// Standard
use std::{collections::HashMap, sync::Arc};

// Library
use vek::*;

// Crate
use crate::{
    terrain::TerrainChunkMeta,
    vol::{BaseVol, ReadVol, SampleVol, SizedVol, VolSize, Vox, WriteVol},
    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
#[derive(Clone)]
pub struct VolMap<V: Vox + Clone, S: VolSize + Clone, M: Clone> {
    chunks: HashMap<Vec3<i32>, Arc<Chunk<V, S, M>>>,
}

impl<V: Vox + Clone, S: VolSize + Clone, M: Clone> 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)]
    pub fn chunk_offs(pos: Vec3<i32>) -> Vec3<i32> {
        pos.map2(S::SIZE, |e, sz| e.rem_euclid(sz as i32))
    }
}

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

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

    /// 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(), ());

        // let mut last_chunk_pos = self.pos_key(range.min);
        // let mut last_chunk = self.get_key(last_chunk_pos);

        // for pos in sample.iter_positions() {
        //     let new_chunk_pos = self.pos_key(range.min + pos);
        //     if last_chunk_pos != new_chunk_pos {
        //         last_chunk = self.get_key(new_chunk_pos);
        //         last_chunk_pos = new_chunk_pos;
        //     }
        //     sample
        //         .set(
        //             pos,
        //             if let Some(chunk) = last_chunk {
        //                 chunk
        //                     .get(Self::chunk_offs(range.min + pos))
        //                     .map(|v| v.clone())
        //                     .unwrap_or(V::empty())
        //             // Fallback in case the chunk doesn't exist
        //             } else {
        //                 self.get(range.min + pos)
        //                     .map(|v| v.clone())
        //                     .unwrap_or(V::empty())
        //             },
        //         )
        //         .map_err(|err| VolMapErr::DynaErr(err))?;
        // }

        // Ok(sample)

        let mut sample = VolMap::new();
        let chunk_min = Self::chunk_key(range.min);
        let chunk_max = Self::chunk_key(range.max);
        for x in chunk_min.x..=chunk_max.x {
            for y in chunk_min.y..=chunk_max.y {
                for z in chunk_min.z..=chunk_max.z {
                    let chunk_key = Vec3::new(x, y, z);

                    let chunk = self.get_key_arc(chunk_key).map(|v| v.clone());

                    if let Some(chunk) = chunk {
                        sample.insert(chunk_key, chunk);
                    }
                }
            }
        }

        Ok(sample)
    }
}

impl<V: Vox + Clone, S: VolSize + Clone, M: Clone> 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);
                Arc::make_mut(chunk)
                    .set(co, vox)
                    .map_err(|err| VolMapErr::ChunkErr(err))
            })
    }
}

impl<V: Vox + Clone, S: VolSize + Clone, M: Clone> 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: Arc<Chunk<V, S, M>>,
    ) -> Option<Arc<Chunk<V, S, M>>> {
        self.chunks.insert(key, chunk)
    }

    pub fn get_key(&self, key: Vec3<i32>) -> Option<&Chunk<V, S, M>> {
        match self.chunks.get(&key) {
            Some(arc_chunk) => Some(arc_chunk.as_ref()),
            None => None,
        }
    }

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

    pub fn remove(&mut self, key: Vec3<i32>) -> Option<Arc<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)
    }

    pub fn pos_key(&self, pos: Vec3<i32>) -> Vec3<i32> {
        Self::chunk_key(pos)
    }

    pub fn iter<'a>(&'a self) -> ChunkIter<'a, V, S, M> {
        ChunkIter {
            iter: self.chunks.iter(),
        }
    }
}

pub struct ChunkIter<'a, V: Vox + Clone, S: VolSize + Clone, M: Clone> {
    iter: std::collections::hash_map::Iter<'a, Vec3<i32>, Arc<Chunk<V, S, M>>>,
}

impl<'a, V: Vox + Clone, S: VolSize + Clone, M: Clone> Iterator for ChunkIter<'a, V, S, M> {
    type Item = (Vec3<i32>, &'a Arc<Chunk<V, S, M>>);

    fn next(&mut self) -> Option<Self::Item> {
        self.iter.next().map(|(k, c)| (*k, c))
    }
}