use crate::ext_error;

use core::ops::{Add, Sub, Mul, Div, Rem};
use core::ops::{AddAssign, SubAssign, MulAssign, DivAssign, RemAssign};
use core::ops::{BitAnd, BitOr, BitXor, Shr, Shl};
use core::ops::{BitAndAssign, BitOrAssign, BitXorAssign, ShrAssign, ShlAssign};
use core::cmp::Ordering;

use alloc::vec::Vec;

use elrond_wasm::BigUintApi;
use elrond_wasm::err_msg;

extern {
    fn bigIntNew(value: i64) -> i32;

    fn bigIntUnsignedByteLength(x: i32) -> i32;
    fn bigIntGetUnsignedBytes(reference: i32, byte_ptr: *mut u8) -> i32;
    fn bigIntSetUnsignedBytes(destination: i32, byte_ptr: *const u8, byte_len: i32);
    
    fn bigIntAdd(dest: i32, x: i32, y: i32);
    fn bigIntSub(dest: i32, x: i32, y: i32);
    fn bigIntMul(dest: i32, x: i32, y: i32);
    fn bigIntTDiv(dest: i32, x: i32, y: i32);
    fn bigIntTMod(dest: i32, x: i32, y: i32);

    fn bigIntCmp(x: i32, y: i32) -> i32;
    fn bigIntSign(x: i32) -> i32;

    fn bigIntNot(dest: i32, x: i32);
    fn bigIntAnd(dest: i32, x: i32, y: i32);
    fn bigIntOr(dest: i32, x: i32, y: i32);
    fn bigIntXor(dest: i32, x: i32, y: i32);
    fn bigIntShr(dest: i32, x: i32, bits: i32);
    fn bigIntShl(dest: i32, x: i32, bits: i32);
}

pub struct ArwenBigUint {
    pub handle: i32 // TODO: fix visibility
}

impl From<u64> for ArwenBigUint {
    fn from(item: u64) -> Self {
        unsafe {
            ArwenBigUint{ handle: bigIntNew(item as i64) }
        }
    }
}

impl From<u32> for ArwenBigUint {
    fn from(item: u32) -> Self {
        unsafe {
            ArwenBigUint{ handle: bigIntNew(item as i64) }
        }
    }
}

impl From<usize> for ArwenBigUint {
    fn from(item: usize) -> Self {
        unsafe {
            ArwenBigUint{ handle: bigIntNew(item as i64) }
        }
    }
}

impl ArwenBigUint {
    pub fn from_i64(value: i64) -> ArwenBigUint {
        unsafe {
            ArwenBigUint{ handle: bigIntNew(value) }
        }
    }
}

impl Clone for ArwenBigUint {
    fn clone(&self) -> Self {
        unsafe {
            let clone_handle = bigIntNew(0);
            bigIntAdd(clone_handle, clone_handle, self.handle);
            ArwenBigUint {handle: clone_handle}
        }        
    }
}

/// Subtracts, but exits with error if the result is negative.
/// The same behaviour can be seen in rust BigUint.
unsafe fn big_uint_safe_sub(dest: i32, x: i32, y: i32) {
    bigIntSub(dest, x, y);
    if bigIntSign(dest) < 0 {
        ext_error::signal_error(err_msg::BIG_UINT_SUB_NEGATIVE)
    }
}

macro_rules! binary_operator {
    ($trait:ident, $method:ident, $api_func:ident) => {
        impl $trait for ArwenBigUint {
            type Output = ArwenBigUint;
        
            fn $method(self, other: ArwenBigUint) -> ArwenBigUint {
                unsafe {
                    let result = bigIntNew(0);
                    $api_func(result, self.handle, other.handle);
                    ArwenBigUint {handle: result}
                }
            }
        }

        impl<'a, 'b> $trait<&'b ArwenBigUint> for &'a ArwenBigUint {
            type Output = ArwenBigUint;
        
            fn $method(self, other: &ArwenBigUint) -> ArwenBigUint {
                unsafe {
                    let result = bigIntNew(0);
                    $api_func(result, self.handle, other.handle);
                    ArwenBigUint {handle: result}
                }
            }
        }
    }
}

binary_operator!{Add, add, bigIntAdd}
binary_operator!{Sub, sub, big_uint_safe_sub}
binary_operator!{Mul, mul, bigIntMul}
binary_operator!{Div, div, bigIntTDiv}
binary_operator!{Rem, rem, bigIntTMod}

binary_operator!{BitAnd, bitand, bigIntAnd}
binary_operator!{BitOr, bitor, bigIntOr}
binary_operator!{BitXor, bitxor, bigIntXor}

macro_rules! binary_assign_operator {
    ($trait:ident, $method:ident, $api_func:ident) => {
        impl $trait<ArwenBigUint> for ArwenBigUint {
            #[inline]
            fn $method(&mut self, other: Self) {
                unsafe {
                    $api_func(self.handle, self.handle, other.handle);
                }
            }
        }
        
        impl $trait<&ArwenBigUint> for ArwenBigUint {
            #[inline]
            fn $method(&mut self, other: &ArwenBigUint) {
                unsafe {
                    $api_func(self.handle, self.handle, other.handle);
                }
            }
        }
    }
}

binary_assign_operator!{AddAssign, add_assign, bigIntAdd}
binary_assign_operator!{SubAssign, sub_assign, big_uint_safe_sub}
binary_assign_operator!{MulAssign, mul_assign, bigIntMul}
binary_assign_operator!{DivAssign, div_assign, bigIntTDiv}
binary_assign_operator!{RemAssign, rem_assign, bigIntTMod}

binary_assign_operator!{BitAndAssign, bitand_assign, bigIntAnd}
binary_assign_operator!{BitOrAssign,  bitor_assign,  bigIntOr}
binary_assign_operator!{BitXorAssign, bitxor_assign, bigIntXor}

macro_rules! shift_traits {
    ($shift_trait:ident, $method:ident, $api_func:ident) => {
        impl $shift_trait<usize> for ArwenBigUint {
            type Output = ArwenBigUint;

            #[inline]
            fn $method(self, rhs: usize) -> ArwenBigUint {
                unsafe {
                    $api_func(self.handle, self.handle, rhs as i32);
                    self
                }
            }
        }
        
        impl<'a> $shift_trait<usize> for &'a ArwenBigUint {
            type Output = ArwenBigUint;

            fn $method(self, rhs: usize) -> ArwenBigUint {
                unsafe {
                    let result = bigIntNew(0);
                    $api_func(result, self.handle, rhs as i32);
                    ArwenBigUint {handle: result}
                }
            }
        }
    }
}

shift_traits!{Shl, shl, bigIntShl}
shift_traits!{Shr, shr, bigIntShr}

macro_rules! shift_assign_traits {
    ($shift_assign_trait:ident, $method:ident, $api_func:ident) => {
        impl $shift_assign_trait<usize> for ArwenBigUint {
            #[inline]
            fn $method(&mut self, rhs: usize) {
                unsafe {
                    $api_func(self.handle, self.handle, rhs as i32);
                }
            }
        }
    }
}

shift_assign_traits!{ShlAssign, shl_assign, bigIntShl}
shift_assign_traits!{ShrAssign, shr_assign, bigIntShr}


impl PartialEq for ArwenBigUint {
    #[inline]
    fn eq(&self, other: &Self) -> bool {
        let arwen_cmp = unsafe { bigIntCmp(self.handle, other.handle) };
        arwen_cmp == 0
    }
}

impl Eq for ArwenBigUint{}

impl PartialOrd for ArwenBigUint {
    #[inline]
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

impl Ord for ArwenBigUint {
    #[inline]
    fn cmp(&self, other: &Self) -> Ordering {
        let arwen_cmp = unsafe { bigIntCmp(self.handle, other.handle) };
        arwen_cmp.cmp(&0)
    }
}

impl PartialEq<u64> for ArwenBigUint {
    #[inline]
    fn eq(&self, other: &u64) -> bool {
        PartialEq::eq(self, &ArwenBigUint::from(*other))
    }
}

impl PartialOrd<u64> for ArwenBigUint {
    #[inline]
    fn partial_cmp(&self, other: &u64) -> Option<Ordering> {
        PartialOrd::partial_cmp(self, &ArwenBigUint::from(*other))
    }
}

use elrond_wasm::elrond_codec::*;

impl Encode for ArwenBigUint {
    const TYPE_INFO: TypeInfo = TypeInfo::BigUint;

    fn using_top_encoded<F: FnOnce(&[u8])>(&self, f: F) -> Result<(), EncodeError> {
        let bytes = self.to_bytes_be();
        f(&bytes);
        Ok(())
    }
    
    fn dep_encode_to<O: Output>(&self, dest: &mut O) -> Result<(), EncodeError> {
        // TODO: vector allocation can be avoided by writing directly to dest
        let bytes = self.to_bytes_be();
        bytes.as_slice().dep_encode_to(dest)
    }
}

impl Decode for ArwenBigUint {
    const TYPE_INFO: TypeInfo = TypeInfo::BigUint;

    fn top_decode<I: Input>(input: &mut I) -> Result<Self, DecodeError> {
        let bytes = input.flush()?;
        Ok(ArwenBigUint::from_bytes_be(bytes))
    }

    fn dep_decode<I: Input>(input: &mut I) -> Result<Self, DecodeError> {
        let size = usize::dep_decode(input)?;
        let bytes = input.read_slice(size)?;
        Ok(ArwenBigUint::from_bytes_be(bytes))
    }
}

impl BigUintApi for ArwenBigUint {
    #[inline]
    fn byte_length(&self) -> i32 {
        unsafe { bigIntUnsignedByteLength(self.handle) }
    }

    fn copy_to_slice_big_endian(&self, slice: &mut [u8]) -> i32 {
        unsafe {
            bigIntGetUnsignedBytes(self.handle, slice.as_mut_ptr())
        }
    }

    fn copy_to_array_big_endian_pad_right(&self, target: &mut [u8; 32]) {
        let byte_len = self.byte_length() as usize;
        if byte_len > 32 {
            ext_error::signal_error(err_msg::BIG_UINT_EXCEEDS_SLICE)
        }
        self.copy_to_slice_big_endian(&mut target[32 - byte_len ..]);
    }

    fn to_bytes_be(&self) -> Vec<u8> {
        unsafe {
            let byte_len = bigIntUnsignedByteLength(self.handle);
            let mut vec = vec![0u8; byte_len as usize];
            bigIntGetUnsignedBytes(self.handle, vec.as_mut_ptr());
            vec
        }
    }

    fn to_bytes_be_pad_right(&self, nr_bytes: usize) -> Option<Vec<u8>> {
        unsafe {
            let byte_len = bigIntUnsignedByteLength(self.handle) as usize;
            if byte_len > nr_bytes {
                return None
            }
            let mut vec = vec![0u8; nr_bytes];
            if byte_len > 0 {
                bigIntGetUnsignedBytes(self.handle, &mut vec[nr_bytes - byte_len]);
            }
            Some(vec)
        }
    }

    fn from_bytes_be(bytes: &[u8]) -> Self {
        unsafe {
            let handle = bigIntNew(0);
            bigIntSetUnsignedBytes(handle, bytes.as_ptr(), bytes.len() as i32);
            ArwenBigUint{ handle }
        }
    }
}