Add beacon.watch (#3362)

> This is currently a WIP and all features are subject to alteration or removal at any time.

## Overview

The successor to #2873.

Contains the backbone of `beacon.watch` including syncing code, the initial API, and several core database tables.

See `watch/README.md` for more information, requirements and usage.

watch/src/client.rs

@@ -0,0 +1,178 @@
+use crate::block_packing::WatchBlockPacking;
+use crate::block_rewards::WatchBlockRewards;
+use crate::database::models::{
+    WatchBeaconBlock, WatchCanonicalSlot, WatchProposerInfo, WatchValidator,
+};
+use crate::suboptimal_attestations::WatchAttestation;
+
+use eth2::types::BlockId;
+use reqwest::Client;
+use serde::de::DeserializeOwned;
+use types::Hash256;
+use url::Url;
+
+#[derive(Debug)]
+pub enum Error {
+    Reqwest(reqwest::Error),
+    Url(url::ParseError),
+}
+
+impl From<reqwest::Error> for Error {
+    fn from(e: reqwest::Error) -> Self {
+        Error::Reqwest(e)
+    }
+}
+
+impl From<url::ParseError> for Error {
+    fn from(e: url::ParseError) -> Self {
+        Error::Url(e)
+    }
+}
+
+pub struct WatchHttpClient {
+    pub client: Client,
+    pub server: Url,
+}
+
+impl WatchHttpClient {
+    async fn get_opt<T: DeserializeOwned>(&self, url: Url) -> Result<Option<T>, Error> {
+        let response = self.client.get(url).send().await?;
+
+        if response.status() == 404 {
+            Ok(None)
+        } else {
+            response
+                .error_for_status()?
+                .json()
+                .await
+                .map_err(Into::into)
+        }
+    }
+
+    pub async fn get_beacon_blocks(
+        &self,
+        block_id: BlockId,
+    ) -> Result<Option<WatchBeaconBlock>, Error> {
+        let url = self
+            .server
+            .join("v1/")?
+            .join("blocks/")?
+            .join(&block_id.to_string())?;
+
+        self.get_opt(url).await
+    }
+
+    pub async fn get_lowest_canonical_slot(&self) -> Result<Option<WatchCanonicalSlot>, Error> {
+        let url = self.server.join("v1/")?.join("slots/")?.join("lowest")?;
+
+        self.get_opt(url).await
+    }
+
+    pub async fn get_highest_canonical_slot(&self) -> Result<Option<WatchCanonicalSlot>, Error> {
+        let url = self.server.join("v1/")?.join("slots/")?.join("highest")?;
+
+        self.get_opt(url).await
+    }
+
+    pub async fn get_lowest_beacon_block(&self) -> Result<Option<WatchBeaconBlock>, Error> {
+        let url = self.server.join("v1/")?.join("blocks/")?.join("lowest")?;
+
+        self.get_opt(url).await
+    }
+
+    pub async fn get_highest_beacon_block(&self) -> Result<Option<WatchBeaconBlock>, Error> {
+        let url = self.server.join("v1/")?.join("blocks/")?.join("highest")?;
+
+        self.get_opt(url).await
+    }
+
+    pub async fn get_next_beacon_block(
+        &self,
+        parent: Hash256,
+    ) -> Result<Option<WatchBeaconBlock>, Error> {
+        let url = self
+            .server
+            .join("v1/")?
+            .join("blocks/")?
+            .join(&format!("{parent:?}/"))?
+            .join("next")?;
+
+        self.get_opt(url).await
+    }
+
+    pub async fn get_validator_by_index(
+        &self,
+        index: i32,
+    ) -> Result<Option<WatchValidator>, Error> {
+        let url = self
+            .server
+            .join("v1/")?
+            .join("validators/")?
+            .join(&format!("{index}"))?;
+
+        self.get_opt(url).await
+    }
+
+    pub async fn get_proposer_info(
+        &self,
+        block_id: BlockId,
+    ) -> Result<Option<WatchProposerInfo>, Error> {
+        let url = self
+            .server
+            .join("v1/")?
+            .join("blocks/")?
+            .join(&format!("{block_id}/"))?
+            .join("proposer")?;
+
+        self.get_opt(url).await
+    }
+
+    pub async fn get_block_reward(
+        &self,
+        block_id: BlockId,
+    ) -> Result<Option<WatchBlockRewards>, Error> {
+        let url = self
+            .server
+            .join("v1/")?
+            .join("blocks/")?
+            .join(&format!("{block_id}/"))?
+            .join("rewards")?;
+
+        self.get_opt(url).await
+    }
+
+    pub async fn get_block_packing(
+        &self,
+        block_id: BlockId,
+    ) -> Result<Option<WatchBlockPacking>, Error> {
+        let url = self
+            .server
+            .join("v1/")?
+            .join("blocks/")?
+            .join(&format!("{block_id}/"))?
+            .join("packing")?;
+
+        self.get_opt(url).await
+    }
+
+    pub async fn get_all_validators(&self) -> Result<Option<Vec<WatchValidator>>, Error> {
+        let url = self.server.join("v1/")?.join("validators/")?.join("all")?;
+
+        self.get_opt(url).await
+    }
+
+    pub async fn get_attestations(
+        &self,
+        epoch: i32,
+    ) -> Result<Option<Vec<WatchAttestation>>, Error> {
+        let url = self
+            .server
+            .join("v1/")?
+            .join("validators/")?
+            .join("all/")?
+            .join("attestation/")?
+            .join(&format!("{epoch}"))?;
+
+        self.get_opt(url).await
+    }
+}