );

                    }

                }

            }

        }

        self.lookup[block.gear_ids()[index as usize].get() as usize - 1] = LookupEntry::default();

        if index < block.elements_count - 1 {

            let relocated_index = block.elements_count as usize - 1;

            let gear_ids = block.gear_ids_mut();

            gear_ids[index as usize] = gear_ids[relocated_index];

            self.lookup[gear_ids[relocated_index].get() as usize - 1] =

                LookupEntry::new(block_index, index);

        }

        block.elements_count -= 1;

    }

    fn write_component<T: Clone>(

        &mut self,

        block_index: u16,

        index: u16,

        type_index: usize,

        value: &T,

    ) {

        debug_assert!(type_index < self.types.len());

        let block = &mut self.blocks[block_index as usize];

        debug_assert!(index < block.elements_count);

        unsafe {

            *(block.component_blocks[type_index].unwrap().as_ptr() as *mut T).add(index as usize) =

                value.clone();

        };

    }

    #[inline]

    fn ensure_block(&mut self, mask: BlockMask) -> u16 {

        if let Some(index) = self

            .block_masks

            .iter()

            .enumerate()

            .position(|(i, m)| *m == mask && !self.blocks[i].is_full())

        {

            index as u16

        } else {

            self.blocks.push(DataBlock::new(

                mask.type_mask,

                &self.element_sizes[0..self.types.len()],

                &self.element_alignments[0..self.types.len()],

            ));

            self.block_masks.push(mask);

            (self.blocks.len() - 1) as u16

        }

    }

    pub fn add<T: Clone + 'static>(&mut self, gear_id: GearId, value: &T) {

        if let Some(type_index) = self.get_type_index::<T>() {

            let type_bit = 1 << type_index as u64;

            let entry = self.lookup[gear_id.get() as usize - 1];

            if let Some(index) = entry.index {

                let mask = self.block_masks[entry.block_index as usize];

                let new_mask = mask.with_type(type_bit);

                if new_mask != mask {

                    let dest_block_index = self.ensure_block(new_mask);

                    let dest_index = self.move_between_blocks(

                        entry.block_index,

                        index.get() - 1,

                        dest_block_index,

                    );

                    self.write_component(dest_block_index, dest_index, type_index, value);

                }

            } else {

                let dest_block_index = self.ensure_block(BlockMask::new(type_bit, 0));

                self.add_to_block(gear_id, dest_block_index, value);

            }

        } else {

            panic!("Unregistered type")