# Nimbus
# Copyright (c) 2023-2024 Status Research & Development GmbH
# Licensed under either of
#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
#    http://www.apache.org/licenses/LICENSE-2.0)
#  * MIT license ([LICENSE-MIT](LICENSE-MIT) or
#    http://opensource.org/licenses/MIT)
# at your option. This file may not be copied, modified, or distributed except
# according to those terms.

{.push raises: [].}

import
  std/typetraits,
  eth/common,
  "../.."/[constants, errors],
  ".."/[kvt, aristo],
  ./backend/aristo_db,
  ./base/[api_tracking, base_config, base_desc, base_helpers]

export
  CoreDbAccRef,
  CoreDbAccount,
  CoreDbApiError,
  CoreDbCtxRef,
  CoreDbErrorCode,
  CoreDbError,
  CoreDbKvtRef,
  CoreDbMptRef,
  CoreDbPersistentTypes,
  CoreDbRef,
  CoreDbTxRef,
  CoreDbType

when CoreDbEnableApiTracking:
  import
    chronicles
  logScope:
    topics = "core_db"
  const
    logTxt = "API"

when CoreDbEnableProfiling:
  export
    CoreDbFnInx,
    CoreDbProfListRef

when CoreDbEnableCaptJournal:
  import
    ./backend/aristo_trace
  type
    CoreDbCaptRef* = distinct TraceLogInstRef
  func `$`(p: CoreDbCaptRef): string =
    if p.distinctBase.isNil: "<nil>" else: "<capt>"
else:
  import
    ../aristo/[
      aristo_delete, aristo_desc, aristo_fetch, aristo_merge, aristo_part,
      aristo_tx],
    ../kvt/[kvt_desc, kvt_utils, kvt_tx]

# ------------------------------------------------------------------------------
# Public context constructors and administration
# ------------------------------------------------------------------------------

proc ctx*(db: CoreDbRef): CoreDbCtxRef =
  ## Get the defauly context. This is a base descriptor which provides the
  ## KVT, MPT, the accounts descriptors as well as the transaction descriptor.
  ## They are kept all in sync, i.e. `persistent()` will store exactly this
  ## context.
  ##
  db.defCtx

proc newCtxByKey*(ctx: CoreDbCtxRef; root: Hash256): CoreDbRc[CoreDbCtxRef] =
  ## Create new context derived from a matching transaction of the currently
  ## active context. If successful, the resulting context has the following
  ## properties:
  ##
  ## * Transaction level is 1
  ## * The state of the accounts column is equal to the argument `root`
  ##
  ## If successful, the resulting descriptor **must** be manually released
  ## with `forget()` when it is not used, anymore.
  ##
  ## Note:
  ##   The underlying `Aristo` backend uses lazy hashing so this function
  ##   might fail simply because there is no computed state when nesting
  ##   the next transaction. If the previous transaction needs to be found,
  ##   then it must called like this:
  ##   ::
  ##     let db = ..                             # Instantiate CoreDb handle
  ##     ...
  ##     discard db.ctx.getAccounts.state()      # Compute state hash
  ##     db.ctx.newTransaction()                 # Enter new transaction
  ##
  ##   However, remember that unused hash computations are contle relative
  ##   to processing time.
  ##
  ctx.setTrackNewApi CtxNewCtxByKeyFn
  result = ctx.newCtxByKey(root, $api)
  ctx.ifTrackNewApi: debug logTxt, api, elapsed, root=($$root),  result

proc swapCtx*(ctx: CoreDbCtxRef; db: CoreDbRef): CoreDbCtxRef =
  ## Activate argument context `ctx` as default and return the previously
  ## active context. This function goes typically together with `forget()`.
  ## A valid scenario might look like
  ## ::
  ##   let db = ..                             # Instantiate CoreDb handle
  ##   ...
  ##   let ctx = newCtxByKey(..).expect "ctx"  # Create new context
  ##   let saved = db.swapCtx ctx              # Swap context dandles
  ##   defer: db.swapCtx(saved).forget()       # Restore
  ##   ...
  ##
  doAssert not ctx.isNil
  assert db.defCtx != ctx # debugging only
  db.setTrackNewApi CtxSwapCtxFn

  # Swap default context with argument `ctx`
  result = db.defCtx
  db.defCtx = ctx

  # Set read-write access and install
  CoreDbAccRef(ctx).call(reCentre, db.ctx.mpt).isOkOr:
    raiseAssert $api & " failed: " & $error
  CoreDbKvtRef(ctx).call(reCentre, db.ctx.kvt).isOkOr:
    raiseAssert $api & " failed: " & $error
  doAssert db.defCtx != result
  db.ifTrackNewApi: debug logTxt, api, elapsed

proc forget*(ctx: CoreDbCtxRef) =
  ## Dispose `ctx` argument context and related columns created with this
  ## context. This function throws an exception `ctx` is the default context.
  ##
  ctx.setTrackNewApi CtxForgetFn
  doAssert ctx !=  ctx.parent.defCtx
  CoreDbAccRef(ctx).call(forget, ctx.mpt).isOkOr:
    raiseAssert $api & ": " & $error
  CoreDbKvtRef(ctx).call(forget, ctx.kvt).isOkOr:
    raiseAssert $api & ": " & $error
  ctx.ifTrackNewApi: debug logTxt, api, elapsed

# ------------------------------------------------------------------------------
# Public base descriptor methods
# ------------------------------------------------------------------------------

proc finish*(db: CoreDbRef; eradicate = false) =
  ## Database destructor. If the argument `eradicate` is set `false`, the
  ## database is left as-is and only the in-memory handlers are cleaned up.
  ##
  ## Otherwise the destructor is allowed to remove the database. This feature
  ## depends on the backend database. Currently, only the `AristoDbRocks` type
  ## backend removes the database on `true`.
  ##
  db.setTrackNewApi BaseFinishFn
  CoreDbKvtRef(db.ctx).call(finish, db.ctx.kvt, eradicate)
  CoreDbAccRef(db.ctx).call(finish, db.ctx.mpt, eradicate)
  db.ifTrackNewApi: debug logTxt, api, elapsed

proc `$$`*(e: CoreDbError): string =
  ## Pretty print error symbol, note that this directive may have side effects
  ## as it calls a backend function.
  ##
  e.toStr()

proc persistent*(
    db: CoreDbRef;
    blockNumber: BlockNumber;
      ): CoreDbRc[void] =
  ## This function stored cached data from the default context (see `ctx()`
  ## below) to the persistent database.
  ##
  ## It also stores the argument block number `blockNumber` as a state record
  ## which can be retrieved via `stateBlockNumber()`.
  ##
  db.setTrackNewApi BasePersistentFn
  block body:
    block:
      let rc = CoreDbKvtRef(db.ctx).call(persist, db.ctx.kvt)
      if rc.isOk or rc.error == TxPersistDelayed:
        # The latter clause is OK: Piggybacking on `Aristo` backend
        discard
      elif CoreDbKvtRef(db.ctx).call(level, db.ctx.kvt) != 0:
        result = err(rc.error.toError($api, TxPending))
        break body
      else:
        result = err(rc.error.toError $api)
        break body
    # Having reached here `Aristo` must not fail as both `Kvt` and `Aristo`
    # are kept in sync. So if there is a legit fail condition it mist be
    # caught in the previous clause.
    CoreDbAccRef(db.ctx).call(persist, db.ctx.mpt, blockNumber).isOkOr:
      raiseAssert $api & ": " & $error
    result = ok()
  db.ifTrackNewApi: debug logTxt, api, elapsed, blockNumber, result

proc stateBlockNumber*(db: CoreDbRef): BlockNumber =
  ## Rhis function returns the block number stored with the latest `persist()`
  ## directive.
  ##
  db.setTrackNewApi BaseStateBlockNumberFn
  result = block:
    let rc = CoreDbAccRef(db.ctx).call(fetchLastSavedState, db.ctx.mpt)
    if rc.isOk:
      rc.value.serial.BlockNumber
    else:
      0u64
  db.ifTrackNewApi: debug logTxt, api, elapsed, result

proc verify*(
    db: CoreDbRef | CoreDbMptRef | CoreDbAccRef;
    proof: openArray[Blob];
    root: Hash256;
    path: openArray[byte];
      ): CoreDbRc[Opt[Blob]] =
  ## This function os the counterpart of any of the `proof()` functions. Given
  ## the argument chain of rlp-encoded nodes `proof`, this function verifies
  ## that the chain represents a partial MPT starting with a root node state
  ## `root` followig the path `key` leading to leaf node encapsulating a
  ## payload which is passed back as return code.
  ##
  ## Note: The `mpt` argument is used for administative purposes (e.g. logging)
  ##       only. The functionality is provided by the `Aristo` database
  ##       function `aristo_part.partUntwigGeneric()` with the same prototype
  ##       arguments except the `db`.
  ##
  template mpt: untyped =
    when db is CoreDbRef:
      CoreDbAccRef(db.defCtx)
    else:
      db
  mpt.setTrackNewApi BaseVerifyFn
  result = block:
    let rc = mpt.call(partUntwigGeneric, proof, root, path)
    if rc.isOk:
      ok(rc.value)
    else:
      err(rc.error.toError($api, ProofVerify))
  mpt.ifTrackNewApi: debug logTxt, api, elapsed, result

proc verifyOk*(
    db: CoreDbRef | CoreDbMptRef | CoreDbAccRef;
    proof: openArray[Blob];
    root: Hash256;
    path: openArray[byte];
    payload: Opt[Blob];
      ): CoreDbRc[void] =
  ## Variant of `verify()` which directly checks the argument `payload`
  ## against what would be the return code in `verify()`.
  ##
  template mpt: untyped =
    when db is CoreDbRef:
      CoreDbAccRef(db.defCtx)
    else:
      db
  mpt.setTrackNewApi BaseVerifyOkFn
  result = block:
    let rc = mpt.call(partUntwigGenericOk, proof, root, path, payload)
    if rc.isOk:
      ok()
    else:
      err(rc.error.toError($api, ProofVerify))
  mpt.ifTrackNewApi: debug logTxt, api, elapsed, result

proc verify*(
    db: CoreDbRef | CoreDbMptRef | CoreDbAccRef;
    proof: openArray[Blob];
    root: Hash256;
    path: Hash256;
      ): CoreDbRc[Opt[Blob]] =
  ## Variant of `verify()`.
  template mpt: untyped =
    when db is CoreDbRef:
      CoreDbAccRef(db.defCtx)
    else:
      db
  mpt.setTrackNewApi BaseVerifyFn
  result = block:
    let rc = mpt.call(partUntwigPath, proof, root, path)
    if rc.isOk:
      ok(rc.value)
    else:
      err(rc.error.toError($api, ProofVerify))
  mpt.ifTrackNewApi: debug logTxt, api, elapsed, result

proc verifyOk*(
    db: CoreDbRef | CoreDbMptRef | CoreDbAccRef;
    proof: openArray[Blob];
    root: Hash256;
    path: Hash256;
    payload: Opt[Blob];
      ): CoreDbRc[void] =
  ## Variant of `verifyOk()`.
  template mpt: untyped =
    when db is CoreDbRef:
      CoreDbAccRef(db.defCtx)
    else:
      db
  mpt.setTrackNewApi BaseVerifyOkFn
  result = block:
    let rc = mpt.call(partUntwigPathOk, proof, root, path, payload)
    if rc.isOk:
      ok()
    else:
      err(rc.error.toError($api, ProofVerify))
  mpt.ifTrackNewApi: debug logTxt, api, elapsed, result

# ------------------------------------------------------------------------------
# Public key-value table methods
# ------------------------------------------------------------------------------

proc getKvt*(ctx: CoreDbCtxRef): CoreDbKvtRef =
  ## This function retrieves the common base object shared with other KVT
  ## descriptors. Any changes are immediately visible to subscribers.
  ## On destruction (when the constructed object gets out of scope), changes
  ## are not saved to the backend database but are still cached and available.
  ##
  CoreDbKvtRef(ctx)

# ----------- KVT ---------------

proc get*(kvt: CoreDbKvtRef; key: openArray[byte]): CoreDbRc[Blob] =
  ## This function always returns a non-empty `Blob` or an error code.
  kvt.setTrackNewApi KvtGetFn
  result = block:
    let rc = kvt.call(get, kvt.kvt, key)
    if rc.isOk:
      ok(rc.value)
    elif rc.error == GetNotFound:
      err(rc.error.toError($api, KvtNotFound))
    else:
      err(rc.error.toError $api)
  kvt.ifTrackNewApi: debug logTxt, api, elapsed, key=key.toStr, result

proc getOrEmpty*(kvt: CoreDbKvtRef; key: openArray[byte]): CoreDbRc[Blob] =
  ## Variant of `get()` returning an empty `Blob` if the key is not found
  ## on the database.
  ##
  kvt.setTrackNewApi KvtGetOrEmptyFn
  result = block:
    let rc = kvt.call(get, kvt.kvt, key)
    if rc.isOk:
      ok(rc.value)
    elif rc.error == GetNotFound:
      CoreDbRc[Blob].ok(EmptyBlob)
    else:
      err(rc.error.toError $api)
  kvt.ifTrackNewApi: debug logTxt, api, elapsed, key=key.toStr, result

proc len*(kvt: CoreDbKvtRef; key: openArray[byte]): CoreDbRc[int] =
  ## This function returns the size of the value associated with `key`.
  kvt.setTrackNewApi KvtLenFn
  result = block:
    let rc = kvt.call(len, kvt.kvt, key)
    if rc.isOk:
      ok(rc.value)
    elif rc.error == GetNotFound:
      err(rc.error.toError($api, KvtNotFound))
    else:
      err(rc.error.toError $api)
  kvt.ifTrackNewApi: debug logTxt, api, elapsed, key=key.toStr, result

proc del*(kvt: CoreDbKvtRef; key: openArray[byte]): CoreDbRc[void] =
  kvt.setTrackNewApi KvtDelFn
  result = block:
    let rc = kvt.call(del, kvt.kvt, key)
    if rc.isOk:
      ok()
    else:
      err(rc.error.toError $api)
  kvt.ifTrackNewApi: debug logTxt, api, elapsed, key=key.toStr, result

proc put*(
    kvt: CoreDbKvtRef;
    key: openArray[byte];
    val: openArray[byte];
      ): CoreDbRc[void] =
  kvt.setTrackNewApi KvtPutFn
  result = block:
    let rc = kvt.call(put, kvt.kvt, key, val)
    if rc.isOk:
      ok()
    else:
      err(rc.error.toError $api)
  kvt.ifTrackNewApi:
    debug logTxt, api, elapsed, key=key.toStr, val=val.toLenStr, result

proc hasKeyRc*(kvt: CoreDbKvtRef; key: openArray[byte]): CoreDbRc[bool] =
  ## For the argument `key` return `true` if `get()` returned a value on
  ## that argument, `false` if it returned `GetNotFound`, and an error
  ## otherwise.
  ##
  kvt.setTrackNewApi KvtHasKeyRcFn
  result = block:
    let rc = kvt.call(hasKeyRc, kvt.kvt, key)
    if rc.isOk:
      ok(rc.value)
    else:
      err(rc.error.toError $api)
  kvt.ifTrackNewApi: debug logTxt, api, elapsed, key=key.toStr, result

proc hasKey*(kvt: CoreDbKvtRef; key: openArray[byte]): bool =
  ## Simplified version of `hasKeyRc` where `false` is returned instead of
  ## an error.
  ##
  ## This function prototype is in line with the `hasKey` function for
  ## `Tables`.
  ##
  kvt.setTrackNewApi KvtHasKeyFn
  result = kvt.call(hasKeyRc, kvt.kvt, key).valueOr: false
  kvt.ifTrackNewApi: debug logTxt, api, elapsed, key=key.toStr, result

# ------------------------------------------------------------------------------
# Public functions for generic columns
# ------------------------------------------------------------------------------

proc getGeneric*(
    ctx: CoreDbCtxRef;
    clearData = false;
      ): CoreDbMptRef =
  ## Get a generic MPT, viewed as column
  ##
  ctx.setTrackNewApi CtxGetGenericFn
  result = CoreDbMptRef(ctx)
  if clearData:
    result.call(deleteGenericTree, ctx.mpt, CoreDbVidGeneric).isOkOr:
      raiseAssert $api & ": " & $error
  ctx.ifTrackNewApi: debug logTxt, api, clearData, elapsed

# ----------- generic MPT ---------------

proc proof*(
    mpt: CoreDbMptRef;
    key: openArray[byte];
      ): CoreDbRc[(seq[Blob],bool)] =
  ## On the generic MPT, collect the nodes along the `key` interpreted as
  ## path. Return these path nodes as a chain of rlp-encoded blobs followed
  ## by a bool value which is `true` if the `key` path exists in the database,
  ## and `false` otherwise. In the latter case, the chain of rlp-encoded blobs
  ## are the nodes proving that the `key` path does not exist.
  ##
  mpt.setTrackNewApi MptProofFn
  result = block:
    let rc = mpt.call(partGenericTwig, mpt.mpt, CoreDbVidGeneric, key)
    if rc.isOk:
      ok(rc.value)
    else:
      err(rc.error.toError($api, ProofCreate))
  mpt.ifTrackNewApi: debug logTxt, api, elapsed, result

proc fetch*(mpt: CoreDbMptRef; key: openArray[byte]): CoreDbRc[Blob] =
  ## Fetch data from the argument `mpt`. The function always returns a
  ## non-empty `Blob` or an error code.
  ##
  mpt.setTrackNewApi MptFetchFn
  result = block:
    let rc = mpt.call(fetchGenericData, mpt.mpt, CoreDbVidGeneric, key)
    if rc.isOk:
      ok(rc.value)
    elif rc.error == FetchPathNotFound:
      err(rc.error.toError($api, MptNotFound))
    else:
      err(rc.error.toError $api)
  mpt.ifTrackNewApi: debug logTxt, api, elapsed, key=key.toStr, result

proc fetchOrEmpty*(mpt: CoreDbMptRef; key: openArray[byte]): CoreDbRc[Blob] =
  ## This function returns an empty `Blob` if the argument `key` is not found
  ## on the database.
  ##
  mpt.setTrackNewApi MptFetchOrEmptyFn
  result = block:
    let rc = mpt.call(fetchGenericData, mpt.mpt, CoreDbVidGeneric, key)
    if rc.isOk:
      ok(rc.value)
    elif rc.error == FetchPathNotFound:
      CoreDbRc[Blob].ok(EmptyBlob)
    else:
      err(rc.error.toError $api)
  mpt.ifTrackNewApi: debug logTxt, api, elapsed, key=key.toStr, result

proc delete*(mpt: CoreDbMptRef; key: openArray[byte]): CoreDbRc[void] =
  mpt.setTrackNewApi MptDeleteFn
  result = block:
    let rc = mpt.call(deleteGenericData, mpt.mpt,CoreDbVidGeneric, key)
    if rc.isOk:
      ok()
    elif rc.error == DelPathNotFound:
      err(rc.error.toError($api, MptNotFound))
    else:
      err(rc.error.toError $api)
  mpt.ifTrackNewApi: debug logTxt, api, elapsed, key=key.toStr, result

proc merge*(
    mpt: CoreDbMptRef;
    key: openArray[byte];
    val: openArray[byte];
      ): CoreDbRc[void] =
  mpt.setTrackNewApi MptMergeFn
  result = block:
    let rc = mpt.call(mergeGenericData, mpt.mpt,CoreDbVidGeneric, key, val)
    if rc.isOk:
      ok()
    else:
      err(rc.error.toError $api)
  mpt.ifTrackNewApi:
    debug logTxt, api, elapsed, key=key.toStr, val=val.toLenStr, result

proc hasPath*(mpt: CoreDbMptRef; key: openArray[byte]): CoreDbRc[bool] =
  ## This function would be named `contains()` if it returned `bool` rather
  ## than a `Result[]`.
  ##
  mpt.setTrackNewApi MptHasPathFn
  result = block:
    let rc = mpt.call(hasPathGeneric, mpt.mpt, CoreDbVidGeneric, key)
    if rc.isOk:
      ok(rc.value)
    else:
      err(rc.error.toError $api)
  mpt.ifTrackNewApi: debug logTxt, api, elapsed, key=key.toStr, result

proc state*(mpt: CoreDbMptRef; updateOk = false): CoreDbRc[Hash256] =
  ## This function retrieves the Merkle state hash of the argument
  ## database column (if acvailable.)
  ##
  ## If the argument `updateOk` is set `true`, the Merkle hashes of the
  ## database will be updated first (if needed, at all).
  ##
  mpt.setTrackNewApi MptStateFn
  result = block:
    let rc = mpt.call(fetchGenericState, mpt.mpt, CoreDbVidGeneric, updateOk)
    if rc.isOk:
      ok(rc.value)
    else:
      err(rc.error.toError $api)
  mpt.ifTrackNewApi: debug logTxt, api, elapsed, updateOK, result

# ------------------------------------------------------------------------------
# Public methods for accounts
# ------------------------------------------------------------------------------

proc getAccounts*(ctx: CoreDbCtxRef): CoreDbAccRef =
  ## Accounts column constructor, will defect on failure.
  ##
  ctx.setTrackNewApi CtxGetAccountsFn
  result =  CoreDbAccRef(ctx)
  ctx.ifTrackNewApi: debug logTxt, api, elapsed

# ----------- accounts ---------------

proc proof*(
    acc: CoreDbAccRef;
    accPath: Hash256;
      ): CoreDbRc[(seq[Blob],bool)] =
  ## On the accounts MPT, collect the nodes along the `accPath` interpreted as
  ## path. Return these path nodes as a chain of rlp-encoded blobs followed
  ## by a bool value which is `true` if the `key` path exists in the database,
  ## and `false` otherwise. In the latter case, the chain of rlp-encoded blobs
  ## are the nodes proving that the `key` path does not exist.
  ##
  acc.setTrackNewApi AccProofFn
  result = block:
    let rc = acc.call(partAccountTwig, acc.mpt, accPath)
    if rc.isOk:
      ok(rc.value)
    else:
      err(rc.error.toError($api, ProofCreate))
  acc.ifTrackNewApi: debug logTxt, api, elapsed, result

proc fetch*(
    acc: CoreDbAccRef;
    accPath: Hash256;
      ): CoreDbRc[CoreDbAccount] =
  ## Fetch the account data record for the particular account indexed by
  ## the key `accPath`.
  ##
  acc.setTrackNewApi AccFetchFn
  result = block:
    let rc = acc.call(fetchAccountRecord, acc.mpt, accPath)
    if rc.isOk:
      ok(rc.value)
    elif rc.error == FetchPathNotFound:
      err(rc.error.toError($api, AccNotFound))
    else:
      err(rc.error.toError $api)
  acc.ifTrackNewApi: debug logTxt, api, elapsed, accPath=($$accPath), result

proc delete*(
    acc: CoreDbAccRef;
    accPath: Hash256;
      ): CoreDbRc[void] =
  ## Delete the particular account indexed by the key `accPath`. This
  ## will also destroy an associated storage area.
  ##
  acc.setTrackNewApi AccDeleteFn
  result = block:
    let rc = acc.call(deleteAccountRecord, acc.mpt, accPath)
    if rc.isOk:
      ok()
    elif rc.error == DelPathNotFound:
      # TODO: Would it be conseqient to just return `ok()` here?
      err(rc.error.toError($api, AccNotFound))
    else:
      err(rc.error.toError $api)
  acc.ifTrackNewApi:
    debug logTxt, api, elapsed, accPath=($$accPath), result

proc clearStorage*(
    acc: CoreDbAccRef;
    accPath: Hash256;
      ): CoreDbRc[void] =
  ## Delete all data slots from the storage area associated with the
  ## particular account indexed by the key `accPath`.
  ##
  acc.setTrackNewApi AccClearStorageFn
  result = block:
    let rc = acc.call(deleteStorageTree, acc.mpt, accPath)
    if rc.isOk or rc.error in {DelStoRootMissing,DelStoAccMissing}:
      ok()
    else:
      err(rc.error.toError $api)
  acc.ifTrackNewApi:
    debug logTxt, api, elapsed, accPath=($$accPath), result

proc merge*(
    acc: CoreDbAccRef;
    accPath: Hash256;
    accRec: CoreDbAccount;
      ): CoreDbRc[void] =
  ## Add or update the argument account data record `account`. Note that the
  ## `account` argument uniquely idendifies the particular account address.
  ##
  acc.setTrackNewApi AccMergeFn
  result = block:
    let rc = acc.call(mergeAccountRecord, acc.mpt, accPath, accRec)
    if rc.isOk:
      ok()
    else:
      err(rc.error.toError $api)
  acc.ifTrackNewApi:
    debug logTxt, api, elapsed, accPath=($$accPath), result

proc hasPath*(
    acc: CoreDbAccRef;
    accPath: Hash256;
      ): CoreDbRc[bool] =
  ## Would be named `contains` if it returned `bool` rather than `Result[]`.
  ##
  acc.setTrackNewApi AccHasPathFn
  result = block:
    let rc = acc.call(hasPathAccount, acc.mpt, accPath)
    if rc.isOk:
      ok(rc.value)
    else:
      err(rc.error.toError $api)
  acc.ifTrackNewApi:
    debug logTxt, api, elapsed, accPath=($$accPath), result

proc state*(acc: CoreDbAccRef; updateOk = false): CoreDbRc[Hash256] =
  ## This function retrieves the Merkle state hash of the accounts
  ## column (if available.)
  ##
  ## If the argument `updateOk` is set `true`, the Merkle hashes of the
  ## database will be updated first (if needed, at all).
  ##
  acc.setTrackNewApi AccStateFn
  result = block:
    let rc = acc.call(fetchAccountState, acc.mpt, updateOk)
    if rc.isOk:
      ok(rc.value)
    else:
      err(rc.error.toError $api)
  acc.ifTrackNewApi: debug logTxt, api, elapsed, updateOK, result

# ------------ storage ---------------

proc slotProof*(
    acc: CoreDbAccRef;
    accPath: Hash256;
    stoPath: Hash256;
      ): CoreDbRc[(seq[Blob],bool)] =
  ## On the storage MPT related to the argument account `acPath`, collect the
  ## nodes along the `stoPath` interpreted as path. Return these path nodes as
  ## a chain of rlp-encoded blobs followed by a bool value which is `true` if
  ## the `key` path exists in the database, and `false` otherwise. In the
  ## latter case, the chain of rlp-encoded blobs are the nodes proving that
  ## the `key` path does not exist.
  ##
  ## Note that the function always returns an error unless the `accPath` is
  ## valid.
  ##
  acc.setTrackNewApi AccSlotProofFn
  result = block:
    let rc = acc.call(partStorageTwig, acc.mpt, accPath, stoPath)
    if rc.isOk:
      ok(rc.value)
    else:
      err(rc.error.toError($api, ProofCreate))
  acc.ifTrackNewApi: debug logTxt, api, elapsed, result

proc slotFetch*(
    acc: CoreDbAccRef;
    accPath: Hash256;
    stoPath: Hash256;
      ):  CoreDbRc[UInt256] =
  ## Like `fetch()` but with cascaded index `(accPath,slot)`.
  acc.setTrackNewApi AccSlotFetchFn
  result = block:
    let rc = acc.call(fetchStorageData, acc.mpt, accPath, stoPath)
    if rc.isOk:
      ok(rc.value)
    elif rc.error == FetchPathNotFound:
      err(rc.error.toError($api, StoNotFound))
    else:
      err(rc.error.toError $api)
  acc.ifTrackNewApi:
    debug logTxt, api, elapsed, accPath=($$accPath),
            stoPath=($$stoPath), result

proc slotDelete*(
    acc: CoreDbAccRef;
    accPath: Hash256;
    stoPath: Hash256;
      ):  CoreDbRc[void] =
  ## Like `delete()` but with cascaded index `(accPath,slot)`.
  acc.setTrackNewApi AccSlotDeleteFn
  result = block:
    let rc = acc.call(deleteStorageData, acc.mpt, accPath, stoPath)
    if rc.isOk or rc.error == DelStoRootMissing:
      # The second `if` clause is insane but legit: A storage column was
      # announced for an account but no data have been added, yet.
      ok()
    elif rc.error == DelPathNotFound:
      err(rc.error.toError($api, StoNotFound))
    else:
      err(rc.error.toError $api)
  acc.ifTrackNewApi:
    debug logTxt, api, elapsed, accPath=($$accPath),
            stoPath=($$stoPath), result

proc slotHasPath*(
    acc: CoreDbAccRef;
    accPath: Hash256;
    stoPath: Hash256;
      ):  CoreDbRc[bool] =
  ## Like `hasPath()` but with cascaded index `(accPath,slot)`.
  acc.setTrackNewApi AccSlotHasPathFn
  result = block:
    let rc = acc.call(hasPathStorage, acc.mpt, accPath, stoPath)
    if rc.isOk:
      ok(rc.value)
    else:
      err(rc.error.toError $api)
  acc.ifTrackNewApi:
    debug logTxt, api, elapsed, accPath=($$accPath),
            stoPath=($$stoPath), result

proc slotMerge*(
    acc: CoreDbAccRef;
    accPath: Hash256;
    stoPath: Hash256;
    stoData: UInt256;
      ):  CoreDbRc[void] =
  ## Like `merge()` but with cascaded index `(accPath,slot)`.
  acc.setTrackNewApi AccSlotMergeFn
  result = block:
    let rc = acc.call(mergeStorageData, acc.mpt, accPath, stoPath, stoData)
    if rc.isOk:
      ok()
    else:
      err(rc.error.toError $api)
  acc.ifTrackNewApi:
    debug logTxt, api, elapsed, accPath=($$accPath),
            stoPath=($$stoPath), stoData, result

proc slotState*(
    acc: CoreDbAccRef;
    accPath: Hash256;
    updateOk = false;
      ):  CoreDbRc[Hash256] =
  ## This function retrieves the Merkle state hash of the storage data
  ## column (if available) related to the account  indexed by the key
  ## `accPath`.`.
  ##
  ## If the argument `updateOk` is set `true`, the Merkle hashes of the
  ## database will be updated first (if needed, at all).
  ##
  acc.setTrackNewApi AccSlotStateFn
  result = block:
    let rc = acc.call(fetchStorageState, acc.mpt, accPath, updateOk)
    if rc.isOk:
      ok(rc.value)
    else:
      err(rc.error.toError $api)
  acc.ifTrackNewApi:
    debug logTxt, api, elapsed, accPath=($$accPath), updateOk, result

proc slotStateEmpty*(
    acc: CoreDbAccRef;
    accPath: Hash256;
      ):  CoreDbRc[bool] =
  ## This function returns `true` if the storage data column is empty or
  ## missing.
  ##
  acc.setTrackNewApi AccSlotStateEmptyFn
  result = block:
    let rc = acc.call(hasStorageData, acc.mpt, accPath)
    if rc.isOk:
      ok(not rc.value)
    else:
      err(rc.error.toError $api)
  acc.ifTrackNewApi:
    debug logTxt, api, elapsed, accPath=($$accPath), result

proc slotStateEmptyOrVoid*(
    acc: CoreDbAccRef;
    accPath: Hash256;
      ): bool =
  ## Convenience wrapper, returns `true` where `slotStateEmpty()` would fail.
  acc.setTrackNewApi AccSlotStateEmptyOrVoidFn
  result = block:
    let rc = acc.call(hasStorageData, acc.mpt, accPath)
    if rc.isOk:
      not rc.value
    else:
      true
  acc.ifTrackNewApi:
    debug logTxt, api, elapsed, accPath=($$accPath), result

# ------------- other ----------------

proc recast*(
    acc: CoreDbAccRef;
    accPath: Hash256;
    accRec: CoreDbAccount;
    updateOk = false;
      ): CoreDbRc[Account] =
  ## Complete the argument `accRec` to the portable Ethereum representation
  ## of an account statement. This conversion may fail if the storage colState
  ## hash (see `slotState()` above) is currently unavailable.
  ##
  acc.setTrackNewApi AccRecastFn
  let rc = acc.call(fetchStorageState, acc.mpt, accPath, updateOk)
  result = block:
    if rc.isOk:
      ok Account(
        nonce:       accRec.nonce,
        balance:     accRec.balance,
        codeHash:    accRec.codeHash,
        storageRoot: rc.value)
    else:
      err(rc.error.toError $api)
  acc.ifTrackNewApi:
    let slotState = if rc.isOk: $$(rc.value) else: "n/a"
    debug logTxt, api, elapsed, accPath=($$accPath), slotState, result

# ------------------------------------------------------------------------------
# Public transaction related methods
# ------------------------------------------------------------------------------

proc level*(db: CoreDbRef): int =
  ## Retrieve transaction level (zero if there is no pending transaction).
  ##
  db.setTrackNewApi BaseLevelFn
  result = CoreDbAccRef(db.ctx).call(level, db.ctx.mpt)
  db.ifTrackNewApi: debug logTxt, api, elapsed, result

proc newTransaction*(ctx: CoreDbCtxRef): CoreDbTxRef =
  ## Constructor
  ##
  ctx.setTrackNewApi BaseNewTxFn
  let
    kTx = CoreDbKvtRef(ctx).call(txBegin, ctx.kvt).valueOr:
      raiseAssert $api & ": " & $error
    aTx = CoreDbAccRef(ctx).call(txBegin, ctx.mpt).valueOr:
      raiseAssert $api & ": " & $error
  result = ctx.bless CoreDbTxRef(kTx: kTx, aTx: aTx)
  ctx.ifTrackNewApi:
    let newLevel = CoreDbAccRef(ctx).call(level, ctx.mpt)
    debug logTxt, api, elapsed, newLevel

proc level*(tx: CoreDbTxRef): int =
  ## Print positive transaction level for argument `tx`
  ##
  tx.setTrackNewApi TxLevelFn
  result = CoreDbAccRef(tx.ctx).call(txLevel, tx.aTx)
  tx.ifTrackNewApi: debug logTxt, api, elapsed, result

proc commit*(tx: CoreDbTxRef) =
  tx.setTrackNewApi TxCommitFn:
    let prvLevel {.used.} = CoreDbAccRef(tx.ctx).call(txLevel, tx.aTx)
  CoreDbAccRef(tx.ctx).call(commit, tx.aTx).isOkOr:
    raiseAssert $api & ": " & $error
  CoreDbKvtRef(tx.ctx).call(commit, tx.kTx).isOkOr:
    raiseAssert $api & ": " & $error
  tx.ifTrackNewApi: debug logTxt, api, elapsed, prvLevel

proc rollback*(tx: CoreDbTxRef) =
  tx.setTrackNewApi TxRollbackFn:
    let prvLevel {.used.} = CoreDbAccRef(tx.ctx).call(txLevel, tx.aTx)
  CoreDbAccRef(tx.ctx).call(rollback, tx.aTx).isOkOr:
    raiseAssert $api & ": " & $error
  CoreDbKvtRef(tx.ctx).call(rollback, tx.kTx).isOkOr:
    raiseAssert $api & ": " & $error
  tx.ifTrackNewApi: debug logTxt, api, elapsed, prvLevel

proc dispose*(tx: CoreDbTxRef) =
  tx.setTrackNewApi TxDisposeFn:
    let prvLevel {.used.} = CoreDbAccRef(tx.ctx).call(txLevel, tx.aTx)
  if CoreDbAccRef(tx.ctx).call(isTop, tx.aTx):
    CoreDbAccRef(tx.ctx).call(rollback, tx.aTx).isOkOr:
      raiseAssert $api & ": " & $error
  if CoreDbKvtRef(tx.ctx).call(isTop, tx.kTx):
    CoreDbKvtRef(tx.ctx).call(rollback, tx.kTx).isOkOr:
      raiseAssert $api & ": " & $error
  tx.ifTrackNewApi: debug logTxt, api, elapsed, prvLevel

# ------------------------------------------------------------------------------
# Public tracer methods
# ------------------------------------------------------------------------------

when CoreDbEnableCaptJournal:
  proc pushCapture*(db: CoreDbRef): CoreDbCaptRef =
    ## ..
    ##
    db.setTrackNewApi BasePushCaptureFn
    if db.tracerHook.isNil:
      db.tracerHook = TraceRecorderRef.init(db)
    else:
      TraceRecorderRef(db.tracerHook).push()
    result = TraceRecorderRef(db.tracerHook).topInst().CoreDbCaptRef
    db.ifTrackNewApi: debug logTxt, api, elapsed, result

  proc level*(cpt: CoreDbCaptRef): int =
    ## Getter, returns the positive number of stacked instances.
    ##
    let log = cpt.distinctBase
    log.db.setTrackNewApi CptLevelFn
    result = log.level()
    log.db.ifTrackNewApi: debug logTxt, api, elapsed, result

  proc kvtLog*(cpt: CoreDbCaptRef): seq[(Blob,Blob)] =
    ## Getter, returns the `Kvt` logger list for the argument instance.
    ##
    let log = cpt.distinctBase
    log.db.setTrackNewApi CptKvtLogFn
    result = log.kvtLogBlobs()
    log.db.ifTrackNewApi: debug logTxt, api, elapsed

  proc pop*(cpt: CoreDbCaptRef) =
    ## Explicitely stop recording the current tracer instance and reset to
    ## previous level.
    ##
    let db = cpt.distinctBase.db
    db.setTrackNewApi CptPopFn
    if not cpt.distinctBase.pop():
      TraceRecorderRef(db.tracerHook).restore()
      db.tracerHook = TraceRecorderRef(nil)
    db.ifTrackNewApi: debug logTxt, api, elapsed, cpt

  proc stopCapture*(db: CoreDbRef) =
    ## Discard capture instances. This function is equivalent to `pop()`-ing
    ## all instances.
    ##
    db.setTrackNewApi CptStopCaptureFn
    if not db.tracerHook.isNil:
      TraceRecorderRef(db.tracerHook).restore()
      db.tracerHook = TraceRecorderRef(nil)
    db.ifTrackNewApi: debug logTxt, api, elapsed

# ------------------------------------------------------------------------------
# End
# ------------------------------------------------------------------------------