//! # NPoS — pallet_staking config (FIX-6 Stage 2b, DC ORIGIN_CHAIN_NPOS_V1)
//!
//! **Infra DORMIDA** (David ratificó NPoS-5 2026-06-12): toda la maquinaria de
//! staking cableada y lista, pero el set de validadores arranca FIJO
//! (`invulnerables` + `ForceEra::ForceNone`) — la cadena corre PoA-equivalente
//! hasta que se cumplan los 5 criterios empíricos de Phase 2 (CHN-1). La
//! activación de la elección-por-stake = un governance flag (`ForceNew`).
//!
//! La **emisión** migra a [`OriginEraPayout`] (por-era, preserva la tasa lineal
//! de FIX-6 Stage 1: `BlockReward` por bloque) con el `RewardRemainder`
//! ([`DealWithEraRemainder`]) ruteando treasury 20% + subsidy 10% — esto
//! mantiene el pool `og/subsy` alimentado (que el `OriginFeeAdapter` de Stage 2a
//! consume; sin él se rompería el subsidio anti-clasista #16).
//!
//! Versiones verificadas (stable2509-3): pallet-staking 43.0.0 +
//! frame-election-provider-support 43.0.0 + sp-staking 41.0.0.

use frame_election_provider_support::onchain;
use frame_election_provider_support::{
    bounds::{ElectionBounds, ElectionBoundsBuilder},
    SequentialPhragmen,
};
use frame_support::parameter_types;
use frame_support::traits::fungible::{Balanced, Credit};
use frame_support::traits::tokens::imbalance::{Imbalance, OnUnbalanced};
use frame_support::traits::{ConstBool, ConstU32, Nothing};
use frame_system::EnsureRoot;
use sp_runtime::traits::AccountIdConversion;
use sp_runtime::Perbill;

use crate::configs::{
    EmissionBlockReward, EmissionSubsidyPalletId, GovernanceTreasuryPalletId, MILLISECS_PER_BLOCK,
};
use crate::{Balance, Balances, ChainAccountId, Runtime, RuntimeEvent, RuntimeHoldReason, Timestamp};

/// Crédito fungible de Balances (el tipo de imbalance que staking entrega a los
/// handlers `RewardRemainder`/`Slash` en stable2509 — API hold-based, NO el
/// `NegativeImbalance` clásico).
type CreditOf = Credit<ChainAccountId, Balances>;

// ─── EraPayout custom: emisión lineal (preserva FIX-6 Stage 1) ───────

/// Emisión por-era que preserva EXACTAMENTE la tasa de FIX-6 Stage 1:
/// `BlockReward` (10 OGC) por bloque, repartido 70% a los validadores
/// (`validator_payout`) y 30% al `RewardRemainder` (`rest` → treasury+subsidy).
/// Lineal-absoluta (fija por tiempo, no curva ideal-staking-rate de Polkadot):
/// `total_era = BlockReward × (era_duration_millis / MILLISECS_PER_BLOCK)`.
/// Ignora `total_staked`/`total_issuance` a propósito (la disinflación natural
/// viene de que el reward fijo pesa menos sobre un issuance creciente).
pub struct OriginEraPayout;

impl pallet_staking::EraPayout<Balance> for OriginEraPayout {
    fn era_payout(
        _total_staked: Balance,
        _total_issuance: Balance,
        era_duration_millis: u64,
    ) -> (Balance, Balance) {
        let blocks = (era_duration_millis / MILLISECS_PER_BLOCK) as u128;
        let total = EmissionBlockReward::get().saturating_mul(blocks);
        // 70% a validadores (AuthorShareBps = 7_000), 30% al remainder.
        let validator_payout = total.saturating_mul(7_000) / 10_000;
        let rest = total.saturating_sub(validator_payout);
        (validator_payout, rest)
    }
}

// ─── RewardRemainder: split treasury (20%) + subsidy (10%) ───────────

parameter_types! {
    /// Cuenta-tesorería (og/gvtry) — la MISMA de governance/emission.
    pub TreasuryAccount: ChainAccountId =
        GovernanceTreasuryPalletId::get().into_account_truncating();
    /// Cuenta del subsidy pool (og/subsy) — alimenta el subsidio #16 que el
    /// OriginFeeAdapter de Stage 2a consume.
    pub SubsidyAccount: ChainAccountId =
        EmissionSubsidyPalletId::get().into_account_truncating();
}

/// Handler del `rest` de cada era (30% del total emitido): lo reparte 2/3
/// treasury + 1/3 subsidy (= 20% + 10% del total de emisión, replicando el
/// split per-block de FIX-6 Stage 1). **Crítico #16**: mantiene `og/subsy`
/// alimentado bajo NPoS — sin esto el adapter de fees degradaría a
/// `pool_covered=0` y el usuario pagaría el 100%.
pub struct DealWithEraRemainder;

/// Reparte el `rest` de una era (30% de la emisión) en `(treasury, subsidy)` =
/// 2/3 + 1/3 = 20% + 10% del total. El residual (dust del redondeo entero) va al
/// subsidy — favorece el pool anti-clasista #16, cero pérdida. Función pura para
/// testear la invariante constitucional sin montar un mock runtime.
pub(crate) fn era_remainder_split(rest: u128) -> (u128, u128) {
    let treasury = rest.saturating_mul(2) / 3;
    let subsidy = rest.saturating_sub(treasury); // residual al subsidy
    (treasury, subsidy)
}

impl OnUnbalanced<CreditOf> for DealWithEraRemainder {
    fn on_nonzero_unbalanced(amount: CreditOf) {
        let (treasury_part, _) = era_remainder_split(amount.peek());
        let (to_treasury, to_subsidy) = amount.split(treasury_part);
        // resolve deposita cada crédito en su cuenta vault; si falla, el crédito
        // se descarta (drop = burn) — nunca se duplica ni se pierde a un tercero.
        let _ = Balances::resolve(&TreasuryAccount::get(), to_treasury);
        let _ = Balances::resolve(&SubsidyAccount::get(), to_subsidy);
    }
}

// ─── onchain ElectionProvider (dormido: ForceNone no dispara elección) ─

/// ZST de config para `OnChainExecution`. Con `ForceEra::ForceNone` la elección
/// casi nunca corre; el provider existe porque el Config lo exige. El genérico
/// de `OnChainExecution<T>` es ESTE struct (NO el Runtime): `System = Runtime`,
/// `DataProvider = Staking`.
pub struct OnChainSeqPhragmen;

parameter_types! {
    /// Bounds de la elección on-chain. Con ForceNone es defensivo; acota voters/
    /// targets para que `elect` nunca panic-falle por tamaño.
    pub OnChainElectionBounds: ElectionBounds =
        ElectionBoundsBuilder::default().build();
}

impl onchain::Config for OnChainSeqPhragmen {
    type Sort = ConstBool<true>;
    type System = Runtime;
    type Solver = SequentialPhragmen<ChainAccountId, Perbill>;
    type MaxBackersPerWinner = ConstU32<512>;
    // Debe ser >= MaxValidatorSet (150) — reusa el mismo techo.
    type MaxWinnersPerPage = MaxValidatorSet;
    type DataProvider = crate::Staking;
    type WeightInfo = ();
    type Bounds = OnChainElectionBounds;
}

// ─── Benchmarking config (obligatorio en no-std) ─────────────────────

/// `BenchmarkingConfig` propio (el `TestBenchmarkingConfig` de pallet_staking
/// solo existe bajo `std`; un runtime wasm lo exige siempre).
pub struct OriginStakingBenchmarkingConfig;

impl pallet_staking::BenchmarkingConfig for OriginStakingBenchmarkingConfig {
    type MaxValidators = ConstU32<150>;
    type MaxNominators = ConstU32<1_000>;
}

// ─── pallet_staking::Config ──────────────────────────────────────────

parameter_types! {
    /// NPoS-6 (David ratificó): techo de 150 validadores activos (CHN-1).
    pub const MaxValidatorSet: u32 = 150;
    /// NPoS-8: 6 sessions × 4h = era de 24h.
    pub const SessionsPerEra: u32 = 6;
    /// NPoS-8: bonding de 7 eras = 7 días (PILAR_4 §6.1).
    pub const BondingDuration: u32 = 7;
    /// SlashDeferDuration < BondingDuration. 0 en dormido (sin slashes; los
    /// invulnerables no se slashan). Se calibra al activar NPoS (NPoS-9).
    pub const SlashDeferDuration: u32 = 0;
}

impl pallet_staking::Config for Runtime {
    // Balances: Currency es fungible hold-based; OldCurrency solo para migración.
    type Currency = Balances;
    type OldCurrency = Balances;
    type RuntimeHoldReason = RuntimeHoldReason;
    type CurrencyBalance = Balance;
    type UnixTime = Timestamp;
    type CurrencyToVote = sp_staking::currency_to_vote::U128CurrencyToVote;

    // Elección on-chain (dormida bajo ForceNone). DataProvider = la propia staking.
    type ElectionProvider = onchain::OnChainExecution<OnChainSeqPhragmen>;
    type GenesisElectionProvider = onchain::OnChainExecution<OnChainSeqPhragmen>;
    type VoterList = pallet_staking::UseNominatorsAndValidatorsMap<Runtime>;
    type TargetList = pallet_staking::UseValidatorsMap<Runtime>;
    type NominationsQuota = pallet_staking::FixedNominationsQuota<16>;

    // Emisión: migra a EraPayout (preserva la tasa de FIX-6 Stage 1).
    type EraPayout = OriginEraPayout;
    type RewardRemainder = DealWithEraRemainder;
    // Invulnerables nunca se slashan; rewards van por payout, no por estos hooks.
    type Slash = ();
    type Reward = ();

    type SessionsPerEra = SessionsPerEra;
    type BondingDuration = BondingDuration;
    type SlashDeferDuration = SlashDeferDuration;
    type AdminOrigin = EnsureRoot<ChainAccountId>;

    // DORMIDO (Paso A): sin session-swap → staking no avanza eras. El swap a
    // `Self` + `Session` (que enciende EraPayout) es el siguiente paso.
    type SessionInterface = ();
    type NextNewSession = ();

    type MaxExposurePageSize = ConstU32<64>;
    type MaxValidatorSet = MaxValidatorSet;
    type MaxUnlockingChunks = ConstU32<32>;
    type MaxControllersInDeprecationBatch = ConstU32<100>;
    type HistoryDepth = ConstU32<84>;

    type EventListeners = ();
    type Filter = Nothing;
    type BenchmarkingConfig = OriginStakingBenchmarkingConfig;
    type WeightInfo = pallet_staking::weights::SubstrateWeight<Runtime>;
    type RuntimeEvent = RuntimeEvent;
}

// ─── Tests de la aritmética constitucional (verificar 70/20/10 ANTES de
//     activar NPoS en Paso C/D — hoy la emisión está dormida) ──────────

#[cfg(test)]
mod tests {
    use super::*;
    use pallet_staking::EraPayout as _;

    const ERA_24H_MILLIS: u64 = 24 * 60 * 60 * 1_000; // 86_400_000

    #[test]
    fn era_payout_preserva_tasa_lineal_y_split_70_30() {
        // Era de 24h = 14_400 bloques de 6s.
        let (validator_payout, rest) = OriginEraPayout::era_payout(0, 0, ERA_24H_MILLIS);
        let blocks = (ERA_24H_MILLIS / MILLISECS_PER_BLOCK) as u128;
        assert_eq!(blocks, 14_400, "14_400 bloques en 24h a 6s");
        let total = EmissionBlockReward::get().saturating_mul(blocks);
        // 70% validadores / 30% rest, y sin pérdida: validator + rest == total.
        assert_eq!(validator_payout, total * 7_000 / 10_000, "70% a validadores");
        assert_eq!(validator_payout + rest, total, "cero pérdida: validator + rest == total");
        // El rest es exactamente el 30% (con el dust del redondeo capturado).
        assert_eq!(rest, total - validator_payout);
    }

    #[test]
    fn era_payout_no_overflow_en_era_larga() {
        // Era de 1 año (peor caso plausible): no debe panic ni saturar mal.
        let one_year_millis: u64 = 365 * ERA_24H_MILLIS;
        let (validator_payout, rest) = OriginEraPayout::era_payout(0, 0, one_year_millis);
        let blocks = (one_year_millis / MILLISECS_PER_BLOCK) as u128;
        let total = EmissionBlockReward::get().saturating_mul(blocks);
        assert_eq!(validator_payout + rest, total, "sin overflow: invariante intacta");
        // ~5.256M bloques/año × 10 OGC = ~5.256e25, lejos del techo u128.
        assert!(total < u128::MAX / 2);
    }

    #[test]
    fn remainder_split_20_10_del_total() {
        // El rest = 30% del total. Su split 2/3+1/3 = 20%+10% del total.
        // Ejemplo redondo: total=100 → rest=30 → treasury=20, subsidy=10.
        let (treasury, subsidy) = era_remainder_split(30);
        assert_eq!(treasury, 20, "2/3 del rest = 20% del total");
        assert_eq!(subsidy, 10, "1/3 del rest = 10% del total");
        assert_eq!(treasury + subsidy, 30, "cero pérdida");
    }

    #[test]
    fn remainder_split_residual_al_subsidy_anti_clasista() {
        // Con rest no divisible por 3, el dust va al SUBSIDY (#16), no al treasury.
        let (treasury, subsidy) = era_remainder_split(31);
        assert_eq!(treasury, 20, "floor(31*2/3) = 20");
        assert_eq!(subsidy, 11, "el residual (11) favorece el pool anti-clasista");
        assert_eq!(treasury + subsidy, 31, "cero pérdida");
    }

    #[test]
    fn remainder_split_invariante_para_montos_reales() {
        // Para un rest real (30% de una era de 24h) la invariante se mantiene.
        let (_, rest) = OriginEraPayout::era_payout(0, 0, ERA_24H_MILLIS);
        let (treasury, subsidy) = era_remainder_split(rest);
        assert_eq!(treasury + subsidy, rest, "cero pérdida en montos reales");
        // treasury ≈ 2× subsidy (dust aparte).
        assert!(treasury >= subsidy, "treasury (20%) >= subsidy (10%)");
        assert!(treasury <= subsidy.saturating_mul(2).saturating_add(2), "ratio ~2:1");
    }
}