use fnv::FnvHashMap;

use crate::MAX_DAG_DEPTH;
use crate::VChildDescriptor;
use crate::Vec3;
use crate::VoxelChunk;
use crate::log_2;



impl VoxelChunk {
    
    /// process a 3D array (`data` with dimensions `dim`) into a SVDAG, mapping values to materials using `f`
    pub fn from_dense_voxels(data : &[i32], dim : [usize; 3]) -> Self {
        
        assert!(dim[0] > 0 && dim[1] > 0 && dim[2] > 0);

        let depth = log_2(dim.iter().cloned().max().unwrap_or(0) - 1) as usize + 1;

        assert!(depth < MAX_DAG_DEPTH, "Depth is too large: {} >= {}", depth, MAX_DAG_DEPTH);

        let size = 1 << depth;

        fn recursive_create_dense(
            s : &mut VoxelChunk, d : usize, min : [usize; 3], size : usize, 
            data : &[i32], dim : [usize; 3],
            dedup : &mut FnvHashMap<VChildDescriptor, i32>
        ) -> i32 {
            if min[0] >= dim[0] || min[1] >= dim[1] || min[2] >= dim[2] {
                // air if the voxel does not intersect the voxel data
                return 0;
            }
            
            if size <= 1 {
                // once we reach size 1, take the material from the data
                let v = data[min[0] + dim[0] * (min[1] + dim[1] * min[2])];
                // prevent awful fractal voxel graphs
                return -v.abs();
            }

            const BOX_OFFSETS : [[usize; 3]; 8] = [
                [0, 0, 0],
                [1, 0, 0],
                [0, 1, 0],
                [1, 1, 0],
                [0, 0, 1],
                [1, 0, 1],
                [0, 1, 1],
                [1, 1, 1]
            ];

            let mut voxel = VChildDescriptor{
                sub_voxels : [0; 8],
            };

            let half_size = size >> 1;

            let mut is_uniform = true;

            for i in 0..8 {
                let bmin = [
                    min[0] + BOX_OFFSETS[i][0] * half_size,
                    min[1] + BOX_OFFSETS[i][1] * half_size,
                    min[2] + BOX_OFFSETS[i][2] * half_size
                ];

                voxel.sub_voxels[i] = recursive_create_dense(s, d - 1, bmin, half_size, data, dim, dedup);

                if voxel.sub_voxels[i] != voxel.sub_voxels[0] || voxel.sub_voxels[i] > 0 {
                    // the subvoxels are not all the same leaf node, so this voxel is not uniform
                    is_uniform = false;
                }
            }

            if is_uniform {
                return voxel.sub_voxels[0];
            }

            if let Some(&id) = dedup.get(&voxel) {
                // this node is a duplicate
                id
            } else {
                // this node is new, so add it
                s.voxels.push(voxel);
                let id = s.voxels.len() as i32;
                dedup.insert(voxel, id);
                id
            }
        }

        let mut chunk = VoxelChunk::empty();
        chunk.voxels.clear();
        // we build a list of unique voxels and store them in here
        let mut dedup = FnvHashMap::default();

        recursive_create_dense(&mut chunk, depth, [0,0,0], size, data, dim, &mut dedup);

        chunk.voxels.reverse();

        //fixup the subvoxel pointers (we reversed the order)
        let n = chunk.voxels.len() as i32;
        for i in 0..(chunk.voxels.len()) {
            for j in 0..8 {
                let sv = chunk.voxels[i].sub_voxels[j];
                if sv > 0 {
                    let svi = n - sv + 1;
                    chunk.voxels[i].sub_voxels[j] = svi;
                }
            }
        }

        chunk
    }

    /// process an implicit 3D array into a DAG.
    pub fn from_implicit_array<F : FnMut(usize, usize, usize) -> i32>(depth : usize, mut implicit : F) -> Self {

        assert!(depth < MAX_DAG_DEPTH, "Depth is too large: {} >= {}", depth, MAX_DAG_DEPTH);

        let size = 1 << depth;

        fn recursive_create_dense_implicit<F : FnMut(usize, usize, usize) -> i32>(
            s : &mut VoxelChunk, min : [usize; 3], size : usize, implicit : &mut F,
            dedup : &mut FnvHashMap<VChildDescriptor, i32>
        ) -> i32 {

            if size <= 1 {
                // once we reach size 1, evaluate the material at the implicit surface
                let v = implicit(min[0], min[1], min[2]);
                // prevent awful fractal voxel graphs
                return -v.abs();
            }

            const BOX_OFFSETS : [[usize; 3]; 8] = [
                [0, 0, 0],
                [1, 0, 0],
                [0, 1, 0],
                [1, 1, 0],
                [0, 0, 1],
                [1, 0, 1],
                [0, 1, 1],
                [1, 1, 1]
            ];

            let mut voxel = VChildDescriptor{
                sub_voxels : [0; 8],
            };

            let half_size = size >> 1;

            let mut is_uniform = true;

            for i in 0..8 {
                let bmin = [
                    min[0] + BOX_OFFSETS[i][0] * half_size,
                    min[1] + BOX_OFFSETS[i][1] * half_size,
                    min[2] + BOX_OFFSETS[i][2] * half_size
                ];

                voxel.sub_voxels[i] = recursive_create_dense_implicit(s, bmin, half_size, implicit, dedup);

                if voxel.sub_voxels[i] != voxel.sub_voxels[0] || voxel.sub_voxels[i] > 0 {
                    // the subvoxels are not all the same leaf node, so this voxel is not uniform
                    is_uniform = false;
                }
            }

            
            if is_uniform {
                return voxel.sub_voxels[0];
            }

            if let Some(&id) = dedup.get(&voxel) {
                // this node is a duplicate
                id
            } else {
                // this node is new, so add it
                s.voxels.push(voxel);
                let id = s.voxels.len() as i32;
                dedup.insert(voxel, id);
                id
            }
        }

        let mut chunk = VoxelChunk::empty();
        chunk.voxels.clear();
        // we build a list of unique voxels and store them in here
        let mut dedup = FnvHashMap::default();

        recursive_create_dense_implicit(&mut chunk, [0,0,0], size, &mut implicit, &mut dedup);

        chunk.voxels.reverse();

        //fixup the subvoxel pointers (we reversed the order)
        let n = chunk.voxels.len() as i32;
        for i in 0..(chunk.voxels.len()) {
            for j in 0..8 {
                let sv = chunk.voxels[i].sub_voxels[j];
                if sv > 0 {
                    let svi = n - sv + 1;
                    chunk.voxels[i].sub_voxels[j] = svi;
                }
            }
        }

        chunk
    }

    /// process a distance equation array into a DAG.
    /// 
    pub fn from_distance_equation<F : FnMut(f32, f32, f32) -> f32>(depth : usize, mut implicit : F) -> Self {

        assert!(depth < MAX_DAG_DEPTH, "Depth is too large: {} >= {}", depth, MAX_DAG_DEPTH);

        let size = 1 << depth;

        fn recurse_distance_equation<F : FnMut(f32, f32, f32) -> f32>(
            s : &mut VoxelChunk, min : [usize; 3], size : usize, implicit : &mut F, rscale : f32,
            dedup : &mut FnvHashMap<VChildDescriptor, i32>
        ) -> i32 {

            const SQRT_THREE : f32 = 1.732050807568877293527446341505872366942805253810380628055;

            let v = implicit(
                rscale * (min[0] as f32 + 0.5 * size as f32),
                rscale * (min[1] as f32 + 0.5 * size as f32),
                rscale * (min[2] as f32 + 0.5 * size as f32)
            );

            let bounding_radius = rscale * size as f32 * SQRT_THREE;

            if size <= 1 {
                // once we reach size 1, check if the object intersects the implicit region
                if min[0] == 0 && min[1] == 0 && min[2] == 0 {
                    // println!("maybe intersection {} < {}", v, bounding_radius);
                }
                return if v < bounding_radius { -1 } else { 0 };
            }
            
            if v > bounding_radius {
                // the voxel does not intersect the cube at all based on the distance equation
                // println!("no intersection {} {}", v, bounding_radius);

                return 0;
            }

            const BOX_OFFSETS : [[usize; 3]; 8] = [
                [0, 0, 0],
                [1, 0, 0],
                [0, 1, 0],
                [1, 1, 0],
                [0, 0, 1],
                [1, 0, 1],
                [0, 1, 1],
                [1, 1, 1]
            ];

            let mut voxel = VChildDescriptor{
                sub_voxels : [0; 8],
            };

            let half_size = size >> 1;

            let mut is_uniform = true;

            for i in 0..8 {
                let bmin = [
                    min[0] + BOX_OFFSETS[i][0] * half_size,
                    min[1] + BOX_OFFSETS[i][1] * half_size,
                    min[2] + BOX_OFFSETS[i][2] * half_size
                ];

                voxel.sub_voxels[i] = recurse_distance_equation(s, bmin, half_size, implicit, rscale, dedup);

                if voxel.sub_voxels[i] != voxel.sub_voxels[0] || voxel.sub_voxels[i] > 0 {
                    // the subvoxels are not all the same leaf node, so this voxel is not uniform
                    is_uniform = false;
                }
            }

            
            if is_uniform {
                return voxel.sub_voxels[0];
            }

            if let Some(&id) = dedup.get(&voxel) {
                // this node is a duplicate
                id
            } else {
                // this node is new, so add it
                s.voxels.push(voxel);
                let id = s.voxels.len() as i32;
                dedup.insert(voxel, id);
                id
            }
        }

        let mut chunk = VoxelChunk::empty();
        chunk.voxels.clear();
        // we build a list of unique voxels and store them in here
        let mut dedup : FnvHashMap<VChildDescriptor, i32> = FnvHashMap::default();

        recurse_distance_equation(&mut chunk, [0,0,0], size, &mut implicit, 1.0 / (size as f32), &mut dedup);

        chunk.voxels.reverse();

        //fixup the subvoxel pointers (we reversed the order)
        let n = chunk.voxels.len() as i32;
        for i in 0..(chunk.voxels.len()) {
            for j in 0..8 {
                let sv = chunk.voxels[i].sub_voxels[j];
                if sv > 0 {
                    let svi = n - sv + 1;
                    chunk.voxels[i].sub_voxels[j] = svi;
                }
            }
        }

        chunk
    }


    /// process a distance equation array into a DAG.
    pub fn from_intersection_test<F : FnMut(Vec3, f32) -> bool>(depth : usize, mut intersect_test : F) -> Self {

        assert!(depth < MAX_DAG_DEPTH, "Depth is too large: {} >= {}", depth, MAX_DAG_DEPTH);

        let size = 1 << depth;

        fn recurse_intersection_test<F : FnMut(Vec3, f32) -> bool>(
            s : &mut VoxelChunk, min : [usize; 3], size : usize, intersect_test : &mut F, rscale : f32,
            dedup : &mut FnvHashMap<VChildDescriptor, i32>
        ) -> i32 {

            let intersects = intersect_test(
                Vec3::new(
                    rscale * (min[0] as f32 + 0.5 * size as f32),
                    rscale * (min[1] as f32 + 0.5 * size as f32),
                    rscale * (min[2] as f32 + 0.5 * size as f32)
                ),
                0.5 * rscale * size as f32
            );

            if size <= 1 {
                // once we reach size 1, check if the object intersects the implicit region
                if min[0] == 0 && min[1] == 0 && min[2] == 0 {
                    // println!("maybe intersection {} < {}", v, bounding_radius);
                }
                return if intersects { -1 } else { 0 };
            }
            
            if !intersects {
                // the voxel does not intersect the cube at all based on the distance equation
                // println!("no intersection {} {}", v, bounding_radius);

                return 0;
            }

            const BOX_OFFSETS : [[usize; 3]; 8] = [
                [0, 0, 0],
                [1, 0, 0],
                [0, 1, 0],
                [1, 1, 0],
                [0, 0, 1],
                [1, 0, 1],
                [0, 1, 1],
                [1, 1, 1]
            ];

            let mut voxel = VChildDescriptor{
                sub_voxels : [0; 8],
            };

            let half_size = size >> 1;

            let mut is_uniform = true;

            for i in 0..8 {
                let bmin = [
                    min[0] + BOX_OFFSETS[i][0] * half_size,
                    min[1] + BOX_OFFSETS[i][1] * half_size,
                    min[2] + BOX_OFFSETS[i][2] * half_size
                ];

                voxel.sub_voxels[i] = recurse_intersection_test(s, bmin, half_size, intersect_test, rscale, dedup);

                if voxel.sub_voxels[i] != voxel.sub_voxels[0] || voxel.sub_voxels[i] > 0 {
                    // the subvoxels are not all the same leaf node, so this voxel is not uniform
                    is_uniform = false;
                }
            }

            
            if is_uniform {
                return voxel.sub_voxels[0];
            }

            if let Some(&id) = dedup.get(&voxel) {
                // this node is a duplicate
                id
            } else {
                // this node is new, so add it
                s.voxels.push(voxel);
                let id = s.voxels.len() as i32;
                dedup.insert(voxel, id);
                id
            }
        }

        let mut chunk = VoxelChunk::empty();
        chunk.voxels.clear();
        // we build a list of unique voxel subtrees and store them in here
        let mut dedup : FnvHashMap<VChildDescriptor, i32> = FnvHashMap::default();

        recurse_intersection_test(&mut chunk, [0,0,0], size, &mut intersect_test, 1.0 / (size as f32), &mut dedup);

        chunk.voxels.reverse();

        //fixup the subvoxel pointers (we reversed the order)
        let n = chunk.voxels.len() as i32;
        for i in 0..(chunk.voxels.len()) {
            for j in 0..8 {
                let sv = chunk.voxels[i].sub_voxels[j];
                if sv > 0 {
                    let svi = n - sv + 1;
                    chunk.voxels[i].sub_voxels[j] = svi;
                }
            }
        }

        chunk
    }
}