use std::{
	borrow::Borrow,
	fmt,
	ops::{Add, Div, Mul, Sub},
	str::FromStr,
};

use num_bigint::{BigInt, TryFromBigIntError};
use num_traits::{Signed, Zero};

use crate::{
	impl_integer_arithmetic,
	lexical::{self, LexicalFormOf},
	Datatype, Integer, NonPositiveIntegerDatatype, ParseXsd, XsdValue,
};

use super::Sign;

#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
pub struct NonPositiveInteger(BigInt);

impl NonPositiveInteger {
	/// Create a new non positive integer from a `BigInt`.
	///
	/// # Safety
	///
	/// The input number must be non positive.
	pub unsafe fn new_unchecked(n: BigInt) -> Self {
		Self(n)
	}

	/// Creates a non positive integer from its unsigned big endian bytes
	/// representation.
	pub fn from_bytes_be(bytes: &[u8]) -> Self {
		Self(BigInt::from_bytes_be(Sign::Minus, bytes))
	}

	/// Creates a non positive integer from its unsigned little endian bytes
	/// representation.
	pub fn from_bytes_le(bytes: &[u8]) -> Self {
		Self(BigInt::from_bytes_le(Sign::Minus, bytes))
	}

	/// Creates a non positive integer from its signed big endian bytes
	/// representation.
	///
	/// # Safety
	///
	/// The represented number must be non positive.
	pub unsafe fn from_signed_bytes_be_unchecked(bytes: &[u8]) -> Self {
		Self(BigInt::from_signed_bytes_be(bytes))
	}

	/// Creates a non positive integer from its signed little endian bytes
	/// representation.
	///
	/// # Safety
	///
	/// The represented number must be non positive.
	pub unsafe fn from_signed_bytes_le_unchecked(bytes: &[u8]) -> Self {
		Self(BigInt::from_signed_bytes_le(bytes))
	}

	pub fn from_signed_bytes_be(bytes: &[u8]) -> Result<Self, IntegerIsPositive> {
		Integer::from_signed_bytes_be(bytes).try_into()
	}

	pub fn from_signed_bytes_le(bytes: &[u8]) -> Result<Self, IntegerIsPositive> {
		Integer::from_signed_bytes_le(bytes).try_into()
	}

	#[inline(always)]
	pub fn into_big_int(self) -> BigInt {
		self.0
	}

	#[inline(always)]
	pub fn zero() -> Self {
		Self(BigInt::zero())
	}

	#[inline(always)]
	pub fn is_zero(&self) -> bool {
		self.0.is_zero()
	}

	#[inline(always)]
	fn non_positive_integer_type(&self) -> NonPositiveIntegerDatatype {
		if self.0 > BigInt::zero() {
			NonPositiveIntegerDatatype::NegativeInteger
		} else {
			NonPositiveIntegerDatatype::NonPositiveInteger
		}
	}

	/// Returns a lexical representation of this non positive integer.
	#[inline(always)]
	pub fn lexical_representation(&self) -> lexical::NonPositiveIntegerBuf {
		unsafe {
			// This is safe because the `Display::fmt` method matches the
			// XSD lexical representation.
			lexical::NonPositiveIntegerBuf::new_unchecked(format!("{}", self))
		}
	}

	pub fn to_bytes_be(&self) -> (Sign, Vec<u8>) {
		self.0.to_bytes_be()
	}

	pub fn to_bytes_le(&self) -> (Sign, Vec<u8>) {
		self.0.to_bytes_le()
	}

	pub fn to_signed_bytes_be(&self) -> Vec<u8> {
		self.0.to_signed_bytes_be()
	}

	pub fn to_signed_bytes_le(&self) -> Vec<u8> {
		self.0.to_signed_bytes_le()
	}
}

impl XsdValue for NonPositiveInteger {
	#[inline(always)]
	fn datatype(&self) -> Datatype {
		self.non_positive_integer_type().into()
	}
}

impl ParseXsd for NonPositiveInteger {
	type LexicalForm = lexical::NonPositiveInteger;
}

impl LexicalFormOf<NonPositiveInteger> for lexical::NonPositiveInteger {
	type ValueError = std::convert::Infallible;

	fn try_as_value(&self) -> Result<NonPositiveInteger, Self::ValueError> {
		Ok(self.value())
	}
}

impl From<NonPositiveInteger> for BigInt {
	fn from(value: NonPositiveInteger) -> Self {
		value.0
	}
}

impl<'a> From<&'a lexical::NonPositiveInteger> for NonPositiveInteger {
	#[inline(always)]
	fn from(value: &'a lexical::NonPositiveInteger) -> Self {
		Self(value.as_str().parse().unwrap())
	}
}

impl From<lexical::NonPositiveIntegerBuf> for NonPositiveInteger {
	#[inline(always)]
	fn from(value: lexical::NonPositiveIntegerBuf) -> Self {
		value.as_non_positive_integer().into()
	}
}

impl FromStr for NonPositiveInteger {
	type Err = lexical::InvalidNonPositiveInteger;

	#[inline(always)]
	fn from_str(s: &str) -> Result<Self, Self::Err> {
		let l = lexical::NonPositiveInteger::new(s)?;
		Ok(l.into())
	}
}

impl fmt::Display for NonPositiveInteger {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		self.0.fmt(f)
	}
}

impl AsRef<BigInt> for NonPositiveInteger {
	#[inline(always)]
	fn as_ref(&self) -> &BigInt {
		&self.0
	}
}

impl Borrow<BigInt> for NonPositiveInteger {
	#[inline(always)]
	fn borrow(&self) -> &BigInt {
		&self.0
	}
}

impl_integer_arithmetic!(
	for NonPositiveInteger where r ( !r.is_positive() ) {
		Integer [.0],
		NonPositiveInteger [.0],
		NegativeInteger [.0],
		super::NonNegativeInteger [.into_big_int()],
		super::PositiveInteger [.into_big_int()],
		i8,
		i16,
		i32,
		i64,
		isize,
		u8,
		u16,
		u32,
		u64,
		usize
	}
);

#[derive(Debug, thiserror::Error)]
#[error("integer out of supported bounds: {0}")]
pub struct NonPositiveIntegerOutOfTargetBounds(pub NonPositiveInteger);

macro_rules! try_into {
	{ $( $ty:ty ),* } => {
		$(
			impl TryFrom<NonPositiveInteger> for $ty {
				type Error = NonPositiveIntegerOutOfTargetBounds;

				fn try_from(value: NonPositiveInteger) -> Result<Self, Self::Error> {
					value.0.try_into().map_err(|e: TryFromBigIntError<BigInt>| NonPositiveIntegerOutOfTargetBounds(NonPositiveInteger(e.into_original())))
				}
			}
		)*
	};
}

try_into!(u8, u16, u32, u64, usize, i8, i16, i32, i64, isize);

#[derive(Debug, thiserror::Error)]
#[error("integer {0} is negative")]
pub struct IntegerIsPositive(Integer);

impl TryFrom<Integer> for NonPositiveInteger {
	type Error = IntegerIsPositive;

	fn try_from(value: Integer) -> Result<Self, Self::Error> {
		if value.is_positive() {
			Err(IntegerIsPositive(value))
		} else {
			Ok(Self(value.into()))
		}
	}
}

#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
pub struct NegativeInteger(BigInt);

impl NegativeInteger {
	/// Creates a new negative integer from the given `BigInt`.
	///
	/// # Safety
	///
	/// The input value *must* but a negative integer.
	pub unsafe fn new_unchecked(n: BigInt) -> Self {
		Self(n)
	}

	/// Creates a negative integer from its unsigned big endian bytes
	/// representation.
	///
	/// # Safety
	///
	/// The represented number must be negative.
	pub unsafe fn from_bytes_be_unchecked(bytes: &[u8]) -> Self {
		Self(BigInt::from_bytes_be(Sign::Minus, bytes))
	}

	/// Creates a negative integer from its unsigned little endian bytes
	/// representation.
	///
	/// # Safety
	///
	/// The represented number must be negative.
	pub unsafe fn from_bytes_le_unchecked(bytes: &[u8]) -> Self {
		Self(BigInt::from_bytes_le(Sign::Minus, bytes))
	}

	/// Creates a negative integer from its signed big endian bytes
	/// representation.
	///
	/// # Safety
	///
	/// The represented number must be negative.
	pub unsafe fn from_signed_bytes_be_unchecked(bytes: &[u8]) -> Self {
		Self(BigInt::from_signed_bytes_be(bytes))
	}

	/// Creates a negative integer from its signed little endian bytes
	/// representation.
	///
	/// # Safety
	///
	/// The represented number must be negative.
	pub unsafe fn from_signed_bytes_le_unchecked(bytes: &[u8]) -> Self {
		Self(BigInt::from_signed_bytes_le(bytes))
	}

	pub fn into_big_int(self) -> BigInt {
		self.0
	}

	pub fn is_minus_one(&self) -> bool {
		matches!(i8::try_from(&self.0), Ok(-1))
	}

	pub fn to_bytes_be(&self) -> (Sign, Vec<u8>) {
		self.0.to_bytes_be()
	}

	pub fn to_bytes_le(&self) -> (Sign, Vec<u8>) {
		self.0.to_bytes_le()
	}

	pub fn to_signed_bytes_be(&self) -> Vec<u8> {
		self.0.to_signed_bytes_be()
	}

	pub fn to_signed_bytes_le(&self) -> Vec<u8> {
		self.0.to_signed_bytes_le()
	}
}

impl XsdValue for NegativeInteger {
	fn datatype(&self) -> Datatype {
		NonPositiveIntegerDatatype::NegativeInteger.into()
	}
}

impl ParseXsd for NegativeInteger {
	type LexicalForm = lexical::NegativeInteger;
}

impl LexicalFormOf<NegativeInteger> for lexical::NegativeInteger {
	type ValueError = std::convert::Infallible;

	fn try_as_value(&self) -> Result<NegativeInteger, Self::ValueError> {
		Ok(self.value())
	}
}

impl fmt::Display for NegativeInteger {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		self.0.fmt(f)
	}
}

impl From<NegativeInteger> for BigInt {
	fn from(value: NegativeInteger) -> Self {
		value.into_big_int()
	}
}

impl_integer_arithmetic!(
	for NegativeInteger where r ( r.is_negative() ) {
		Integer [.0],
		NonPositiveInteger [.0],
		NegativeInteger [.0],
		super::NonNegativeInteger [.into_big_int()],
		super::PositiveInteger [.into_big_int()],
		i8,
		i16,
		i32,
		i64,
		isize,
		u8,
		u16,
		u32,
		u64,
		usize
	}
);