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// Copyright 2018 Palantir Technologies, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
use serde::de::{self, IntoDeserializer};
use std::fmt;
use std::marker::PhantomData;

pub fn valid_enum_variant(s: &str) -> bool {
    if s.is_empty() {
        return false;
    }

    s.as_bytes()
        .iter()
        .all(|b| matches!(b, b'A'..=b'Z' | b'0'..=b'9' | b'_'))
}

pub enum UnionField_<T> {
    Type,
    Value(T),
}

impl<'de, T> de::Deserialize<'de> for UnionField_<T>
where
    T: de::Deserialize<'de>,
{
    fn deserialize<D>(d: D) -> Result<UnionField_<T>, D::Error>
    where
        D: de::Deserializer<'de>,
    {
        d.deserialize_str(UnionFieldVisitor(PhantomData))
    }
}

struct UnionFieldVisitor<T>(PhantomData<T>);

impl<'de, T> de::Visitor<'de> for UnionFieldVisitor<T>
where
    T: de::Deserialize<'de>,
{
    type Value = UnionField_<T>;

    fn expecting(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        fmt.write_str("string")
    }

    fn visit_str<E>(self, value: &str) -> Result<UnionField_<T>, E>
    where
        E: de::Error,
    {
        match value {
            "type" => Ok(UnionField_::Type),
            value => T::deserialize(value.into_deserializer()).map(UnionField_::Value),
        }
    }
}

pub struct UnionTypeField_;

impl<'de> de::Deserialize<'de> for UnionTypeField_ {
    fn deserialize<D>(d: D) -> Result<UnionTypeField_, D::Error>
    where
        D: de::Deserializer<'de>,
    {
        d.deserialize_str(UnionTypeFieldVisitor)
    }
}

struct UnionTypeFieldVisitor;

impl<'de> de::Visitor<'de> for UnionTypeFieldVisitor {
    type Value = UnionTypeField_;

    fn expecting(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        fmt.write_str("type field")
    }

    fn visit_str<E>(self, value: &str) -> Result<UnionTypeField_, E>
    where
        E: de::Error,
    {
        match value {
            "type" => Ok(UnionTypeField_),
            value => Err(E::invalid_value(de::Unexpected::Str(value), &self)),
        }
    }
}