pub mod bool {
    /// Function that always returns `true`, for use in `serde(default)` attributes.
    pub fn yes() -> bool {
        true
    }
}

pub mod string {
    use std::fmt::Display;
    use std::str::FromStr;

    use serde::{Deserialize, Deserializer, Serializer, de};

    pub fn serialize<T, S>(value: &T, serializer: S) -> Result<S::Ok, S::Error>
    where
        T: Display,
        S: Serializer,
    {
        serializer.collect_str(value)
    }

    pub fn deserialize<'de, T, D>(deserializer: D) -> Result<T, D::Error>
    where
        T: FromStr,
        T::Err: Display,
        D: Deserializer<'de>,
    {
        String::deserialize(deserializer)?
            .parse()
            .map_err(de::Error::custom)
    }
}

/// Return true if the given value is the default for that type.
pub fn is_default<T: Default + PartialEq>(t: &T) -> bool {
    t == &T::default()
}

/// Deserialize a value, but if it fails, return the default value.
pub fn ok_or_default<'de, T, D>(deserializer: D) -> Result<T, D::Error>
where
    T: serde::Deserialize<'de> + Default,
    D: serde::Deserializer<'de>,
{
    let v: serde_json::Value = serde::Deserialize::deserialize(deserializer)?;
    Ok(T::deserialize(v).unwrap_or_default())
}

/// Deserialize a value, but if it is `null`, return the default value.
#[cfg(feature = "tor")]
pub(crate) fn null_to_default<'de, D, T>(deserializer: D) -> Result<T, D::Error>
where
    T: serde::Deserialize<'de> + Default,
    D: serde::Deserializer<'de>,
{
    use serde::Deserialize as _;
    Ok(Option::deserialize(deserializer)?.unwrap_or_default())
}

/// A helper that makes it easy to use `Option<T>` with the `serde(default)`
/// attribute, in case a default of `Some(T::default())` is desired instead
/// of `None`.
pub(crate) fn some_default<T: Default>() -> Option<T> {
    Some(T::default())
}

/// Like [`is_default`], but for use in combination with [`some_default`].
pub(crate) fn is_some_default<T: Default + PartialEq>(t: &Option<T>) -> bool {
    t.as_ref() == Some(&T::default())
}