use std::slice::Iter;
use std::borrow::Cow;
use std::convert::AsRef;
use serde::de::{self, Deserializer, Visitor, Error as DeError};

use httprequest::HttpRequest;


macro_rules! unsupported_type {
    ($trait_fn:ident, $name:expr) => {
        fn $trait_fn<V>(self, _: V) -> Result<V::Value, Self::Error>
            where V: Visitor<'de>
        {
            Err(de::value::Error::custom(concat!("unsupported type: ", $name)))
        }
    };
}

macro_rules! parse_single_value {
    ($trait_fn:ident, $visit_fn:ident, $tp:tt) => {
        fn $trait_fn<V>(self, visitor: V) -> Result<V::Value, Self::Error>
            where V: Visitor<'de>
        {
            if self.req.match_info().len() != 1 {
                Err(de::value::Error::custom(
                    format!("wrong number of parameters: {} expected 1",
                            self.req.match_info().len()).as_str()))
            } else {
                let v = self.req.match_info()[0].parse().map_err(
                    |_| de::value::Error::custom(
                        format!("can not parse {:?} to a {}",
                                &self.req.match_info()[0], $tp)))?;
                visitor.$visit_fn(v)
            }
        }
    }
}

pub struct PathDeserializer<'de, S: 'de> {
    req: &'de HttpRequest<S>
}

impl<'de, S: 'de> PathDeserializer<'de, S> {
    pub fn new(req: &'de HttpRequest<S>) -> Self {
        PathDeserializer{req}
    }
}

impl<'de, S: 'de> Deserializer<'de> for PathDeserializer<'de, S>
{
    type Error = de::value::Error;

    fn deserialize_map<V>(self, visitor: V) -> Result<V::Value, Self::Error>
        where V: Visitor<'de>,
    {
        visitor.visit_map(ParamsDeserializer{
            params: self.req.match_info().iter(),
            current: None,
        })
    }

    fn deserialize_struct<V>(self, _: &'static str, _: &'static [&'static str], visitor: V)
                             -> Result<V::Value, Self::Error>
        where V: Visitor<'de>,
    {
        self.deserialize_map(visitor)
    }

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

    fn deserialize_unit_struct<V>(self, _: &'static str, visitor: V)
                                  -> Result<V::Value, Self::Error>
        where V: Visitor<'de>
    {
        self.deserialize_unit(visitor)
    }

    fn deserialize_newtype_struct<V>(self, _: &'static str, visitor: V)
                                     -> Result<V::Value, Self::Error>
        where V: Visitor<'de>,
    {
        visitor.visit_newtype_struct(self)
    }

    fn deserialize_tuple<V>(self, len: usize, visitor: V) -> Result<V::Value, Self::Error>
        where V: Visitor<'de>
    {
        if self.req.match_info().len() < len {
            Err(de::value::Error::custom(
                format!("wrong number of parameters: {} expected {}",
                        self.req.match_info().len(), len).as_str()))
        } else {
            visitor.visit_seq(ParamsSeq{params: self.req.match_info().iter()})
        }
    }

    fn deserialize_tuple_struct<V>(self, _: &'static str, len: usize, visitor: V)
                                   -> Result<V::Value, Self::Error>
        where V: Visitor<'de>
    {
        if self.req.match_info().len() < len {
            Err(de::value::Error::custom(
                format!("wrong number of parameters: {} expected {}",
                        self.req.match_info().len(), len).as_str()))
        } else {
            visitor.visit_seq(ParamsSeq{params: self.req.match_info().iter()})
        }
    }

    fn deserialize_enum<V>(self, _: &'static str, _: &'static [&'static str], _: V)
                           -> Result<V::Value, Self::Error>
        where V: Visitor<'de>
    {
        Err(de::value::Error::custom("unsupported type: enum"))
    }

    fn deserialize_str<V>(self, visitor: V) -> Result<V::Value, Self::Error>
        where V: Visitor<'de>,
    {
        if self.req.match_info().len() != 1 {
            Err(de::value::Error::custom(
                format!("wrong number of parameters: {} expected 1",
                        self.req.match_info().len()).as_str()))
        } else {
            visitor.visit_str(&self.req.match_info()[0])
        }
    }

    fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value, Self::Error>
        where V: Visitor<'de>
    {
        visitor.visit_seq(ParamsSeq{params: self.req.match_info().iter()})
    }

    unsupported_type!(deserialize_any, "'any'");
    unsupported_type!(deserialize_bytes, "bytes");
    unsupported_type!(deserialize_option, "Option<T>");
    unsupported_type!(deserialize_identifier, "identifier");
    unsupported_type!(deserialize_ignored_any, "ignored_any");

    parse_single_value!(deserialize_bool, visit_bool, "bool");
    parse_single_value!(deserialize_i8, visit_i8, "i8");
    parse_single_value!(deserialize_i16, visit_i16, "i16");
    parse_single_value!(deserialize_i32, visit_i32, "i16");
    parse_single_value!(deserialize_i64, visit_i64, "i64");
    parse_single_value!(deserialize_u8, visit_u8, "u8");
    parse_single_value!(deserialize_u16, visit_u16, "u16");
    parse_single_value!(deserialize_u32, visit_u32, "u32");
    parse_single_value!(deserialize_u64, visit_u64, "u64");
    parse_single_value!(deserialize_f32, visit_f32, "f32");
    parse_single_value!(deserialize_f64, visit_f64, "f64");
    parse_single_value!(deserialize_string, visit_string, "String");
    parse_single_value!(deserialize_byte_buf, visit_string, "String");
    parse_single_value!(deserialize_char, visit_char, "char");
}

struct ParamsDeserializer<'de> {
    params: Iter<'de, (Cow<'de, str>, Cow<'de, str>)>,
    current: Option<(&'de str, &'de str)>,
}

impl<'de> de::MapAccess<'de> for ParamsDeserializer<'de>
{
    type Error = de::value::Error;

    fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Self::Error>
        where K: de::DeserializeSeed<'de>,
    {
        self.current = self.params.next().map(|&(ref k, ref v)| (k.as_ref(), v.as_ref()));
        match self.current {
            Some((key, _)) => Ok(Some(seed.deserialize(Key{key})?)),
            None => Ok(None),
        }
    }

    fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Self::Error>
        where V: de::DeserializeSeed<'de>,
    {
        if let Some((_, value)) = self.current.take() {
            seed.deserialize(Value { value })
        } else {
            Err(de::value::Error::custom("unexpected item"))
        }
    }
}

struct Key<'de> {
    key: &'de str,
}

impl<'de> Deserializer<'de> for Key<'de> {
    type Error = de::value::Error;

    fn deserialize_identifier<V>(self, visitor: V) -> Result<V::Value, Self::Error>
        where V: Visitor<'de>,
    {
        visitor.visit_str(self.key)
    }

    fn deserialize_any<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
        where V: Visitor<'de>,
    {
        Err(de::value::Error::custom("Unexpected"))
    }

    forward_to_deserialize_any! {
        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
            byte_buf option unit unit_struct newtype_struct seq tuple
            tuple_struct map struct enum ignored_any
    }
}

macro_rules! parse_value {
    ($trait_fn:ident, $visit_fn:ident, $tp:tt) => {
        fn $trait_fn<V>(self, visitor: V) -> Result<V::Value, Self::Error>
            where V: Visitor<'de>
        {
            let v = self.value.parse().map_err(
                |_| de::value::Error::custom(
                    format!("can not parse {:?} to a {}", self.value, $tp)))?;
            visitor.$visit_fn(v)
        }
    }
}

struct Value<'de> {
    value: &'de str,
}

impl<'de> Deserializer<'de> for Value<'de>
{
    type Error = de::value::Error;

    parse_value!(deserialize_bool, visit_bool, "bool");
    parse_value!(deserialize_i8, visit_i8, "i8");
    parse_value!(deserialize_i16, visit_i16, "i16");
    parse_value!(deserialize_i32, visit_i32, "i16");
    parse_value!(deserialize_i64, visit_i64, "i64");
    parse_value!(deserialize_u8, visit_u8, "u8");
    parse_value!(deserialize_u16, visit_u16, "u16");
    parse_value!(deserialize_u32, visit_u32, "u32");
    parse_value!(deserialize_u64, visit_u64, "u64");
    parse_value!(deserialize_f32, visit_f32, "f32");
    parse_value!(deserialize_f64, visit_f64, "f64");
    parse_value!(deserialize_string, visit_string, "String");
    parse_value!(deserialize_byte_buf, visit_string, "String");
    parse_value!(deserialize_char, visit_char, "char");

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

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

    fn deserialize_unit_struct<V>(
        self, _: &'static str, visitor: V) -> Result<V::Value, Self::Error>
        where V: Visitor<'de>
    {
        visitor.visit_unit()
    }

    fn deserialize_bytes<V>(self, visitor: V) -> Result<V::Value, Self::Error>
        where V: Visitor<'de>,
    {
        visitor.visit_borrowed_bytes(self.value.as_bytes())
    }

    fn deserialize_str<V>(self, visitor: V) -> Result<V::Value, Self::Error>
        where V: Visitor<'de>,
    {
        visitor.visit_borrowed_str(self.value)
    }

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

    fn deserialize_enum<V>(self, _: &'static str, _: &'static [&'static str], visitor: V)
                           -> Result<V::Value, Self::Error>
        where V: Visitor<'de>,
    {
        visitor.visit_enum(ValueEnum {value: self.value})
    }

    fn deserialize_newtype_struct<V>(self, _: &'static str, visitor: V)
                                     -> Result<V::Value, Self::Error>
        where V: Visitor<'de>,
    {
        visitor.visit_newtype_struct(self)
    }

    fn deserialize_tuple<V>(self, _: usize, _: V) -> Result<V::Value, Self::Error>
        where V: Visitor<'de>
    {
        Err(de::value::Error::custom("unsupported type: tuple"))
    }

    fn deserialize_struct<V>(self, _: &'static str, _: &'static [&'static str], _: V)
                             -> Result<V::Value, Self::Error>
        where V: Visitor<'de>
    {
        Err(de::value::Error::custom("unsupported type: struct"))
    }

    fn deserialize_tuple_struct<V>(self, _: &'static str, _: usize, _: V)
                                   -> Result<V::Value, Self::Error>
        where V: Visitor<'de>
    {
        Err(de::value::Error::custom("unsupported type: tuple struct"))
    }

    unsupported_type!(deserialize_any, "any");
    unsupported_type!(deserialize_seq, "seq");
    unsupported_type!(deserialize_map, "map");
    unsupported_type!(deserialize_identifier, "identifier");
}

struct ParamsSeq<'de> {
    params: Iter<'de, (Cow<'de, str>, Cow<'de, str>)>,
}

impl<'de> de::SeqAccess<'de> for ParamsSeq<'de>
{
    type Error = de::value::Error;

    fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Self::Error>
        where T: de::DeserializeSeed<'de>,
    {
        match self.params.next() {
            Some(item) => Ok(Some(seed.deserialize(Value { value: item.1.as_ref() })?)),
            None => Ok(None),
        }
    }
}

struct ValueEnum<'de> {
    value: &'de str,
}

impl<'de> de::EnumAccess<'de> for ValueEnum<'de> {
    type Error = de::value::Error;
    type Variant = UnitVariant;

    fn variant_seed<V>(self, seed: V) -> Result<(V::Value, Self::Variant), Self::Error>
        where V: de::DeserializeSeed<'de>,
    {
        Ok((seed.deserialize(Key { key: self.value })?, UnitVariant))
    }
}

struct UnitVariant;

impl<'de> de::VariantAccess<'de> for UnitVariant {
    type Error = de::value::Error;

    fn unit_variant(self) -> Result<(), Self::Error> {
        Ok(())
    }

    fn newtype_variant_seed<T>(self, _seed: T) -> Result<T::Value, Self::Error>
        where T: de::DeserializeSeed<'de>,
    {
        Err(de::value::Error::custom("not supported"))
    }

    fn tuple_variant<V>(self, _len: usize, _visitor: V) -> Result<V::Value, Self::Error>
        where V: Visitor<'de>,
    {
        Err(de::value::Error::custom("not supported"))
    }

    fn struct_variant<V>(self, _: &'static [&'static str], _: V)
                         -> Result<V::Value, Self::Error>
        where V: Visitor<'de>,
    {
        Err(de::value::Error::custom("not supported"))
    }
}