## Nim-Codex
## Copyright (c) 2021 Status Research & Development GmbH
## Licensed under either of
##  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
##  * MIT license ([LICENSE-MIT](LICENSE-MIT))
## at your option.
## This file may not be copied, modified, or distributed except according to
## those terms.

import pkg/upraises

push: {.upraises: [].}

import pkg/chronos
import pkg/chronicles
import pkg/datastore/sqlite_datastore
import pkg/libp2p
import pkg/questionable
import pkg/questionable/results
import pkg/sqlite3_abi

import ./blockstore
import ./cachestore

export blockstore, sqlite_datastore

logScope:
  topics = "codex sqlitestore"

type
  ListBlocksQueryResponse = string

  ListBlocksQueryStmt = SQLiteStmt[(string), void]

  SQLiteStore* = ref object of BlockStore
    cache: BlockStore
    datastore: SQLiteDatastore

const
  listBlocksQueryStmtStr = """
    SELECT """ & idColName & """ FROM """ & tableName & """;
  """

  listBlocksQueryStmtIdCol = 0

proc new*(
  T: type SQLiteStore,
  repoDir: string,
  cache: BlockStore = CacheStore.new()): T =

  let
    datastoreRes = SQLiteDatastore.new(repoDir)

  if datastoreRes.isErr:
    raise (ref Defect)(msg: datastoreRes.error.msg)

  T(cache: cache, datastore: datastoreRes.get)

proc datastore*(self: SQLiteStore): SQLiteDatastore =
  self.datastore

proc blockKey*(blockCid: Cid): ?!Key =
  let
    keyRes = Key.init($blockCid)

  if keyRes.isErr:
    trace "Unable to construct CID from key", cid = $blockCid, error = keyRes.error.msg

  keyRes

method getBlock*(
  self: SQLiteStore,
  cid: Cid): Future[?!Block] {.async.} =
  ## Get a block from the cache or database.
  ## Save a copy to the cache if present in the database but not in the cache
  ##

  if not self.cache.isNil:
    trace "Getting block from cache or database", cid = $cid
  else:
    trace "Getting block from database", cid = $cid

  if cid.isEmpty:
    trace "Empty block, ignoring"
    return success cid.emptyBlock

  if not self.cache.isNil:
    let
      cachedBlockRes = await self.cache.getBlock(cid)

    if cachedBlockRes.isOk:
      return success cachedBlockRes.get
    else:
      trace "Unable to read block from cache", cid = $cid, error = cachedBlockRes.error.msg

  without blkKey =? blockKey(cid), error:
    return failure error

  without dataOpt =? await self.datastore.get(blkKey), error:
    trace "Error requesting block from database", key = blkKey.id, error = error.msg
    return failure error

  without data =? dataOpt:
    return failure (ref BlockNotFoundError)(msg: "Block not in database")

  without blk =? Block.new(cid, data), error:
    trace "Unable to construct block from data", cid = $cid, error = error.msg
    return failure error

  if not self.cache.isNil:
    let
      putCachedRes = await self.cache.putBlock(blk)

    if putCachedRes.isErr:
      trace "Unable to store block in cache", cid = $cid, error = putCachedRes.error.msg

  return success blk

method putBlock*(
  self: SQLiteStore,
  blk: Block): Future[?!void] {.async.} =
  ## Write a block's contents to the database with key based on blk.cid.
  ## Save a copy to the cache
  ##

  if not self.cache.isNil:
    trace "Putting block into database and cache", cid = $blk.cid
  else:
    trace "Putting block into database", cid = $blk.cid

  if blk.isEmpty:
    trace "Empty block, ignoring"
    return success()

  without blkKey =? blockKey(blk.cid), error:
    return failure error

  let
    putRes = await self.datastore.put(blkKey, blk.data)

  if putRes.isErr:
    trace "Unable to store block in database", key = blkKey.id, error = putRes.error.msg
    return failure putRes.error

  if not self.cache.isNil:
    let
      putCachedRes = await self.cache.putBlock(blk)

    if putCachedRes.isErr:
      trace "Unable to store block in cache", cid = $blk.cid, error = putCachedRes.error.msg

  return success()

method delBlock*(
  self: SQLiteStore,
  cid: Cid): Future[?!void] {.async.} =
  ## Delete a block from the cache and database
  ##

  if not self.cache.isNil:
    trace "Deleting block from cache and database", cid = $cid
  else:
    trace "Deleting block from database", cid = $cid

  if cid.isEmpty:
    trace "Empty block, ignoring"
    return success()

  if not self.cache.isNil:
    let
      delCachedRes = await self.cache.delBlock(cid)

    if delCachedRes.isErr:
      trace "Unable to delete block from cache", cid = $cid, error = delCachedRes.error.msg

  without blkKey =? blockKey(cid), error:
    return failure error

  let
    delRes = await self.datastore.delete(blkKey)

  if delRes.isErr:
    trace "Unable to delete block from database", key = blkKey.id, error = delRes.error.msg
    return failure delRes.error

  return success()

method hasBlock*(
  self: SQLiteStore,
  cid: Cid): Future[?!bool] {.async.} =
  ## Check if a block exists in the database
  ##

  trace "Checking database for block existence", cid = $cid

  if cid.isEmpty:
    trace "Empty block, ignoring"
    return true.success

  without blkKey =? blockKey(cid), error:
    return failure error

  return await self.datastore.contains(blkKey)

iterator listBlocksQuery(self: SQLiteStore): ListBlocksQueryResponse =
  without listBlocksQueryStmt =? ListBlocksQueryStmt.prepare(self.datastore.env,
    listBlocksQueryStmtStr), error:

    raise (ref Defect)(msg: error.msg)

  let
    s = RawStmtPtr(listBlocksQueryStmt)

  defer:
    discard sqlite3_reset(s)
    s.dispose

  while true:
    let
      v = sqlite3_step(s)

    case v
    of SQLITE_ROW:
      yield $sqlite3_column_text_not_null(s, listBlocksQueryStmtIdCol)
    of SQLITE_DONE:
      break
    else:
      raise (ref Defect)(msg: $sqlite3_errstr(v))

method listBlocks*(
  self: SQLiteStore,
  onBlock: OnBlock): Future[?!void] {.async.} =
  ## Process list of all blocks in the database via callback.
  ## This is an intensive operation
  ##

  for id in self.listBlocksQuery():
    let
      # keys stored in id column of SQLiteDatastore are serialized Key
      # instances that start with "/", so drop the first character
      cidRes = Cid.init(id[1..^1])

    if cidRes.isOk:
      await onBlock(cidRes.get)
    else:
      trace "Unable to construct CID from key", key = id, error = $cidRes.error

  return success()

method close*(self: SQLiteStore): Future[void] {.async.} =
  ## Close the underlying cache and SQLite datastore
  ##

  if not self.cache.isNil: await self.cache.close
  if not self.datastore.isNil: self.datastore.close