// [dependencies]
// serde = "1.0"
// serde_json = { version = "1.0.78", features = ["raw_value"] }

use serde::de::value::BorrowedStrDeserializer;
use serde::de::{Deserialize, DeserializeSeed, Deserializer, MapAccess, SeqAccess, Visitor};
use serde_json::value::RawValue;
use std::collections::HashMap;
use std::fmt;

fn main() {
    let j = r#" {"abc\"def": "012\"345"} "#;
    let mut de = serde_json::Deserializer::from_str(j);
    let map = HashMap::<&str, &str>::deserialize(NoUnescape(&mut de)).unwrap();
    for (k, v) in map {
        println!("{} = {}", k, v);
    }
}

struct NoUnescape<D>(D);

impl<'de, D> Visitor<'de> for NoUnescape<D>
where
    D: Visitor<'de>,
{
    type Value = D::Value;

    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        self.0.expecting(formatter)
    }

    fn visit_map<A>(self, map: A) -> Result<Self::Value, A::Error>
    where
        A: MapAccess<'de>,
    {
        self.0.visit_map(NoUnescape(map))
    }

    fn visit_seq<A>(self, map: A) -> Result<Self::Value, A::Error>
    where
        A: SeqAccess<'de>,
    {
        self.0.visit_seq(NoUnescape(map))
    }
}

impl<'de, D> MapAccess<'de> for NoUnescape<D>
where
    D: MapAccess<'de>,
{
    type Error = D::Error;

    fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Self::Error>
    where
        K: DeserializeSeed<'de>,
    {
        let json = match self.0.next_key::<&RawValue>()? {
            None => return Ok(None),
            Some(raw_value) => raw_value.get(),
        };
        let string = &json[1..json.len() - 1];
        let key = seed.deserialize(BorrowedStrDeserializer::new(string))?;
        Ok(Some(key))
    }

    fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Self::Error>
    where
        V: DeserializeSeed<'de>,
    {
        let json = self.0.next_value::<&RawValue>()?.get();
        if json.starts_with('"') {
            let string = &json[1..json.len() - 1];
            seed.deserialize(BorrowedStrDeserializer::new(string))
        } else {
            let mut de = serde_json::Deserializer::from_str(json);
            seed.deserialize(NoUnescape(&mut de))
                .map_err(serde::de::Error::custom)
        }
    }
}

impl<'de, D> SeqAccess<'de> for NoUnescape<D>
where
    D: SeqAccess<'de>,
{
    type Error = D::Error;

    fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Self::Error>
    where
        T: DeserializeSeed<'de>,
    {
        let json = match self.0.next_element::<&RawValue>()? {
            None => return Ok(None),
            Some(raw_value) => raw_value.get(),
        };
        if json.starts_with('"') {
            let string = &json[1..json.len() - 1];
            seed.deserialize(BorrowedStrDeserializer::new(string))
                .map(Some)
        } else {
            let mut de = serde_json::Deserializer::from_str(json);
            seed.deserialize(NoUnescape(&mut de))
                .map(Some)
                .map_err(serde::de::Error::custom)
        }
    }
}

impl<'de, D> Deserializer<'de> for NoUnescape<D>
where
    D: Deserializer<'de>,
{
    type Error = D::Error;

    fn deserialize_any<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_bool<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_i8<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_i16<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_i32<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_i64<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_u8<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_u16<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_u32<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_u64<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_f32<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_f64<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_char<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_str<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_string<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_bytes<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_byte_buf<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_option<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_unit<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_unit_struct<V>(
        self,
        _name: &'static str,
        _visitor: V,
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_newtype_struct<V>(
        self,
        _name: &'static str,
        _visitor: V,
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        self.0.deserialize_seq(NoUnescape(visitor))
    }

    fn deserialize_tuple<V>(self, _len: usize, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_tuple_struct<V>(
        self,
        _name: &'static str,
        _len: usize,
        _visitor: V,
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_map<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        self.0.deserialize_map(NoUnescape(visitor))
    }

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

    fn deserialize_enum<V>(
        self,
        _name: &'static str,
        _variants: &'static [&'static str],
        _visitor: V,
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_identifier<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }

    fn deserialize_ignored_any<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        todo!()
    }
}