// Copyright (C) Moondance Labs Ltd.

// This file is part of Tanssi.

// Tanssi 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.

// Tanssi 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 Tanssi.  If not, see <http://www.gnu.org/licenses/>

//! A staking pallet based on pools of shares.

//!

//! This pallet works with pools inspired by AMM liquidity pools to easily distribute

//! rewards with support for both non-compounding and compounding rewards.

//!

//! Each candidate internally have 3 pools:

//! - a pool for all delegators willing to auto compound.

//! - a pool for all delegators not willing to auto compound.

//! - a pool for all delegators that are in the process of removing stake.

//!

//! When delegating the funds of the delegator are reserved, and shares allow to easily

//! distribute auto compounding rewards (by simply increasing the total shared amount)

//! and easily slash (each share loose part of its value). Rewards are distributed to an account

//! id dedicated to the staking pallet, and delegators can call an extrinsic to transfer their rewards

//! to their own account (but as reserved). Keeping funds reserved in user accounts allow them to

//! participate in other processes such as gouvernance.

#![cfg_attr(not(feature = "std"), no_std)]

extern crate alloc;

mod calls;

mod candidate;

mod pools;

pub mod traits;

#[cfg(test)]

mod mock;

#[cfg(test)]

mod tests;

#[cfg(feature = "runtime-benchmarks")]

mod benchmarking;

#[cfg(any(feature = "migrations", feature = "try-runtime"))]

pub mod migrations;

pub mod weights;

use frame_support::pallet;

pub use weights::WeightInfo;

pub use {

    candidate::EligibleCandidate,

    pallet::*,

    pools::{ActivePoolKind, CandidateSummary, DelegatorCandidateSummary, PoolKind},

};

#[cfg(feature = "runtime-benchmarks")]

use frame_support::traits::fungible::Mutate;

pub mod pallet {

    use {

        super::*,

        crate::{

            traits::{IsCandidateEligible, Timer},

            weights::WeightInfo,

        },

        alloc::vec::Vec,

        calls::Calls,

        core::marker::PhantomData,

        frame_support::{

            pallet_prelude::*,

            storage::types::{StorageDoubleMap, StorageValue, ValueQuery},

            traits::{fungible, tokens::Balance, IsType},

            Blake2_128Concat,

        },

        frame_system::pallet_prelude::*,

        parity_scale_codec::{Decode, DecodeWithMemTracking, Encode, FullCodec},

        scale_info::TypeInfo,

        serde::{Deserialize, Serialize},

        sp_core::Get,

        sp_runtime::{BoundedVec, Perbill},

        tp_maths::MulDiv,

    };

    /// A reason for this pallet placing a hold on funds.

    #[pallet::composite_enum]

    pub enum HoldReason {

    }

    // Type aliases for better readability.

    pub type Candidate<T> = <T as frame_system::Config>::AccountId;

    pub type CreditOf<T> =

        fungible::Credit<<T as frame_system::Config>::AccountId, <T as Config>::Currency>;

    pub type Delegator<T> = <T as frame_system::Config>::AccountId;

    /// Key used by the `Pools` StorageDoubleMap, avoiding lots of maps.

    /// StorageDoubleMap first key is the account id of the candidate.

    #[derive(

        RuntimeDebug,

        PartialEq,

        Eq,

        Encode,

        Clone,

        Serialize,

        Deserialize,

        MaxEncodedLen,

    )]

    pub enum PoolsKey<A: FullCodec> {

        CandidateTotalStake,

        /// Amount of joining shares a delegator have for that candidate.

        JoiningShares { delegator: A },

        JoiningSharesSupply,

        JoiningSharesTotalStaked,

        /// Amount of currency held in the delegator account.

        JoiningSharesHeldStake { delegator: A },

        /// Amount of auto compounding shares a delegator have for that candidate.

        AutoCompoundingShares { delegator: A },

        AutoCompoundingSharesSupply,

        AutoCompoundingSharesTotalStaked,

        /// Amount of currency held in the delegator account.

        AutoCompoundingSharesHeldStake { delegator: A },

        /// Amount of manual rewards shares a delegator have for that candidate.

        ManualRewardsShares { delegator: A },

        ManualRewardsSharesSupply,

        ManualRewardsSharesTotalStaked,

        /// Amount of currency held in the delegator account.

        ManualRewardsSharesHeldStake { delegator: A },

        /// Is safe to wrap around the maximum value of the balance type.

        ManualRewardsCounter,

        /// Value of the counter at the last time the delegator claimed its rewards or changed its amount of shares

        /// (changing the amount of shares automatically claims pending rewards).

        /// The difference between the checkpoint and the counter is the amount of claimable reward per share for

        /// that delegator.

        ManualRewardsCheckpoint { delegator: A },

        /// Amount of shares of that delegator in the leaving pool of that candidate.

        /// When leaving delegating funds are placed in the leaving pool until the leaving period is elapsed.

        /// While in the leaving pool the funds are still slashable.

        LeavingShares { delegator: A },

        LeavingSharesSupply,

        LeavingSharesTotalStaked,

        /// Amount of currency held in the delegator account.

        LeavingSharesHeldStake { delegator: A },

    }

    /// Key used by the "PendingOperations" StorageDoubleMap.

    /// StorageDoubleMap first key is the account id of the delegator who made the request.

    /// Value is the amount of shares in the joining/leaving pool.

    #[derive(

        RuntimeDebug,

        PartialEq,

        Eq,

        Encode,

        Clone,

        Serialize,

        Deserialize,

        MaxEncodedLen,

    )]

    #[allow(clippy::multiple_bound_locations)]

    pub enum PendingOperationKey<A: FullCodec, J: FullCodec, L: FullCodec> {

        /// Candidate requested to join the auto compounding pool of a candidate.

        JoiningAutoCompounding { candidate: A, at: J },

        /// Candidate requested to join the manual rewards pool of a candidate.

        JoiningManualRewards { candidate: A, at: J },

        /// Candidate requested to to leave a pool of a candidate.

        Leaving { candidate: A, at: L },

    }

    pub type PendingOperationKeyOf<T> = PendingOperationKey<

        <T as frame_system::Config>::AccountId,

        <<T as Config>::JoiningRequestTimer as Timer>::Instant,

        <<T as Config>::LeavingRequestTimer as Timer>::Instant,

    >;

    #[derive(

        PartialEq,

        Eq,

        Encode,

        Decode,

        Clone,

        Serialize,

        Deserialize,

    )]

    #[allow(clippy::multiple_bound_locations)]

    pub struct PendingOperationQuery<A: FullCodec, J: FullCodec, L: FullCodec> {

        pub delegator: A,

        pub operation: PendingOperationKey<A, J, L>,

    }

    pub type PendingOperationQueryOf<T> = PendingOperationQuery<

        <T as frame_system::Config>::AccountId,

        <<T as Config>::JoiningRequestTimer as Timer>::Instant,

        <<T as Config>::LeavingRequestTimer as Timer>::Instant,

    >;

    /// Allow calls to be performed using either share amounts or stake.

    /// When providing stake, calls will convert them into share amounts that are

    /// worth up to the provided stake. The amount of stake thus will be at most the provided

    /// amount.

    #[derive(

        RuntimeDebug,

        PartialEq,

        Eq,

        Encode,

        Clone,

        Serialize,

        Deserialize,

    )]

    pub enum SharesOrStake<T> {

        Shares(T),

        Stake(T),

    }

    /// Wrapper type for an amount of shares.

    #[derive(

        Default,

        PartialEq,

        Eq,

        Encode,

        Decode,

        Copy,

        Clone,

        Serialize,

        Deserialize,

    )]

    pub struct Shares<T>(pub T);

    /// Wrapper type for an amount of staked currency.

    #[derive(

        Default,

        PartialEq,

        Eq,

        Encode,

        Decode,

        Copy,

        Clone,

        Serialize,

        Deserialize,

    )]

    pub struct Stake<T>(pub T);

    const STORAGE_VERSION: StorageVersion = StorageVersion::new(1);

    /// Pooled Staking pallet.

    #[pallet::storage_version(STORAGE_VERSION)]

    pub struct Pallet<T>(PhantomData<T>);

    #[pallet::config]

    pub trait Config: frame_system::Config {

        /// Overarching event type

        type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;

        /// The currency type.

        /// Shares will use the same Balance type.

        type Currency: fungible::Inspect<Self::AccountId, Balance = Self::Balance>

            + fungible::Mutate<Self::AccountId>

            + fungible::Balanced<Self::AccountId>

            + fungible::MutateHold<Self::AccountId, Reason = Self::RuntimeHoldReason>;

        /// Same as Currency::Balance. Must impl `MulDiv` which perform

        /// multiplication followed by division using a bigger type to avoid

        /// overflows.

        type Balance: Balance + MulDiv;

        /// Account holding Currency of all delegators.

        #[pallet::constant]

        type StakingAccount: Get<Self::AccountId>;

        /// When creating the first Shares for a candidate the supply can be arbitrary.

        /// Picking a value too low will make an higher supply, which means each share will get

        /// less rewards, and rewards calculations will have more impactful rounding errors.

        /// Picking a value too high is a barrier of entry for staking.

        #[pallet::constant]

        type InitialManualClaimShareValue: Get<Self::Balance>;

        /// When creating the first Shares for a candidate the supply can arbitrary.

        /// Picking a value too high is a barrier of entry for staking, which will increase overtime

        /// as the value of each share will increase due to auto compounding.

        #[pallet::constant]

        type InitialAutoCompoundingShareValue: Get<Self::Balance>;

        /// Minimum amount of stake a Candidate must delegate (stake) towards itself. Not reaching

        /// this minimum prevents from being elected.

        #[pallet::constant]

        type MinimumSelfDelegation: Get<Self::Balance>;

        /// Part of the rewards that will be sent exclusively to the collator.

        #[pallet::constant]

        type RewardsCollatorCommission: Get<Perbill>;

        /// The overarching runtime hold reason.

        type RuntimeHoldReason: From<HoldReason>;

        /// Condition for when a joining request can be executed.

        type JoiningRequestTimer: Timer;

        /// Condition for when a leaving request can be executed.

        type LeavingRequestTimer: Timer;

        /// All eligible candidates are stored in a sorted list that is modified each time

        /// delegations changes. It is safer to bound this list, in which case eligible candidate

        /// could fall out of this list if they have less stake than the top `EligibleCandidatesBufferSize`

        /// eligible candidates. One of this top candidates leaving will then not bring the dropped candidate

        /// in the list. An extrinsic is available to manually bring back such dropped candidate.

        #[pallet::constant]

        type EligibleCandidatesBufferSize: Get<u32>;

        /// Additional filter for candidates to be eligible.

        type EligibleCandidatesFilter: IsCandidateEligible<Self::AccountId>;

        type WeightInfo: WeightInfo;

    }

    /// Keeps a list of all eligible candidates, sorted by the amount of stake backing them.

    /// This can be quickly updated using a binary search, and allow to easily take the top

    /// `MaxCollatorSetSize`.

    pub type SortedEligibleCandidates<T: Config> = StorageValue<

        _,

        BoundedVec<

            candidate::EligibleCandidate<Candidate<T>, T::Balance>,

            T::EligibleCandidatesBufferSize,

        >,

        ValueQuery,

    >;

    /// Pools balances.

    pub type Pools<T: Config> = StorageDoubleMap<

        _,

        Blake2_128Concat,

        Candidate<T>,

        Blake2_128Concat,

        PoolsKey<T::AccountId>,

        T::Balance,

        ValueQuery,

    >;

    /// Pending operations balances.

    /// Balances are expressed in joining/leaving shares amounts.

    pub type PendingOperations<T: Config> = StorageDoubleMap<

        _,

        Blake2_128Concat,

        Delegator<T>,

        Blake2_128Concat,

        PendingOperationKeyOf<T>,

        T::Balance,

        ValueQuery,

    >;

    /// Summary of a delegator's delegation.

    /// Used to quickly fetch all delegations of a delegator.

    pub type DelegatorCandidateSummaries<T: Config> = StorageDoubleMap<

        _,

        Blake2_128Concat,

        Delegator<T>,

        Blake2_128Concat,

        Candidate<T>,

        DelegatorCandidateSummary,

        ValueQuery,

    >;

    /// Summary of a candidate state.

    pub type CandidateSummaries<T: Config> =

        StorageMap<_, Blake2_128Concat, Candidate<T>, CandidateSummary, ValueQuery>;

    /// Pauses the ability to modify pools through extrinsics.

    ///

    /// Currently added only to run the multi-block migration to compute

    /// `DelegatorCandidateSummaries` and `CandidateSummaries`. It will NOT

    /// prevent to distribute rewards, which is fine as the reward distribution

    /// process doesn't alter the pools in a way that will mess with the migration.

    pub type PausePoolsExtrinsics<T: Config> = StorageValue<_, bool, ValueQuery>;

    pub enum Event<T: Config> {

        /// Stake of the candidate has changed, which may have modified its

        /// position in the eligible candidates list.

        UpdatedCandidatePosition {

            candidate: Candidate<T>,

            stake: T::Balance,

            self_delegation: T::Balance,

            before: Option<u32>,

            after: Option<u32>,

        },

        /// User requested to delegate towards a candidate.

        RequestedDelegate {

            candidate: Candidate<T>,

            delegator: Delegator<T>,

            pool: ActivePoolKind,

            pending: T::Balance,

        },

        /// Delegation request was executed. `staked` has been properly staked

        /// in `pool`, while the rounding when converting to shares has been

        /// `released`.

        ExecutedDelegate {

            candidate: Candidate<T>,

            delegator: Delegator<T>,

            pool: ActivePoolKind,

            staked: T::Balance,

            released: T::Balance,

        },

        /// User requested to undelegate from a candidate.

        /// Stake was removed from a `pool` and is `pending` for the request

        /// to be executed. The rounding when converting to leaving shares has

        /// been `released` immediately.

        RequestedUndelegate {

            candidate: Candidate<T>,

            delegator: Delegator<T>,

            from: ActivePoolKind,

            pending: T::Balance,

            released: T::Balance,

        },

        /// Undelegation request was executed.

        ExecutedUndelegate {

            candidate: Candidate<T>,

            delegator: Delegator<T>,

            released: T::Balance,

        },

        /// Stake of that Candidate increased.

        IncreasedStake {

            candidate: Candidate<T>,

            stake_diff: T::Balance,

        },

        /// Stake of that Candidate decreased.

        DecreasedStake {

            candidate: Candidate<T>,

            stake_diff: T::Balance,

        },

        /// Delegator staked towards a Candidate for AutoCompounding Shares.

        StakedAutoCompounding {

            candidate: Candidate<T>,

            delegator: Delegator<T>,

            shares: T::Balance,

            stake: T::Balance,

        },

        /// Delegator unstaked towards a candidate with AutoCompounding Shares.

        UnstakedAutoCompounding {

            candidate: Candidate<T>,

            delegator: Delegator<T>,

            shares: T::Balance,

            stake: T::Balance,

        },

        /// Delegator staked towards a candidate for ManualRewards Shares.

        StakedManualRewards {

            candidate: Candidate<T>,

            delegator: Delegator<T>,

            shares: T::Balance,

            stake: T::Balance,

        },

        /// Delegator unstaked towards a candidate with ManualRewards Shares.

        UnstakedManualRewards {

            candidate: Candidate<T>,

            delegator: Delegator<T>,

            shares: T::Balance,

            stake: T::Balance,

        },

        /// Collator has been rewarded.

        RewardedCollator {

            collator: Candidate<T>,

            auto_compounding_rewards: T::Balance,

            manual_claim_rewards: T::Balance,

        },

        /// Delegators have been rewarded.

        RewardedDelegators {

            collator: Candidate<T>,

            auto_compounding_rewards: T::Balance,

            manual_claim_rewards: T::Balance,

        },

        /// Rewards manually claimed.

        ClaimedManualRewards {

            candidate: Candidate<T>,

            delegator: Delegator<T>,

            rewards: T::Balance,

        },

        /// Swapped between AutoCompounding and ManualReward shares

        SwappedPool {

            candidate: Candidate<T>,

            delegator: Delegator<T>,

            source_pool: ActivePoolKind,

            source_shares: T::Balance,

            source_stake: T::Balance,

            target_shares: T::Balance,

            target_stake: T::Balance,

            pending_leaving: T::Balance,

            released: T::Balance,

        },

    }

    pub enum Error<T> {

        RequestCannotBeExecuted(u16),

    }

    impl<T: Config> From<tp_maths::OverflowError> for Error<T> {

    }

    impl<T: Config> From<tp_maths::UnderflowError> for Error<T> {

    }

    impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {

        #[cfg(feature = "try-runtime")]

        fn try_state(_n: BlockNumberFor<T>) -> Result<(), sp_runtime::TryRuntimeError> {

            use alloc::collections::btree_set::BTreeSet;

            use frame_support::storage_alias;

            let mut all_candidates = BTreeSet::new();

            for (candidate, _k2) in Pools::<T>::iter_keys() {

                all_candidates.insert(candidate);

            }

            for candidate in all_candidates {

                pools::check_candidate_consistency::<T>(&candidate)?;

            }

            // Sorted storage items are sorted

            fn assert_is_sorted_and_unique<T: Ord>(x: &[T], name: &str) {

                assert!(

                    x.windows(2).all(|w| w[0] < w[1]),

                    "sorted list not sorted or not unique: {}",

                    name,

                );

            }

            assert_is_sorted_and_unique(

                &SortedEligibleCandidates::<T>::get(),

                "SortedEligibleCandidates",

            );

            if Pallet::<T>::on_chain_storage_version() < 1 {

                return Ok(());

            }

            // Summaries updated dynamically matches summaries generated entirely from shares.

            #[storage_alias(pallet_name)]

            pub type TryStateDelegatorSummaries<T: Config> = StorageDoubleMap<

                Pallet<T>,

                Blake2_128Concat,

                Delegator<T>,

                Blake2_128Concat,

                Candidate<T>,

                DelegatorCandidateSummary,

                ValueQuery,

            >;

            #[storage_alias(pallet_name)]

            pub type TryStateCandidateSummaries<T: Config> =

                StorageMap<Pallet<T>, Blake2_128Concat, Candidate<T>, CandidateSummary, ValueQuery>;

            assert!(

                migrations::stepped_generate_summaries::<

                    T,

                    TryStateDelegatorSummaries<T>,

                    TryStateCandidateSummaries<T>,

                >(

                    None,

                    &mut frame_support::weights::WeightMeter::new(), // call with no limit on weight

                )

                .expect("to generate summaries without errors")

                .is_none(),

                "failed to generate all summaries"

            );

            let mut candidate_summaries_count = 0;

            for (candidate, summary) in TryStateCandidateSummaries::<T>::iter() {

                candidate_summaries_count += 1;

                assert_eq!(

                    CandidateSummaries::<T>::get(&candidate),

                    summary,

                    "candidate summary for {candidate:?} didn't match"

                );

            }

            assert_eq!(

                candidate_summaries_count,

                CandidateSummaries::<T>::iter().count(),

                "count of candidate summaries didn't match"

            );

            let mut delegator_summaries_count = 0;

            for (delegator, candidate, summary) in TryStateDelegatorSummaries::<T>::iter() {

                delegator_summaries_count += 1;

                assert_eq!(

                    DelegatorCandidateSummaries::<T>::get(&delegator, &candidate),

                    summary,

                    "delegator summary for {delegator:?} to {candidate:?} didn't match"

                );

            }

            assert_eq!(

                delegator_summaries_count,

                DelegatorCandidateSummaries::<T>::iter().count(),

                "count of delegator summaries didn't match"

            );

            Ok(())

        }

    }

    impl<T: Config> Pallet<T> {

        #[pallet::call_index(0)]

        #[pallet::weight(T::WeightInfo::rebalance_hold())]

        #[allow(clippy::useless_conversion)]

        pub fn rebalance_hold(

            origin: OriginFor<T>,

            candidate: Candidate<T>,

            delegator: Delegator<T>,

            pool: PoolKind,

        }

        #[pallet::call_index(1)]

        #[pallet::weight(T::WeightInfo::request_delegate())]

        #[allow(clippy::useless_conversion)]

        pub fn request_delegate(

            origin: OriginFor<T>,

            candidate: Candidate<T>,

            pool: ActivePoolKind,

            stake: T::Balance,

        }

        /// Execute pending operations can incur in claim manual rewards per operation, we simply add the worst case

        #[pallet::call_index(2)]

        #[pallet::weight(T::WeightInfo::execute_pending_operations(operations.len() as u32).saturating_add(T::WeightInfo::claim_manual_rewards(operations.len() as u32)))]

        #[allow(clippy::useless_conversion)]

        pub fn execute_pending_operations(

            origin: OriginFor<T>,

            operations: Vec<PendingOperationQueryOf<T>>,

        }

        /// Request undelegate can incur in either claim manual rewards or hold rebalances, we simply add the worst case

        #[pallet::call_index(3)]

        #[pallet::weight(T::WeightInfo::request_undelegate().saturating_add(T::WeightInfo::claim_manual_rewards(1).max(T::WeightInfo::rebalance_hold())))]

        #[allow(clippy::useless_conversion)]

        pub fn request_undelegate(

            origin: OriginFor<T>,

            candidate: Candidate<T>,

            pool: ActivePoolKind,

            amount: SharesOrStake<T::Balance>,

        }

        #[pallet::call_index(4)]

        #[pallet::weight(T::WeightInfo::claim_manual_rewards(pairs.len() as u32))]

        #[allow(clippy::useless_conversion)]

        pub fn claim_manual_rewards(

            origin: OriginFor<T>,

            pairs: Vec<(Candidate<T>, Delegator<T>)>,

        }

        #[pallet::call_index(5)]

        #[pallet::weight(T::WeightInfo::update_candidate_position(candidates.len() as u32))]

        #[allow(clippy::useless_conversion)]

        pub fn update_candidate_position(

            origin: OriginFor<T>,

            candidates: Vec<Candidate<T>>,

        }

        #[pallet::call_index(6)]

        #[pallet::weight(T::WeightInfo::swap_pool())]

        #[allow(clippy::useless_conversion)]

        pub fn swap_pool(

            origin: OriginFor<T>,

            candidate: Candidate<T>,

            source_pool: ActivePoolKind,

            amount: SharesOrStake<T::Balance>,

        }

    }

    impl<T: Config> Pallet<T> {

            use pools::Pool;

                PoolKind::AutoCompounding => {

                }

                PoolKind::ManualRewards => {

                }

            }

    }

    impl<T: Config> tp_traits::DistributeRewards<Candidate<T>, CreditOf<T>> for Pallet<T> {

    }

    impl<T: Config> tp_traits::StakingCandidateHelper<Candidate<T>> for Pallet<T> {

        #[cfg(feature = "runtime-benchmarks")]

        fn make_collator_eligible_candidate(collator: &Candidate<T>) {

            use alloc::vec;

            let minimum_stake = T::MinimumSelfDelegation::get();

            T::Currency::set_balance(collator, minimum_stake + minimum_stake);

            T::EligibleCandidatesFilter::make_candidate_eligible(collator, true);

            Calls::<T>::request_delegate(

                collator.clone(),

                collator.clone(),

                ActivePoolKind::AutoCompounding,

                minimum_stake,

            )

            .expect("request_delegate should not fail in benchmarks");

            let timer = T::JoiningRequestTimer::now();

            T::JoiningRequestTimer::skip_to_elapsed();

            Calls::<T>::execute_pending_operations(vec![PendingOperationQuery {

                delegator: collator.clone(),

                operation: PendingOperationKey::JoiningAutoCompounding {

                    candidate: collator.clone(),

                    at: timer.clone(),

                },

            }])

            .expect("execute_pending_operations should not fail in benchmarks");

        }

    }

}