use std::fmt;
use std::iter;

use serde::{ser, de};
use serde::de::value::{self, ValueDeserializer};

#[derive(Clone, PartialEq, Debug)]
pub enum Token<'a> {
    Bool(bool),
    Isize(isize),
    I8(i8),
    I16(i16),
    I32(i32),
    I64(i64),
    Usize(usize),
    U8(u8),
    U16(u16),
    U32(u32),
    U64(u64),
    F32(f32),
    F64(f64),
    Char(char),
    Str(&'a str),
    String(String),
    Bytes(&'a [u8]),

    Option(bool),

    Unit,
    UnitStruct(&'a str),

    StructNewtype(&'a str),

    EnumStart(&'a str),
    EnumUnit(&'a str, &'a str),
    EnumNewtype(&'a str, &'a str),
    EnumSeqStart(&'a str, &'a str, Option<usize>),
    EnumMapStart(&'a str, &'a str, Option<usize>),

    SeqStart(Option<usize>),
    TupleStructStart(&'a str, Option<usize>),
    SeqSep,
    SeqEnd,

    MapStart(Option<usize>),
    StructStart(&'a str, Option<usize>),
    MapSep,
    MapEnd,
}

//////////////////////////////////////////////////////////////////////////////

pub struct Serializer<I> {
    tokens: I,
}

impl<'a, I> Serializer<I>
    where I: Iterator<Item=&'a Token<'a>>
{
    pub fn new(tokens: I) -> Serializer<I> {
        Serializer {
            tokens: tokens,
        }
    }

    fn visit_sequence<V>(&mut self, mut visitor: V) -> Result<(), ()>
        where V: ser::SeqVisitor
    {
        while let Some(()) = try!(visitor.visit(self)) { }

        assert_eq!(self.tokens.next(), Some(&Token::SeqEnd));

        Ok(())
    }

    fn visit_mapping<V>(&mut self, mut visitor: V) -> Result<(), ()>
        where V: ser::MapVisitor
    {
        while let Some(()) = try!(visitor.visit(self)) { }

        assert_eq!(self.tokens.next(), Some(&Token::MapEnd));

        Ok(())
    }
}

impl<'a, I> ser::Serializer for Serializer<I>
    where I: Iterator<Item=&'a Token<'a>>,
{
    type Error = ();

    fn visit_unit(&mut self) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::Unit));
        Ok(())
    }

    fn visit_newtype_variant<T>(&mut self,
                                name: &str,
                                _variant_index: usize,
                                variant: &str,
                                value: T) -> Result<(), ()>
        where T: ser::Serialize,
    {
        assert_eq!(self.tokens.next(), Some(&Token::EnumNewtype(name, variant)));
        value.serialize(self)
    }

    fn visit_unit_struct(&mut self, name: &str) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::UnitStruct(name)));
        Ok(())
    }

    fn visit_unit_variant(&mut self,
                          name: &str,
                          _variant_index: usize,
                          variant: &str) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::EnumUnit(name, variant)));

        Ok(())
    }

    fn visit_bool(&mut self, v: bool) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::Bool(v)));
        Ok(())
    }

    fn visit_isize(&mut self, v: isize) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::Isize(v)));
        Ok(())
    }

    fn visit_i8(&mut self, v: i8) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::I8(v)));
        Ok(())
    }

    fn visit_i16(&mut self, v: i16) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::I16(v)));
        Ok(())
    }

    fn visit_i32(&mut self, v: i32) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::I32(v)));
        Ok(())
    }

    fn visit_i64(&mut self, v: i64) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::I64(v)));
        Ok(())
    }

    fn visit_usize(&mut self, v: usize) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::Usize(v)));
        Ok(())
    }

    fn visit_u8(&mut self, v: u8) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::U8(v)));
        Ok(())
    }

    fn visit_u16(&mut self, v: u16) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::U16(v)));
        Ok(())
    }

    fn visit_u32(&mut self, v: u32) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::U32(v)));
        Ok(())
    }

    fn visit_u64(&mut self, v: u64) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::U64(v)));
        Ok(())
    }

    fn visit_f32(&mut self, v: f32) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::F32(v)));
        Ok(())
    }

    fn visit_f64(&mut self, v: f64) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::F64(v)));
        Ok(())
    }

    fn visit_char(&mut self, v: char) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::Char(v)));
        Ok(())
    }

    fn visit_str(&mut self, v: &str) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::Str(v)));
        Ok(())
    }

    fn visit_none(&mut self) -> Result<(), ()> {
        assert_eq!(self.tokens.next(), Some(&Token::Option(false)));
        Ok(())
    }

    fn visit_some<V>(&mut self, value: V) -> Result<(), ()>
        where V: ser::Serialize,
    {
        assert_eq!(self.tokens.next(), Some(&Token::Option(true)));
        value.serialize(self)
    }


    fn visit_seq<V>(&mut self, visitor: V) -> Result<(), ()>
        where V: ser::SeqVisitor
    {
        let len = visitor.len();

        assert_eq!(self.tokens.next(), Some(&Token::SeqStart(len)));

        self.visit_sequence(visitor)
    }

    fn visit_newtype_struct<T>(&mut self,
                               name: &'static str,
                               value: T) -> Result<(), ()>
        where T: ser::Serialize,
    {
        assert_eq!(self.tokens.next(), Some(&Token::StructNewtype(name)));
        value.serialize(self)
    }

    fn visit_tuple_struct<V>(&mut self, name: &str, visitor: V) -> Result<(), ()>
        where V: ser::SeqVisitor
    {
        let len = visitor.len();

        assert_eq!(self.tokens.next(), Some(&Token::TupleStructStart(name, len)));

        self.visit_sequence(visitor)
    }

    fn visit_tuple_variant<V>(&mut self,
                              name: &str,
                              _variant_index: usize,
                              variant: &str,
                              visitor: V) -> Result<(), ()>
        where V: ser::SeqVisitor
    {
        let len = visitor.len();

        assert_eq!(self.tokens.next(), Some(&Token::EnumSeqStart(name, variant, len)));

        self.visit_sequence(visitor)
    }

    fn visit_seq_elt<T>(&mut self, value: T) -> Result<(), ()>
        where T: ser::Serialize
    {
        assert_eq!(self.tokens.next(), Some(&Token::SeqSep));
        value.serialize(self)
    }

    fn visit_map<V>(&mut self, visitor: V) -> Result<(), ()>
        where V: ser::MapVisitor
    {
        let len = visitor.len();

        assert_eq!(self.tokens.next(), Some(&Token::MapStart(len)));

        self.visit_mapping(visitor)
    }

    fn visit_struct<V>(&mut self, name: &str, visitor: V) -> Result<(), ()>
        where V: ser::MapVisitor
    {
        let len = visitor.len();

        assert_eq!(self.tokens.next(), Some(&Token::StructStart(name, len)));

        self.visit_mapping(visitor)
    }

    fn visit_struct_variant<V>(&mut self,
                               name: &str,
                               _variant_index: usize,
                               variant: &str,
                               visitor: V) -> Result<(), ()>
        where V: ser::MapVisitor
    {
        let len = visitor.len();

        assert_eq!(self.tokens.next(), Some(&Token::EnumMapStart(name, variant, len)));

        self.visit_mapping(visitor)
    }

    fn visit_map_elt<K, V>(&mut self, key: K, value: V) -> Result<(), ()>
        where K: ser::Serialize,
              V: ser::Serialize,
    {
        assert_eq!(self.tokens.next(), Some(&Token::MapSep));

        try!(key.serialize(self));
        value.serialize(self)
    }

    fn format() -> &'static str {
        "token"
    }
}

//////////////////////////////////////////////////////////////////////////////

#[derive(Clone, PartialEq, Debug)]
enum Error {
    SyntaxError,
    EndOfStreamError,
    UnknownFieldError(String),
    MissingFieldError(&'static str),
    InvalidName(&'static str),
    UnexpectedToken(Token<'static>),
    ValueError(value::Error),
}

impl de::Error for Error {
    fn syntax(_: &str) -> Error { Error::SyntaxError }

    fn end_of_stream() -> Error { Error::EndOfStreamError }

    fn unknown_field(field: &str) -> Error {
        Error::UnknownFieldError(field.to_string())
    }

    fn missing_field(field: &'static str) -> Error {
        Error::MissingFieldError(field)
    }
}

impl From<value::Error> for Error {
    fn from(error: value::Error) -> Error {
        Error::ValueError(error)
    }
}

struct Deserializer<I> where I: Iterator<Item=Token<'static>> {
    tokens: iter::Peekable<I>,
}

impl<I> Deserializer<I>
    where I: Iterator<Item=Token<'static>>
{
    fn new(tokens: I) -> Deserializer<I> {
        Deserializer {
            tokens: tokens.peekable(),
        }
    }

    fn visit_seq<V>(&mut self, len: Option<usize>, mut visitor: V) -> Result<V::Value, Error>
        where V: de::Visitor,
    {
        visitor.visit_seq(DeserializerSeqVisitor {
            de: self,
            len: len,
        })
    }

    fn visit_map<V>(&mut self, len: Option<usize>, mut visitor: V) -> Result<V::Value, Error>
        where V: de::Visitor,
    {
        visitor.visit_map(DeserializerMapVisitor {
            de: self,
            len: len,
        })
    }
}

impl<I> de::Deserializer for Deserializer<I>
    where I: Iterator<Item=Token<'static>>
{
    type Error = Error;

    fn visit<V>(&mut self, mut visitor: V) -> Result<V::Value, Error>
        where V: de::Visitor,
    {
        println!("visit {:?}", self.tokens.peek());
        match self.tokens.next() {
            Some(Token::Bool(v)) => visitor.visit_bool(v),
            Some(Token::Isize(v)) => visitor.visit_isize(v),
            Some(Token::I8(v)) => visitor.visit_i8(v),
            Some(Token::I16(v)) => visitor.visit_i16(v),
            Some(Token::I32(v)) => visitor.visit_i32(v),
            Some(Token::I64(v)) => visitor.visit_i64(v),
            Some(Token::Usize(v)) => visitor.visit_usize(v),
            Some(Token::U8(v)) => visitor.visit_u8(v),
            Some(Token::U16(v)) => visitor.visit_u16(v),
            Some(Token::U32(v)) => visitor.visit_u32(v),
            Some(Token::U64(v)) => visitor.visit_u64(v),
            Some(Token::F32(v)) => visitor.visit_f32(v),
            Some(Token::F64(v)) => visitor.visit_f64(v),
            Some(Token::Char(v)) => visitor.visit_char(v),
            Some(Token::Str(v)) => visitor.visit_str(v),
            Some(Token::String(v)) => visitor.visit_string(v),
            Some(Token::Bytes(v)) => visitor.visit_bytes(v),
            Some(Token::Option(false)) => visitor.visit_none(),
            Some(Token::Option(true)) => visitor.visit_some(self),
            Some(Token::Unit) => visitor.visit_unit(),
            Some(Token::UnitStruct(name)) => visitor.visit_unit_struct(name),
            Some(Token::SeqStart(len)) | Some(Token::TupleStructStart(_, len)) => {
                self.visit_seq(len, visitor)
            }
            Some(Token::MapStart(len)) | Some(Token::StructStart(_, len)) => {
                self.visit_map(len, visitor)
            }
            //Some(Token::Name(_)) => self.visit(visitor),
            Some(token) => Err(Error::UnexpectedToken(token)),
            None => Err(Error::EndOfStreamError),
        }
    }

    /// Hook into `Option` deserializing so we can treat `Unit` as a
    /// `None`, or a regular value as `Some(value)`.
    fn visit_option<V>(&mut self, mut visitor: V) -> Result<V::Value, Error>
        where V: de::Visitor,
    {
        match self.tokens.peek() {
            Some(&Token::Option(false)) => {
                self.tokens.next();
                visitor.visit_none()
            }
            Some(&Token::Option(true)) => {
                self.tokens.next();
                visitor.visit_some(self)
            }
            Some(&Token::Unit) => {
                self.tokens.next();
                visitor.visit_none()
            }
            Some(_) => visitor.visit_some(self),
            None => Err(Error::EndOfStreamError),
        }
    }

    fn visit_enum<V>(&mut self,
                     name: &str,
                     _variants: &'static [&'static str],
                     mut visitor: V) -> Result<V::Value, Error>
        where V: de::EnumVisitor,
    {
        match self.tokens.peek() {
            Some(&Token::EnumStart(n)) if name == n => {
                self.tokens.next();

                visitor.visit(DeserializerVariantVisitor {
                    de: self,
                })
            }
            Some(&Token::EnumUnit(n, _))
            | Some(&Token::EnumNewtype(n, _))
            | Some(&Token::EnumSeqStart(n, _, _))
            | Some(&Token::EnumMapStart(n, _, _)) if name == n => {
                visitor.visit(DeserializerVariantVisitor {
                    de: self,
                })
            }
            Some(_) => {
                let token = self.tokens.next().unwrap();
                Err(Error::UnexpectedToken(token))
            }
            None => { return Err(Error::EndOfStreamError); }
        }
    }

    fn visit_unit_struct<V>(&mut self, name: &str, mut visitor: V) -> Result<V::Value, Error>
        where V: de::Visitor,
    {
        match self.tokens.peek() {
            Some(&Token::UnitStruct(n)) => {
                self.tokens.next();
                if name == n {
                    visitor.visit_unit()
                } else {
                    Err(Error::InvalidName(n))
                }
            }
            Some(_) => self.visit(visitor),
            None => Err(Error::EndOfStreamError),
        }
    }

    fn visit_newtype_struct<V>(&mut self,
                               name: &str,
                               mut visitor: V) -> Result<V::Value, Error>
        where V: de::Visitor,
    {
        match self.tokens.peek() {
            Some(&Token::StructNewtype(n)) => {
                self.tokens.next();
                if name == n {
                    visitor.visit_newtype_struct(self)
                } else {
                    Err(Error::InvalidName(n))
                }
            }
            Some(_) => self.visit(visitor),
            None => Err(Error::EndOfStreamError),
        }
    }

    fn visit_tuple_struct<V>(&mut self,
                             name: &str,
                             len: usize,
                             mut visitor: V) -> Result<V::Value, Error>
        where V: de::Visitor,
    {
        match self.tokens.peek() {
            Some(&Token::UnitStruct(n)) => {
                self.tokens.next();
                if name == n {
                    visitor.visit_unit()
                } else {
                    Err(Error::InvalidName(n))
                }
            }
            Some(&Token::TupleStructStart(n, _)) => {
                self.tokens.next();
                if name == n {
                    self.visit_seq(Some(len), visitor)
                } else {
                    Err(Error::InvalidName(n))
                }
            }
            Some(&Token::SeqStart(_)) => {
                self.tokens.next();
                self.visit_seq(Some(len), visitor)
            }
            Some(_) => self.visit(visitor),
            None => Err(Error::EndOfStreamError),
        }
    }

    fn visit_struct<V>(&mut self,
                       name: &str,
                       fields: &'static [&'static str],
                       visitor: V) -> Result<V::Value, Error>
        where V: de::Visitor,
    {
        match self.tokens.peek() {
            Some(&Token::StructStart(n, _)) => {
                self.tokens.next();
                if name == n {
                    self.visit_map(Some(fields.len()), visitor)
                } else {
                    Err(Error::InvalidName(n))
                }
            }
            Some(&Token::MapStart(_)) => {
                self.tokens.next();
                self.visit_map(Some(fields.len()), visitor)
            }
            Some(_) => self.visit(visitor),
            None => Err(Error::EndOfStreamError),
        }
    }

    fn format() -> &'static str {
        "token"
    }
}

//////////////////////////////////////////////////////////////////////////

struct DeserializerSeqVisitor<'a, I: 'a> where I: Iterator<Item=Token<'static>> {
    de: &'a mut Deserializer<I>,
    len: Option<usize>,
}

impl<'a, I> de::SeqVisitor for DeserializerSeqVisitor<'a, I>
    where I: Iterator<Item=Token<'static>>,
{
    type Error = Error;

    fn visit<T>(&mut self) -> Result<Option<T>, Error>
        where T: de::Deserialize,
    {
        match self.de.tokens.peek() {
            Some(&Token::SeqSep) => {
                self.de.tokens.next();
                self.len = self.len.map(|len| len - 1);
                Ok(Some(try!(de::Deserialize::deserialize(self.de))))
            }
            Some(&Token::SeqEnd) => Ok(None),
            Some(_) => {
                let token = self.de.tokens.next().unwrap();
                Err(Error::UnexpectedToken(token))
            }
            None => Err(Error::EndOfStreamError),
        }
    }

    fn end(&mut self) -> Result<(), Error> {
        //assert_eq!(self.len.unwrap_or(0), 0);
        match self.de.tokens.next() {
            Some(Token::SeqEnd) => Ok(()),
            Some(token) => Err(Error::UnexpectedToken(token)),
            None => Err(Error::EndOfStreamError),
        }
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        let len = self.len.unwrap_or(0);
        (len, self.len)
    }
}

//////////////////////////////////////////////////////////////////////////

struct DeserializerMapVisitor<'a, I: 'a> where I: Iterator<Item=Token<'static>> {
    de: &'a mut Deserializer<I>,
    len: Option<usize>,
}

impl<'a, I> de::MapVisitor for DeserializerMapVisitor<'a, I>
    where I: Iterator<Item=Token<'static>>,
{
    type Error = Error;

    fn visit_key<K>(&mut self) -> Result<Option<K>, Error>
        where K: de::Deserialize,
    {
        match self.de.tokens.peek() {
            Some(&Token::MapSep) => {
                self.de.tokens.next();
                self.len = self.len.map(|len| len - 1);
                Ok(Some(try!(de::Deserialize::deserialize(self.de))))
            }
            Some(&Token::MapEnd) => Ok(None),
            Some(_) => {
                let token = self.de.tokens.next().unwrap();
                Err(Error::UnexpectedToken(token))
            }
            None => Err(Error::EndOfStreamError),
        }
    }

    fn visit_value<V>(&mut self) -> Result<V, Error>
        where V: de::Deserialize,
    {
        Ok(try!(de::Deserialize::deserialize(self.de)))
    }

    fn end(&mut self) -> Result<(), Error> {
        //assert_eq!(self.len.unwrap_or(0), 0);
        match self.de.tokens.next() {
            Some(Token::MapEnd) => Ok(()),
            Some(token) => Err(Error::UnexpectedToken(token)),
            None => Err(Error::EndOfStreamError),
        }
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        let len = self.len.unwrap_or(0);
        (len, self.len)
    }
}

//////////////////////////////////////////////////////////////////////////

struct DeserializerVariantVisitor<'a, I: 'a> where I: Iterator<Item=Token<'static>> {
    de: &'a mut Deserializer<I>,
}

impl<'a, I> de::VariantVisitor for DeserializerVariantVisitor<'a, I>
    where I: Iterator<Item=Token<'static>>,
{
    type Error = Error;

    fn visit_variant<V>(&mut self) -> Result<V, Error>
        where V: de::Deserialize,
    {
        match self.de.tokens.peek() {
            Some(&Token::EnumUnit(_, v))
            | Some(&Token::EnumNewtype(_, v))
            | Some(&Token::EnumSeqStart(_, v, _))
            | Some(&Token::EnumMapStart(_, v, _)) => {
                let value = try!(de::Deserialize::deserialize(&mut v.into_deserializer()));
                Ok(value)
            }
            Some(_) => {
                de::Deserialize::deserialize(self.de)
            }
            None => Err(Error::EndOfStreamError),
        }
    }

    fn visit_unit(&mut self) -> Result<(), Error> {
        match self.de.tokens.peek() {
            Some(&Token::EnumUnit(_, _)) => {
                self.de.tokens.next();
                Ok(())
            }
            Some(_) => {
                de::Deserialize::deserialize(self.de)
            }
            None => Err(Error::EndOfStreamError),
        }
    }

    fn visit_newtype<T>(&mut self) -> Result<T, Self::Error>
        where T: de::Deserialize,
    {
        match self.de.tokens.peek() {
            Some(&Token::EnumNewtype(_, _)) => {
                self.de.tokens.next();
                de::Deserialize::deserialize(self.de)
            }
            Some(_) => {
                de::Deserialize::deserialize(self.de)
            }
            None => Err(Error::EndOfStreamError),
        }
    }

    fn visit_tuple<V>(&mut self,
                      len: usize,
                      visitor: V) -> Result<V::Value, Error>
        where V: de::Visitor,
    {
        match self.de.tokens.peek() {
            Some(&Token::EnumSeqStart(_, _, Some(enum_len))) => {
                let token = self.de.tokens.next().unwrap();

                if len == enum_len {
                    self.de.visit_seq(Some(len), visitor)
                } else {
                    Err(Error::UnexpectedToken(token))
                }
            }
            Some(_) => {
                de::Deserialize::deserialize(self.de)
            }
            None => Err(Error::EndOfStreamError),
        }
    }

    fn visit_struct<V>(&mut self,
                       fields: &'static [&'static str],
                       visitor: V) -> Result<V::Value, Error>
        where V: de::Visitor,
    {
        match self.de.tokens.peek() {
            Some(&Token::EnumMapStart(_, _, Some(enum_len))) => {
                let token = self.de.tokens.next().unwrap();

                if fields.len() == enum_len {
                    self.de.visit_map(Some(fields.len()), visitor)
                } else {
                    Err(Error::UnexpectedToken(token))
                }
            }
            Some(_) => {
                de::Deserialize::deserialize(self.de)
            }
            None => Err(Error::EndOfStreamError),
        }
    }
}

//////////////////////////////////////////////////////////////////////////////

pub fn assert_ser_tokens<T>(value: &T, tokens: &[Token])
    where T: ser::Serialize,
{
    let mut ser = Serializer::new(tokens.iter());
    assert_eq!(ser::Serialize::serialize(value, &mut ser), Ok(()));
    assert_eq!(ser.tokens.next(), None);
}

pub fn assert_de_tokens<T>(value: &T, tokens: Vec<Token<'static>>)
    where T: de::Deserialize + PartialEq + fmt::Debug,
{
    let mut de = Deserializer::new(tokens.into_iter());
    let v: Result<T, Error> = de::Deserialize::deserialize(&mut de);
    assert_eq!(v.as_ref(), Ok(value));
    assert_eq!(de.tokens.next(), None);
}

pub fn assert_tokens<T>(value: &T, tokens: Vec<Token<'static>>)
    where T: ser::Serialize + de::Deserialize + PartialEq + fmt::Debug,
{
    assert_ser_tokens(value, &tokens[..]);
    assert_de_tokens(value, tokens);
}