// Standard
use std::collections::HashMap;

// Library
use vek::*;

// Crate
use crate::{
    vol::{
        Vox,
        BaseVol,
        SizedVol,
        ReadVol,
        SampleVol,
        WriteVol,
        VolSize,
    },
    volumes::{
        chunk::{Chunk, ChunkErr},
        dyna::{Dyna, DynaErr},
    },
};

#[derive(Debug)]
pub enum VolMapErr {
    NoSuchChunk,
    ChunkErr(ChunkErr),
    DynaErr(DynaErr),
}

// V = Voxel
// S = Size (replace with a const when const generics is a thing)
// M = Chunk metadata
pub struct VolMap<V: Vox, S: VolSize, M> {
    chunks: HashMap<Vec3<i32>, Chunk<V, S, M>>,
}

impl<V: Vox, S: VolSize, M> VolMap<V, S, M> {
    #[inline(always)]
    fn chunk_key(pos: Vec3<i32>) -> Vec3<i32> {
        pos.map2(S::SIZE, |e, sz| e.div_euclid(sz as i32))
    }

    #[inline(always)]
    fn chunk_offs(pos: Vec3<i32>) -> Vec3<i32> {
        pos.map2(S::SIZE, |e, sz| e.rem_euclid(sz as i32))
    }
}

impl<V: Vox, S: VolSize, M> BaseVol for VolMap<V, S, M> {
    type Vox = V;
    type Err = VolMapErr;
}

impl<V: Vox, S: VolSize, M> ReadVol for VolMap<V, S, M> {
    #[inline(always)]
    fn get(&self, pos: Vec3<i32>) -> Result<&V, VolMapErr> {
        let ck = Self::chunk_key(pos);
        self.chunks.get(&ck)
            .ok_or(VolMapErr::NoSuchChunk)
            .and_then(|chunk| {
                let co = Self::chunk_offs(pos);
                chunk.get(co).map_err(|err| VolMapErr::ChunkErr(err))
            })
    }
}

impl<V: Vox + Clone, S: VolSize, M> SampleVol for VolMap<V, S, M> {
    type Sample = Dyna<V, ()>;

    /// Take a sample of the terrain by cloning the voxels within the provided range.
    ///
    /// Note that the resultant volume does not carry forward metadata from the original chunks.
    fn sample(&self, range: Aabb<i32>) -> Result<Self::Sample, VolMapErr> {
        // Return early if we don't have all the needed chunks that we need!
        let min_chunk = Self::chunk_key(range.min);
        let max_chunk = Self::chunk_key(range.max - Vec3::one());
        for x in min_chunk.x..=max_chunk.x {
            for y in min_chunk.y..=max_chunk.y {
                for z in min_chunk.z..=max_chunk.z {
                    if self.chunks.get(&Vec3::new(x, y, z)).is_none() {
                        return Err(VolMapErr::NoSuchChunk);
                    }
                }
            }
        }

        let mut sample = Dyna::filled(
            range.size().map(|e| e as u32).into(),
            V::empty(),
            (),
        );

        for pos in sample.iter_positions() {
            sample.set(pos, self.get(range.min + pos)?.clone())
                .map_err(|err| VolMapErr::DynaErr(err))?;
        }

        Ok(sample)
    }
}

impl<V: Vox, S: VolSize, M> WriteVol for VolMap<V, S, M> {
    #[inline(always)]
    fn set(&mut self, pos: Vec3<i32>, vox: V) -> Result<(), VolMapErr> {
        let ck = Self::chunk_key(pos);
        self.chunks.get_mut(&ck)
            .ok_or(VolMapErr::NoSuchChunk)
            .and_then(|chunk| {
                let co = Self::chunk_offs(pos);
                chunk.set(co, vox).map_err(|err| VolMapErr::ChunkErr(err))
            })
    }
}

impl<V: Vox, S: VolSize, M> VolMap<V, S, M> {
    pub fn new() -> Self {
        Self {
            chunks: HashMap::new(),
        }
    }

    pub fn chunk_size() -> Vec3<u32> { S::SIZE }

    pub fn insert(&mut self, key: Vec3<i32>, chunk: Chunk<V, S, M>) -> Option<Chunk<V, S, M>> {
        self.chunks.insert(key, chunk)
    }

    pub fn get_key(&self, key: Vec3<i32>) -> Option<&Chunk<V, S, M>> {
        self.chunks.get(&key)
    }

    pub fn remove(&mut self, key: Vec3<i32>) -> Option<Chunk<V, S, M>> {
        self.chunks.remove(&key)
    }

    pub fn key_pos(&self, key: Vec3<i32>) -> Vec3<i32> {
        key * S::SIZE.map(|e| e as i32)
    }
}