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// Copyright 2019-2021 Parity Technologies (UK) Ltd.
// This file is part of Parity Bridges Common.

// Parity Bridges Common is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity Bridges Common 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 General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.

//! Defines traits which represent a common interface for Substrate pallets which want to
//! incorporate bridge functionality.

use crate::bridges::runtime::ChainId;
use codec::{Codec, Decode, Encode, EncodeLike, MaxEncodedLen};
use core::{clone::Clone, cmp::Eq, default::Default, fmt::Debug};
use scale_info::TypeInfo;
#[cfg(feature = "std")]
use serde::{Deserialize, Serialize};
use sp_consensus_grandpa::{AuthorityList, ConsensusLog, SetId, GRANDPA_ENGINE_ID};
use sp_runtime::{generic::OpaqueDigestItemId, traits::Header as HeaderT, RuntimeDebug};
pub mod justification;

/// A type that can be used as a parameter in a dispatchable function.
///
/// When using `decl_module` all arguments for call functions must implement this trait.
pub trait Parameter: Codec + EncodeLike + Clone + Eq + Debug {}

impl<T> Parameter for T where T: Codec + EncodeLike + Clone + Eq + Debug {}

/// A GRANDPA Authority List and ID.
#[derive(Default, Encode, Decode, RuntimeDebug, TypeInfo, PartialEq, Eq, Clone)]
#[cfg_attr(feature = "std", derive(Serialize, Deserialize))]
pub struct AuthoritySet {
    /// List of GRANDPA authorities for the current round.
    pub authorities: AuthorityList,
    /// Monotonic identifier of the current GRANDPA authority set.
    pub set_id: SetId,
}

impl MaxEncodedLen for AuthoritySet {
    fn max_encoded_len() -> usize {
        4096
    }
}
impl AuthoritySet {
    /// Create a new GRANDPA Authority Set.
    pub fn new(authorities: AuthorityList, set_id: SetId) -> Self {
        Self {
            authorities,
            set_id,
        }
    }
}

/// Data required for initializing the bridge pallet.
///
/// The bridge needs to know where to start its sync from, and this provides that initial context.
#[derive(Default, Encode, Decode, RuntimeDebug, TypeInfo, PartialEq, Eq, Clone)]
#[cfg_attr(feature = "std", derive(Serialize, Deserialize))]
pub struct InitializationData<H: HeaderT> {
    /// The header from which we should start syncing.
    pub header: H,
    /// The initial authorities of the pallet.
    pub authority_list: AuthorityList,
    /// The ID of the initial authority set.
    pub set_id: SetId,
    /// Should the pallet block transaction immediately after initialization.
    pub is_halted: bool,
    /// 4-byte gateway identifier.
    pub gateway_id: ChainId,
}

/// base trait for verifying transaction inclusion proofs.
pub trait InclusionProofVerifier {
    /// Transaction type.
    type Transaction: Parameter;
    /// Transaction inclusion proof type.
    type TransactionInclusionProof: Parameter;

    /// Verify that transaction is a part of given block.
    ///
    /// Returns Some(transaction) if proof is valid and None otherwise.
    fn verify_transaction_inclusion_proof(
        proof: &Self::TransactionInclusionProof,
    ) -> Option<Self::Transaction>;
}

/// A trait for pallets which want to keep track of finalized headers from a bridged chain.
pub trait HeaderChain<H, E> {
    /// Get the best finalized header known to the header chain.
    fn best_finalized() -> H;

    /// Get the best authority set known to the header chain.
    fn authority_set() -> AuthoritySet;

    /// Write a header finalized by GRANDPA to the underlying pallet storage.
    fn append_header(header: H) -> Result<(), E>;
}

impl<H: Default, E> HeaderChain<H, E> for () {
    fn best_finalized() -> H {
        H::default()
    }

    fn authority_set() -> AuthoritySet {
        AuthoritySet::default()
    }

    fn append_header(_header: H) -> Result<(), E> {
        Ok(())
    }
}

/// Abstract finality proof that is justifying block finality.
pub trait FinalityProof<Number>: Clone + Send + Sync + Debug {
    /// Return number of header that this proof is generated for.
    fn target_header_number(&self) -> Number;
}

/// Find header digest that schedules next GRANDPA authorities set.
pub fn find_grandpa_authorities_scheduled_change<H: HeaderT>(
    header: &H,
) -> Option<sp_consensus_grandpa::ScheduledChange<H::Number>> {
    let id = OpaqueDigestItemId::Consensus(&GRANDPA_ENGINE_ID);

    let filter_log = |log: ConsensusLog<H::Number>| match log {
        ConsensusLog::ScheduledChange(change) => Some(change),
        _ => None,
    };

    // find the first consensus digest with the right ID which converts to
    // the right kind of consensus log.
    header
        .digest()
        .convert_first(|l| l.try_to(id).and_then(filter_log))
}

/// Inclusion proofs of different tries
#[derive(Encode, Decode, Clone, Debug, PartialEq, Eq, TypeInfo)]
#[cfg_attr(feature = "std", derive(Serialize, Deserialize))]
pub enum ProofTriePointer {
    /// Proof is a merkle path in the state trie
    State,
    /// Proof is a merkle path in the transaction trie (extrisics in Substrate)
    Transaction,
    /// Proof is a merkle path in the receipts trie (in Substrate logs are entries in state trie, this doesn't apply)
    Receipts,
}