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// Copyright (c) The Diem Core Contributors
// SPDX-License-Identifier: Apache-2.0

// Copyright 2021 Conflux Foundation. All rights reserved.
// Conflux is free software and distributed under GNU General Public License.
// See http://www.gnu.org/licenses/

//! This file defines transaction store APIs that are related to committed
//! signed transactions.

use crate::{
    change_set::ChangeSet,
    errors::DiemDbError,
    schema::{
        transaction::TransactionSchema,
        transaction_by_account::TransactionByAccountSchema,
    },
};
use anyhow::{ensure, format_err, Result};
use diem_types::{
    account_address::AccountAddress,
    block_metadata::BlockMetadata,
    transaction::{Transaction, Version},
};
use schemadb::{SchemaIterator, DB};
use std::sync::Arc;

#[derive(Debug)]
pub(crate) struct TransactionStore {
    db: Arc<DB>,
}

impl TransactionStore {
    pub fn new(db: Arc<DB>) -> Self { Self { db } }

    /// Gets the version of a transaction by the sender `address` and
    /// `sequence_number`.
    pub fn lookup_transaction_by_account(
        &self, address: AccountAddress, sequence_number: u64,
        ledger_version: Version,
    ) -> Result<Option<Version>> {
        if let Some(version) = self
            .db
            .get::<TransactionByAccountSchema>(&(address, sequence_number))?
        {
            if version <= ledger_version {
                return Ok(Some(version));
            }
        }

        Ok(None)
    }

    /// Get signed transaction given `version`
    pub fn get_transaction(&self, version: Version) -> Result<Transaction> {
        self.db.get::<TransactionSchema>(&version)?.ok_or_else(|| {
            DiemDbError::NotFound(format!("Txn {}", version)).into()
        })
    }

    /// Gets an iterator that yields `num_transactions` transactions starting
    /// from `start_version`.
    pub fn get_transaction_iter(
        &self, start_version: Version, num_transactions: usize,
    ) -> Result<TransactionIter> {
        let mut iter = self.db.iter::<TransactionSchema>(Default::default())?;
        iter.seek(&start_version)?;
        Ok(TransactionIter {
            inner: iter,
            expected_next_version: start_version,
            end_version: start_version
                .checked_add(num_transactions as u64)
                .ok_or_else(|| {
                    format_err!("Too many transactions requested.")
                })?,
        })
    }

    /// Returns the block metadata carried on the block metadata transaction at
    /// or preceding `version`, together with the version of the block
    /// metadata transaction. Returns None if there's no such transaction at
    /// or preceding `version` (it's likely the genesis version 0).
    pub fn get_block_metadata(
        &self, version: Version,
    ) -> Result<Option<(Version, BlockMetadata)>> {
        // Maximum TPS from benchmark is around 1000.
        const MAX_VERSIONS_TO_SEARCH: usize = 1000 * 3;

        // Linear search via `DB::rev_iter()` here, NOT expecting performance
        // hit, due to the fact that the iterator caches data block and
        // that there are limited number of transactions in each block.
        let mut iter =
            self.db.rev_iter::<TransactionSchema>(Default::default())?;
        iter.seek(&version)?;
        for res in iter.take(MAX_VERSIONS_TO_SEARCH) {
            let (v, txn) = res?;
            if let Transaction::BlockMetadata(block_meta) = txn {
                return Ok(Some((v, block_meta)));
            } else if v == 0 {
                return Ok(None);
            }
        }

        Err(DiemDbError::NotFound(format!(
            "BlockMetadata preceding version {}",
            version
        ))
        .into())
    }

    /// Save signed transaction at `version`
    pub fn put_transaction(
        &self, version: Version, transaction: &Transaction, cs: &mut ChangeSet,
    ) -> Result<()> {
        if let Transaction::UserTransaction(txn) = transaction {
            // TODO(lpl): Find a proper way to keep account-related info.
            cs.batch.put::<TransactionByAccountSchema>(
                &(txn.sender(), 0),
                &version,
            )?;
        }
        cs.batch.put::<TransactionSchema>(&version, &transaction)?;

        Ok(())
    }
}

pub struct TransactionIter<'a> {
    inner: SchemaIterator<'a, TransactionSchema>,
    expected_next_version: Version,
    end_version: Version,
}

impl<'a> TransactionIter<'a> {
    fn next_impl(&mut self) -> Result<Option<Transaction>> {
        if self.expected_next_version >= self.end_version {
            return Ok(None);
        }

        let ret = match self.inner.next().transpose()? {
            Some((version, transaction)) => {
                ensure!(
                    version == self.expected_next_version,
                    "Transaction versions are not consecutive.",
                );
                self.expected_next_version += 1;
                Some(transaction)
            }
            None => None,
        };

        Ok(ret)
    }
}

impl<'a> Iterator for TransactionIter<'a> {
    type Item = Result<Transaction>;

    fn next(&mut self) -> Option<Self::Item> { self.next_impl().transpose() }
}

#[cfg(test)]
mod test;