//! This module supports deserializing from primitives with the `ValueDeserializer` trait.

use std::collections::{
    BTreeMap,
    BTreeSet,
    HashMap,
    HashSet,
    btree_map,
    btree_set,
    hash_map,
    hash_set,
};
use std::hash::Hash;
use std::error;
use std::fmt;
use std::vec;
use std::marker::PhantomData;

use de;
use bytes;

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

/// This represents all the possible errors that can occur using the `ValueDeserializer`.
#[derive(Clone, Debug, PartialEq)]
pub enum Error {
    /// The value had some custom error.
    Custom(String),

    /// The value had an incorrect type.
    InvalidType(de::Type),

    /// The value had an invalid length.
    InvalidLength(usize),

    /// The value is invalid and cannot be deserialized.
    InvalidValue(String),

    /// EOF while deserializing a value.
    EndOfStream,

    /// Unknown variant in enum.
    UnknownVariant(String),

    /// Unknown field in struct.
    UnknownField(String),

    /// Struct is missing a field.
    MissingField(&'static str),
}

impl de::Error for Error {
    fn custom<T: Into<String>>(msg: T) -> Self { Error::Custom(msg.into()) }
    fn end_of_stream() -> Self { Error::EndOfStream }
    fn invalid_type(ty: de::Type) -> Self { Error::InvalidType(ty) }
    fn invalid_value(msg: &str) -> Self { Error::InvalidValue(msg.to_owned()) }
    fn invalid_length(len: usize) -> Self { Error::InvalidLength(len) }
    fn unknown_variant(variant: &str) -> Self { Error::UnknownVariant(String::from(variant)) }
    fn unknown_field(field: &str) -> Self { Error::UnknownField(String::from(field)) }
    fn missing_field(field: &'static str) -> Self { Error::MissingField(field) }
}

impl fmt::Display for Error {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        match *self {
            Error::Custom(ref s) => write!(formatter, "{}", s),
            Error::EndOfStream => formatter.write_str("End of stream"),
            Error::InvalidType(ty) => write!(formatter, "Invalid type, expected `{:?}`", ty),
            Error::InvalidValue(ref value) => write!(formatter, "Invalid value: {}", value),
            Error::InvalidLength(len) => write!(formatter, "Invalid length: {}", len),
            Error::UnknownVariant(ref variant) => {
                write!(formatter, "Unknown variant: {}", variant)
            }
            Error::UnknownField(ref field) => write!(formatter, "Unknown field: {}", field),
            Error::MissingField(ref field) => write!(formatter, "Missing field: {}", field),
        }
    }
}

impl error::Error for Error {
    fn description(&self) -> &str {
        "Serde Deserialization Error"
    }

    fn cause(&self) -> Option<&error::Error> {
        None
    }
}

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

/// This trait converts primitive types into a deserializer.
pub trait ValueDeserializer<E: de::Error = Error> {
    /// The actual deserializer type.
    type Deserializer: de::Deserializer<Error=E>;

    /// Convert this value into a deserializer.
    fn into_deserializer(self) -> Self::Deserializer;
}

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

impl<E> ValueDeserializer<E> for ()
    where E: de::Error,
{
    type Deserializer = UnitDeserializer<E>;

    fn into_deserializer(self) -> UnitDeserializer<E> {
        UnitDeserializer(PhantomData)
    }
}

/// A helper deserializer that deserializes a `()`.
pub struct UnitDeserializer<E>(PhantomData<E>);

impl<E> de::Deserializer for UnitDeserializer<E>
    where E: de::Error
{
    type Error = E;

    fn deserialize<V>(&mut self, mut visitor: V) -> Result<V::Value, Self::Error>
        where V: de::Visitor,
    {
        visitor.visit_unit()
    }

    fn deserialize_option<V>(&mut self, mut visitor: V) -> Result<V::Value, Self::Error>
        where V: de::Visitor,
    {
        visitor.visit_none()
    }
}

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

macro_rules! primitive_deserializer {
    ($ty:ty, $name:ident, $method:ident) => {
        /// A helper deserializer that deserializes a number.
        pub struct $name<E>(Option<$ty>, PhantomData<E>);

        impl<E> ValueDeserializer<E> for $ty
            where E: de::Error,
        {
            type Deserializer = $name<E>;

            fn into_deserializer(self) -> $name<E> {
                $name(Some(self), PhantomData)
            }
        }

        impl<E> de::Deserializer for $name<E>
            where E: de::Error,
        {
            type Error = E;

            fn deserialize<V>(&mut self, mut visitor: V) -> Result<V::Value, Self::Error>
                where V: de::Visitor,
            {
                match self.0.take() {
                    Some(v) => visitor.$method(v),
                    None => Err(de::Error::end_of_stream()),
                }
            }
        }
    }
}

primitive_deserializer!(bool, BoolDeserializer, visit_bool);
primitive_deserializer!(i8, I8Deserializer, visit_i8);
primitive_deserializer!(i16, I16Deserializer, visit_i16);
primitive_deserializer!(i32, I32Deserializer, visit_i32);
primitive_deserializer!(i64, I64Deserializer, visit_i64);
primitive_deserializer!(isize, IsizeDeserializer, visit_isize);
primitive_deserializer!(u8, U8Deserializer, visit_u8);
primitive_deserializer!(u16, U16Deserializer, visit_u16);
primitive_deserializer!(u32, U32Deserializer, visit_u32);
primitive_deserializer!(u64, U64Deserializer, visit_u64);
primitive_deserializer!(usize, UsizeDeserializer, visit_usize);
primitive_deserializer!(f32, F32Deserializer, visit_f32);
primitive_deserializer!(f64, F64Deserializer, visit_f64);
primitive_deserializer!(char, CharDeserializer, visit_char);

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

/// A helper deserializer that deserializes a `&str`.
pub struct StrDeserializer<'a, E>(Option<&'a str>, PhantomData<E>);

impl<'a, E> ValueDeserializer<E> for &'a str
    where E: de::Error,
{
    type Deserializer = StrDeserializer<'a, E>;

    fn into_deserializer(self) -> StrDeserializer<'a, E> {
        StrDeserializer(Some(self), PhantomData)
    }
}

impl<'a, E> de::Deserializer for StrDeserializer<'a, E>
    where E: de::Error,
{
    type Error = E;

    fn deserialize<V>(&mut self, mut visitor: V) -> Result<V::Value, Self::Error>
        where V: de::Visitor,
    {
        match self.0.take() {
            Some(v) => visitor.visit_str(v),
            None => Err(de::Error::end_of_stream()),
        }
    }

    fn deserialize_enum<V>(&mut self,
                     _name: &str,
                     _variants: &'static [&'static str],
                     mut visitor: V) -> Result<V::Value, Self::Error>
        where V: de::EnumVisitor,
    {
        visitor.visit(self)
    }
}

impl<'a, E> de::VariantVisitor for StrDeserializer<'a, E>
    where E: de::Error,
{
    type Error = E;

    fn visit_variant<T>(&mut self) -> Result<T, Self::Error>
        where T: de::Deserialize,
    {
        de::Deserialize::deserialize(self)
    }

    fn visit_unit(&mut self) -> Result<(), Self::Error> {
        Ok(())
    }
}

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

/// A helper deserializer that deserializes a `String`.
pub struct StringDeserializer<E>(Option<String>, PhantomData<E>);

impl<E> ValueDeserializer<E> for String
    where E: de::Error,
{
    type Deserializer = StringDeserializer<E>;

    fn into_deserializer(self) -> StringDeserializer<E> {
        StringDeserializer(Some(self), PhantomData)
    }
}

impl<E> de::Deserializer for StringDeserializer<E>
    where E: de::Error,
{
    type Error = E;

    fn deserialize<V>(&mut self, mut visitor: V) -> Result<V::Value, Self::Error>
        where V: de::Visitor,
    {
        match self.0.take() {
            Some(string) => visitor.visit_string(string),
            None => Err(de::Error::end_of_stream()),
        }
    }

    fn deserialize_enum<V>(&mut self,
                     _name: &str,
                     _variants: &'static [&'static str],
                     mut visitor: V) -> Result<V::Value, Self::Error>
        where V: de::EnumVisitor,
    {
        visitor.visit(self)
    }
}

impl<'a, E> de::VariantVisitor for StringDeserializer<E>
    where E: de::Error,
{
    type Error = E;

    fn visit_variant<T>(&mut self) -> Result<T, Self::Error>
        where T: de::Deserialize,
    {
        de::Deserialize::deserialize(self)
    }

    fn visit_unit(&mut self) -> Result<(), Self::Error> {
        Ok(())
    }
}

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

/// A helper deserializer that deserializes a sequence.
pub struct SeqDeserializer<I, E> {
    iter: I,
    len: usize,
    marker: PhantomData<E>,
}

impl<I, E> SeqDeserializer<I, E>
    where E: de::Error,
{
    /// Construct a new `SeqDeserializer<I>`.
    pub fn new(iter: I, len: usize) -> Self {
        SeqDeserializer {
            iter: iter,
            len: len,
            marker: PhantomData,
        }
    }
}

impl<I, T, E> de::Deserializer for SeqDeserializer<I, E>
    where I: Iterator<Item=T>,
          T: ValueDeserializer<E>,
          E: de::Error,
{
    type Error = E;

    fn deserialize<V>(&mut self, mut visitor: V) -> Result<V::Value, Self::Error>
        where V: de::Visitor,
    {
        visitor.visit_seq(self)
    }
}

impl<I, T, E> de::SeqVisitor for SeqDeserializer<I, E>
    where I: Iterator<Item=T>,
          T: ValueDeserializer<E>,
          E: de::Error,
{
    type Error = E;

    fn visit<V>(&mut self) -> Result<Option<V>, Self::Error>
        where V: de::Deserialize
    {
        match self.iter.next() {
            Some(value) => {
                self.len -= 1;
                let mut de = value.into_deserializer();
                Ok(Some(try!(de::Deserialize::deserialize(&mut de))))
            }
            None => Ok(None),
        }
    }

    fn end(&mut self) -> Result<(), Self::Error> {
        if self.len == 0 {
            Ok(())
        } else {
            Err(de::Error::invalid_length(self.len))
        }
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        (self.len, Some(self.len))
    }
}

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

impl<T, E> ValueDeserializer<E> for Vec<T>
    where T: ValueDeserializer<E>,
          E: de::Error,
{
    type Deserializer = SeqDeserializer<vec::IntoIter<T>, E>;

    fn into_deserializer(self) -> Self::Deserializer {
        let len = self.len();
        SeqDeserializer::new(self.into_iter(), len)
    }
}

impl<T, E> ValueDeserializer<E> for BTreeSet<T>
    where T: ValueDeserializer<E> + Eq + Ord,
          E: de::Error,
{
    type Deserializer = SeqDeserializer<btree_set::IntoIter<T>, E>;

    fn into_deserializer(self) -> Self::Deserializer {
        let len = self.len();
        SeqDeserializer::new(self.into_iter(), len)
    }
}

impl<T, E> ValueDeserializer<E> for HashSet<T>
    where T: ValueDeserializer<E> + Eq + Hash,
          E: de::Error,
{
    type Deserializer = SeqDeserializer<hash_set::IntoIter<T>, E>;

    fn into_deserializer(self) -> Self::Deserializer {
        let len = self.len();
        SeqDeserializer::new(self.into_iter(), len)
    }
}

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

/// A helper deserializer that deserializes a sequence using a `SeqVisitor`.
pub struct SeqVisitorDeserializer<V_, E> {
    visitor: V_,
    marker: PhantomData<E>,
}

impl<V_, E> SeqVisitorDeserializer<V_, E>
    where V_: de::SeqVisitor<Error = E>,
          E: de::Error,
{
    /// Construct a new `SeqVisitorDeserializer<V_, E>`.
    pub fn new(visitor: V_) -> Self {
        SeqVisitorDeserializer{
            visitor: visitor,
            marker: PhantomData
        }
    }
}

impl<V_, E> de::Deserializer for SeqVisitorDeserializer<V_, E>
    where V_: de::SeqVisitor<Error = E>,
          E: de::Error,
{
    type Error = E;

    fn deserialize<V: de::Visitor>(&mut self, mut visitor: V) -> Result<V::Value, Self::Error> {
        visitor.visit_seq(&mut self.visitor)
    }
}

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

/// A helper deserializer that deserializes a map.
pub struct MapDeserializer<I, K, V, E>
    where I: Iterator<Item=(K, V)>,
          K: ValueDeserializer<E>,
          V: ValueDeserializer<E>,
          E: de::Error,
{
    iter: I,
    value: Option<V>,
    len: usize,
    marker: PhantomData<E>,
}

impl<I, K, V, E> MapDeserializer<I, K, V, E>
    where I: Iterator<Item=(K, V)>,
          K: ValueDeserializer<E>,
          V: ValueDeserializer<E>,
          E: de::Error,
{
    /// Construct a new `MapDeserializer<I, K, V>`.
    pub fn new(iter: I, len: usize) -> Self {
        MapDeserializer {
            iter: iter,
            value: None,
            len: len,
            marker: PhantomData,
        }
    }
}

impl<I, K, V, E> de::Deserializer for MapDeserializer<I, K, V, E>
    where I: Iterator<Item=(K, V)>,
          K: ValueDeserializer<E>,
          V: ValueDeserializer<E>,
          E: de::Error,
{
    type Error = E;

    fn deserialize<V_>(&mut self, mut visitor: V_) -> Result<V_::Value, Self::Error>
        where V_: de::Visitor,
    {
        visitor.visit_map(self)
    }
}

impl<I, K, V, E> de::MapVisitor for MapDeserializer<I, K, V, E>
    where I: Iterator<Item=(K, V)>,
          K: ValueDeserializer<E>,
          V: ValueDeserializer<E>,
          E: de::Error,
{
    type Error = E;

    fn visit_key<T>(&mut self) -> Result<Option<T>, Self::Error>
        where T: de::Deserialize,
    {
        match self.iter.next() {
            Some((key, value)) => {
                self.len -= 1;
                self.value = Some(value);
                let mut de = key.into_deserializer();
                Ok(Some(try!(de::Deserialize::deserialize(&mut de))))
            }
            None => Ok(None),
        }
    }

    fn visit_value<T>(&mut self) -> Result<T, Self::Error>
        where T: de::Deserialize,
    {
        match self.value.take() {
            Some(value) => {
                let mut de = value.into_deserializer();
                de::Deserialize::deserialize(&mut de)
            }
            None => {
                Err(de::Error::end_of_stream())
            }
        }
    }

    fn end(&mut self) -> Result<(), Self::Error> {
        if self.len == 0 {
            Ok(())
        } else {
            Err(de::Error::invalid_length(self.len))
        }
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        (self.len, Some(self.len))
    }
}

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

impl<K, V, E> ValueDeserializer<E> for BTreeMap<K, V>
    where K: ValueDeserializer<E> + Eq + Ord,
          V: ValueDeserializer<E>,
          E: de::Error,
{
    type Deserializer = MapDeserializer<btree_map::IntoIter<K, V>, K, V, E>;

    fn into_deserializer(self) -> Self::Deserializer {
        let len = self.len();
        MapDeserializer::new(self.into_iter(), len)
    }
}

impl<K, V, E> ValueDeserializer<E> for HashMap<K, V>
    where K: ValueDeserializer<E> + Eq + Hash,
          V: ValueDeserializer<E>,
          E: de::Error,
{
    type Deserializer = MapDeserializer<hash_map::IntoIter<K, V>, K, V, E>;

    fn into_deserializer(self) -> Self::Deserializer {
        let len = self.len();
        MapDeserializer::new(self.into_iter(), len)
    }
}

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

/// A helper deserializer that deserializes a map using a `MapVisitor`.
pub struct MapVisitorDeserializer<V_, E> {
    visitor: V_,
    marker: PhantomData<E>,
}

impl<V_, E> MapVisitorDeserializer<V_, E>
    where V_: de::MapVisitor<Error = E>,
          E: de::Error,
{
    /// Construct a new `MapVisitorDeserializer<V_, E>`.
    pub fn new(visitor: V_) -> Self {
        MapVisitorDeserializer{
            visitor: visitor,
            marker: PhantomData
        }
    }
}

impl<V_, E> de::Deserializer for MapVisitorDeserializer<V_, E>
    where V_: de::MapVisitor<Error = E>,
          E: de::Error,
{
    type Error = E;

    fn deserialize<V: de::Visitor>(&mut self, mut visitor: V) -> Result<V::Value, Self::Error> {
        visitor.visit_map(&mut self.visitor)
    }
}

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

impl<'a, E> ValueDeserializer<E> for bytes::Bytes<'a>
    where E: de::Error,
{
    type Deserializer = BytesDeserializer<'a, E>;

    fn into_deserializer(self) -> BytesDeserializer<'a, E> {
        BytesDeserializer(Some(self.into()), PhantomData)
    }
}

/// A helper deserializer that deserializes a `&[u8]`.
pub struct BytesDeserializer<'a, E> (Option<&'a [u8]>, PhantomData<E>);

impl<'a, E> de::Deserializer for BytesDeserializer<'a, E>
    where E: de::Error
{
    type Error = E;

    fn deserialize<V>(&mut self, mut visitor: V) -> Result<V::Value, Self::Error>
        where V: de::Visitor,
    {
        match self.0.take() {
            Some(bytes) => visitor.visit_bytes(bytes),
            None => Err(de::Error::end_of_stream()),
        }
    }
}


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

impl<E> ValueDeserializer<E> for bytes::ByteBuf
    where E: de::Error,
{
    type Deserializer = ByteBufDeserializer<E>;

    fn into_deserializer(self) -> Self::Deserializer {
        ByteBufDeserializer(Some(self.into()), PhantomData)
    }
}

/// A helper deserializer that deserializes a `Vec<u8>`.
pub struct ByteBufDeserializer<E>(Option<Vec<u8>>, PhantomData<E>);

impl<E> de::Deserializer for ByteBufDeserializer<E>
    where E: de::Error,
{
    type Error = E;

    fn deserialize<V>(&mut self, mut visitor: V) -> Result<V::Value, Self::Error>
        where V: de::Visitor,
    {
        match self.0.take() {
            Some(bytes) => visitor.visit_byte_buf(bytes),
            None => Err(de::Error::end_of_stream()),
        }
    }
}