Create a dedicated crate for the extension

contracts/extension/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "serai-extension"
+version = "0.1.0"
+description = "An ink! extension for exposing Serai to ink"
+license = "AGPL-3.0-only"
+authors = ["Luke Parker <lukeparker5132@gmail.com>"]
+edition = "2021"
+
+[dependencies]
+ink_env = { version = "3", default-features = false }
+ink_lang = { version = "3", default-features = false }
+
+[features]
+default = ["std"]
+std = ["ink_env/std"]
+ink-as-dependency = []

contracts/extension/src/lib.rs

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+#![cfg_attr(not(feature = "std"), no_std)]
+
+use ink_lang as ink;
+use ink_env::{Environment, DefaultEnvironment, AccountId};
+
+#[ink::chain_extension]
+pub trait SeraiExtension {
+  type ErrorCode = ();
+
+  /// Returns the amount of active validators on the current chain.
+  #[ink(extension = 0, handle_status = false, returns_result = false)]
+  fn active_validators_len() -> u16;
+
+  /// Returns the ID for the current validator set for the current chain.
+  // TODO: Decide if this should be an increasing unsigned integer instead of a hash.
+  #[ink(extension = 1, handle_status = false, returns_result = false)]
+  fn validator_set_id() -> [u8; 32];
+
+  /// Returns if the specified account is an active validator for the current chain.
+  #[ink(extension = 2, handle_status = false, returns_result = false)]
+  fn is_active_validator(account: &AccountId) -> bool;
+}
+
+pub struct SeraiEnvironment;
+impl Environment for SeraiEnvironment {
+  const MAX_EVENT_TOPICS: usize = <DefaultEnvironment as Environment>::MAX_EVENT_TOPICS;
+
+  type AccountId = <DefaultEnvironment as Environment>::AccountId;
+  type Balance = <DefaultEnvironment as Environment>::Balance;
+  type Hash = <DefaultEnvironment as Environment>::Hash;
+  type BlockNumber = <DefaultEnvironment as Environment>::BlockNumber;
+  type Timestamp = <DefaultEnvironment as Environment>::Timestamp;
+
+  type ChainExtension = SeraiExtension;
+}