ovtile/

util.rs

use crate::{BBox, BBox3D, Point, Point3D, BBOX};

use libm::round;

use alloc::{vec, vec::Vec};

use core::cmp::Ordering;

/// Manager for float based comparisons
pub trait CustomOrd {
    /// Custom comparison
    fn custom_cmp(&self, other: &Self) -> Ordering;
}
impl CustomOrd for u64 {
    fn custom_cmp(&self, other: &Self) -> Ordering {
        self.partial_cmp(other).unwrap_or(Ordering::Equal)
    }
}
impl CustomOrd for i64 {
    fn custom_cmp(&self, other: &Self) -> Ordering {
        self.partial_cmp(other).unwrap_or(Ordering::Equal)
    }
}
impl CustomOrd for f32 {
    fn custom_cmp(&self, other: &Self) -> Ordering {
        if self.is_nan() || other.is_nan() {
            Ordering::Equal // Or handle NaNs differently if needed
        } else {
            self.partial_cmp(other).unwrap_or(Ordering::Equal)
        }
    }
}
impl CustomOrd for f64 {
    fn custom_cmp(&self, other: &Self) -> Ordering {
        if self.is_nan() || other.is_nan() {
            Ordering::Equal // Or handle NaNs differently if needed
        } else {
            self.partial_cmp(other).unwrap_or(Ordering::Equal)
        }
    }
}
/// Wrapper struct for custom ordering
#[derive(Debug, Default, Clone, Copy)]
pub struct CustomOrdWrapper<T>(pub T);
impl<T: CustomOrd> CustomOrd for CustomOrdWrapper<T> {
    fn custom_cmp(&self, other: &Self) -> Ordering {
        self.0.custom_cmp(&other.0)
    }
}
impl<T: CustomOrd> PartialOrd for CustomOrdWrapper<T> {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}
impl<T: CustomOrd> Eq for CustomOrdWrapper<T> {}
impl<T: CustomOrd> PartialEq for CustomOrdWrapper<T> {
    fn eq(&self, other: &Self) -> bool {
        self.0.custom_cmp(&other.0) == Ordering::Equal
    }
}
impl<T: CustomOrd> Ord for CustomOrdWrapper<T> {
    fn cmp(&self, other: &Self) -> Ordering {
        self.custom_cmp(other)
    }
}

/// Encode a command with the given length of the data that follows.
pub fn command_encode(cmd: u8, len: u32) -> u64 {
    ((len << 3) + ((cmd as u32) & 0x7)) as u64
}

/// A command container. Decoding of a comand and length
#[derive(Debug, PartialEq)]
pub struct Command {
    /// The command
    pub cmd: u8,
    /// The length
    pub len: u32,
}

/// Decode a command with the given length of the data that follows.
pub fn command_decode(cmd: u64) -> Command {
    Command { cmd: (cmd & 0x7) as u8, len: (cmd >> 3) as u32 }
}

/// Applies zigzag encoding to transform a signed integer into an unsigned integer.
pub fn zigzag(n: i32) -> u32 {
    ((n << 1) ^ (n >> 31)) as u32
}

/// Applies zigzag decoding to transform an unsigned integer into a signed integer.
pub fn zagzig(n: u32) -> i32 {
    ((n >> 1) as i32) ^ -(n as i32 & 1)
}

/// Interweave two 16-bit numbers into a 32-bit number.
/// In theory two small numbers can end up varint encoded to use less space.
pub fn weave_2d(a: u16, b: u16) -> u32 {
    let mut a = a as u32;
    let mut b = b as u32;
    let mut result: u32 = 0;
    for i in 0..16 {
        result |= (a & 1) << (i * 2); // Take ith bit from `a` and put it at position 2*i
        result |= (b & 1) << (i * 2 + 1); // Take ith bit from `b` and put it at position 2*i+1
                                          // move to next bit
        a >>= 1;
        b >>= 1;
    }

    result
}

/// Deweave a 32-bit number into two 16-bit numbers.
pub fn unweave_2d(num: u32) -> (u16, u16) {
    let mut num = num;
    let mut a: u16 = 0;
    let mut b: u16 = 0;
    for i in 0..16 {
        let bit = 1 << i;
        if num & 1 != 0 {
            a |= bit;
        }
        if num & 2 != 0 {
            b |= bit;
        }
        num >>= 2;
    }

    (a, b)
}

/// Interweave three 16-bit numbers into a 48-bit number.
/// In theory three small numbers can end up varint encoded to use less space.
pub fn weave_3d(a: u16, b: u16, c: u16) -> u64 {
    // return result
    let mut result: u64 = 0;
    let mut a: u64 = a.into();
    let mut b: u64 = b.into();
    let mut c: u64 = c.into();

    for i in 0..16 {
        if a & 1 != 0 {
            result |= 1 << (i * 3);
        } // Take ith bit from `a` and put it at position 3*i
        if b & 1 != 0 {
            result |= 1 << (i * 3 + 1);
        } // Take ith bit from `b` and put it at position 3*i+1
        if c & 1 != 0 {
            result |= 1 << (i * 3 + 2);
        } // Take ith bit from `c` and put it at position 3*i+2
          // Move to the next bit
        a >>= 1;
        b >>= 1;
        c >>= 1;
    }

    result
}

/// Deweave a 48-bit number into three 16-bit numbers.
/// Returns the three 16-bit numbers in a tuple.
pub fn unweave_3d(num: u64) -> (u32, u32, u32) {
    let mut a = 0;
    let mut b = 0;
    let mut c = 0;
    let mut num = num; // Make a mutable copy of the input

    for i in 0..16 {
        let bit = 1 << i;
        if (num & 1) != 0 {
            a |= bit;
        }
        if (num & 2) != 0 {
            b |= bit;
        }
        if (num & 4) != 0 {
            c |= bit;
        }
        num >>= 3; // Right shift the number by 3 positions
    }

    (a, b, c)
}

/// Encode an array of points using interweaving and delta encoding.
pub fn weave_and_delta_encode_array(array: &[Point]) -> Vec<u64> {
    let mut res = Vec::new();
    let mut prev_x = 0;
    let mut prev_y = 0;

    for point in array.iter() {
        let pos_x = zigzag(point.x - prev_x);
        let pos_y = zigzag(point.y - prev_y);
        res.push(weave_2d(pos_x as u16, pos_y as u16).into());
        prev_x = point.x;
        prev_y = point.y;
    }

    res
}

/// Decode an array of points that were encoded using interweaving and delta encoding.
pub fn unweave_and_delta_decode_array(array: &[u64]) -> Vec<Point> {
    let mut res = Vec::new();
    let mut prev_x = 0;
    let mut prev_y = 0;

    for &encoded_num in array {
        let (a, b) = unweave_2d(encoded_num as u32);
        let x = zagzig(a as u32) + prev_x;
        let y = zagzig(b as u32) + prev_y;
        res.push(Point::new(x, y));
        prev_x = x;
        prev_y = y;
    }

    res
}

/// Encode an array of 3D points using interweaving and delta encoding.
pub fn weave_and_delta_encode_3d_array(array: &[Point3D]) -> Vec<u64> {
    let mut res = Vec::new();
    let mut offset_x = 0;
    let mut offset_y = 0;
    let mut offset_z = 0;

    for point in array.iter() {
        let pos_x = zigzag(point.x - offset_x);
        let pos_y = zigzag(point.y - offset_y);
        let pos_z = zigzag(point.z - offset_z);
        res.push(weave_3d(pos_x as u16, pos_y as u16, pos_z as u16));
        offset_x = point.x;
        offset_y = point.y;
        offset_z = point.z;
    }

    res
}

/// Decode an array of 3D points that were encoded using interweaving and delta encoding.
pub fn unweave_and_delta_decode_3d_array(array: &[u64]) -> Vec<Point3D> {
    let mut res = Vec::new();
    let mut offset_x = 0;
    let mut offset_y = 0;
    let mut offset_z = 0;

    for &encoded_num in array {
        let (a, b, c) = unweave_3d(encoded_num);
        let x = zagzig(a) + offset_x;
        let y = zagzig(b) + offset_y;
        let z = zagzig(c) + offset_z;
        res.push(Point3D::new(x, y, z));
        offset_x = x;
        offset_y = y;
        offset_z = z;
    }

    res
}

/// Encode an array using delta encoding.
pub fn delta_encode_array(array: &[u32]) -> Vec<u32> {
    let mut res = Vec::new();
    let mut offset = 0;

    for &num in array {
        let num = num as i32;
        let encoded = zigzag(num - offset);
        res.push(encoded);
        offset = num;
    }

    res
}

/// Decode an array that was encoded using delta encoding.
pub fn delta_decode_array(array: &[u32]) -> Vec<u32> {
    let mut res = Vec::new();
    let mut offset = 0;

    for &encoded_num in array {
        let num = zagzig(encoded_num) + offset;
        res.push(num as u32);
        offset = num;
    }

    res
}

/// Encode a sorted array using delta encoding.
pub fn delta_encode_sorted_array(array: &[i32]) -> Vec<u32> {
    let mut res = Vec::new();
    let mut offset = 0;

    for &num in array {
        let delta = (num - offset) as u32; // Safe conversion as the array is sorted
        res.push(delta);
        offset = num;
    }

    res
}

/// Decode a sorted array that was encoded using delta encoding.
pub fn delta_decode_sorted_array(array: &[u32]) -> Vec<i32> {
    let mut res = Vec::new();
    let mut offset = 0;

    for &encoded_num in array {
        let num = encoded_num as i32 + offset; // Casting to i32; since encoded as non-negative delta
        res.push(num);
        offset = num;
    }

    res
}

/// 24-bit quantization
/// ~0.000021457672119140625 degrees precision
/// ~2.388 meters precision
pub fn quantize_lon(lon: f64) -> i32 {
    round((lon + 180.0) * 16_777_215.0 / 360.0) as i32
}

/// 24-bit quantization
/// ~0.000010728836059570312 degrees precision
/// ~1.194 meters precision
pub fn quantize_lat(lat: f64) -> i32 {
    ((lat + 90.0) * 16_777_215.0 / 180.0) as i32
}

/// Converts quantized longitude back to geographical longitude
pub fn dequantize_lon(q_lon: i32) -> f64 {
    (q_lon as f64 * 360.0 / 16_777_215.0) - 180.0
}

/// Converts quantized latitude back to geographical latitude
pub fn dequantize_lat(q_lat: i32) -> f64 {
    (q_lat as f64 * 180.0 / 16_777_215.0) - 90.0
}

/// Packs a 24-bit integer into a buffer at the specified offset.
pub fn pack24_bit_uint(buffer: &mut [u8], value: i32, offset: usize) {
    buffer[offset] = ((value >> 16) & 0xff) as u8;
    buffer[offset + 1] = ((value >> 8) & 0xff) as u8;
    buffer[offset + 2] = (value & 0xff) as u8;
}

/// Unpacks a 24-bit integer from a buffer at the specified offset.
pub fn unpack24_bit_uint(buffer: &[u8], offset: usize) -> i32 {
    ((buffer[offset] as i32) << 16)
        | ((buffer[offset + 1] as i32) << 8)
        | (buffer[offset + 2] as i32)
}

/// Packs a float into a buffer at the specified offset using little-endian format.
pub fn pack_float(buffer: &mut [u8], value: f32, offset: usize) {
    let bytes: [u8; 4] = value.to_le_bytes(); // Converts the float to little-endian byte array
    buffer[offset..offset + 4].copy_from_slice(&bytes);
}

/// Unpacks a float from a buffer at the specified offset using little-endian format.
pub fn unpack_float(buffer: &[u8], offset: usize) -> f32 {
    f32::from_le_bytes(buffer[offset..offset + 4].try_into().unwrap()) // Converts little-endian bytes back to a float
}

// | Decimal Places | Approximate Accuracy in Distance       |
// |----------------|----------------------------------------|
// | 0              | 111 km (69 miles)                      |
// | 1              | 11.1 km (6.9 miles)                    |
// | 2              | 1.11 km (0.69 miles)                   |
// | 3              | 111 meters (364 feet)                  |
// | 4              | 11.1 meters (36.4 feet)                |
// | 5              | 1.11 meters (3.64 feet)                |
// | 6              | 0.111 meters (11.1 cm or 4.39 inches)  |
// | 7              | 1.11 cm (0.44 inches)                  |
// | 8              | 1.11 mm (0.044 inches)                 |
// 24-bit quantization for longitude and latitude
// LONGITUDE:
// - ~0.000021457672119140625 degrees precision
// - ~2.388 meters precision
// LATITUDE:
// - ~0.000010728836059570312 degrees precision
// - ~1.194 meters precision
impl BBox {
    /// Returns a quantized version of the BBox
    pub fn quantize(&self) -> Vec<u8> {
        let mut buffer = vec![0u8; 12];

        let q_lon1 = quantize_lon(self.left);
        let q_lat1 = quantize_lat(self.bottom);
        let q_lon2 = quantize_lon(self.right);
        let q_lat2 = quantize_lat(self.top);

        pack24_bit_uint(&mut buffer, q_lon1, 0);
        pack24_bit_uint(&mut buffer, q_lat1, 3);
        pack24_bit_uint(&mut buffer, q_lon2, 6);
        pack24_bit_uint(&mut buffer, q_lat2, 9);

        buffer
    }

    /// Dequantize the BBox
    pub fn dequantize(buf: &[u8]) -> BBox {
        let q_lon1 = unpack24_bit_uint(buf, 0);
        let q_lat1 = unpack24_bit_uint(buf, 3);
        let q_lon2 = unpack24_bit_uint(buf, 6);
        let q_lat2 = unpack24_bit_uint(buf, 9);

        BBox {
            left: dequantize_lon(q_lon1),
            bottom: dequantize_lat(q_lat1),
            right: dequantize_lon(q_lon2),
            top: dequantize_lat(q_lat2),
        }
    }
}
impl BBox3D {
    /// Quantize the BBox3D
    pub fn quantize(&self) -> Vec<u8> {
        let mut buffer = vec![0u8; 20];

        let q_lon1 = quantize_lon(self.left);
        let q_lat1 = quantize_lat(self.bottom);
        let q_lon2 = quantize_lon(self.right);
        let q_lat2 = quantize_lat(self.top);

        pack24_bit_uint(&mut buffer, q_lon1, 0);
        pack24_bit_uint(&mut buffer, q_lat1, 3);
        pack24_bit_uint(&mut buffer, q_lon2, 6);
        pack24_bit_uint(&mut buffer, q_lat2, 9);

        pack_float(&mut buffer, self.near as f32, 12);
        pack_float(&mut buffer, self.far as f32, 16);

        buffer
    }

    /// Dequantize the BBox3D
    pub fn dequantize(buf: &[u8]) -> BBox3D {
        let q_lon1 = unpack24_bit_uint(buf, 0);
        let q_lat1 = unpack24_bit_uint(buf, 3);
        let q_lon2 = unpack24_bit_uint(buf, 6);
        let q_lat2 = unpack24_bit_uint(buf, 9);

        let near = unpack_float(buf, 12) as f64;
        let far = unpack_float(buf, 16) as f64;

        BBox3D {
            left: dequantize_lon(q_lon1),
            bottom: dequantize_lat(q_lat1),
            right: dequantize_lon(q_lon2),
            top: dequantize_lat(q_lat2),
            near,
            far,
        }
    }
}

impl BBOX {
    /// Quantize the BBOX
    pub fn quantize(&self) -> Vec<u8> {
        match self {
            BBOX::BBox(bbox) => bbox.quantize(),
            BBOX::BBox3D(bbox) => bbox.quantize(),
        }
    }

    /// Dequantize the BBOX
    pub fn dequantize(buf: &[u8]) -> BBOX {
        buf.into()
    }
}

impl From<&[u8]> for BBOX {
    fn from(buf: &[u8]) -> Self {
        if buf.len() == 12 {
            BBOX::BBox(BBox::dequantize(buf))
        } else {
            BBOX::BBox3D(BBox3D::dequantize(buf))
        }
    }
}