use crate::error::{self, ExpectedKind, io_eof};
use crate::value::Domain;

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,
    DomainDecode,
    Map,
    NestedValue,
    Record,
    Set,
    Value,

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

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

impl<'de, 'src, S: BinarySource<'de>> BinarySource<'de> for PackedReader<'de, 'src, S> {
    type Mark = S::Mark;
    #[inline(always)]
    fn mark(&mut self) -> io::Result<Self::Mark> {
        self.source.mark()
    }
    #[inline(always)]
    fn restore(&mut self, mark: &Self::Mark) -> 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, 'src, S: BinarySource<'de>> PackedReader<'de, 'src, S> {
    #[inline(always)]
    pub fn new(source: &'src mut S) -> Self {
        PackedReader { source, phantom: PhantomData }
    }

    #[inline(always)]
    fn peek_noeof(&mut self) -> io::Result<u8> {
        self.peek()?.ok_or_else(io_eof)
    }

    #[inline(always)]
    fn read(&mut self) -> io::Result<u8> {
        let v = self.peek_noeof()?;
        self.skip()?;
        Ok(v)
    }

    #[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))
        }
    }

    fn gather_annotations<N: NestedValue, Dec: DomainDecode<N::Embedded>>(
        &mut self,
        dec: &mut Dec,
    ) -> io::Result<Vec<N>> {
        let mut annotations = vec![self.demand_next_domain(true, dec)?];
        while Tag::try_from(self.peek_noeof()?)? == Tag::Annotation {
            self.skip()?;
            annotations.push(self.demand_next_domain(true, dec)?);
        }
        Ok(annotations)
    }

    fn skip_annotations(&mut self) -> io::Result<()> {
        self.skip_value()?;
        while Tag::try_from(self.peek_noeof()?)? == Tag::Annotation {
            self.skip()?;
            self.skip_value()?;
        }
        Ok(())
    }

    fn next_upto_end<N: NestedValue, Dec: DomainDecode<N::Embedded>>(
        &mut self,
        read_annotations: bool,
        dec: &mut Dec,
    ) -> io::Result<Option<N>> {
        match self.peekend()? {
            true => Ok(None),
            false => Ok(Some(self.demand_next_domain(read_annotations, dec)?)),
        }
    }

    #[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<'de, 'src, S: BinarySource<'de>> Reader<'de> for PackedReader<'de, 'src, S> {
    fn next_domain<N: NestedValue, Dec: DomainDecode<N::Embedded>>(
        &mut self,
        read_annotations: bool,
        dec: &mut Dec,
    ) -> io::Result<Option<N>> {
        match self.peek()? {
            None => return Ok(None),
            Some(_) => (),
        }
        Ok(Some(match Tag::try_from(self.read()?)? {
            Tag::False => N::new(false),
            Tag::True => N::new(true),
            Tag::Float => {
                let mut bs = [0; 4];
                self.readbytes_into(&mut bs)?;
                Value::from(f32::from_bits(u32::from_be_bytes(bs))).wrap()
            }
            Tag::Double => {
                let mut bs = [0; 8];
                self.readbytes_into(&mut bs)?;
                Value::from(f64::from_bits(u64::from_be_bytes(bs))).wrap()
            }
            Tag::Annotation => {
                if read_annotations {
                    let mut annotations = self.gather_annotations(dec)?;
                    let (existing_annotations, v) = self.demand_next_domain::<N, _>(read_annotations, dec)?.pieces();
                    if let Some(vs) = existing_annotations {
                        annotations.extend_from_slice(&vs[..]);
                    }
                    N::wrap(Some(Box::new(annotations)), v)
                } else {
                    self.skip_annotations()?;
                    self.demand_next_domain(read_annotations, dec)?
                }
            }
            Tag::Embedded => {
                Value::Embedded(dec.decode_embedded(self, read_annotations)?).wrap()
            }
            Tag::SmallInteger(v) => {
                // TODO: prebuild these in value.rs
                Value::from(v).wrap()
            }
            Tag::MediumInteger(count) => {
                let n = self.read_signed_integer(count.into())?;
                Value::SignedInteger(n).wrap()
            }
            Tag::SignedInteger => {
                let count = self.varint()?;
                let n = self.read_signed_integer(count)?;
                Value::SignedInteger(n).wrap()
            }
            Tag::String => {
                let count = self.varint()?;
                let bs = self.readbytes(count)?;
                Value::String(self.decodestr(bs)?.into_owned()).wrap()
            }
            Tag::ByteString => {
                let count = self.varint()?;
                Value::ByteString(self.readbytes(count)?.into_owned()).wrap()
            }
            Tag::Symbol => {
                let count = self.varint()?;
                let bs = self.readbytes(count)?;
                Value::Symbol(self.decodestr(bs)?.into_owned()).wrap()
            }
            Tag::Record => {
                let mut vs = Vec::new();
                while let Some(v) = self.next_upto_end(read_annotations, dec)? { vs.push(v); }
                if vs.is_empty() {
                    return Err(self.syntax_error("Too few elements in encoded record"))
                }
                Value::Record(Record(vs)).wrap()
            }
            Tag::Sequence => {
                let mut vs = Vec::new();
                while let Some(v) = self.next_upto_end(read_annotations, dec)? { vs.push(v); }
                Value::Sequence(vs).wrap()
            }
            Tag::Set => {
                let mut s = Set::new();
                while let Some(v) = self.next_upto_end(read_annotations, dec)? { s.insert(v); }
                Value::Set(s).wrap()
            }
            Tag::Dictionary => {
                let mut d = Map::new();
                while let Some(k) = self.next_upto_end(read_annotations, dec)? {
                    match self.next_upto_end(read_annotations, dec)? {
                        Some(v) => { d.insert(k, v); }
                        None => return Err(self.syntax_error("Missing dictionary value")),
                    }
                }
                Value::Dictionary(d).wrap()
            }
            tag @ Tag::End => {
                return Err(self.syntax_error(&format!("Invalid tag: {:?}", tag)));
            }
        }))
    }

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

    #[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(())
    }

    type Mark = S::Mark;

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

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

    fn next_token<D: Domain, Dec: DomainDecode<D>>(
        &mut self,
        read_embedded_annotations: bool,
        decode_embedded: &mut Dec,
    ) -> io::Result<Token<D>> {
        loop {
            return Ok(match Tag::try_from(self.peek_noeof()?)? {
                Tag::Embedded => {
                    self.skip()?;
                    Token::Embedded(decode_embedded.decode_embedded(self, read_embedded_annotations)?)
                }
                Tag::False |
                Tag::True |
                Tag::Float |
                Tag::Double |
                Tag::SmallInteger(_) |
                Tag::MediumInteger(_) |
                Tag::SignedInteger |
                Tag::String |
                Tag::ByteString |
                Tag::Symbol =>
                    Token::Atom(self.demand_next_domain(false, decode_embedded)?),

                Tag::Record => { self.skip()?; Token::Compound(CompoundClass::Record) }
                Tag::Sequence => { self.skip()?; Token::Compound(CompoundClass::Sequence) }
                Tag::Set => { self.skip()?; Token::Compound(CompoundClass::Set) }
                Tag::Dictionary => { self.skip()?; Token::Compound(CompoundClass::Dictionary) }

                Tag::End => { self.skip()?; Token::End }

                Tag::Annotation => {
                    self.skip()?;
                    self.skip_annotations()?;
                    continue
                }
            })
        }
    }

    #[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_f32(&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_f64(&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)?)
    }
}