use fpnum::FPNum;

use std::{

    collections::BinaryHeap,

    num::NonZeroU16,

    ops::{Add, Index, IndexMut},

};

pub type GearId = NonZeroU16;

pub trait GearData {}

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

#[repr(transparent)]

pub struct Millis(u32);

impl Millis {

    #[inline]

    pub fn new(value: u32) -> Self {

        Self(value)

    }

    #[inline]

    pub fn get(self) -> u32 {

        self.0

    }

    #[inline]

    pub fn to_fixed(self) -> FPNum {

        FPNum::new(self.0 as i32, 1000)

    }

}

impl Add for Millis {

    type Output = Self;

    fn add(self, rhs: Self) -> Self::Output {

        Self(self.0 + rhs.0)

    }

}

pub trait GearDataProcessor<T: GearData> {

    fn add(&mut self, gear_id: GearId, gear_data: T);

    fn remove(&mut self, gear_id: GearId);

    fn get(&mut self, gear_id: GearId) -> Option<T>;

}

pub trait GearDataAggregator<T: GearData> {

    fn find_processor(&mut self) -> &mut GearDataProcessor<T>;

}

pub struct GearAllocator {

    max_id: u16,

    free_ids: BinaryHeap<GearId>,

}

impl GearAllocator {

    pub fn new() -> Self {

        Self {

            max_id: 0,

            free_ids: BinaryHeap::with_capacity(1024),

        }

    }

    pub fn alloc(&mut self) -> Option<GearId> {

        self.free_ids.pop().or_else(|| {

            self.max_id.checked_add(1).and_then(|new_max_id| {

                self.max_id = new_max_id;

                NonZeroU16::new(new_max_id)

            })

        })

    }

    pub fn free(&mut self, gear_id: GearId) {

        self.free_ids.push(gear_id)

    }

}

#[derive(Clone, Copy, Default)]

pub struct LookupEntry<T> {

    index: Option<NonZeroU16>,

    value: T,

}

impl<T> LookupEntry<T> {

    #[inline]

    pub fn index(&self) -> u16 {

        self.index.map(|i| i.get()).unwrap_or(0) - 1

    }

    #[inline]

    pub fn set_index(&mut self, index: u16) {

        self.index = unsafe { Some(NonZeroU16::new_unchecked(index.saturating_add(1))) };

    }

    #[inline]

    pub fn value(&self) -> &T {

        &self.value

    }

    #[inline]

    pub fn value_mut(&mut self) -> &mut T {

        &mut self.value

    }

    #[inline]

    pub fn set_value(&mut self, value: T) {

        self.value = value;

    }

}

pub struct GearDataLookup<T> {

    lookup: Box<[LookupEntry<T>]>,

}

impl<T: Default + Copy> GearDataLookup<T> {

    pub fn new() -> Self {

        Self {

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

        }

    }

}

impl<T> GearDataLookup<T> {

    pub fn add(&mut self, gear_id: GearId, index: u16, value: T) {

        // All possible Gear IDs are valid indices

        let entry = unsafe { self.lookup.get_unchecked_mut(gear_id.get() as usize - 1) };

        entry.set_index(index);

        entry.set_value(value);

    }

    pub fn get(&self, gear_id: GearId) -> Option<&LookupEntry<T>> {

        // All possible Gear IDs are valid indices

        let entry = unsafe { self.lookup.get_unchecked(gear_id.get() as usize - 1) };

        if let Some(index) = entry.index {

            Some(entry)

        } else {

            None

        }

    }

    pub fn get_mut(&mut self, gear_id: GearId) -> Option<&mut LookupEntry<T>> {

        // All possible Gear IDs are valid indices

        let entry = unsafe { self.lookup.get_unchecked_mut(gear_id.get() as usize - 1) };

        if let Some(index) = entry.index {

            Some(entry)

        } else {

            None

        }

    }

}

impl<T> Index<GearId> for GearDataLookup<T> {

    type Output = LookupEntry<T>;

    fn index(&self, index: GearId) -> &Self::Output {

        self.get(index).unwrap()

    }

}

impl<T> IndexMut<GearId> for GearDataLookup<T> {

    fn index_mut(&mut self, index: GearId) -> &mut Self::Output {

        self.get_mut(index).unwrap()

    }

}