use crate::{
    containers::{
        dependency::Dependency,
        price_sort::PriceSort,
        time_sort::TimeSort,
    },
    ports::TxPoolDb,
    service::TxStatusChange,
    types::*,
    Config,
    Error,
    TxInfo,
};
use fuel_core_metrics::txpool_metrics::TXPOOL_METRICS;
use fuel_core_types::{
    fuel_tx::{
        Chargeable,
        Transaction,
        UniqueIdentifier,
    },
    fuel_vm::checked_transaction::{
        CheckedTransaction,
        IntoChecked,
    },
    services::txpool::{
        ArcPoolTx,
        InsertionResult,
    },
};
use std::{
    cmp::Reverse,
    collections::HashMap,
    ops::Deref,
    sync::Arc,
};

#[derive(Debug, Clone)]
pub struct TxPool<DB> {
    by_hash: HashMap<TxId, TxInfo>,
    by_gas_price: PriceSort,
    by_time: TimeSort,
    by_dependency: Dependency,
    config: Config,
    database: DB,
}

impl<DB> TxPool<DB>
where
    DB: TxPoolDb,
{
    pub fn new(config: Config, database: DB) -> Self {
        let max_depth = config.max_depth;

        Self {
            by_hash: HashMap::new(),
            by_gas_price: PriceSort::default(),
            by_time: TimeSort::default(),
            by_dependency: Dependency::new(max_depth, config.utxo_validation),
            config,
            database,
        }
    }

    pub fn txs(&self) -> &HashMap<TxId, TxInfo> {
        &self.by_hash
    }

    pub fn dependency(&self) -> &Dependency {
        &self.by_dependency
    }

    #[tracing::instrument(level = "info", skip_all, fields(tx_id = %tx.id()), ret, err)]
    // this is atomic operation. Return removed(pushed out/replaced) transactions
    fn insert_inner(
        &mut self,
        // TODO: Pass `&Transaction`
        tx: Arc<Transaction>,
    ) -> anyhow::Result<InsertionResult> {
        let current_height = self.database.current_block_height()?;

        if tx.is_mint() {
            return Err(Error::NotSupportedTransactionType.into())
        }

        // verify gas price is at least the minimum
        self.verify_tx_min_gas_price(&tx)?;

        let tx: CheckedTransaction = if self.config.utxo_validation {
            tx.deref()
                .clone()
                .into_checked(
                    current_height.into(),
                    &self.config.chain_config.transaction_parameters,
                    &self.config.chain_config.gas_costs,
                )?
                .into()
        } else {
            tx.deref()
                .clone()
                .into_checked_basic(
                    current_height.into(),
                    &self.config.chain_config.transaction_parameters,
                )?
                .into()
        };

        let tx = Arc::new(match tx {
            CheckedTransaction::Script(script) => PoolTransaction::Script(script),
            CheckedTransaction::Create(create) => PoolTransaction::Create(create),
            CheckedTransaction::Mint(_) => unreachable!(),
        });

        if !tx.is_computed() {
            return Err(Error::NoMetadata.into())
        }

        // verify max gas is less than block limit
        if tx.max_gas() > self.config.chain_config.block_gas_limit {
            return Err(Error::NotInsertedMaxGasLimit {
                tx_gas: tx.max_gas(),
                block_limit: self.config.chain_config.block_gas_limit,
            }
            .into())
        }

        if self.by_hash.contains_key(&tx.id()) {
            return Err(Error::NotInsertedTxKnown.into())
        }

        let mut max_limit_hit = false;
        // check if we are hitting limit of pool
        if self.by_hash.len() >= self.config.max_tx {
            max_limit_hit = true;
            // limit is hit, check if we can push out lowest priced tx
            let lowest_price = self.by_gas_price.lowest_value().unwrap_or_default();
            if lowest_price >= tx.price() {
                return Err(Error::NotInsertedLimitHit.into())
            }
        }
        if self.config.metrics {
            TXPOOL_METRICS
                .gas_price_histogram
                .observe(tx.price() as f64);

            TXPOOL_METRICS
                .tx_size_histogram
                .observe(tx.metered_bytes_size() as f64);
        }
        // check and insert dependency
        let rem = self
            .by_dependency
            .insert(&self.by_hash, &self.database, &tx)?;
        let info = TxInfo::new(tx.clone());
        self.by_gas_price.insert(&info);
        self.by_time.insert(&info);
        self.by_hash.insert(tx.id(), info);

        // if some transaction were removed so we don't need to check limit
        let removed = if rem.is_empty() {
            if max_limit_hit {
                // remove last tx from sort
                let rem_tx = self.by_gas_price.lowest_tx().unwrap(); // safe to unwrap limit is hit
                self.remove_inner(&rem_tx);
                vec![rem_tx]
            } else {
                Vec::new()
            }
        } else {
            // remove ret from by_hash and from by_price
            for rem in rem.iter() {
                self.remove_tx(&rem.id());
            }

            rem
        };

        Ok(InsertionResult {
            inserted: tx,
            removed,
        })
    }

    /// Return all sorted transactions that are includable in next block.
    pub fn sorted_includable(&self) -> impl Iterator<Item = ArcPoolTx> + '_ {
        self.by_gas_price
            .sort
            .iter()
            .rev()
            .map(|(_, tx)| tx.clone())
    }

    pub fn remove_inner(&mut self, tx: &ArcPoolTx) -> Vec<ArcPoolTx> {
        self.remove_by_tx_id(&tx.id())
    }

    /// remove transaction from pool needed on user demand. Low priority
    // TODO: Seems this function should be recursive
    pub fn remove_by_tx_id(&mut self, tx_id: &TxId) -> Vec<ArcPoolTx> {
        if let Some(tx) = self.remove_tx(tx_id) {
            let removed = self
                .by_dependency
                .recursively_remove_all_dependencies(&self.by_hash, tx.tx().clone());
            for remove in removed.iter() {
                self.remove_tx(&remove.id());
            }
            return removed
        }
        Vec::new()
    }

    fn remove_tx(&mut self, tx_id: &TxId) -> Option<TxInfo> {
        let info = self.by_hash.remove(tx_id);
        if let Some(info) = &info {
            self.by_time.remove(info);
            self.by_gas_price.remove(info);
        }

        info
    }

    /// Removes transaction from `TxPool` with assumption that it is committed into the blockchain.
    // TODO: Don't remove recursively dependent transactions on block commit.
    //  The same logic should be fixed in the `select_transactions`.
    //  This method is used during `select_transactions`, so we need to handle the case
    //  when transaction was skipped during block execution(`ExecutionResult.skipped_transaction`).
    pub fn remove_committed_tx(&mut self, tx_id: &TxId) -> Vec<ArcPoolTx> {
        self.remove_by_tx_id(tx_id)
    }

    fn verify_tx_min_gas_price(&mut self, tx: &Transaction) -> Result<(), Error> {
        let price = match tx {
            Transaction::Script(script) => script.price(),
            Transaction::Create(create) => create.price(),
            Transaction::Mint(_) => unreachable!(),
        };
        if self.config.metrics {
            // Gas Price metrics are recorded here to avoid double matching for
            // every single transaction, but also means metrics aren't collected on gas
            // price if there is no minimum gas price
            TXPOOL_METRICS.gas_price_histogram.observe(price as f64);
        }
        if price < self.config.min_gas_price {
            return Err(Error::NotInsertedGasPriceTooLow)
        }
        Ok(())
    }

    #[tracing::instrument(level = "info", skip_all)]
    /// Import a set of transactions from network gossip or GraphQL endpoints.
    pub fn insert(
        &mut self,
        tx_status_sender: &TxStatusChange,
        txs: &[Arc<Transaction>],
    ) -> Vec<anyhow::Result<InsertionResult>> {
        // Check if that data is okay (witness match input/output, and if recovered signatures ara valid).
        // should be done before transaction comes to txpool, or before it enters RwLocked region.
        let mut res = Vec::new();
        for tx in txs.iter() {
            res.push(self.insert_inner(tx.clone()))
        }
        // announce to subscribers
        for ret in res.iter() {
            match ret {
                Ok(InsertionResult { removed, inserted }) => {
                    for removed in removed {
                        // small todo there is possibility to have removal reason (ReplacedByHigherGas, DependencyRemoved)
                        // but for now it is okay to just use Error::Removed.
                        tx_status_sender.send_squeezed_out(removed.id(), Error::Removed);
                    }
                    tx_status_sender.send_submitted(inserted.id());
                }
                Err(_) => {
                    // @dev should not broadcast tx if error occurred
                }
            }
        }
        res
    }

    /// find all tx by its hash
    pub fn find(&self, hashes: &[TxId]) -> Vec<Option<TxInfo>> {
        let mut res = Vec::with_capacity(hashes.len());
        for hash in hashes {
            res.push(self.txs().get(hash).cloned());
        }
        res
    }

    pub fn find_one(&self, hash: &TxId) -> Option<TxInfo> {
        self.txs().get(hash).cloned()
    }

    /// find all dependent tx and return them with requested dependencies in one list sorted by Price.
    pub fn find_dependent(&self, hashes: &[TxId]) -> Vec<ArcPoolTx> {
        let mut seen = HashMap::new();
        {
            for hash in hashes {
                if let Some(tx) = self.txs().get(hash) {
                    self.dependency().find_dependent(
                        tx.tx().clone(),
                        &mut seen,
                        self.txs(),
                    );
                }
            }
        }
        let mut list: Vec<_> = seen.into_values().collect();
        // sort from high to low price
        list.sort_by_key(|tx| Reverse(tx.price()));

        list
    }

    /// The number of pending transaction in the pool.
    pub fn pending_number(&self) -> usize {
        self.by_hash.len()
    }

    /// The amount of gas in all includable transactions combined
    pub fn consumable_gas(&self) -> u64 {
        self.by_hash.values().map(|tx| tx.limit()).sum()
    }

    /// Return all sorted transactions that are includable in next block.
    /// This is going to be heavy operation, use it only when needed.
    pub fn includable(&mut self) -> impl Iterator<Item = ArcPoolTx> + '_ {
        self.sorted_includable()
    }

    /// When block is updated we need to receive all spend outputs and remove them from txpool.
    pub fn block_update(
        &mut self,
        tx_status_sender: &TxStatusChange,
        transactions: &[TxId],
        // spend_outputs: [Input], added_outputs: [AddedOutputs]
    ) {
        for tx_id in transactions {
            tx_status_sender.send_complete(*tx_id);
            self.remove_committed_tx(tx_id);
        }
    }

    /// remove transaction from pool needed on user demand. Low priority
    pub fn remove(
        &mut self,
        tx_status_sender: &TxStatusChange,
        tx_ids: &[TxId],
    ) -> Vec<ArcPoolTx> {
        let mut removed = Vec::new();
        for tx_id in tx_ids {
            let rem = self.remove_by_tx_id(tx_id);
            tx_status_sender.send_squeezed_out(*tx_id, Error::Removed);
            removed.extend(rem.into_iter());
        }
        removed
    }

    /// Remove all old transactions from the pool.
    pub fn prune_old_txs(&mut self) -> Vec<ArcPoolTx> {
        let deadline = tokio::time::Instant::now() - self.config.transaction_ttl;

        let mut result = vec![];

        while let Some((oldest_time, oldest_tx)) = self.by_time.lowest() {
            let oldest_tx = oldest_tx.clone();
            if oldest_time.created() <= &deadline {
                let removed = self.remove_inner(&oldest_tx);
                result.extend(removed.into_iter());
            } else {
                break
            }
        }

        result
    }
}

#[cfg(test)]
mod test_helpers;
#[cfg(test)]
mod tests;