use std::borrow::Cow;
use std::io::{Read, Error};
use std::marker::PhantomData;
use super::value::{NestedValue, IOValue};
use crate::error::{self, ExpectedKind, Received, io_eof};

pub type IOResult<T> = std::result::Result<T, Error>;
pub type ReaderResult<T> = std::result::Result<T, error::Error>;

pub trait Reader<'de> {
    type CompoundInfo: Copy;

    fn next(&mut self, read_annotations: bool) -> IOResult<Option<IOValue>>;
    fn open_record(&mut self, arity: Option<usize>) -> ReaderResult<CompoundBody<Self::CompoundInfo>>;
    fn open_sequence_or_set(&mut self) -> ReaderResult<CompoundBody<Self::CompoundInfo>>;
    fn open_sequence(&mut self) -> ReaderResult<CompoundBody<Self::CompoundInfo>>;
    fn open_set(&mut self) -> ReaderResult<CompoundBody<Self::CompoundInfo>>;
    fn open_dictionary(&mut self) -> ReaderResult<CompoundBody<Self::CompoundInfo>>;
    fn close_compound_counted(&mut self, info: Self::CompoundInfo) -> ReaderResult<()>;
    fn close_compound_stream(&mut self, info: Self::CompoundInfo) -> ReaderResult<bool>;

    //---------------------------------------------------------------------------

    fn skip_value(&mut self) -> IOResult<()> {
        // TODO efficient skipping in specific impls of this trait
        let _ = self.demand_next(false)?;
        Ok(())
    }

    fn demand_next(&mut self, read_annotations: bool) -> IOResult<IOValue> {
        match self.next(read_annotations)? {
            None => Err(io_eof()),
            Some(v) => Ok(v)
        }
    }

    fn next_boolean(&mut self) -> ReaderResult<bool> { self.demand_next(false)?.value().to_boolean() }
    fn next_i8(&mut self) -> ReaderResult<i8> { self.demand_next(false)?.value().to_i8() }
    fn next_u8(&mut self) -> ReaderResult<u8> { self.demand_next(false)?.value().to_u8() }
    fn next_i16(&mut self) -> ReaderResult<i16> { self.demand_next(false)?.value().to_i16() }
    fn next_u16(&mut self) -> ReaderResult<u16> { self.demand_next(false)?.value().to_u16() }
    fn next_i32(&mut self) -> ReaderResult<i32> { self.demand_next(false)?.value().to_i32() }
    fn next_u32(&mut self) -> ReaderResult<u32> { self.demand_next(false)?.value().to_u32() }
    fn next_i64(&mut self) -> ReaderResult<i64> { self.demand_next(false)?.value().to_i64() }
    fn next_u64(&mut self) -> ReaderResult<u64> { self.demand_next(false)?.value().to_u64() }
    fn next_i128(&mut self) -> ReaderResult<i128> { self.demand_next(false)?.value().to_i128() }
    fn next_u128(&mut self) -> ReaderResult<u128> { self.demand_next(false)?.value().to_u128() }
    fn next_float(&mut self) -> ReaderResult<f32> { self.demand_next(false)?.value().to_float() }
    fn next_double(&mut self) -> ReaderResult<f64> { self.demand_next(false)?.value().to_double() }
    fn next_char(&mut self) -> ReaderResult<char> { self.demand_next(false)?.value().to_char() }

    fn next_str(&mut self) -> ReaderResult<Cow<'de, str>> {
        Ok(Cow::Owned(self.demand_next(false)?.value().to_string()?.to_owned()))
    }

    fn next_bytestring(&mut self) -> ReaderResult<Cow<'de, [u8]>> {
        Ok(Cow::Owned(self.demand_next(false)?.value().to_bytestring()?.to_owned()))
    }

    fn next_symbol(&mut self) -> ReaderResult<Cow<'de, str>> {
        Ok(Cow::Owned(self.demand_next(false)?.value().to_symbol()?.to_owned()))
    }

    fn open_option(&mut self) ->
        ReaderResult<(bool, CompoundBody<Self::CompoundInfo>)>
    where
        Self: Sized
    {
        let mut compound_body = self.open_record(None)?;
        let label: &str = &compound_body.next_symbol(self)?.ok_or(error::Error::MissingItem)?;
        match label {
            "None" => Ok((false, compound_body)),
            "Some" => Ok((true, compound_body)),
            _ => Err(error::Error::Expected(ExpectedKind::Option,
                                            Received::ReceivedRecordWithLabel(label.to_owned()))),
        }
    }

    fn open_simple_record(&mut self, name: &str, arity: Option<usize>) ->
        ReaderResult<CompoundBody<Self::CompoundInfo>>
    where
        Self: Sized
    {
        let mut compound_body = self.open_record(arity)?;
        let label: &str = &compound_body.next_symbol(self)?.ok_or(error::Error::MissingItem)?;
        if label == name {
            Ok(compound_body)
        } else {
            Err(error::Error::Expected(ExpectedKind::SimpleRecord(name.to_owned(), arity),
                                       Received::ReceivedRecordWithLabel(label.to_owned())))
        }
    }

    fn configured(self, read_annotations: bool) -> ConfiguredReader<'de, Self>
    where
        Self: std::marker::Sized
    {
        ConfiguredReader {
            reader: self,
            read_annotations,
            phantom: PhantomData,
        }
    }
}

impl<'r, 'de, R: Reader<'de>> Reader<'de> for &'r mut R {
    type CompoundInfo = R::CompoundInfo;

    fn next(&mut self, read_annotations: bool) -> IOResult<Option<IOValue>> {
        (*self).next(read_annotations)
    }

    fn open_record(&mut self, arity: Option<usize>) -> ReaderResult<CompoundBody<Self::CompoundInfo>> {
        (*self).open_record(arity)
    }

    fn open_sequence_or_set(&mut self) -> ReaderResult<CompoundBody<Self::CompoundInfo>> {
        (*self).open_sequence_or_set()
    }

    fn open_sequence(&mut self) -> ReaderResult<CompoundBody<Self::CompoundInfo>> {
        (*self).open_sequence()
    }

    fn open_set(&mut self) -> ReaderResult<CompoundBody<Self::CompoundInfo>> {
        (*self).open_set()
    }

    fn open_dictionary(&mut self) -> ReaderResult<CompoundBody<Self::CompoundInfo>> {
        (*self).open_dictionary()
    }

    fn close_compound_counted(&mut self, info: Self::CompoundInfo) -> ReaderResult<()> {
        (*self).close_compound_counted(info)
    }

    fn close_compound_stream(&mut self, info: Self::CompoundInfo) -> ReaderResult<bool> {
        (*self).close_compound_stream(info)
    }
}

#[derive(Debug)]
pub struct CompoundBody<I: Copy> {
    pub info: I,
    pub limit: CompoundLimit,
}

#[derive(Debug)]
pub enum CompoundLimit {
    Counted(usize),
    Streaming,
    Finished,
}

impl<I: Copy> CompoundBody<I> {
    pub fn counted(info: I, size: usize) -> Self {
        CompoundBody { info, limit: CompoundLimit::Counted(size) }
    }

    pub fn streaming(info: I) -> Self {
        CompoundBody { info, limit: CompoundLimit::Streaming }
    }

    pub fn more_expected<'de, R: Reader<'de, CompoundInfo = I>>(&mut self, read: &mut R) -> ReaderResult<bool> {
        match self.limit {
            CompoundLimit::Counted(ref mut n) =>
                if *n == 0 {
                    read.close_compound_counted(self.info)?;
                    self.limit = CompoundLimit::Finished;
                    Ok(false)
                } else {
                    *n = *n - 1;
                    Ok(true)
                },
            CompoundLimit::Streaming =>
                Ok(!read.close_compound_stream(self.info)?),
            CompoundLimit::Finished =>
                Ok(false),
        }
    }

    pub fn next_symbol<'de, R: Reader<'de, CompoundInfo = I>>(&mut self, read: &mut R) -> ReaderResult<Option<Cow<'de, str>>> {
        match self.more_expected(read)? {
            false => Ok(None),
            true => Ok(Some(read.next_symbol()?)),
        }
    }

    pub fn next_value<'de, R: Reader<'de, CompoundInfo = I>>(&mut self, read: &mut R, read_annotations: bool) ->
        ReaderResult<Option<IOValue>>
    {
        match self.more_expected(read)? {
            false => Ok(None),
            true => Ok(Some(read.demand_next(read_annotations)?)),
        }
    }

    pub fn remainder<'de, R: Reader<'de, CompoundInfo = I>>(&mut self, read: &mut R, read_annotations: bool) ->
        ReaderResult<Vec<IOValue>>
    {
        let mut result = Vec::new();
        while let Some(v) = self.next_value(read, read_annotations)? {
            result.push(v);
        }
        Ok(result)
    }

    pub fn skip_remainder<'de, R: Reader<'de, CompoundInfo = I>>(&mut self, read: &mut R) ->
        ReaderResult<()>
    {
        while let true = self.more_expected(read)? {
            read.skip_value()?;
        }
        Ok(())
    }

    pub fn ensure_more_expected<'de, R: Reader<'de, CompoundInfo = I>>(&mut self, read: &mut R) -> ReaderResult<()> {
        if self.more_expected(read)? {
            Ok(())
        } else {
            Err(error::Error::MissingItem)
        }
    }

    pub fn ensure_complete<'de, R: Reader<'de, CompoundInfo = I>>(&mut self, read: &mut R) -> ReaderResult<()> {
        if self.more_expected(read)? {
            Err(error::Error::MissingCloseDelimiter)
        } else {
            Ok(())
        }
    }
}

pub trait BinarySource<'de> {
    fn skip(&mut self) -> IOResult<()>;
    fn peek(&mut self) -> IOResult<u8>;
    fn readbytes(&mut self, count: usize) -> IOResult<Cow<'de, [u8]>>;
    fn readbytes_into(&mut self, bs: &mut [u8]) -> IOResult<()>;
}

pub struct IOBinarySource<'a, R: Read> {
    pub read: &'a mut R,
    pub buf: Option<u8>,
}

impl<'a, R: Read> IOBinarySource<'a, R> {
    pub fn new(read: &'a mut R) -> Self {
        IOBinarySource { read, buf: None }
    }
}

impl<'de, 'a, R: Read> BinarySource<'de> for IOBinarySource<'a, R> {
    fn skip(&mut self) -> IOResult<()> {
        if let None = self.buf { unreachable!(); }
        self.buf = None;
        Ok(())
    }

    fn peek(&mut self) -> IOResult<u8> {
        match self.buf {
            Some(b) => Ok(b),
            None => {
                let b = &mut [0];
                match self.read.read(b)? {
                    0 => Err(io_eof()),
                    1 => {
                        self.buf = Some(b[0]);
                        Ok(b[0])
                    }
                    _ => unreachable!(),
                }
            }
        }
    }

    fn readbytes(&mut self, count: usize) -> IOResult<Cow<'de, [u8]>> {
        if let Some(_) = self.buf { unreachable!(); }
        let mut bs = vec![0; count];
        self.read.read_exact(&mut bs)?;
        Ok(Cow::Owned(bs))
    }

    fn readbytes_into(&mut self, bs: &mut [u8]) -> IOResult<()> {
        if let Some(_) = self.buf { unreachable!(); }
        self.read.read_exact(bs)
    }
}

pub struct BytesBinarySource<'de> {
    pub bytes: &'de [u8],
    pub index: usize,
}

impl<'de> BytesBinarySource<'de> {
    pub fn new(bytes: &'de [u8]) -> Self {
        BytesBinarySource { bytes, index: 0 }
    }
}

impl<'de> BinarySource<'de> for BytesBinarySource<'de> {
    fn skip(&mut self) -> IOResult<()> {
        if self.index >= self.bytes.len() { unreachable!(); }
        self.index += 1;
        Ok(())
    }

    fn peek(&mut self) -> IOResult<u8> {
        if self.index >= self.bytes.len() {
            Err(io_eof())
        } else {
            Ok(self.bytes[self.index])
        }
    }

    fn readbytes(&mut self, count: usize) -> IOResult<Cow<'de, [u8]>> {
        if self.index + count > self.bytes.len() {
            Err(io_eof())
        } else {
            let bs = &self.bytes[self.index..self.index+count];
            self.index += count;
            Ok(Cow::Borrowed(bs))
        }
    }

    fn readbytes_into(&mut self, bs: &mut [u8]) -> IOResult<()> {
        let count = bs.len();
        if self.index + count > self.bytes.len() {
            Err(io_eof())
        } else {
            bs.copy_from_slice(&self.bytes[self.index..self.index+count]);
            self.index += count;
            Ok(())
        }
    }
}

pub struct ConfiguredReader<'de, R: Reader<'de>> {
    pub reader: R,
    pub read_annotations: bool,
    phantom: PhantomData<&'de ()>,
}

impl<'de, R: Reader<'de>> ConfiguredReader<'de, R> {
    pub fn new(reader: R) -> Self {
        reader.configured(true)
    }

    pub fn set_read_annotations(&mut self, read_annotations: bool) {
        self.read_annotations = read_annotations
    }

    pub fn demand_next(&mut self) -> IOResult<IOValue> {
        self.reader.demand_next(self.read_annotations)
    }
}

impl<'de, R: Reader<'de>> std::iter::Iterator for ConfiguredReader<'de, R> {
    type Item = IOResult<IOValue>;
    fn next(&mut self) -> Option<Self::Item> {
        match self.reader.next(self.read_annotations) {
            Err(e) => Some(Err(e)),
            Ok(None) => None,
            Ok(Some(v)) => Some(Ok(v)),
        }
    }
}