/// Cache control value
///
/// # 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
///     }
///
///     #[graphql(cache_control(no_cache))]
///     async fn value3(&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
///     }
/// );
///
/// assert_eq!(
///     schema
///         .execute("{ value1 value2 value3 }")
///         .await
///         .into_result()
///         .unwrap()
///         .cache_control,
///     CacheControl {
///         public: false,
///         max_age: -1
///     }
/// );
/// # });
/// ```
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub struct CacheControl {
    /// Scope is public, default is true.
    pub public: bool,

    /// Cache max age, `-1` represent `no-cache`, default is 0.
    pub max_age: i32,
}

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> {
        let mut value = if self.max_age > 0 {
            format!("max-age={}", self.max_age)
        } else if self.max_age == -1 {
            "no-cache".to_string()
        } else {
            String::new()
        };

        if !self.public {
            if !value.is_empty() {
                value += ", ";
            }
            value += "private";
        }

        if !value.is_empty() {
            Some(value)
        } else {
            None
        }
    }
}

impl CacheControl {
    #[must_use]
    pub(crate) fn merge(self, other: &CacheControl) -> CacheControl {
        CacheControl {
            public: self.public && other.public,
            max_age: match (self.max_age, other.max_age) {
                (-1, _) => -1,
                (_, -1) => -1,
                (a, 0) => a,
                (0, b) => b,
                (a, b) => a.min(b),
            },
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn to_value() {
        assert_eq!(
            CacheControl {
                public: true,
                max_age: 0,
            }
            .value(),
            None
        );

        assert_eq!(
            CacheControl {
                public: false,
                max_age: 0,
            }
            .value(),
            Some("private".to_string())
        );

        assert_eq!(
            CacheControl {
                public: false,
                max_age: 10,
            }
            .value(),
            Some("max-age=10, private".to_string())
        );

        assert_eq!(
            CacheControl {
                public: true,
                max_age: 10,
            }
            .value(),
            Some("max-age=10".to_string())
        );

        assert_eq!(
            CacheControl {
                public: true,
                max_age: -1,
            }
            .value(),
            Some("no-cache".to_string())
        );

        assert_eq!(
            CacheControl {
                public: false,
                max_age: -1,
            }
            .value(),
            Some("no-cache, private".to_string())
        );
    }
}