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/*!
# Etag `if-none-match` Request Guard for Rocket Framework

This crate provides a request guard used for getting `if-none-match` header.

See `examples`.
*/

extern crate rocket;

pub use rocket::http::hyper::header::EntityTag;
use rocket::request::{self, FromRequest, Request};
use rocket::Outcome;

/// The request guard used for getting `if-none-match` header.
#[derive(Debug, Clone)]
pub struct EtagIfNoneMatch {
    pub etag: Option<EntityTag>,
}

macro_rules! impl_request_guard {
    ($request:ident) => {
        {
            let raw_etag: Option<&str> = $request.headers().get("if-none-match").next(); // Only fetch the first one.

            match raw_etag {
                Some(raw_etag) => match raw_etag.parse::<EntityTag>() {
                    Ok(etag) => {
                        EtagIfNoneMatch {
                            etag: Some(etag)
                        }
                    }
                    Err(_) => {
                        EtagIfNoneMatch {
                            etag: None
                        }
                    }
                }
                None => {
                    EtagIfNoneMatch {
                        etag: None
                    }
                }
            }
        }
    }
}

impl<'a, 'r> FromRequest<'a, 'r> for EtagIfNoneMatch {
    type Error = ();

    fn from_request(request: &'a Request<'r>) -> request::Outcome<Self, Self::Error> {
        Outcome::Success(impl_request_guard!(request))
    }
}

impl<'a, 'r> FromRequest<'a, 'r> for &'a EtagIfNoneMatch {
    type Error = ();

    fn from_request(request: &'a Request<'r>) -> request::Outcome<Self, Self::Error> {
        Outcome::Success(request.local_cache(|| impl_request_guard!(request)))
    }
}

impl EtagIfNoneMatch {
    /// For weak comparison two entity-tags are equivalent if their opaque-tags match character-by-character, regardless of either or both being tagged as "weak".
    pub fn weak_eq(&self, other_etag: &EntityTag) -> bool {
        match &self.etag {
            Some(etag) => etag.weak_eq(other_etag),
            None => false,
        }
    }

    /// For strong comparison two entity-tags are equivalent if both are not weak and their opaque-tags match character-by-character.
    pub fn strong_eq(&self, other_etag: &EntityTag) -> bool {
        match &self.etag {
            Some(etag) => etag.strong_eq(other_etag),
            None => false,
        }
    }
}