Distance Oracle

close #10 (closed)

client/distance/src/lib.rs

+// Copyright 2022 Axiom-Team
+//
+// This file is part of Substrate-Libre-Currency.
+//
+// Substrate-Libre-Currency is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, version 3 of the License.
+//
+// Substrate-Libre-Currency is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with Substrate-Libre-Currency. If not, see <https://www.gnu.org/licenses/>.
+
+use codec::{Decode, Encode};
+use frame_support::pallet_prelude::*;
+use sc_client_api::{ProvideUncles, StorageKey, StorageProvider};
+use scale_info::TypeInfo;
+use sp_runtime::{generic::BlockId, traits::Block as BlockT, AccountId32};
+use std::path::PathBuf;
+
+type IdtyIndex = u32;
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error<B: BlockT> {
+    #[error("Could not retrieve the block hash for block id: {0:?}")]
+    NoHashForBlockId(BlockId<B>),
+}
+
+/// Create a new [`sp_distance::InherentDataProvider`] at the given block.
+pub fn create_distance_inherent_data_provider<B, C, Backend>(
+    client: &C,
+    parent: B::Hash,
+    distance_dir: PathBuf,
+    owner_keys: &[sp_core::sr25519::Public],
+) -> Result<sp_distance::InherentDataProvider<IdtyIndex>, sc_client_api::blockchain::Error>
+where
+    B: BlockT,
+    C: ProvideUncles<B> + StorageProvider<B, Backend>,
+    Backend: sc_client_api::Backend<B>,
+    IdtyIndex: Decode + Encode + PartialEq + TypeInfo,
+{
+    let &[owner_key] = owner_keys else {
+        return Ok(sp_distance::InherentDataProvider::<IdtyIndex>::new(
+            None
+        ))
+    };
+    let owner_key = sp_runtime::AccountId32::new(owner_key.0);
+
+    let session_index = client
+        .storage(
+            &parent,
+            &StorageKey(
+                frame_support::storage::storage_prefix(b"Session", b"CurrentIndex").to_vec(),
+            ),
+        )
+        .expect("CurrentIndex is Err")
+        .map_or(0, |raw| {
+            u32::decode(&mut &raw.0[..]).expect("cannot decode CurrentIndex")
+        });
+
+    let published_results = client
+        .storage(
+            &parent,
+            &StorageKey(
+                frame_support::storage::storage_prefix(
+                    b"Distance",
+                    match session_index % 3 {
+                        0 => b"StoragePublishedResults1",
+                        1 => b"StoragePublishedResults2",
+                        2 => b"StoragePublishedResults0",
+                        _ => unreachable!("n%3<3"),
+                    },
+                )
+                .to_vec(),
+            ),
+        )?
+        .map_or_else(Default::default, |raw| {
+            pallet_distance::EvaluationPool::<AccountId32, IdtyIndex>::decode(&mut &raw.0[..])
+                .expect("cannot decode EvaluationPool")
+        });
+
+    // Have we already published a result for this session?
+    if published_results.evaluators.contains(&owner_key) {
+        return Ok(sp_distance::InherentDataProvider::<IdtyIndex>::new(None));
+    }
+
+    // Read evaluation result from file, if it exists
+    let evaluation_result = match std::fs::read(distance_dir.join(session_index.to_string())) {
+        Ok(data) => data,
+        Err(e) => {
+            match e.kind() {
+                std::io::ErrorKind::NotFound => {}
+                _ => {
+                    log::error!("Cannot read distance evaluation result file: {e:?}");
+                }
+            }
+            return Ok(sp_distance::InherentDataProvider::<IdtyIndex>::new(None));
+        }
+    };
+
+    Ok(sp_distance::InherentDataProvider::<IdtyIndex>::new(Some(
+        sp_distance::ComputationResult::decode(&mut evaluation_result.as_slice()).unwrap(),
+    )))
+}