flow-value 0.3.0

use crate::{Error, Map, Value};
use serde::de::IntoDeserializer;
use std::borrow::Cow;

pub struct MapDeserializer {
    pub iter: <Map as IntoIterator>::IntoIter,
    pub value: Option<Value>,
}

impl MapDeserializer {
    pub fn new(map: Map) -> Self {
        MapDeserializer {
            iter: map.into_iter(),
            value: None,
        }
    }
}

impl<'de> serde::de::MapAccess<'de> for MapDeserializer {
    type Error = Error;

    fn next_key_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Error>
    where
        T: serde::de::DeserializeSeed<'de>,
    {
        match self.iter.next() {
            Some((key, value)) => {
                self.value = Some(value);
                let key_de = MapKeyDeserializer {
                    key: Cow::Owned(key),
                };
                seed.deserialize(key_de).map(Some)
            }
            None => Ok(None),
        }
    }

    fn next_value_seed<T>(&mut self, seed: T) -> Result<T::Value, Error>
    where
        T: serde::de::DeserializeSeed<'de>,
    {
        match self.value.take() {
            Some(value) => seed.deserialize(value),
            None => Err(serde::de::Error::custom("value is missing")),
        }
    }

    fn size_hint(&self) -> Option<usize> {
        match self.iter.size_hint() {
            (lower, Some(upper)) if lower == upper => Some(upper),
            _ => None,
        }
    }
}

pub struct MapKeyDeserializer<'de> {
    pub key: Cow<'de, str>,
}

macro_rules! deserialize_integer_key {
    ($method:ident => $visit:ident) => {
        fn $method<V>(self, visitor: V) -> Result<V::Value, Error>
        where
            V: serde::de::Visitor<'de>,
        {
            match (self.key.parse(), self.key) {
                (Ok(integer), _) => visitor.$visit(integer),
                (Err(_), Cow::Borrowed(s)) => visitor.visit_borrowed_str(s),
                (Err(_), Cow::Owned(s)) => visitor.visit_string(s),
            }
        }
    };
}

impl<'de> serde::Deserializer<'de> for MapKeyDeserializer<'de> {
    type Error = Error;

    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Error>
    where
        V: serde::de::Visitor<'de>,
    {
        BorrowedCowStrDeserializer::new(self.key).deserialize_any(visitor)
    }

    deserialize_integer_key!(deserialize_i8 => visit_i8);
    deserialize_integer_key!(deserialize_i16 => visit_i16);
    deserialize_integer_key!(deserialize_i32 => visit_i32);
    deserialize_integer_key!(deserialize_i64 => visit_i64);
    deserialize_integer_key!(deserialize_u8 => visit_u8);
    deserialize_integer_key!(deserialize_u16 => visit_u16);
    deserialize_integer_key!(deserialize_u32 => visit_u32);
    deserialize_integer_key!(deserialize_u64 => visit_u64);

    #[inline]
    fn deserialize_option<V>(self, visitor: V) -> Result<V::Value, Error>
    where
        V: serde::de::Visitor<'de>,
    {
        // Map keys cannot be null.
        visitor.visit_some(self)
    }

    #[inline]
    fn deserialize_newtype_struct<V>(
        self,
        _name: &'static str,
        visitor: V,
    ) -> Result<V::Value, Error>
    where
        V: serde::de::Visitor<'de>,
    {
        visitor.visit_newtype_struct(self)
    }

    fn deserialize_enum<V>(
        self,
        name: &'static str,
        variants: &'static [&'static str],
        visitor: V,
    ) -> Result<V::Value, Error>
    where
        V: serde::de::Visitor<'de>,
    {
        self.key
            .into_deserializer()
            .deserialize_enum(name, variants, visitor)
    }

    serde::forward_to_deserialize_any! {
        bool f32 f64 char str string bytes byte_buf unit unit_struct seq tuple
        tuple_struct map struct identifier ignored_any
    }
}

pub struct BorrowedCowStrDeserializer<'de> {
    pub value: Cow<'de, str>,
}

impl<'de> BorrowedCowStrDeserializer<'de> {
    pub fn new(value: Cow<'de, str>) -> Self {
        BorrowedCowStrDeserializer { value }
    }
}

impl<'de> serde::de::Deserializer<'de> for BorrowedCowStrDeserializer<'de> {
    type Error = Error;

    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Error>
    where
        V: serde::de::Visitor<'de>,
    {
        match self.value {
            Cow::Borrowed(string) => visitor.visit_borrowed_str(string),
            Cow::Owned(string) => visitor.visit_string(string),
        }
    }

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

    serde::forward_to_deserialize_any! {
        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
        bytes byte_buf option unit unit_struct newtype_struct seq tuple
        tuple_struct map struct identifier ignored_any
    }
}

impl<'de> serde::de::EnumAccess<'de> for BorrowedCowStrDeserializer<'de> {
    type Error = Error;
    type Variant = UnitOnly;

    fn variant_seed<T>(self, seed: T) -> Result<(T::Value, Self::Variant), Error>
    where
        T: serde::de::DeserializeSeed<'de>,
    {
        let value = seed.deserialize(self)?;
        Ok((value, UnitOnly))
    }
}

pub struct UnitOnly;

impl<'de> serde::de::VariantAccess<'de> for UnitOnly {
    type Error = Error;

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

    fn newtype_variant_seed<T>(self, _seed: T) -> Result<T::Value, Error>
    where
        T: serde::de::DeserializeSeed<'de>,
    {
        Err(serde::de::Error::invalid_type(
            serde::de::Unexpected::UnitVariant,
            &"newtype variant",
        ))
    }

    fn tuple_variant<V>(self, _len: usize, _visitor: V) -> Result<V::Value, Error>
    where
        V: serde::de::Visitor<'de>,
    {
        Err(serde::de::Error::invalid_type(
            serde::de::Unexpected::UnitVariant,
            &"tuple variant",
        ))
    }

    fn struct_variant<V>(
        self,
        _fields: &'static [&'static str],
        _visitor: V,
    ) -> Result<V::Value, Error>
    where
        V: serde::de::Visitor<'de>,
    {
        Err(serde::de::Error::invalid_type(
            serde::de::Unexpected::UnitVariant,
            &"struct variant",
        ))
    }
}