// Copyright (c) 2020-2022 Weird Constructor <weirdconstructor@gmail.com>
// This is a part of WLambda. See README.md and COPYING for details.

/*!

  Implements utilitiy functions that are used by the WLambda
  standard library. For instance a SplitMix64 random number
  generator.

*/

//- splitmix64 (http://xoroshiro.di.unimi.it/splitmix64.c) 
//"""
//  Written in 2015 by Sebastiano Vigna (vigna@acm.org)
//
//  To the extent possible under law, the author has dedicated all copyright
//  and related and neighboring rights to this software to the public domain
//  worldwide. This software is distributed without any warranty.
//
//  See <http://creativecommons.org/publicdomain/zero/1.0/>. 
//"""
//
// Written by Alexander Stocko <as@coder.gg>
//
// To the extent possible under law, the author has dedicated all copyright
// and related and neighboring rights to this software to the public domain
// worldwide. This software is distributed without any warranty.
//
// See <LICENSE or http://creativecommons.org/publicdomain/zero/1.0/>


use std::num::Wrapping as w;
use std::cell::RefCell;

thread_local! {
    static RAND_STATE: RefCell<SplitMix64> =
        RefCell::new(SplitMix64::new(1_234_567_890));
}

pub fn srand(seed: i64) {
    RAND_STATE.with(|si| {
        *si.borrow_mut() = SplitMix64::new(seed as u64);
    })
}

pub fn rand_closed_open01() -> f64 {
    RAND_STATE.with(|si| {
        u64_to_closed_open01(si.borrow_mut().next_u64())
    })
}

pub fn rand_i(max: u64) -> i64 {
    RAND_STATE.with(|si| {
        (si.borrow_mut().next_u64() % max) as i64
    })
}

pub fn rand_full_i() -> i64 {
    RAND_STATE.with(|si| {
        si.borrow_mut().next_i64()
    })
}

/// The `SplitMix64` random number generator.
#[derive(Copy, Clone)]
pub struct SplitMix64(pub u64);

impl SplitMix64 {
    pub fn new(seed: u64) -> Self { Self(seed) }
    pub fn new_from_i64(seed: i64) -> Self {
        Self::new(u64::from_be_bytes(seed.to_be_bytes()))
    }

    #[inline]
    pub fn next_u64(&mut self) -> u64 {
        let mut z = w(self.0) + w(0x9E37_79B9_7F4A_7C15_u64);
        self.0 = z.0;
        z = (z ^ (z >> 30)) * w(0xBF58_476D_1CE4_E5B9_u64);
        z = (z ^ (z >> 27)) * w(0x94D0_49BB_1331_11EB_u64);
        (z ^ (z >> 31)).0
    }

    #[inline]
    pub fn next_i64(&mut self) -> i64 {
        i64::from_be_bytes(
            self.next_u64().to_be_bytes())
    }
}

// Taken from rand::distributions
// Licensed under the Apache License, Version 2.0
// Copyright 2018 Developers of the Rand project.
pub fn u64_to_open01(u: u64) -> f64 {
    use core::f64::EPSILON;
    let float_size         = std::mem::size_of::<f64>() as u32 * 8;
    let fraction           = u >> (float_size - 52);
    let exponent_bits: u64 = 1023_u64 << 52;
    f64::from_bits(fraction | exponent_bits) - (1.0 - EPSILON / 2.0)
}

// Taken from rand::distributions
// Licensed under the Apache License, Version 2.0
// Copyright 2018 Developers of the Rand project.
pub fn u64_to_closed_open01(u: u64) -> f64 {
    // Multiply-based method; 24/53 random bits; [0, 1) interval.
    // We use the most significant bits because for simple RNGs
    // those are usually more random.
    let float_size = std::mem::size_of::<f64>() as u32 * 8;
    let precision = 52 + 1;
    let scale = 1.0 / ((1_u64 << precision) as f64);

    let value = u >> (float_size - precision);
    scale * (value as f64)
}

// Taken from rand::distributions
// Licensed under the Apache License, Version 2.0
// Copyright 2018 Developers of the Rand project.
pub fn u64_to_open_closed01(u: u64) -> f64 {
    // Multiply-based method; 24/53 random bits; [0, 1) interval.
    // We use the most significant bits because for simple RNGs
    // those are usually more random.
    let float_size = std::mem::size_of::<f64>() as u32 * 8;
    let precision = 52 + 1;
    let scale = 1.0 / ((1_u64 << precision) as f64);

    let value = u >> (float_size - precision);
    scale * ((value + 1) as f64)
}

/// Original FNV Rust implementation taken from fnv crate on
/// crates.io by Alex Crichton <alex@alexcrichton.com>
/// under Apache-2.0 / MIT license Copyright 2018.
///
/// An implementation of the Fowler–Noll–Vo hash function.
///
/// See the [crate documentation](index.html) for more details.
#[derive(Copy, Clone, Debug)]
pub struct FnvHasher(u64);

impl Default for FnvHasher {
    #[inline]
    fn default() -> FnvHasher {
        FnvHasher(0xcbf2_9ce4_8422_2325)
    }
}

impl FnvHasher {
    #[inline]
    #[allow(dead_code)]
    pub fn with_key(key: u64) -> FnvHasher {
        FnvHasher(key)
    }

    #[inline]
    fn finish(self) -> u64 {
        self.0
    }

    #[inline]
    pub fn finish_i64(self) -> i64 {
        i64::from_be_bytes(
            self.finish().to_be_bytes())
    }

    #[inline]
    pub fn write_f64(&mut self, f: f64) {
            self.write(&f.to_bits().to_be_bytes());
    }

    #[inline]
    pub fn write_i64(&mut self, i: i64) {
        self.write(&i.to_be_bytes());
    }

    #[inline]
    #[allow(clippy::cast_lossless)]
    pub fn write(&mut self, bytes: &[u8]) {
        let FnvHasher(mut hash) = *self;

        for byte in bytes.iter() {
            hash ^= *byte as u64;
            hash = hash.wrapping_mul(0x0100_0000_01b3);
        }

        *self = FnvHasher(hash);
    }
}

pub fn now_timestamp() -> u64 {
    std::time::SystemTime::now()
    .duration_since(std::time::SystemTime::UNIX_EPOCH)
    .unwrap()
    .as_secs() as u64
}

pub fn rgba2hsvaf(rgba: (f64, f64, f64, f64)) -> (f64, f64, f64, f64) {
    let (h, s, v) = rgb2hsv(rgba.0, rgba.1, rgba.2);
    (h, s, v, rgba.3)
}

pub fn rgb2hsv(r: f64, g: f64, b: f64) -> (f64, f64, f64) {
    let c_max = r.max(g.max(b));
    let c_min = r.min(g.min(b));
    let delta = c_max - c_min;
    let mut hue =
        if delta < 0.000_001 { 0.0 }
        else if (r - c_max).abs() < 0.000_001  { 60.0 * (((g - b) / delta) % 6.0) }
        else if (g - c_max).abs() < 0.000_001  { 60.0 * (((b - r) / delta) + 2.0) }
        else                                   { 60.0 * (((r - g) / delta) + 4.0) };
    if hue < 0.0   { hue += 360.0 }
    if hue > 360.0 { hue -= 360.0 }
    let sat = if c_max < 0.000_001 { 0.0 } else { delta / c_max };
    let val = c_max;
    (hue, sat, val)
}

pub fn hsva2rgba(hsva: (f64, f64, f64, f64)) -> (f64, f64, f64, f64) {
    let (r, g, b) = hsv2rgb(hsva.0, hsva.1, hsva.2);
    (r, g, b, hsva.3)
}

pub fn hsv2rgb(hue: f64, sat: f64, val: f64) -> (f64, f64, f64) {
    let c = val * sat;
    let x = c * (1.0 - ((hue / 60.0) % 2.0 - 1.0).abs());
    let m = val - c;
    let (r_, g_, b_) =
        if        (0.0..60.0).contains(&hue) {
            (c, x, 0.0)
        } else if (60.0..120.0).contains(&hue) {
            (x, c, 0.0)
        } else if (120.0..180.0).contains(&hue) {
            (0.0, c, x)
        } else if (180.0..240.0).contains(&hue) {
            (0.0, x, c)
        } else if (240.0..300.0).contains(&hue) {
            (x, 0.0, c)
        } else { // if hue >= 300.0 && hue < 360.0 {
            (c, 0.0, x)
        };
//    println!("in: h={}, s={}, v={}, r:{}, g:{}, b: {}", hue, sat, val,
//        (r_ + m) * 255.0,
//        (g_ + m) * 255.0,
//        (b_ + m) * 255.0);
    (r_ + m, g_ + m, b_ + m)
}

pub fn rgba2hexf(rgba: (f64, f64, f64, f64)) -> String {
    format!("{:02x}{:02x}{:02x}{:02x}",
        (rgba.0 * 255.0).round() as u8,
        (rgba.1 * 255.0).round() as u8,
        (rgba.2 * 255.0).round() as u8,
        (rgba.3 * 255.0).round() as u8)
}

pub fn rgba2hex(rgba: (u8, u8, u8, u8)) -> String {
    format!("{:02x}{:02x}{:02x}{:02x}",
        rgba.0, rgba.1, rgba.2, rgba.3)
}

pub fn hex2hsvaf(s: &str) -> (f64, f64, f64, f64) {
    let (h, s, v, a) = hex2rgbaf(s);
    (h * 360.0, s * 100.0, v * 100.0, a * 100.0)
}

pub fn hsva2hexf(hsva: (f64, f64, f64, f64)) -> String {
    format!("{:02x}{:02x}{:02x}{:02x}",
        ((hsva.0 / 360.0) * 255.0).round() as u8,
        (hsva.1 * 255.0).round() as u8,
        (hsva.2 * 255.0).round() as u8,
        (hsva.3 * 255.0).round() as u8)
}

pub fn hex2rgbaf(hex_str: &str) -> (f64, f64, f64, f64) {
    let (r, g, b, a) = hex2rgba(hex_str);
    (r as f64 / 255.0,
     g as f64 / 255.0,
     b as f64 / 255.0,
     a as f64 / 255.0)
}

fn shiftaddup4(u: u8) -> u8 { (u << 4) | u }

pub fn hex2rgba(s: &str) -> (u8, u8, u8, u8) {
    match s.len() {
        8 => (
            u8::from_str_radix(&s[0..2], 16).unwrap_or(0),
            u8::from_str_radix(&s[2..4], 16).unwrap_or(0),
            u8::from_str_radix(&s[4..6], 16).unwrap_or(0),
            u8::from_str_radix(&s[6..8], 16).unwrap_or(255)
        ),
        6 => (
            u8::from_str_radix(&s[0..2], 16).unwrap_or(0),
            u8::from_str_radix(&s[2..4], 16).unwrap_or(0),
            u8::from_str_radix(&s[4..6], 16).unwrap_or(0),
            255
        ),
        4 => (
            shiftaddup4(u8::from_str_radix(&s[0..1], 16).unwrap_or(0)),
            shiftaddup4(u8::from_str_radix(&s[1..2], 16).unwrap_or(0)),
            shiftaddup4(u8::from_str_radix(&s[2..3], 16).unwrap_or(0)),
            shiftaddup4(u8::from_str_radix(&s[3..4], 16).unwrap_or(0xFF)),
        ),
        3 => (
            shiftaddup4(u8::from_str_radix(&s[0..1], 16).unwrap_or(0)),
            shiftaddup4(u8::from_str_radix(&s[1..2], 16).unwrap_or(0)),
            shiftaddup4(u8::from_str_radix(&s[2..3], 16).unwrap_or(0)),
            255
        ),
        2 => (
            shiftaddup4(u8::from_str_radix(&s[0..1], 16).unwrap_or(0)),
            shiftaddup4(u8::from_str_radix(&s[0..1], 16).unwrap_or(0)),
            shiftaddup4(u8::from_str_radix(&s[0..1], 16).unwrap_or(0)),
            255
        ),
        _ => (255, 0, 255, 255),
    }
}


// Taken from https://github.com/febeling/edit-distance/blob/master/src/lib.rs
// Apache-2.0 License
/// Returns the edit distance between strings `a` and `b`.
///
/// The runtime complexity is `O(m*n)`, where `m` and `n` are the
/// strings' lengths.
#[allow(clippy::needless_range_loop)]
pub fn edit_distance(a: &str, b: &str) -> usize {
    let len_a = a.chars().count();
    let len_b = b.chars().count();
    if len_a < len_b {
        return edit_distance(b, a);
    }
    // handle special case of 0 length
    if len_a == 0 {
        return len_b;
    } else if len_b == 0 {
        return len_a;
    }

    let len_b = len_b + 1;

    let mut pre;
    let mut tmp;
    let mut cur = vec![0; len_b];

    // initialize string b
    for i in 1..len_b {
        cur[i] = i;
    }

    // calculate edit distance
    for (i, ca) in a.chars().enumerate() {
        // get first column for this row
        pre = cur[0];
        cur[0] = i + 1;
        for (j, cb) in b.chars().enumerate() {
            tmp = cur[j + 1];
            cur[j + 1] = std::cmp::min(
                // deletion
                tmp + 1,
                std::cmp::min(
                    // insertion
                    cur[j] + 1,
                    // match or substitution
                    pre + if ca == cb { 0 } else { 1 },
                ),
            );
            pre = tmp;
        }
    }
    cur[len_b - 1]
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn util_rgb2hsv() {
        assert_eq!(
            hsva2hexf(rgba2hsvaf(hex2rgbaf("FF0000FF"))),
            "00ffffff");
        assert_eq!(
            hsva2hexf(rgba2hsvaf(hex2rgbaf("00FF00FF"))),
            "55ffffff");
        assert_eq!(
            hsva2hexf(rgba2hsvaf(hex2rgbaf("0000FFFF"))),
            "aaffffff");
        assert_eq!(
            rgba2hsvaf(hex2rgbaf("FF00FFFF")),
            (300.0, 1.0, 1.0, 1.0));
        assert_eq!(
            rgba2hsvaf(hex2rgbaf("00FFFFFF")),
            (180.0, 1.0, 1.0, 1.0));
        assert_eq!(
            rgba2hsvaf(hex2rgbaf("FFFF00FF")),
            (60.0, 1.0, 1.0, 1.0));

        assert_eq!(
            rgba2hexf(hsva2rgba((300.0, 1.0, 1.0, 1.0))),
            "ff00ffff");
        assert_eq!(
            rgba2hexf(hsva2rgba((180.0, 1.0, 1.0, 1.0))),
            "00ffffff");
        assert_eq!(
            rgba2hexf(hsva2rgba((60.0, 1.0, 1.0, 1.0))),
            "ffff00ff");
        assert_eq!(
            rgba2hexf(hsva2rgba((100.0, 0.5, 0.25, 1.0))),
            "2b4020ff");
    }
}