use num::bigint::BigInt;
use num::traits::cast::{FromPrimitive, ToPrimitive};
use std::borrow::Cow;
use std::convert::TryFrom;
use std::convert::TryInto;
use std::marker::PhantomData;
use super::super::signed_integer::SignedInteger;
use super::super::value::{Value, NestedValue, IOValue, FALSE, TRUE, Map, Set, Record, Annotations};

use super::constants::{Op, InvalidOp, AtomMinor, CompoundMinor};
use super::super::reader::{
    BinarySource,
    BytesBinarySource,
    CompoundBody,
    CompoundLimit,
    ConfiguredReader,
    IOBinarySource,
    IOResult,
    Reader,
    ReaderResult,
};

use crate::error::{self, ExpectedKind, Received, is_eof_io_error, io_syntax_error};

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

impl<'de, S: BinarySource<'de>> BinarySource<'de> for PackedReader<'de, S> {
    fn skip(&mut self) -> IOResult<()> {
        self.source.skip()
    }
    fn peek(&mut self) -> IOResult<u8> {
        self.source.peek()
    }
    fn readbytes(&mut self, count: usize) -> IOResult<Cow<'de, [u8]>> {
        self.source.readbytes(count)
    }
    fn readbytes_into(&mut self, bs: &mut [u8]) -> IOResult<()> {
        self.source.readbytes_into(bs)
    }
}

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

impl<'de> PackedReader<'de, BytesBinarySource<'de>> {
    pub fn decode_bytes(bytes: &'de [u8]) -> Self {
        PackedReader::new(BytesBinarySource::new(bytes))
    }
}

impl<'de, 'a, IOR: std::io::Read> PackedReader<'de, IOBinarySource<'a, IOR>> {
    pub fn decode_read(read: &'a mut IOR) -> Self {
        PackedReader::new(IOBinarySource::new(read))
    }
}

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

    fn read(&mut self) -> IOResult<u8> {
        let v = self.peek()?;
        self.skip()?;
        Ok(v)
    }

    fn expected(&mut self, k: ExpectedKind) -> error::Error {
        match self.demand_next(true) {
            Ok(v) => error::Error::Expected(k, Received::ReceivedOtherValue(v)),
            Err(e) => e.into()
        }
    }

    fn varint(&mut self) -> IOResult<usize> {
        let mut shift = 0;
        let mut acc: usize = 0;
        loop {
            let v = self.read()?;
            acc = acc | (((v & 0x7f) as usize) << shift);
            shift = shift + 7;
            if v & 0x80 == 0 { return Ok(acc) }
        }
    }

    fn wirelength(&mut self, arg: u8) -> IOResult<usize> {
        if arg < 15 {
            Ok(usize::from(arg))
        } else {
            self.varint()
        }
    }

    fn peekend(&mut self) -> IOResult<bool> {
        if self.peek()? == 4 {
            self.skip()?;
            Ok(true)
        } else {
            Ok(false)
        }
    }

    fn gather_chunks(&mut self) -> IOResult<Vec<u8>> {
        let mut bs = Vec::with_capacity(256);
        while !self.peekend()? {
            match decodeop(self.peek()?)? {
                (Op::Atom(AtomMinor::ByteString), arg) => {
                    self.skip()?;
                    let count = self.wirelength(arg)?;
                    if count == 0 {
                        return Err(io_syntax_error("Empty binary chunks are forbidden"));
                    }
                    bs.extend_from_slice(&self.readbytes(count)?)
                },
                _ => return Err(io_syntax_error("Unexpected non-format-B-ByteString chunk"))
            }
        }
        Ok(bs)
    }

    fn peek_next_nonannotation_op(&mut self) -> ReaderResult<(Op, u8)> {
        loop {
            match decodeop(self.peek()?)? {
                (Op::Misc(0), 5) => {
                    self.skip()?;
                    self.skip_value()?;
                },
                other => return Ok(other),
            }
        }
    }

    fn next_atomic(&mut self, minor: AtomMinor, k: ExpectedKind) -> ReaderResult<Cow<'de, [u8]>> {
        match self.peek_next_nonannotation_op()? {
            (Op::Atom(actual_minor), arg) if actual_minor == minor => {
                self.skip()?;
                let count = self.wirelength(arg)?;
                Ok(self.readbytes(count)?)
            }
            (Op::Misc(2), arg) => match Op::try_from(arg)? {
                Op::Atom(actual_minor) if actual_minor == minor => {
                    self.skip()?;
                    Ok(Cow::Owned(self.gather_chunks()?))
                }
                _ => Err(self.expected(k)),
            },
            _ => Err(self.expected(k)),
        }
    }

    fn next_compound(&mut self, minor: CompoundMinor, k: ExpectedKind) ->
        ReaderResult<CompoundBody<CompoundMinor>>
    {
        match self.peek_next_nonannotation_op()? {
            (Op::Compound(actual_minor), arg) if actual_minor == minor => {
                self.skip()?;
                Ok(CompoundBody::counted(minor, self.wirelength(arg)?))
            }
            (Op::Misc(2), arg) => match Op::try_from(arg)? {
                Op::Compound(actual_minor) if actual_minor == minor => {
                    self.skip()?;
                    Ok(CompoundBody::streaming(minor))
                }
                _ => Err(self.expected(k)),
            },
            _ => Err(self.expected(k)),
        }
    }

    fn read_number_format_b(&mut self, count: usize) -> IOResult<SignedInteger> {
        if count == 0 {
            return Ok(SignedInteger::from(0 as i128));
        }

        if count > 16 {
            let bs = self.readbytes(count)?;
            if (bs[0] & 0x80) == 0 {
                // Positive or zero.
                let mut i = 0;
                while i < count && bs[i] == 0 { i = 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 = 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)))
        }
    }

    fn next_unsigned<T: FromPrimitive, F>(&mut self, f: F) -> ReaderResult<T>
    where
        F: FnOnce(u128) -> Option<T>
    {
        match self.peek_next_nonannotation_op()? {
            (Op::Misc(3), arg) => {
                self.skip()?;
                if arg > 12 {
                    Err(out_of_range((arg as i8) - 16))
                } else {
                    f(arg as u128).ok_or_else(|| out_of_range(arg))
                }
            }
            (Op::Atom(AtomMinor::SignedInteger), arg) => {
                self.skip()?;
                let count = self.wirelength(arg)?;
                let n = &self.read_number_format_b(count)?;
                let i = n.try_into().or_else(|_| Err(out_of_range(n)))?;
                f(i).ok_or_else(|| out_of_range(i))
            }
            _ => {
                let n_value = self.demand_next(false)?;
                let n = n_value.value().to_signedinteger()?;
                let i = n.try_into().or_else(|_| Err(out_of_range(n)))?;
                f(i).ok_or_else(|| out_of_range(i))
            }
        }
    }

    fn next_signed<T: FromPrimitive, F>(&mut self, f: F) -> ReaderResult<T>
    where
        F: FnOnce(i128) -> Option<T>
    {
        match self.peek_next_nonannotation_op()? {
            (Op::Misc(3), arg) => {
                self.skip()?;
                let n = arg as i128;
                let n = if n > 12 { n - 16 } else { n };
                f(n).ok_or_else(|| out_of_range(n))
            }
            (Op::Atom(AtomMinor::SignedInteger), arg) => {
                self.skip()?;
                let count = self.wirelength(arg)?;
                let n = &self.read_number_format_b(count)?;
                let i = n.try_into().or_else(|_| Err(out_of_range(n)))?;
                f(i).ok_or_else(|| out_of_range(i))
            }
            _ => {
                let n_value = self.demand_next(false)?;
                let n = n_value.value().to_signedinteger()?;
                let i = n.try_into().or_else(|_| Err(out_of_range(n)))?;
                f(i).ok_or_else(|| out_of_range(i))
            }
        }
    }
}

impl<'de, S: BinarySource<'de>> Reader<'de> for PackedReader<'de, S> {
    type CompoundInfo = CompoundMinor;

    fn next(&mut self, read_annotations: bool) -> IOResult<Option<IOValue>> {
        match self.peek() {
            Err(e) if is_eof_io_error(&e) => return Ok(None),
            Err(e) => return Err(e),
            Ok(_) => (),
        }
        loop {
            return Ok(Some(match decodeop(self.read()?)? {
                (Op::Misc(0), 0) => FALSE.clone(),
                (Op::Misc(0), 1) => TRUE.clone(),
                (Op::Misc(0), 2) => {
                    let mut bs = [0; 4];
                    self.readbytes_into(&mut bs)?;
                    Value::from(f32::from_bits(u32::from_be_bytes(bs))).wrap()
                }
                (Op::Misc(0), 3) => {
                    let mut bs = [0; 8];
                    self.readbytes_into(&mut bs)?;
                    Value::from(f64::from_bits(u64::from_be_bytes(bs))).wrap()
                }
                (Op::Misc(0), 5) => {
                    if read_annotations {
                        let mut annotations = vec![self.demand_next(read_annotations)?];
                        while decodeop(self.peek()?)? == (Op::Misc(0), 5) {
                            self.skip()?;
                            annotations.push(self.demand_next(read_annotations)?);
                        }
                        let (existing_annotations, v) = self.demand_next(read_annotations)?.pieces();
                        annotations.extend_from_slice(existing_annotations.slice());
                        IOValue::wrap(Annotations::new(Some(annotations)), v)
                    } else {
                        self.skip_value()?;
                        continue;
                    }
                }
                (Op::Misc(0), _) => Err(io_syntax_error("Invalid format A encoding"))?,
                (Op::Misc(1), _) => Err(io_syntax_error("Invalid format A encoding"))?,
                (Op::Misc(2), arg) => match Op::try_from(arg)? {
                    Op::Atom(minor) =>
                        decodebinary(minor, Cow::Owned(self.gather_chunks()?))?,
                    Op::Compound(minor) => decodecompound(minor, DelimitedStream {
                        reader: self.configured(read_annotations),
                    })?,
                    _ => Err(io_syntax_error("Invalid format C start byte"))?,
                }
                (Op::Misc(3), arg) => {
                    let n = if arg > 12 { i32::from(arg) - 16 } else { i32::from(arg) };
                    // TODO: prebuild these in value.rs
                    Value::from(n).wrap()
                }
                (Op::Misc(_), _) => unreachable!(),
                (Op::Atom(AtomMinor::SignedInteger), arg) => {
                    let count = self.wirelength(arg)?;
                    let n = self.read_number_format_b(count)?;
                    Value::SignedInteger(n).wrap()
                }
                (Op::Atom(minor), arg) => {
                    let count = self.wirelength(arg)?;
                    decodebinary(minor, self.readbytes(count)?)?
                }
                (Op::Compound(minor), arg) => {
                    let count = self.wirelength(arg)?;
                    decodecompound(minor, CountedStream {
                        reader: self.configured(read_annotations),
                        count,
                    })?
                }
                (Op::Reserved(3), 15) => continue,
                (Op::Reserved(_), _) => return Err(InvalidOp.into()),
            }))
        }
    }

    fn open_record(&mut self, arity: Option<usize>) -> ReaderResult<CompoundBody<Self::CompoundInfo>> {
        if let Some(expected_arity) = arity {
            let compound_format =
                self.next_compound(CompoundMinor::Record, ExpectedKind::Record(arity))?;
            if let CompoundLimit::Counted(count) = compound_format.limit {
                if count != expected_arity + 1 /* we add 1 for the label */ {
                    return Err(error::Error::Expected(ExpectedKind::Record(arity),
                                                      Received::ReceivedSomethingElse));
                }
            }
            Ok(compound_format)
        } else {
            self.next_compound(CompoundMinor::Record, ExpectedKind::Record(None))
        }
    }

    fn open_sequence_or_set(&mut self) -> ReaderResult<CompoundBody<Self::CompoundInfo>> {
        match self.peek_next_nonannotation_op()? {
            (Op::Compound(minor), arg)
                if CompoundMinor::Sequence == minor || CompoundMinor::Set == minor => {
                    self.skip()?;
                    Ok(CompoundBody::counted(minor, self.wirelength(arg)?))
                }
            (Op::Misc(2), arg) => match Op::try_from(arg)? {
                Op::Compound(minor)
                    if CompoundMinor::Sequence == minor || CompoundMinor::Set == minor => {
                        self.skip()?;
                        Ok(CompoundBody::streaming(minor))
                    }
                _ => Err(self.expected(ExpectedKind::SequenceOrSet)),
            }
            _ => Err(self.expected(ExpectedKind::SequenceOrSet)),
        }
    }

    fn open_sequence(&mut self) -> ReaderResult<CompoundBody<Self::CompoundInfo>> {
        self.next_compound(CompoundMinor::Sequence, ExpectedKind::Sequence)
    }

    fn open_set(&mut self) -> ReaderResult<CompoundBody<Self::CompoundInfo>> {
        self.next_compound(CompoundMinor::Set, ExpectedKind::Set)
    }

    fn open_dictionary(&mut self) -> ReaderResult<CompoundBody<Self::CompoundInfo>> {
        self.next_compound(CompoundMinor::Dictionary, ExpectedKind::Dictionary)
    }

    fn close_compound_counted(&mut self, _minor: Self::CompoundInfo) -> ReaderResult<()> {
        // Nothing to do -- no close delimiter to consume
        Ok(())
    }

    fn close_compound_stream(&mut self, _minor: Self::CompoundInfo) -> ReaderResult<bool> {
        Ok(self.peekend()?)
    }

    fn next_boolean(&mut self) -> ReaderResult<bool> {
        match self.peek_next_nonannotation_op()? {
            (Op::Misc(0), 0) => { self.skip()?; Ok(false) }
            (Op::Misc(0), 1) => { self.skip()?; Ok(true) }
            _ => Err(self.expected(ExpectedKind::Boolean)),
        }
    }

    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_op()? {
            (Op::Misc(0), 2) => {
                self.skip()?;
                let mut bs = [0; 4];
                self.readbytes_into(&mut bs)?;
                Ok(f32::from_bits(u32::from_be_bytes(bs)))
            },
            (Op::Misc(0), 3) => {
                self.skip()?;
                let mut bs = [0; 8];
                self.readbytes_into(&mut bs)?;
                Ok(f64::from_bits(u64::from_be_bytes(bs)) as f32)
            },
            _ => Err(self.expected(ExpectedKind::Float)),
        }
    }

    fn next_double(&mut self) -> ReaderResult<f64> {
        match self.peek_next_nonannotation_op()? {
            (Op::Misc(0), 2) => {
                self.skip()?;
                let mut bs = [0; 4];
                self.readbytes_into(&mut bs)?;
                Ok(f32::from_bits(u32::from_be_bytes(bs)) as f64)
            },
            (Op::Misc(0), 3) => {
                self.skip()?;
                let mut bs = [0; 8];
                self.readbytes_into(&mut bs)?;
                Ok(f64::from_bits(u64::from_be_bytes(bs)))
            },
            _ => Err(self.expected(ExpectedKind::Double)),
        }
    }

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

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

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

struct CountedStream<'de, R: Reader<'de>> {
    reader: ConfiguredReader<'de, R>,
    count: usize,
}

impl<'de, R: Reader<'de>> Iterator for CountedStream<'de, R>
{
    type Item = IOResult<IOValue>;
    fn next(&mut self) -> Option<Self::Item> {
        if self.count == 0 { return None }
        self.count -= 1;
        Some(self.reader.reader.demand_next(self.reader.read_annotations))
    }
}

struct DelimitedStream<'a, 'de, S: BinarySource<'de>> {
    reader: ConfiguredReader<'de, &'a mut PackedReader<'de, S>>,
}

impl<'a, 'de, S: BinarySource<'de>> Iterator for DelimitedStream<'a, 'de, S>
{
    type Item = IOResult<IOValue>;
    fn next(&mut self) -> Option<Self::Item> {
        match self.reader.reader.peekend() {
            Err(e) => Some(Err(e)),
            Ok(true) => None,
            Ok(false) => Some(self.reader.reader.demand_next(self.reader.read_annotations)),
        }
    }
}

pub fn decodeop(b: u8) -> IOResult<(Op, u8)> {
    Ok((Op::try_from(b >> 4)?, b & 15))
}

pub fn decodestr<'de>(cow: Cow<'de, [u8]>) -> IOResult<Cow<'de, str>> {
    match cow {
        Cow::Borrowed(bs) =>
            Ok(Cow::Borrowed(std::str::from_utf8(bs).map_err(|_| io_syntax_error("Invalid UTF-8"))?)),
        Cow::Owned(bs) =>
            Ok(Cow::Owned(String::from_utf8(bs).map_err(|_| io_syntax_error("Invalid UTF-8"))?.to_owned())),
    }
}

pub fn decodebinary<'de>(minor: AtomMinor, bs: Cow<'de, [u8]>) -> IOResult<IOValue> {
    Ok(match minor {
        AtomMinor::SignedInteger => Value::from(&BigInt::from_signed_bytes_be(&bs)).wrap(),
        AtomMinor::String => Value::String(decodestr(bs)?.into_owned()).wrap(),
        AtomMinor::ByteString => Value::ByteString(bs.into_owned()).wrap(),
        AtomMinor::Symbol => Value::Symbol(decodestr(bs)?.into_owned()).wrap(),
    })
}

pub fn decodecompound<'de, I: Iterator<Item = IOResult<IOValue>>>(
    minor: CompoundMinor,
    mut iter: I
) ->
    IOResult<IOValue>
{
    match minor {
        CompoundMinor::Record => {
            let vs = iter.collect::<IOResult<Vec<IOValue>>>()?;
            if vs.len() < 1 {
                Err(io_syntax_error("Too few elements in encoded record"))
            } else {
                Ok(Value::Record(Record(vs)).wrap())
            }
        }
        CompoundMinor::Sequence => {
            let vs = iter.collect::<IOResult<Vec<IOValue>>>()?;
            Ok(Value::Sequence(vs).wrap())
        }
        CompoundMinor::Set => {
            let mut s = Set::new();
            for res in iter { s.insert(res?); }
            Ok(Value::Set(s).wrap())
        }
        CompoundMinor::Dictionary => {
            let mut d = Map::new();
            while let Some(kres) = iter.next() {
                let k = kres?;
                match iter.next() {
                    Some(vres) => {
                        let v = vres?;
                        d.insert(k, v);
                    }
                    None => return Err(io_syntax_error("Missing dictionary value")),
                }
            }
            Ok(Value::Dictionary(d).wrap())
        }
    }
}