use fs2::FileExt;
pub use std::fs::OpenOptions;
use std::{
    collections::HashMap,
    fs::File,
    mem::replace,
    ops::{Bound, RangeBounds},
    path::Path,
    str,
    sync::Arc,
};

pub use crate::id::RecRef;
use crate::index::{
    config::{IndexType, IndexTypeId, Indexes, ValueMode, INDEX_DATA_PREFIX, INDEX_META_PREFIX},
    keeper::{IndexKeeper, IndexRawIter},
    tree::{
        nodes::{PageIter, PageIterBack, Value},
        Index,
    },
};
use crate::transaction::{
    PreparedState, SyncMode, Transaction, TxRead,
    TxSegCheck::{CREATED, DROPPED, NONE},
};
use crate::{
    address::Address,
    allocator::Allocator,
    config::{Config, TransactionConfig},
    discref::{Device, DiscRef, MemRef, PageOps, PAGE_METADATA_SIZE},
    error::{PRes, PersyError},
    id::{IndexId, PersyId, SegmentId, ToIndexId, ToSegmentId},
    io::{
        InfallibleRead, InfallibleReadFormat, InfallibleReadVarInt, InfallibleWrite, InfallibleWriteFormat,
        InfallibleWriteVarInt,
    },
    journal::{Journal, JournalId, JOURNAL_PAGE_EXP},
    record_scanner::{SegmentRawIter, SegmentSnapshotRawIter, TxSegmentRawIter},
    snapshot::{release_snapshot, EntryCase, SegmentSnapshop, SnapshotId, Snapshots},
};

#[cfg(feature = "background_ops")]
use crate::background::BackgroundOps;

const DEFAULT_PAGE_EXP: u8 = 10; // 2^10

pub struct PersyImpl {
    config: Arc<Config>,
    journal: Arc<Journal>,
    address: Address,
    indexes: Indexes,
    allocator: Arc<Allocator>,
    snapshots: Arc<Snapshots>,
    #[cfg(feature = "background_ops")]
    background_ops: BackgroundOps<SnapshotId>,
}

pub struct TxFinalize {
    transaction: Transaction,
    prepared: PreparedState,
}

/// Possible state of a transaction in the log
#[derive(PartialEq, Debug, Clone)]
pub enum RecoverStatus {
    /// Started but not completed
    Started,
    /// Successfully prepared
    PrepareCommit,
    /// rollback-ed
    Rollback,
    /// Successfully committed after prepared
    Commit,
    /// Successfully cleaned up resources after commit
    Cleanup,
}

/// Possible option for recover a transaction in prepared commit state
#[derive(PartialEq, Debug)]
pub enum CommitStatus {
    Rollback,
    Commit,
}
pub struct RecoverImpl {
    tx_id: HashMap<Vec<u8>, JournalId>,
    transactions: HashMap<JournalId, (RecoverStatus, Transaction, Option<CommitStatus>)>,
    order: Vec<JournalId>,
    journal_pages: Vec<u64>,
}

impl RecoverImpl {
    pub fn apply<C>(&mut self, recover: C) -> PRes<()>
    where
        C: Fn(&Vec<u8>) -> bool,
    {
        for (id, status) in self.list_transactions()? {
            if status == RecoverStatus::PrepareCommit {
                if recover(&id) {
                    self.commit(id)?;
                } else {
                    self.rollback(id)?;
                }
            }
        }
        Ok(())
    }

    pub fn list_transactions(&self) -> PRes<Vec<(Vec<u8>, RecoverStatus)>> {
        let mut res = Vec::new();
        for id in &self.order {
            if let Some((id, status)) = self
                .transactions
                .get(id)
                .map(|(s, tx, _)| (tx.meta_id().clone(), s.clone()))
            {
                res.push((id, status));
            }
        }
        Ok(res)
    }

    pub fn status(&self, tx_id: Vec<u8>) -> PRes<Option<RecoverStatus>> {
        if let Some(id) = self.tx_id.get(&tx_id) {
            Ok(self.transactions.get(id).map(|(s, _, _)| s.clone()))
        } else {
            Ok(None)
        }
    }

    pub fn commit(&mut self, tx_id: Vec<u8>) -> PRes<()> {
        if let Some(id) = self.tx_id.get(&tx_id) {
            if let Some(tx) = self.transactions.get_mut(id) {
                tx.2 = Some(CommitStatus::Commit);
            }
        }
        Ok(())
    }

    pub fn rollback(&mut self, tx_id: Vec<u8>) -> PRes<()> {
        if let Some(id) = self.tx_id.get(&tx_id) {
            if let Some(tx) = self.transactions.get_mut(id) {
                tx.2 = Some(CommitStatus::Rollback);
            }
        }
        Ok(())
    }
}

#[derive(Clone)]
/// Index definition details
pub struct IndexInfo {
    pub id: IndexId,
    pub value_mode: ValueMode,
    pub key_type: IndexTypeId,
    pub value_type: IndexTypeId,
}

#[cfg(feature = "background_ops")]
fn create_background_ops(
    journal: Arc<Journal>,
    allocator: Arc<Allocator>,
    snapshots: Arc<Snapshots>,
) -> PRes<BackgroundOps<SnapshotId>> {
    let all_sync = allocator.clone();
    BackgroundOps::new(
        move || all_sync.disc().sync(),
        move |all: &[SnapshotId]| {
            for snap in all {
                release_snapshot(*snap, &snapshots, &allocator, &journal)?;
            }
            Ok(())
        },
    )
}

impl PersyImpl {
    pub fn create(path: &Path) -> PRes<()> {
        let f = OpenOptions::new().write(true).read(true).create_new(true).open(path)?;
        PersyImpl::create_from_file(f)
    }

    pub fn create_from_file(f: File) -> PRes<()> {
        f.try_lock_exclusive()?;
        PersyImpl::init_file(f)?;
        Ok(())
    }

    fn init_file(fl: File) -> PRes<()> {
        PersyImpl::init(Box::new(DiscRef::new(fl)?))?;
        Ok(())
    }

    fn init(device: Box<dyn Device>) -> PRes<Box<dyn Device>> {
        // root_page is every time 0
        let root_page = device.create_page_raw(DEFAULT_PAGE_EXP)?;
        let (allocator_page, allocator) = Allocator::init(device, &Config::new())?;
        let address_page = Address::init(&allocator)?;
        let journal_page = Journal::init(&allocator)?;
        {
            let mut root = allocator.disc().load_page_raw(root_page, DEFAULT_PAGE_EXP)?;
            // Version of the disc format
            root.write_u16(0);
            // Position of the start of address structure
            root.write_u64(address_page);
            // Start of the Log data, if shutdown well this will be every time 0
            root.write_u64(journal_page);
            root.write_u64(allocator_page);
            allocator.flush_page(root)?;
            // TODO: check this never go over the first page
        }
        allocator.disc().sync()?;
        Ok(allocator.release())
    }

    fn new(disc: Box<dyn Device>, config: Config) -> PRes<PersyImpl> {
        let address_page;
        let journal_page;
        let allocator_page;
        {
            let mut pg = disc.load_page_raw(0, DEFAULT_PAGE_EXP)?;
            pg.read_u16(); //THIS NOW is 0 all the times
            address_page = pg.read_u64();
            journal_page = pg.read_u64();
            allocator_page = pg.read_u64();
        }
        let config = Arc::new(config);
        let allocator = Arc::new(Allocator::new(disc, &config, allocator_page)?);
        let address = Address::new(&allocator, &config, address_page)?;
        let journal = Arc::new(Journal::new(&allocator, journal_page)?);
        let indexes = Indexes::new(&config);
        let snapshots = Arc::new(Snapshots::new());
        #[cfg(feature = "background_ops")]
        let background_ops = create_background_ops(journal.clone(), allocator.clone(), snapshots.clone())?;
        Ok(PersyImpl {
            config,
            journal,
            address,
            indexes,
            allocator,
            snapshots,
            #[cfg(feature = "background_ops")]
            background_ops,
        })
    }

    fn recover(&self) -> PRes<RecoverImpl> {
        let mut commit_order = Vec::new();
        let mut transactions = HashMap::new();
        let journal = &self.journal;
        let jp = journal.recover(|record, id| {
            let tx = transactions
                .entry(id.clone())
                .or_insert_with(|| (RecoverStatus::Started, Transaction::recover(id.clone()), None));
            tx.0 = match record.recover(&mut tx.1) {
                Err(_) => RecoverStatus::Rollback,
                Ok(_) if tx.0 == RecoverStatus::Rollback => RecoverStatus::Rollback,
                Ok(x) => match x {
                    RecoverStatus::Started => RecoverStatus::Started,
                    RecoverStatus::PrepareCommit => {
                        commit_order.push(id.clone());
                        RecoverStatus::PrepareCommit
                    }
                    RecoverStatus::Rollback => RecoverStatus::Rollback,
                    RecoverStatus::Commit => {
                        commit_order.push(id.clone());
                        RecoverStatus::Commit
                    }
                    RecoverStatus::Cleanup => RecoverStatus::Cleanup,
                },
            }
        })?;

        let mut transactions_id = HashMap::new();
        for (id, (_, tx, _)) in &transactions {
            transactions_id.insert(tx.meta_id().clone(), id.clone());
        }
        Ok(RecoverImpl {
            tx_id: transactions_id,
            transactions,
            order: commit_order,
            journal_pages: jp,
        })
    }
    pub fn final_recover(&self, mut recover: RecoverImpl) -> PRes<()> {
        let mut last_id = None;
        let allocator = &self.allocator;
        for id in recover.order {
            if let Some((status, mut tx, choosed)) = recover.transactions.remove(&id) {
                if status == RecoverStatus::PrepareCommit {
                    if choosed == Some(CommitStatus::Commit) || choosed.is_none() {
                        let prepared = tx.recover_prepare(self)?;
                        tx.recover_commit(self, prepared)?;
                        last_id = Some(id);
                    } else {
                        tx.recover_rollback(self)?;
                    }
                } else if status == RecoverStatus::Commit {
                    tx.recover_cleanup(self)?;
                }
            }
        }
        for p in recover.journal_pages {
            allocator.remove_from_free(p, JOURNAL_PAGE_EXP)?;
        }

        for (_, (_, tx, _)) in recover.transactions.iter_mut() {
            tx.recover_rollback(self)?;
        }
        if let Some(id) = last_id {
            self.journal.finished_to_clean(&[id])?;
        }
        allocator.trim_free_at_end()?;
        Ok(())
    }

    pub fn open_recover(f: File, config: Config) -> PRes<(PersyImpl, RecoverImpl)> {
        f.try_lock_exclusive()?;
        let persy = PersyImpl::new(Box::new(DiscRef::new(f)?), config)?;
        let rec = persy.recover()?;
        Ok((persy, rec))
    }

    pub fn memory(config: Config) -> PRes<PersyImpl> {
        let device = PersyImpl::init(Box::new(MemRef::new()?))?;
        PersyImpl::new(device, config)
    }

    pub fn begin_with(&self, mut config: TransactionConfig) -> PRes<Transaction> {
        let journal = &self.journal;
        let strategy = if let Some(st) = config.tx_strategy {
            st
        } else {
            self.config.tx_strategy().clone()
        };
        let meta_id = if let Some(id) = replace(&mut config.transaction_id, None) {
            id
        } else {
            Vec::new()
        };
        let sync_mode = if Some(true) == config.background_sync {
            SyncMode::BackgroundSync
        } else {
            SyncMode::Sync
        };

        Ok(Transaction::new(journal, &strategy, sync_mode, meta_id)?)
    }

    pub fn create_segment(&self, tx: &mut Transaction, segment: &str) -> PRes<SegmentId> {
        match tx.exists_segment(segment) {
            DROPPED => {}
            CREATED(_) => {
                return Err(PersyError::SegmentAlreadyExists);
            }
            NONE => {
                if self.address.exists_segment(&segment)? {
                    return Err(PersyError::SegmentAlreadyExists);
                }
            }
        }
        let (segment_id, first_segment_page) = self.address.create_temp_segment(segment)?;
        tx.add_create_segment(&self.journal, segment, segment_id, first_segment_page)?;
        Ok(segment_id)
    }

    pub fn drop_segment(&self, tx: &mut Transaction, segment: &str) -> PRes<()> {
        let (_, segment_id) = self.check_segment_tx(tx, segment)?;
        tx.add_drop_segment(&self.journal, segment, segment_id)?;
        Ok(())
    }

    pub fn exists_segment(&self, segment: &str) -> PRes<bool> {
        self.address.exists_segment(segment)
    }

    pub fn exists_segment_tx(&self, tx: &Transaction, segment: &str) -> PRes<bool> {
        match tx.exists_segment(segment) {
            DROPPED => Ok(false),
            CREATED(_) => Ok(true),
            NONE => self.address.exists_segment(segment),
        }
    }
    pub fn exists_index(&self, index: &str) -> PRes<bool> {
        self.exists_segment(&format!("{}{}", INDEX_META_PREFIX, index))
    }

    pub fn exists_index_tx(&self, tx: &Transaction, index: &str) -> PRes<bool> {
        self.exists_segment_tx(tx, &format!("{}{}", INDEX_META_PREFIX, index))
    }

    pub fn solve_segment_id(&self, segment: impl ToSegmentId) -> PRes<SegmentId> {
        segment.to_segment_id(&self.address)
    }

    pub fn solve_segment_id_tx(&self, tx: &Transaction, segment: impl ToSegmentId) -> PRes<SegmentId> {
        let (sid, _) = segment.to_segment_id_tx(self, tx)?;
        Ok(sid)
    }

    pub fn solve_segment_id_snapshot(&self, snapshot: SnapshotId, segment: impl ToSegmentId) -> PRes<SegmentId> {
        segment.to_segment_id_snapshot(&self.snapshots, snapshot)
    }

    pub fn solve_index_id(&self, index: impl ToIndexId) -> PRes<IndexId> {
        index.to_index_id(&self.address)
    }

    pub fn solve_index_id_tx(&self, tx: &Transaction, index: impl ToIndexId) -> PRes<(IndexId, bool)> {
        index.to_index_id_tx(self, tx)
    }

    pub fn solve_index_id_snapshot(&self, snapshot: SnapshotId, index: impl ToIndexId) -> PRes<IndexId> {
        index.to_index_id_snapshot(&self.snapshots, snapshot)
    }

    /// check if a segment exist persistent or in tx.
    ///
    /// @return true if the segment was created in tx.
    pub fn check_segment_tx(&self, tx: &Transaction, segment: &str) -> PRes<(bool, SegmentId)> {
        match tx.exists_segment(segment) {
            DROPPED => Err(PersyError::SegmentNotFound),
            CREATED(segment_id) => Ok((true, segment_id)),
            NONE => self
                .address
                .segment_id(segment)?
                .map_or(Err(PersyError::SegmentNotFound), |id| Ok((false, id))),
        }
    }

    pub fn write_record_metadata(len: u64, id: &RecRef) -> Vec<u8> {
        let mut val = Vec::new();
        val.write_u8(0);
        val.write_varint_u64(len);
        id.write(&mut val);
        val
    }
    pub fn read_record_metadata(meta: &mut dyn InfallibleRead) -> (u64, RecRef) {
        let _metadata_version = meta.read_u8();
        let len = meta.read_varint_u64();
        let id = RecRef::read(meta);
        (len, id)
    }

    pub fn insert_record(&self, tx: &mut Transaction, segment: impl ToSegmentId, rec: &[u8]) -> PRes<RecRef> {
        let (segment_id, in_tx) = segment.to_segment_id_tx(self, tx)?;
        let len = rec.len() as u64;
        let allocator = &self.allocator;
        let address = &self.address;
        let (rec_ref, maybe_new_page) = if in_tx {
            address.allocate_temp(segment_id)
        } else {
            address.allocate(segment_id)
        }?;
        let metadata = PersyImpl::write_record_metadata(len, &rec_ref);
        let allocation_exp = exp_from_content_size(len + metadata.len() as u64);
        let mut pg = allocator.allocate(allocation_exp)?;
        let page = pg.get_index();
        tx.add_insert(&self.journal, segment_id, &rec_ref, page)?;
        if let Some(new_page) = maybe_new_page {
            tx.add_new_segment_page(&self.journal, segment_id, new_page.new_page, new_page.previus_page)?;
        }
        pg.write_all(&metadata);
        pg.write_all(rec);
        allocator.flush_page(pg)?;
        Ok(rec_ref)
    }

    fn read_snapshot(&self) -> PRes<SnapshotId> {
        self.snapshots.current_snapshot()
    }

    pub fn snapshot(&self) -> PRes<SnapshotId> {
        let snapshot_id = self.snapshots.read_snapshot()?;
        let segs = self
            .address
            .snapshot_list()?
            .into_iter()
            .map(|(name, id, first_page)| SegmentSnapshop::new(&name, id, first_page))
            .collect::<Vec<_>>();
        self.snapshots.fill_segments(snapshot_id, &segs)?;
        Ok(snapshot_id)
    }

    pub fn release_snapshot(&self, snapshot_id: SnapshotId) -> PRes<()> {
        release_snapshot(snapshot_id, &self.snapshots, &self.allocator, &self.journal)
    }

    fn read_ref_segment(
        &self,
        tx: &Transaction,
        segment_id: SegmentId,
        rec_ref: &RecRef,
    ) -> PRes<Option<(u64, u16, SegmentId)>> {
        Ok(match tx.read(rec_ref) {
            TxRead::RECORD(rec) => Some((rec.0, rec.1, segment_id)),
            TxRead::DELETED => None,
            TxRead::NONE => self
                .address
                .read(rec_ref, segment_id)?
                .map(|(pos, version)| (pos, version, segment_id)),
        })
    }

    fn read_page(&self, match_id: &RecRef, page: u64) -> PRes<Option<Vec<u8>>> {
        self.read_page_fn(match_id, page, |x| Vec::from(x))
    }

    fn read_page_fn<T>(&self, match_id: &RecRef, page: u64, f: fn(&[u8]) -> T) -> PRes<Option<T>> {
        if let Some(mut pg) = self.allocator.load_page_not_free(page)? {
            let (len, id) = PersyImpl::read_record_metadata(&mut pg);
            if id.page == match_id.page && id.pos == match_id.pos {
                Ok(Some(f(pg.slice(len as usize))))
            } else {
                Ok(None)
            }
        } else {
            Ok(None)
        }
    }

    pub fn read_tx_internal_fn<T>(
        &self,
        tx: &Transaction,
        segment_id: SegmentId,
        id: &RecRef,
        f: fn(&[u8]) -> T,
    ) -> PRes<Option<(T, u16)>> {
        loop {
            if let Some((page, version, _)) = self.read_ref_segment(tx, segment_id, id)? {
                if let Some(record) = self.read_page_fn(id, page, f)? {
                    break Ok(Some((record, version)));
                }
            } else {
                break Ok(None);
            }
        }
    }

    pub fn read_tx_internal(
        &self,
        tx: &Transaction,
        segment_id: SegmentId,
        id: &RecRef,
    ) -> PRes<Option<(Vec<u8>, u16)>> {
        self.read_tx_internal_fn(tx, segment_id, id, |x| Vec::from(x))
    }

    pub fn read_tx(&self, tx: &mut Transaction, segment: SegmentId, id: &RecRef) -> PRes<Option<Vec<u8>>> {
        if let Some((rec, version)) = self.read_tx_internal(tx, segment, id)? {
            tx.add_read(&self.journal, segment, id, version)?;
            Ok(Some(rec))
        } else {
            Ok(None)
        }
    }

    pub fn lock_record(
        &self,
        tx: &mut Transaction,
        segment: impl ToSegmentId,
        id: &RecRef,
        version: u16,
    ) -> PRes<bool> {
        let segment_id = segment.to_segment_id(&self.address)?;
        tx.lock_record(&self.address, segment_id, id, version)
    }

    pub fn unlock_record(&self, tx: &mut Transaction, segment: impl ToSegmentId, id: &RecRef) -> PRes<()> {
        let segment_id = segment.to_segment_id(&self.address)?;
        tx.unlock_record(&self.address, segment_id, id)
    }

    pub fn read(&self, segment: SegmentId, rec_ref: &RecRef) -> PRes<Option<Vec<u8>>> {
        loop {
            if let Some((page, _)) = self.address.read(rec_ref, segment)? {
                if let Some(record) = self.read_page(rec_ref, page)? {
                    break Ok(Some(record));
                }
            } else {
                break Ok(None);
            }
        }
    }

    pub fn read_snap(&self, segment: SegmentId, rec_ref: &RecRef, snapshot: SnapshotId) -> PRes<Option<Vec<u8>>> {
        self.read_snap_fn(segment, rec_ref, snapshot, |x| Vec::from(x))
    }

    pub fn read_snap_fn<T>(
        &self,
        segment: SegmentId,
        rec_ref: &RecRef,
        snapshot: SnapshotId,
        f: fn(&[u8]) -> T,
    ) -> PRes<Option<T>> {
        let segment_id = segment;
        loop {
            if let Some(rec_vers) = self.snapshots.read(snapshot, rec_ref)? {
                match rec_vers.case {
                    EntryCase::Change(change) => {
                        if let Some(record) = self.read_page_fn(rec_ref, change.pos, f)? {
                            break Ok(Some(record));
                        }
                    }
                    EntryCase::Insert => {
                        break Ok(None);
                    }
                }
            } else if let Some((page, _)) = self.address.read(rec_ref, segment_id)? {
                if let Some(record) = self.read_page_fn(rec_ref, page, f)? {
                    break Ok(Some(record));
                }
            } else {
                break Ok(None);
            }
        }
    }

    pub fn scan(&self, segment: SegmentId) -> PRes<SegmentRawIter> {
        let read_snapshot = self.read_snapshot()?;
        Ok(SegmentRawIter::new(segment, self.address.scan(segment)?, read_snapshot))
    }

    pub fn scan_snapshot_index(&self, segment_id: SegmentId, snapshot: SnapshotId) -> PRes<SegmentSnapshotRawIter> {
        let res = if let Some(r) = self.snapshots.scan(snapshot, segment_id)? {
            r
        } else {
            self.address.scan(segment_id)?
        };
        Ok(SegmentSnapshotRawIter::new(segment_id, res, snapshot))
    }

    pub fn scan_snapshot(&self, segment_id: SegmentId, snapshot: SnapshotId) -> PRes<SegmentSnapshotRawIter> {
        let res = self.snapshots.scan(snapshot, segment_id)?.unwrap();
        Ok(SegmentSnapshotRawIter::new(segment_id, res, snapshot))
    }

    pub fn scan_tx<'a>(&'a self, tx: &'a Transaction, segment_id: SegmentId) -> PRes<TxSegmentRawIter> {
        let read_snapshot = self.read_snapshot()?;
        Ok(TxSegmentRawIter::new(
            tx,
            segment_id,
            self.address.scan(segment_id)?,
            read_snapshot,
        ))
    }

    pub fn update(&self, tx: &mut Transaction, segment: SegmentId, rec_ref: &RecRef, rec: &[u8]) -> PRes<()> {
        if let Some((_, version, segment)) = self.read_ref_segment(tx, segment, rec_ref)? {
            let allocator = &self.allocator;
            let journal = &self.journal;
            let len = rec.len();
            let metadata = PersyImpl::write_record_metadata(len as u64, &rec_ref);
            let allocation_exp = exp_from_content_size((len + metadata.len()) as u64);
            let mut pg = allocator.allocate(allocation_exp)?;
            let page = pg.get_index();
            tx.add_update(journal, segment, &rec_ref, page, version)?;
            pg.write_all(&metadata);
            pg.write_all(rec);
            allocator.flush_page(pg)
        } else {
            Err(PersyError::RecordNotFound(PersyId(rec_ref.clone())))
        }
    }

    pub fn delete(&self, tx: &mut Transaction, segment: SegmentId, rec_ref: &RecRef) -> PRes<()> {
        if let Some((_, version, seg)) = self.read_ref_segment(tx, segment, rec_ref)? {
            tx.add_delete(&self.journal, seg, &rec_ref, version)
        } else {
            Err(PersyError::RecordNotFound(PersyId(rec_ref.clone())))
        }
    }

    pub fn rollback(&self, mut tx: Transaction) -> PRes<()> {
        tx.rollback(self)
    }

    pub fn prepare(&self, tx: Transaction) -> PRes<TxFinalize> {
        let (tx, prepared) = tx.prepare(self)?;

        Ok(TxFinalize {
            transaction: tx,
            prepared,
        })
    }

    pub fn rollback_prepared(&self, finalizer: &mut TxFinalize) -> PRes<()> {
        let prepared = finalizer.prepared.clone();
        let tx = &mut finalizer.transaction;
        tx.rollback_prepared(self, prepared)
    }

    pub fn commit(&self, finalizer: &mut TxFinalize) -> PRes<()> {
        let prepared = finalizer.prepared.clone();
        let tx = &mut finalizer.transaction;
        tx.commit(self, prepared)
    }

    pub fn create_index<K, V>(&self, tx: &mut Transaction, index_name: &str, value_mode: ValueMode) -> PRes<()>
    where
        K: IndexType,
        V: IndexType,
    {
        Indexes::create_index::<K, V>(self, tx, index_name, 32, 128, value_mode)
    }

    pub fn drop_index(&self, tx: &mut Transaction, index_name: &str) -> PRes<()> {
        Indexes::drop_index(self, tx, index_name)
    }

    pub fn put<K, V>(&self, tx: &mut Transaction, index_id: IndexId, k: K, v: V) -> PRes<()>
    where
        K: IndexType,
        V: IndexType,
    {
        Indexes::check_index::<K, V>(self, tx, &index_id)?;
        tx.add_put(index_id, k, v);
        Ok(())
    }

    pub fn remove<K, V>(&self, tx: &mut Transaction, index_id: IndexId, k: K, v: Option<V>) -> PRes<()>
    where
        K: IndexType,
        V: IndexType,
    {
        Indexes::check_index::<K, V>(self, tx, &index_id)?;
        tx.add_remove(index_id, k, v);
        Ok(())
    }

    pub fn get_tx<K, V>(&self, tx: &mut Transaction, index_id: IndexId, k: &K) -> PRes<Option<Value<V>>>
    where
        K: IndexType,
        V: IndexType,
    {
        let (result, vm) = {
            let mut ik = Indexes::get_index_keeper_tx::<K, V>(self, tx, &index_id)?;
            self.indexes.read_lock(index_id.clone())?;
            (ik.get(k)?, IndexKeeper::<K, V>::value_mode(&ik))
        };
        self.indexes.read_unlock(index_id.clone())?;
        tx.apply_changes::<K, V>(vm, index_id, k, result)
    }

    pub fn get<K, V>(&self, index_id: IndexId, k: &K) -> PRes<Option<Value<V>>>
    where
        K: IndexType,
        V: IndexType,
    {
        let read_snapshot = self.snapshots.read_snapshot()?;
        let r = self.get_snapshot(index_id, read_snapshot, k);
        release_snapshot(read_snapshot, &self.snapshots, &self.allocator, &self.journal)?;
        r
    }

    pub fn get_snapshot<K, V>(&self, index_id: IndexId, snapshot: SnapshotId, k: &K) -> PRes<Option<Value<V>>>
    where
        K: IndexType,
        V: IndexType,
    {
        Indexes::get_index_keeper::<K, V>(self, snapshot, &index_id)?.get(k)
    }

    pub fn index_next<K, V>(
        &self,
        index_id: &IndexId,
        read_snapshot: SnapshotId,
        next: Bound<&K>,
    ) -> PRes<PageIter<K, V>>
    where
        K: IndexType,
        V: IndexType,
    {
        Indexes::get_index_keeper::<K, V>(self, read_snapshot, index_id)?.iter_from(next)
    }

    pub fn index_back<K, V>(
        &self,
        index_id: &IndexId,
        read_snapshot: SnapshotId,
        next: Bound<&K>,
    ) -> PRes<PageIterBack<K, V>>
    where
        K: IndexType,
        V: IndexType,
    {
        Indexes::get_index_keeper::<K, V>(self, read_snapshot, index_id)?.back_iter_from(next)
    }

    pub fn range<K, V, R>(&self, index_id: IndexId, range: R) -> PRes<(ValueMode, IndexRawIter<K, V>)>
    where
        K: IndexType,
        V: IndexType,
        R: RangeBounds<K>,
    {
        let read_snapshot = self.snapshots.read_snapshot()?;
        self.range_snapshot(index_id, read_snapshot, range, true)
    }

    pub fn range_snapshot<K, V, R>(
        &self,
        index_id: IndexId,
        snapshot: SnapshotId,
        range: R,
        release_snapshot: bool,
    ) -> PRes<(ValueMode, IndexRawIter<K, V>)>
    where
        K: IndexType,
        V: IndexType,
        R: RangeBounds<K>,
    {
        let mut ik = Indexes::get_index_keeper::<K, V>(self, snapshot, &index_id)?;
        let after = ik.iter_from(range.start_bound())?;
        let before = ik.back_iter_from(range.end_bound())?;
        Ok((
            IndexKeeper::<K, V>::value_mode(&ik),
            IndexRawIter::new(index_id, snapshot, after, before, release_snapshot),
        ))
    }

    pub fn segment_name_tx(&self, tx: &Transaction, id: SegmentId) -> PRes<Option<(String, bool)>> {
        if tx.segment_created_in_tx(id) {
            Ok(tx.segment_name_by_id(id).map(|x| (x, true)))
        } else {
            self.address.segment_name_by_id(id).map(|k| k.map(|x| (x, false)))
        }
    }

    pub fn list_segments(&self) -> PRes<Vec<(String, SegmentId)>> {
        Ok(self
            .address
            .list()?
            .into_iter()
            .filter(|(name, _)| !name.starts_with(INDEX_META_PREFIX) && !name.starts_with(INDEX_DATA_PREFIX))
            .collect())
    }

    pub fn list_segments_snapshot(&self, snapshot_id: SnapshotId) -> PRes<Vec<(String, SegmentId)>> {
        let list = self.snapshots.list(snapshot_id)?;
        Ok(list
            .into_iter()
            .filter(|(name, _)| !name.starts_with(INDEX_META_PREFIX) && !name.starts_with(INDEX_DATA_PREFIX))
            .collect())
    }

    pub fn list_indexes(&self) -> PRes<Vec<(String, IndexInfo)>> {
        let snapshot = self.snapshot()?;
        let res = self.list_indexes_snapshot(snapshot);
        release_snapshot(snapshot, &self.snapshots, &self.allocator, &self.journal)?;
        res
    }

    pub fn list_indexes_snapshot(&self, snapshot: SnapshotId) -> PRes<Vec<(String, IndexInfo)>> {
        let list = self.snapshots.list(snapshot)?;
        list.into_iter()
            .filter(|(name, _)| name.starts_with(INDEX_META_PREFIX))
            .map(|(mut name, _id)| -> PRes<(String, IndexInfo)> {
                name.drain(..INDEX_META_PREFIX.len());
                let info = self.index_info(snapshot, &name)?;
                Ok((name, info))
            })
            .collect()
    }

    pub fn list_segments_tx(&self, tx: &Transaction) -> PRes<Vec<(String, SegmentId)>> {
        Ok(tx
            .filter_list(&self.address.list()?)
            .filter(|(name, _)| !name.starts_with(INDEX_META_PREFIX) && !name.starts_with(INDEX_DATA_PREFIX))
            .map(|(name, id)| (name.to_string(), id))
            .collect())
    }

    pub fn list_indexes_tx(&self, tx: &Transaction) -> PRes<Vec<(String, IndexInfo)>> {
        tx.filter_list(&self.address.list()?)
            .filter(|(name, _)| name.starts_with(INDEX_META_PREFIX))
            .map(|(name, id)| (name.to_string(), id))
            .map(|(mut name, _id)| -> PRes<(String, IndexInfo)> {
                name.drain(..INDEX_META_PREFIX.len());
                let info = self.index_info_tx(tx, &name)?;
                Ok((name, info))
            })
            .collect()
    }

    fn index_info(&self, snapshot: SnapshotId, name: &str) -> PRes<IndexInfo> {
        let id = self.solve_index_id_snapshot(snapshot, name)?;
        let index = Indexes::get_index(self, snapshot, &id)?;
        Ok(IndexInfo {
            id,
            value_mode: index.value_mode,
            key_type: IndexTypeId::from(index.key_type),
            value_type: IndexTypeId::from(index.value_type),
        })
    }
    fn index_info_tx(&self, tx: &Transaction, name: &str) -> PRes<IndexInfo> {
        let id = self.solve_index_id_tx(tx, name)?.0;
        let (index, _version) = Indexes::get_index_tx(self, tx, &id)?;
        Ok(IndexInfo {
            id,
            value_mode: index.value_mode,
            key_type: IndexTypeId::from(index.key_type),
            value_type: IndexTypeId::from(index.value_type),
        })
    }

    pub(crate) fn journal(&self) -> &Journal {
        &self.journal
    }

    pub(crate) fn address(&self) -> &Address {
        &self.address
    }

    pub(crate) fn allocator(&self) -> &Allocator {
        &self.allocator
    }

    pub(crate) fn indexes(&self) -> &Indexes {
        &self.indexes
    }

    pub(crate) fn snapshots(&self) -> &Snapshots {
        &self.snapshots
    }

    #[cfg(feature = "background_ops")]
    pub(crate) fn transaction_sync(&self, sync_mode: &SyncMode, snapshot_id: SnapshotId) -> PRes<()> {
        match sync_mode {
            SyncMode::Sync => {
                let allocator = self.allocator();
                allocator.disc().sync()
            }
            SyncMode::BackgroundSync => {
                self.snapshots.acquire(snapshot_id)?;
                self.background_ops.add_pending(snapshot_id)
            }
        }
    }

    #[cfg(not(feature = "background_ops"))]
    pub(crate) fn transaction_sync(&self, sync_mode: &SyncMode, _snapshot_id: SnapshotId) -> PRes<()> {
        match sync_mode {
            SyncMode::Sync => {
                let allocator = self.allocator();
                allocator.disc().sync()
            }
            SyncMode::BackgroundSync => unreachable!(),
        }
    }
}

pub fn exp_from_content_size(size: u64) -> u8 {
    // content + size + match_pointer:page+ match_pointer:pos  + page_header
    let final_size = size + u64::from(PAGE_METADATA_SIZE);
    let final_size = u64::max(final_size, 32);
    // Should be there a better way, so far is OK.
    let mut res: u8 = 1;
    loop {
        if final_size < (1 << res) {
            return res;
        }
        res += 1;
    }
}