tea-protocol 0.1.0

use std::fmt;

use serde::Deserializer;
use serde::de::{MapAccess, SeqAccess, Visitor};
use serde_json::{Map, Number, Value};

use crate::{CURRENT_PROTOCOL_VERSION, ProtocolVersion};

pub(crate) fn validate_read_version(version: ProtocolVersion) -> Result<(), &'static str> {
    if version.major() == CURRENT_PROTOCOL_VERSION.major() {
        Ok(())
    } else {
        Err("unsupported protocol major version")
    }
}

pub(crate) fn deserialize_unique_value<'de, D>(deserializer: D) -> Result<Value, D::Error>
where
    D: Deserializer<'de>,
{
    deserializer.deserialize_any(UniqueValueVisitor)
}

struct UniqueValueVisitor;

impl<'de> Visitor<'de> for UniqueValueVisitor {
    type Value = Value;

    fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter.write_str("a JSON value without duplicate object keys")
    }

    fn visit_bool<E>(self, value: bool) -> Result<Self::Value, E> {
        Ok(Value::Bool(value))
    }

    fn visit_i64<E>(self, value: i64) -> Result<Self::Value, E> {
        Ok(Value::Number(Number::from(value)))
    }

    fn visit_u64<E>(self, value: u64) -> Result<Self::Value, E> {
        Ok(Value::Number(Number::from(value)))
    }

    fn visit_f64<E>(self, value: f64) -> Result<Self::Value, E>
    where
        E: serde::de::Error,
    {
        Number::from_f64(value)
            .map(Value::Number)
            .ok_or_else(|| E::custom("non-finite JSON number"))
    }

    fn visit_str<E>(self, value: &str) -> Result<Self::Value, E> {
        Ok(Value::String(value.to_owned()))
    }

    fn visit_string<E>(self, value: String) -> Result<Self::Value, E> {
        Ok(Value::String(value))
    }

    fn visit_none<E>(self) -> Result<Self::Value, E> {
        Ok(Value::Null)
    }

    fn visit_unit<E>(self) -> Result<Self::Value, E> {
        Ok(Value::Null)
    }

    fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
    where
        D: Deserializer<'de>,
    {
        deserialize_unique_value(deserializer)
    }

    fn visit_seq<A>(self, mut sequence: A) -> Result<Self::Value, A::Error>
    where
        A: SeqAccess<'de>,
    {
        let mut values = Vec::with_capacity(sequence.size_hint().unwrap_or(0));
        while let Some(value) = sequence.next_element_seed(UniqueValueSeed)? {
            values.push(value);
        }
        Ok(Value::Array(values))
    }

    fn visit_map<A>(self, mut object: A) -> Result<Self::Value, A::Error>
    where
        A: MapAccess<'de>,
    {
        let mut values = Map::new();
        while let Some(key) = object.next_key::<String>()? {
            if values.contains_key(&key) {
                return Err(serde::de::Error::custom(format_args!(
                    "duplicate JSON object key: {key}"
                )));
            }
            let value = object.next_value_seed(UniqueValueSeed)?;
            values.insert(key, value);
        }
        Ok(Value::Object(values))
    }
}

struct UniqueValueSeed;

impl<'de> serde::de::DeserializeSeed<'de> for UniqueValueSeed {
    type Value = Value;

    fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
    where
        D: Deserializer<'de>,
    {
        deserialize_unique_value(deserializer)
    }
}