Preimage registrar and Scheduler integration (#10356)

* initial idea

* more

* fix compile

* add clear and request logic

* improve some docs

* Add and implement trait

* continuing to improve

* refcount type

* infallible system preimage upload

* fmt

* fix requests

* Make it simple

* Make it simple

* Formatting

* Initial draft

* request when scheduled

* Docs

* Scheduler good

* Scheduler good

* Scheduler tests working

* Add new files

* Missing stuff

* Repotting, add weights.

* Add some tests to preimage pallet

* More tests

* Fix benchmarks

* preimage benchmarks

* All preimage benchmarks

* Tidy cargo

* Update weights.rs

* Allow hash provision in benchmarks

* Initial work on new benchmarks for Scheduler

* Tests working, refactor looks good

* Tests for new Scheduler functionality

* Use real weight, make tests work with runtimes without Preimage

* Rename

* Update benchmarks

* Formatting

* Formatting

* Fix weird formatting

* Update frame/preimage/src/lib.rs

* Fix try-runtime build

* Fixes

* Fixes

* Update frame/support/src/traits/tokens/currency.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Update frame/support/src/traits/tokens/currency/reservable.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Update frame/support/src/traits/tokens/imbalance.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Update frame/preimage/src/mock.rs

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* Update frame/scheduler/src/lib.rs

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* Update frame/preimage/src/lib.rs

* Fixes

* Fixes

* Formatting

* Fixes

* Fixes

* cargo run --quiet --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_scheduler --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/scheduler/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* cargo run --quiet --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_preimage --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/preimage/src/weights.rs --template=./.maintain/frame-weight-template.hbs

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>
Co-authored-by: Parity Bot <admin@parity.io>

substrate/frame/support/src/traits/misc.rs

@@ -94,6 +94,12 @@ pub trait TryDrop: Sized {
 	fn try_drop(self) -> Result<(), Self>;
 }
 
+impl TryDrop for () {
+	fn try_drop(self) -> Result<(), Self> {
+		Ok(())
+	}
+}
+
 /// Return type used when we need to return one of two items, each of the opposite direction or
 /// sign, with one (`Same`) being of the same type as the `self` or primary argument of the function
 /// that returned it.
@@ -577,6 +583,65 @@ impl<T: TypeInfo + 'static> TypeInfo for WrapperKeepOpaque<T> {
 	}
 }
 
+/// A interface for looking up preimages from their hash on chain.
+pub trait PreimageProvider<Hash> {
+	/// Returns whether a preimage exists for a given hash.
+	///
+	/// A value of `true` implies that `get_preimage` is `Some`.
+	fn have_preimage(hash: &Hash) -> bool;
+
+	/// Returns the preimage for a given hash.
+	fn get_preimage(hash: &Hash) -> Option<Vec<u8>>;
+
+	/// Returns whether a preimage request exists for a given hash.
+	fn preimage_requested(hash: &Hash) -> bool;
+
+	/// Request that someone report a preimage. Providers use this to optimise the economics for
+	/// preimage reporting.
+	fn request_preimage(hash: &Hash);
+
+	/// Cancel a previous preimage request.
+	fn unrequest_preimage(hash: &Hash);
+}
+
+impl<Hash> PreimageProvider<Hash> for () {
+	fn have_preimage(_: &Hash) -> bool {
+		false
+	}
+	fn get_preimage(_: &Hash) -> Option<Vec<u8>> {
+		None
+	}
+	fn preimage_requested(_: &Hash) -> bool {
+		false
+	}
+	fn request_preimage(_: &Hash) {}
+	fn unrequest_preimage(_: &Hash) {}
+}
+
+/// A interface for managing preimages to hashes on chain.
+///
+/// Note that this API does not assume any underlying user is calling, and thus
+/// does not handle any preimage ownership or fees. Other system level logic that
+/// uses this API should implement that on their own side.
+pub trait PreimageRecipient<Hash>: PreimageProvider<Hash> {
+	/// Maximum size of a preimage.
+	type MaxSize: Get<u32>;
+
+	/// Store the bytes of a preimage on chain.
+	fn note_preimage(bytes: crate::BoundedVec<u8, Self::MaxSize>);
+
+	/// Clear a previously noted preimage. This is infallible and should be treated more like a
+	/// hint - if it was not previously noted or if it is now requested, then this will not do
+	/// anything.
+	fn unnote_preimage(hash: &Hash);
+}
+
+impl<Hash> PreimageRecipient<Hash> for () {
+	type MaxSize = ();
+	fn note_preimage(_: crate::BoundedVec<u8, Self::MaxSize>) {}
+	fn unnote_preimage(_: &Hash) {}
+}
+
 #[cfg(test)]
 mod test {
 	use super::*;