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use core::fmt::Debug;
use core::hash::{Hash, Hasher};
use toad_array::{AppendCopy, Array};
use toad_hash::Blake2Hasher;
use crate::repeat::{PATH, QUERY};
use crate::{Message, MessageOptions, OptionMap};
/// Default hasher used for [`CacheKey`]
///
/// Hashes:
/// - [Message Code](toad_msg::Message.code)
/// - [Uri-Path](toad_msg::opt::known::no_repeat::HOST)
/// - [Uri-Query](toad_msg::opt::known::no_repeat::HOST)
/// - [Accept](toad_msg::opt::known::no_repeat::ACCEPT)
#[derive(Debug, Clone, Default)]
pub struct DefaultCacheKey(Blake2Hasher);
impl DefaultCacheKey {
/// Create a new `DefaultCacheKey`
pub fn new() -> Self {
Self::default()
}
}
impl CacheKey for DefaultCacheKey {
type Hasher = Blake2Hasher;
fn hasher(&mut self) -> &mut Self::Hasher {
&mut self.0
}
fn add_cache_key<P, O>(&mut self, msg: &Message<P, O>)
where P: Array<Item = u8> + AppendCopy<u8>,
O: OptionMap
{
msg.code.hash(&mut self.0);
msg.opts.iter().for_each(|(num, vals)| {
if num.include_in_cache_key() {
vals.iter().for_each(|v| v.hash(&mut self.0))
}
});
}
}
/// The cache key can be used to compare messages for representing
/// the same action against the same resource; for example requests
/// with different IDs but the same method and cache-key affecting options
/// (ex. path, query parameters) will yield the same cache-key.
///
/// Extends [`core::hash::Hash`] with the ability to build a cache-key of a message
/// in the hasher's state.
///
/// [`DefaultCacheKey`] Provides a default implementation.
pub trait CacheKey
where Self: Sized + Debug
{
/// Type used to generate hashes
type Hasher: Hasher;
#[allow(missing_docs)]
fn hasher(&mut self) -> &mut Self::Hasher;
/// Add this message's cache key to the hasher's internal state.
///
/// After invoking this, to get the [`u64`] hash use [`Hasher::finish`].
///
/// Alternately, use [`CacheKey::cache_key`] to go directly to the [`u64`] hash.
fn add_cache_key<P, O>(&mut self, msg: &Message<P, O>)
where P: Array<Item = u8> + AppendCopy<u8>,
O: OptionMap;
/// Add this message's cache key to the hasher's internal state and yield the [`u64`] hash.
///
/// ```
/// use core::hash::Hasher;
///
/// use toad_msg::alloc::Message;
/// use toad_msg::Type::Con;
/// use toad_msg::{CacheKey, Code, ContentFormat, DefaultCacheKey, Id, MessageOptions, Token};
///
/// let mut msg_a = Message::new(Con, Code::GET, Id(1), Token(Default::default()));
/// msg_a.set_path("foo/bar");
/// msg_a.set_accept(ContentFormat::Text);
/// let mut ha = DefaultCacheKey::new();
/// ha.cache_key(&msg_a);
///
/// let mut msg_b = Message::new(Con, Code::GET, Id(2), Token(Default::default()));
/// msg_b.set_accept(ContentFormat::Text);
/// msg_b.set_path("foo/bar");
/// let mut hb = DefaultCacheKey::new();
/// hb.cache_key(&msg_b);
///
/// assert_eq!(ha.hasher().finish(), hb.hasher().finish());
/// ```
fn cache_key<P, O>(&mut self, msg: &Message<P, O>) -> u64
where P: Array<Item = u8> + AppendCopy<u8>,
O: OptionMap
{
self.add_cache_key(msg);
self.hasher().finish()
}
}
impl<T> CacheKey for &mut T where T: CacheKey
{
type Hasher = T::Hasher;
fn hasher(&mut self) -> &mut Self::Hasher {
<T as CacheKey>::hasher(self)
}
fn add_cache_key<P, O>(&mut self, msg: &Message<P, O>)
where P: Array<Item = u8> + AppendCopy<u8>,
O: OptionMap
{
<T as CacheKey>::add_cache_key(self, msg)
}
}
#[cfg(test)]
mod test {
use core::hash::Hasher;
use crate::alloc::Message;
use crate::{CacheKey, Code, ContentFormat, DefaultCacheKey, Id, MessageOptions, Token, Type};
#[test]
pub fn cache_key() {
fn req<F>(stuff: F) -> u64
where F: FnOnce(&mut Message)
{
let mut req = Message::new(Type::Con, Code::GET, Id(1), Token(Default::default()));
stuff(&mut req);
let mut h = DefaultCacheKey::new();
h.cache_key(&req);
h.hasher().finish()
}
assert_ne!(req(|r| {
r.set_path("a/b/c").ok();
}),
req(|_| {}));
assert_eq!(req(|r| {
r.set_path("a/b/c").ok();
}),
req(|r| {
r.set_path("a/b/c").ok();
}));
assert_ne!(req(|r| {
r.set_path("a/b/c").ok();
r.add_query("filter[temp](less_than)=123").ok();
}),
req(|r| {
r.set_path("a/b/c").ok();
}));
assert_ne!(req(|r| {
r.set_path("a/b/c").ok();
r.add_query("filter[temp](less_than)=123").ok();
r.set_accept(ContentFormat::Json).ok();
}),
req(|r| {
r.set_path("a/b/c").ok();
r.add_query("filter[temp](less_than)=123").ok();
r.set_accept(ContentFormat::Text).ok();
}));
assert_eq!(req(|r| {
r.set_path("a/b/c").ok();
r.add_query("filter[temp](less_than)=123").ok();
r.set_accept(ContentFormat::Json).ok();
}),
req(|r| {
r.set_path("a/b/c").ok();
r.add_query("filter[temp](less_than)=123").ok();
r.set_accept(ContentFormat::Json).ok();
}));
}
}