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/// Cache control values
///
/// # Examples
///
/// ```rust
/// use async_graphql::*;
///
/// struct Query;
///
/// #[Object(cache_control(max_age = 60))]
/// impl Query {
///     #[graphql(cache_control(max_age = 30))]
///     async fn value1(&self) -> i32 {
///         0
///     }
///
///     #[graphql(cache_control(private))]
///     async fn value2(&self) -> i32 {
///         0
///     }
/// }
///
/// # tokio::runtime::Runtime::new().unwrap().block_on(async {
/// let schema = Schema::new(Query, EmptyMutation, EmptySubscription);
/// assert_eq!(
///     schema
///         .execute("{ value1 }")
///         .await
///         .into_result()
///         .unwrap()
///         .cache_control,
///     CacheControl {
///         public: true,
///         max_age: 30
///     }
/// );
/// assert_eq!(
///     schema
///         .execute("{ value2 }")
///         .await
///         .into_result()
///         .unwrap()
///         .cache_control,
///     CacheControl {
///         public: false,
///         max_age: 60
///     }
/// );
/// assert_eq!(
///     schema
///         .execute("{ value1 value2 }")
///         .await
///         .into_result()
///         .unwrap()
///         .cache_control,
///     CacheControl {
///         public: false,
///         max_age: 30
///     }
/// );
/// # });
/// ```
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub struct CacheControl {
    /// Scope is public, default is true.
    pub public: bool,

    /// Cache max age, default is 0.
    pub max_age: usize,
}

impl Default for CacheControl {
    fn default() -> Self {
        Self {
            public: true,
            max_age: 0,
        }
    }
}

impl CacheControl {
    /// Get 'Cache-Control' header value.
    #[must_use]
    pub fn value(&self) -> Option<String> {
        if self.max_age > 0 {
            Some(format!(
                "max-age={}{}",
                self.max_age,
                if self.public { "" } else { ", private" }
            ))
        } else {
            None
        }
    }
}

impl CacheControl {
    #[must_use]
    pub(crate) fn merge(self, other: &CacheControl) -> CacheControl {
        CacheControl {
            public: self.public && other.public,
            max_age: if self.max_age == 0 {
                other.max_age
            } else if other.max_age == 0 {
                self.max_age
            } else {
                self.max_age.min(other.max_age)
            },
        }
    }
}