use crate::{ValueClass, AtomClass, Atom};
use crate::error::{self, ExpectedKind};

use num_bigint::BigInt;
use num_traits::cast::{FromPrimitive, ToPrimitive};

use std::borrow::Cow;
use std::convert::TryFrom;
use std::convert::TryInto;
use std::io;
use std::marker::PhantomData;

use super::constants::Tag;
use super::super::{
    CompoundClass,

    boundary as B,
    reader::{
        NextToken,
        Reader,
        ReaderResult,
    },
    signed_integer::SignedInteger,
    source::BinarySource,
};

pub struct PackedReader<'de, S: BinarySource<'de>> {
    pub source: S,
    phantom: PhantomData<&'de ()>,
}

impl<'de, S: BinarySource<'de>> BinarySource<'de> for PackedReader<'de, S> {
    #[inline(always)]
    fn mark(&mut self) -> io::Result<usize> {
        self.source.mark()
    }
    #[inline(always)]
    fn restore(&mut self, mark: usize) -> io::Result<()> {
        self.source.restore(mark)
    }
    #[inline(always)]
    fn skip(&mut self) -> io::Result<()> {
        self.source.skip()
    }
    #[inline(always)]
    fn peek(&mut self) -> io::Result<Option<u8>> {
        self.source.peek()
    }
    #[inline(always)]
    fn readbytes(&mut self, count: u64) -> io::Result<Cow<'de, [u8]>> {
        self.source.readbytes(count)
    }
    #[inline(always)]
    fn readbytes_into(&mut self, bs: &mut [u8]) -> io::Result<()> {
        self.source.readbytes_into(bs)
    }
    #[inline(always)]
    fn input_position(&mut self) -> io::Result<Option<usize>> {
        self.source.input_position()
    }
    #[inline(always)]
    fn discard(&mut self, count: u64) -> io::Result<()> {
        self.source.discard(count)
    }
    #[inline(always)]
    fn read_to_end(&mut self) -> io::Result<Cow<'de, [u8]>> {
        self.source.read_to_end()
    }
}

fn out_of_range<I: Into<BigInt>>(i: I) -> error::Error {
    error::Error::NumberOutOfRange(i.into())
}

impl<'de, S: BinarySource<'de>> PackedReader<'de, S> {
    #[inline(always)]
    pub fn new(source: S) -> Self {
        PackedReader { source, phantom: PhantomData }
    }

    #[inline(always)]
    fn varint(&mut self) -> io::Result<u64> {
        let mut shift = 0;
        let mut acc: u64 = 0;
        loop {
            let v = self.read()?;
            if shift == 63 && v > 1 { Err(error::Error::Message("PackedReader length too long".to_string()))? }
            acc |= ((v & 0x7f) as u64) << shift;
            shift += 7;
            if v & 0x80 == 0 { return Ok(acc) }
            if shift >= 70 { Err(error::Error::Message("PackedReader length too long".to_string()))? }
        }
    }

    #[inline(always)]
    fn peekend(&mut self) -> io::Result<bool> {
        if self.peek()? == Some(Tag::End.into()) {
            self.skip()?;
            Ok(true)
        } else {
            Ok(false)
        }
    }

    #[inline(always)]
    fn peek_next_nonannotation_tag(&mut self) -> ReaderResult<Tag> {
        loop {
            match Tag::try_from(self.peek_noeof()?)? {
                Tag::Annotation => {
                    self.skip()?;
                    self.skip_value()?;
                },
                other => return Ok(other),
            }
        }
    }

    fn next_atomic(&mut self, expected_tag: Tag, k: ExpectedKind) -> ReaderResult<Cow<'de, [u8]>> {
        let actual_tag = self.peek_next_nonannotation_tag()?;
        if actual_tag == expected_tag {
            self.skip()?;
            let count = self.varint()?;
            Ok(self.readbytes(count)?)
        } else {
            Err(error::Error::Expected(k))
        }
    }

    fn next_compound(&mut self, expected_tag: Tag, k: ExpectedKind) -> ReaderResult<()>
    {
        let actual_tag = self.peek_next_nonannotation_tag()?;
        if actual_tag == expected_tag {
            self.skip()?;
            Ok(())
        } else {
            Err(error::Error::Expected(k))
        }
    }

    #[inline(always)]
    fn read_signed_integer(&mut self, count: u64) -> io::Result<SignedInteger> {
        let count_u64 = count;
        let count: usize = count.try_into().map_err(
            |_| error::Error::Message("Signed integer too long".to_string()))?;

        if count == 0 {
            return Ok(SignedInteger::from(0_i128));
        }

        if count > 16 {
            let bs = self.readbytes(count_u64)?;
            if (bs[0] & 0x80) == 0 {
                // Positive or zero.
                let mut i = 0;
                while i < count && bs[i] == 0 { i += 1; }
                if count - i <= 16 {
                    Ok(SignedInteger::from(u128::from_be_bytes(bs[bs.len() - 16..].try_into().unwrap())))
                } else {
                    Ok(SignedInteger::from(Cow::Owned(BigInt::from_bytes_be(num_bigint::Sign::Plus, &bs[i..]))))
                }
            } else {
                // Negative.
                let mut i = 0;
                while i < count && bs[i] == 0xff { i += 1; }
                if count - i <= 16 {
                    Ok(SignedInteger::from(i128::from_be_bytes(bs[bs.len() - 16..].try_into().unwrap())))
                } else {
                    Ok(SignedInteger::from(Cow::Owned(BigInt::from_signed_bytes_be(&bs))))
                }
            }
        } else {
            let first_byte = self.read()?;
            let prefix_byte = if (first_byte & 0x80) == 0 { 0x00 } else { 0xff };
            let mut bs = [prefix_byte; 16];
            bs[16 - count] = first_byte;
            self.readbytes_into(&mut bs[16 - (count - 1)..])?;
            Ok(SignedInteger::from(i128::from_be_bytes(bs)))
        }
    }

    #[inline(always)]
    fn next_unsigned<T: FromPrimitive, F>(&mut self, f: F) -> ReaderResult<T>
    where
        F: FnOnce(u128) -> Option<T>
    {
        let tag = self.peek_next_nonannotation_tag()?;
        match tag {
            Tag::SmallInteger(v) => {
                self.skip()?;
                if v < 0 {
                    Err(out_of_range(v))
                } else {
                    f(v as u128).ok_or_else(|| out_of_range(v))
                }
            }
            Tag::MediumInteger(count) => {
                self.skip()?;
                let n = &self.read_signed_integer(count.into())?;
                let i = n.try_into().map_err(|_| out_of_range(n))?;
                f(i).ok_or_else(|| out_of_range(i))
            }
            Tag::SignedInteger => {
                self.skip()?;
                let count = self.varint()?;
                let n = &self.read_signed_integer(count)?;
                let i = n.try_into().map_err(|_| out_of_range(n))?;
                f(i).ok_or_else(|| out_of_range(i))
            }
            _ => Err(error::Error::Expected(ExpectedKind::SignedInteger))
        }
    }

    #[inline(always)]
    fn next_signed<T: FromPrimitive, F>(&mut self, f: F) -> ReaderResult<T>
    where
        F: FnOnce(i128) -> Option<T>
    {
        let tag = self.peek_next_nonannotation_tag()?;
        match tag {
            Tag::SmallInteger(v) => {
                self.skip()?;
                f(v.into()).ok_or_else(|| out_of_range(v))
            }
            Tag::MediumInteger(count) => {
                self.skip()?;
                let n = &self.read_signed_integer(count.into())?;
                let i = n.try_into().map_err(|_| out_of_range(n))?;
                f(i).ok_or_else(|| out_of_range(i))
            }
            Tag::SignedInteger => {
                self.skip()?;
                let count = self.varint()?;
                let n = &self.read_signed_integer(count)?;
                let i = n.try_into().map_err(|_| out_of_range(n))?;
                f(i).ok_or_else(|| out_of_range(i))
            }
            _ => Err(error::Error::Expected(ExpectedKind::SignedInteger))
        }
    }

    #[inline(always)]
    fn decodestr<'a>(&mut self, cow: Cow<'a, [u8]>) -> io::Result<Cow<'a, str>> {
        match cow {
            Cow::Borrowed(bs) =>
                Ok(Cow::Borrowed(std::str::from_utf8(bs).map_err(|_| self.syntax_error("Invalid UTF-8"))?)),
            Cow::Owned(bs) =>
                Ok(Cow::Owned(String::from_utf8(bs).map_err(|_| self.syntax_error("Invalid UTF-8"))?)),
        }
    }
}

impl From<Tag> for Option<NextToken> {
    #[inline(always)]
    fn from(tag: Tag) -> Self {
        match tag {
            Tag::False => Some(NextToken::Value(ValueClass::Atomic(AtomClass::Boolean))),
            Tag::True => Some(NextToken::Value(ValueClass::Atomic(AtomClass::Boolean))),
            Tag::Float => Some(NextToken::Value(ValueClass::Atomic(AtomClass::Float))),
            Tag::Double => Some(NextToken::Value(ValueClass::Atomic(AtomClass::Double))),
            Tag::Annotation => Some(NextToken::Annotation),
            Tag::Embedded => Some(NextToken::Value(ValueClass::Embedded)),
            Tag::SmallInteger(_) => Some(NextToken::Value(ValueClass::Atomic(AtomClass::SignedInteger))),
            Tag::MediumInteger(_) => Some(NextToken::Value(ValueClass::Atomic(AtomClass::SignedInteger))),
            Tag::SignedInteger => Some(NextToken::Value(ValueClass::Atomic(AtomClass::SignedInteger))),
            Tag::String => Some(NextToken::Value(ValueClass::Atomic(AtomClass::String))),
            Tag::ByteString => Some(NextToken::Value(ValueClass::Atomic(AtomClass::ByteString))),
            Tag::Symbol => Some(NextToken::Value(ValueClass::Atomic(AtomClass::Symbol))),
            Tag::Record => Some(NextToken::Value(ValueClass::Compound(CompoundClass::Record))),
            Tag::Sequence => Some(NextToken::Value(ValueClass::Compound(CompoundClass::Sequence))),
            Tag::Set => Some(NextToken::Value(ValueClass::Compound(CompoundClass::Set))),
            Tag::Dictionary => Some(NextToken::Value(ValueClass::Compound(CompoundClass::Dictionary))),
            Tag::End => None,
        }
    }
}

impl<'de, S: BinarySource<'de>> Reader<'de> for PackedReader<'de, S> {
    fn peek_class(&mut self) -> io::Result<Option<NextToken>> {
        let tag = Tag::try_from(match self.peek()? {
            None => return Ok(None),
            Some(b) => b,
        })?;
        match tag.into() {
            Some(n) => Ok(Some(n)),
            None => Err(self.syntax_error("Unexpected tag")),
        }
    }

    fn next_atom(&mut self) -> ReaderResult<Atom<'de>> {
        match Tag::try_from(self.read()?)? {
            Tag::False => Ok(Atom::Boolean(false)),
            Tag::True => Ok(Atom::Boolean(true)),
            Tag::Float => {
                let mut bs = [0; 4];
                self.readbytes_into(&mut bs)?;
                Ok(Atom::Float(f32::from_bits(u32::from_be_bytes(bs))))
            }
            Tag::Double => {
                let mut bs = [0; 8];
                self.readbytes_into(&mut bs)?;
                Ok(Atom::Double(f64::from_bits(u64::from_be_bytes(bs))))
            }
            Tag::SmallInteger(v) => Ok(Atom::SignedInteger(Cow::Owned(v.into()))),
            Tag::MediumInteger(count) => Ok(Atom::SignedInteger(Cow::Owned(self.read_signed_integer(count.into())?))),
            Tag::SignedInteger => {
                let count = self.varint()?;
                Ok(Atom::SignedInteger(Cow::Owned(self.read_signed_integer(count)?)))
            }
            Tag::String => {
                let count = self.varint()?;
                let bs = self.readbytes(count)?;
                Ok(Atom::String(self.decodestr(bs)?))
            }
            Tag::ByteString => {
                let count = self.varint()?;
                Ok(Atom::ByteString(self.readbytes(count)?))
            }
            Tag::Symbol => {
                let count = self.varint()?;
                let bs = self.readbytes(count)?;
                Ok(Atom::Symbol(self.decodestr(bs)?))
            }
            _ => Err(self.syntax_error("Expected atomic value"))?,
        }
    }

    #[inline(always)]
    fn boundary(&mut self, _b: &B::Type) -> ReaderResult<()> {
        Ok(())
    }

    #[inline(always)]
    fn open_record(&mut self) -> ReaderResult<()> {
        self.next_compound(Tag::Record, ExpectedKind::Record)
    }

    #[inline(always)]
    fn open_sequence(&mut self) -> ReaderResult<()> {
        self.next_compound(Tag::Sequence, ExpectedKind::Sequence)
    }

    #[inline(always)]
    fn open_set(&mut self) -> ReaderResult<()> {
        self.next_compound(Tag::Set, ExpectedKind::Set)
    }

    #[inline(always)]
    fn open_dictionary(&mut self) -> ReaderResult<()> {
        self.next_compound(Tag::Dictionary, ExpectedKind::Dictionary)
    }

    #[inline(always)]
    fn close_compound(&mut self, _b: &mut B::Type, _i: &B::Item) -> ReaderResult<bool> {
        Ok(self.peekend()?)
    }

    #[inline(always)]
    fn open_embedded(&mut self) -> ReaderResult<()> {
        self.next_compound(Tag::Embedded, ExpectedKind::Embedded)
    }

    #[inline(always)]
    fn close_embedded(&mut self) -> ReaderResult<()> {
        Ok(())
    }

    #[inline(always)]
    fn mark(&mut self) -> io::Result<usize> {
        self.source.mark()
    }

    #[inline(always)]
    fn restore(&mut self, mark: usize) -> io::Result<()> {
        self.source.restore(mark)
    }

    #[inline(always)]
    fn next_boolean(&mut self) -> ReaderResult<bool> {
        match self.peek_next_nonannotation_tag()? {
            Tag::False => { self.skip()?; Ok(false) }
            Tag::True => { self.skip()?; Ok(true) }
            _ => Err(error::Error::Expected(ExpectedKind::Boolean)),
        }
    }

    fn next_signedinteger(&mut self) -> ReaderResult<SignedInteger> {
        let tag = self.peek_next_nonannotation_tag()?;
        match tag {
            Tag::SmallInteger(v) => {
                self.skip()?;
                Ok(SignedInteger::from(v as i32))
            }
            Tag::MediumInteger(count) => {
                self.skip()?;
                Ok(self.read_signed_integer(count.into())?)
            }
            Tag::SignedInteger => {
                self.skip()?;
                let count = self.varint()?;
                Ok(self.read_signed_integer(count)?)
            }
            _ => Err(error::Error::Expected(ExpectedKind::SignedInteger))
        }
    }

    fn next_i8(&mut self)  -> ReaderResult<i8>    { self.next_signed(|n| n.to_i8()) }
    fn next_i16(&mut self) -> ReaderResult<i16>   { self.next_signed(|n| n.to_i16()) }
    fn next_i32(&mut self) -> ReaderResult<i32>   { self.next_signed(|n| n.to_i32()) }
    fn next_i64(&mut self) -> ReaderResult<i64>   { self.next_signed(|n| n.to_i64()) }
    fn next_i128(&mut self) -> ReaderResult<i128> { self.next_signed(|n| n.to_i128()) }

    fn next_u8(&mut self)  -> ReaderResult<u8>    { self.next_unsigned(|n| n.to_u8()) }
    fn next_u16(&mut self) -> ReaderResult<u16>   { self.next_unsigned(|n| n.to_u16()) }
    fn next_u32(&mut self) -> ReaderResult<u32>   { self.next_unsigned(|n| n.to_u32()) }
    fn next_u64(&mut self) -> ReaderResult<u64>   { self.next_unsigned(|n| n.to_u64()) }
    fn next_u128(&mut self) -> ReaderResult<u128> { self.next_unsigned(|n| n.to_u128()) }

    fn next_float(&mut self) -> ReaderResult<f32> {
        match self.peek_next_nonannotation_tag()? {
            Tag::Float => {
                self.skip()?;
                let mut bs = [0; 4];
                self.readbytes_into(&mut bs)?;
                Ok(f32::from_bits(u32::from_be_bytes(bs)))
            },
            Tag::Double => {
                self.skip()?;
                let mut bs = [0; 8];
                self.readbytes_into(&mut bs)?;
                Ok(f64::from_bits(u64::from_be_bytes(bs)) as f32)
            },
            _ => Err(error::Error::Expected(ExpectedKind::Float)),
        }
    }

    fn next_double(&mut self) -> ReaderResult<f64> {
        match self.peek_next_nonannotation_tag()? {
            Tag::Float => {
                self.skip()?;
                let mut bs = [0; 4];
                self.readbytes_into(&mut bs)?;
                Ok(f32::from_bits(u32::from_be_bytes(bs)) as f64)
            },
            Tag::Double => {
                self.skip()?;
                let mut bs = [0; 8];
                self.readbytes_into(&mut bs)?;
                Ok(f64::from_bits(u64::from_be_bytes(bs)))
            },
            _ => Err(error::Error::Expected(ExpectedKind::Double)),
        }
    }

    fn next_str(&mut self) -> ReaderResult<Cow<'de, str>> {
        let bs = self.next_atomic(Tag::String, ExpectedKind::Symbol)?;
        Ok(self.decodestr(bs)?)
    }

    fn next_bytestring(&mut self) -> ReaderResult<Cow<'de, [u8]>> {
        self.next_atomic(Tag::ByteString, ExpectedKind::Symbol)
    }

    fn next_symbol(&mut self) -> ReaderResult<Cow<'de, str>> {
        let bs = self.next_atomic(Tag::Symbol, ExpectedKind::Symbol)?;
        Ok(self.decodestr(bs)?)
    }

    fn open_annotation(&mut self) -> ReaderResult<()> {
        if let Tag::Annotation = Tag::try_from(self.peek_noeof()?)? {
            Ok(self.skip()?)
        } else {
            Err(error::Error::Expected(ExpectedKind::Annotation))
        }
    }

    fn close_annotation(&mut self) -> ReaderResult<()> {
        Ok(())
    }

    fn specialized(&mut self) -> Option<(&str, &mut dyn BinarySource<'de>)> {
        Some(("packed", &mut self.source))
    }
}