use crate::{Arc, BTreeSet, Data, HashMap, Rc, RefCell};

/// In debug mode or feature unsafe_opt not enabled, same as debug_assert! otherwise unsafe compiler hint.
#[cfg(any(debug_assertions, not(feature = "unsafe-optim")))]
macro_rules! unsafe_assert {
    ( $cond: expr ) => {
        debug_assert!($cond)
    };
}

/// In debug mode or feature unsafe_opt not enabled, same as debug_assert! otherwise unsafe compiler hint.
#[cfg(all(not(debug_assertions), feature = "unsafe-optim"))]
macro_rules! unsafe_assert {
    ( $cond: expr ) => {
        if !$cond {
            unsafe { std::hint::unreachable_unchecked() }
        }
    };
}

/// In debug mode or feature unsafe_opt not enabled, same as panic! otherwise unsafe compiler hint.
#[cfg(any(debug_assertions, not(feature = "unsafe-optim")))]
macro_rules! unsafe_panic {
    () => {
        panic!()
    };
}

/// In debug mode or feature unsafe_opt not enabled, same as debug_assert! otherwise unsafe compiler hint.
#[cfg(all(not(debug_assertions), feature = "unsafe-optim"))]
macro_rules! unsafe_panic {
    () => {{
        unsafe { std::hint::unreachable_unchecked() }
    }};
}

/// Wrap a type in Rc + RefCell.
pub fn new<T>(x: T) -> std::rc::Rc<std::cell::RefCell<T>> {
    Rc::new(RefCell::new(x))
}

/// New Data ( `Arc::new(Vec::new())` ).
pub fn nd() -> Data {
    Arc::new(Vec::new())
}

/// Construct a new map wrapped in a RefCell.
pub fn newmap<K, T>() -> RefCell<HashMap<K, T>> {
    RefCell::new(HashMap::default())
}

/// Extract u64 from byte data.
pub fn getu64(data: &[u8], off: usize) -> u64 {
    unsafe_assert!(off + 8 <= data.len());
    let data = &data[off..off + 8];
    u64::from_le_bytes(data.try_into().unwrap())
}

/// Store u64 to byte data.
pub fn setu64(data: &mut [u8], val: u64) {
    unsafe_assert!(data.len() >= 8);
    data[0..8].copy_from_slice(&val.to_le_bytes());
}

/// Extract f64 from byte data.
pub fn getf64(data: &[u8], off: usize) -> f64 {
    let data = &data[off..off + 8];
    f64::from_le_bytes(data.try_into().unwrap())
}

/// Extract f32 from byte data.
pub fn getf32(data: &[u8], off: usize) -> f32 {
    let data = &data[off..off + 4];
    f32::from_le_bytes(data.try_into().unwrap())
}

/// Extract unsigned value of n bytes from data.
pub fn get(data: &[u8], off: usize, n: usize) -> u64 {
    let mut buf = [0_u8; 8];
    unsafe_assert!(off + n <= data.len());
    buf[0..n].copy_from_slice(&data[off..off + n]);
    u64::from_le_bytes(buf)
}

/// Extract signed value of n bytes from data.
pub fn iget(data: &[u8], off: usize, n: usize) -> i64 {
    let mut x: u64 = get(data, off, n);
    if n < 8 {
        let sign_bit = 1 << (n * 8 - 1);
        if (sign_bit & x) != 0 {
            x += u64::MAX << (n * 8);
        }
    }
    x as i64
}

/// Store signed value of n bytes to data ( with overflow check ).
pub fn iset(data: &mut [u8], off: usize, val: i64, n: usize) {
    if n < 8 {
        let chk = val + (1 << ((n * 8) - 1));
        if chk < 0 || chk >= (1 << (n * 8)) {
            panic!("overflow storing value {} in {} bytes", val, n);
        }
    }
    let bytes = val.to_le_bytes();
    data[off..off + n].copy_from_slice(&bytes[0..n]);
}

/// Store unsigned value of n bytes to data.
pub fn set(data: &mut [u8], off: usize, val: u64, n: usize) {
    let bytes = val.to_le_bytes();
    data[off..off + n].copy_from_slice(&bytes[0..n]);
}

// Bitfield  macros

/// The mask to extract $len bits at bit offset $off.
macro_rules! bitmask {
    ( $off: expr, $len: expr ) => {
        ((1 << $len) - 1) << $off
    };
}

/// Extract $len bits from $val at bit offset $off.
macro_rules! getbits {
    ( $val: expr, $off: expr, $len: expr ) => {
        ($val & bitmask!($off, $len)) >> $off
    };
}

/// Update $len bits in $var at bit offset $off to $val.
macro_rules! setbits {
    ( $var: expr, $off: expr, $len: expr, $val: expr ) => {
        $var = ($var & !bitmask!($off, $len)) | (($val << $off) & bitmask!($off, $len))
    };
}

/// Convert a hex char byte to a byte in range 0..15.
pub fn hex(c: u8) -> u8 //
{
    match c {
        b'0'..=b'9' => c - b'0',
        b'A'..=b'F' => c + 10 - b'A',
        b'a'..=b'f' => c + 10 - b'a',
        _ => {
            panic!()
        }
    }
}

/// Convert hex literal to bytes.
pub fn parse_hex(s: &[u8]) -> Vec<u8> {
    let n = s.len() / 2;
    let mut result = Vec::<u8>::with_capacity(n);
    for i in 0..n {
        result.push(hex(s[i * 2]) * 16 + hex(s[i * 2 + 1]));
    }
    result
}

/// Convert bytes to hex string.
pub fn to_hex(bytes: &[u8]) -> String {
    const HEX: &[u8; 16] = b"0123456789abcdef";
    let mut s = vec![b'0', b'x'];
    for b in bytes {
        let b = *b as usize;
        s.push(HEX[b / 16]);
        s.push(HEX[b % 16]);
    }
    String::from_utf8(s).unwrap()
}

/// Set of usize, optimised for elements < 64. default() is empty set.
#[derive(Default)]
pub struct SmallSet {
    /// Holds elements < 64 as a bitmap.
    bitset: u64,
    /// Holds elements >= 64.
    overflow: BTreeSet<usize>,
}

impl SmallSet {
    /*
        /// The set is empty.
        pub fn is_empty(&self) -> bool {
            self.bitset == 0 && self.overflow.len() == 0
        }
    */

    /// Insert x into set.
    pub fn insert(&mut self, x: usize) {
        if x < 64 {
            self.bitset |= 1 << x;
        } else {
            self.overflow.insert(x);
        }
    }

    /// Test whether set contains x.
    pub fn contains(&self, x: usize) -> bool {
        if x < 64 {
            self.bitset & (1 << x) != 0
        } else {
            self.overflow.contains(&x)
        }
    }

    /// Remove x from set, result is whether set contained x.
    pub fn remove(&mut self, x: usize) -> bool {
        if x < 64 {
            let bit: u64 = 1 << x;
            let result = self.bitset & bit != 0;
            self.bitset &= u64::MAX - bit;
            result
        } else {
            self.overflow.remove(&x)
        }
    }
}

/// Function to compare bytes. Length is taken from a. Calls d for each range that is different.
/// Interior equal ranges less than min_eq are taken as different.
pub fn diff<F>(a: &[u8], b: &[u8], min_eq: usize, mut d: F)
where
    F: FnMut(usize, usize),
{
    let mut check = 0;
    let mut i = 0;
    let n = a.len();
    while i < n && a[i] == b[i] {
        i += 1;
    }
    while i < n {
        let start = i;
        let mut end;
        loop {
            loop {
                i += 1;
                if i == n || a[i] == b[i] {
                    break;
                }
            }
            end = i;
            // Check that following equal range is at least min_eq.
            while i < n && a[i] == b[i] {
                i += 1;
            }
            if i - end >= min_eq || i == n {
                break;
            }
        }
        assert_eq!(a[check..start], b[check..start]);
        check = end;
        d(start, end - start);
    }
    assert_eq!(a[check..n], b[check..n]);
}

#[test]
fn difftest() {
    use rand::Rng;
    let mut rng = rand::thread_rng();
    for _ in 0..1000 {
        let mut v = Vec::new();
        for _i in 0..100 {
            v.push(0);
        }
        let mut v2 = v.clone();
        for _ in 0..rng.gen::<usize>() % 50 {
            v2[rng.gen::<usize>() % 100] = 1;
        }
        let mut x = 0;
        diff(&v, &v2, 2, |off, len| {
            //println!("off={off} len={len}");
            assert_eq!(v[x..off], v2[x..off]);
            x = off + len;
        });
        assert_eq!(v[x..], v2[x..]);
        //println!("Done a test");
    }
}