nim-datastore/datastore/backend.nim

import std/algorithm
import std/options

import pkg/questionable/results

import ./threads/databuffer
import ./types

export databuffer, types, SortOrder

type
  DbQueryResponse*[K, V] = tuple[key: Option[K], data: V]

  DbQuery*[K] = object
    key*: K         # Key to be queried
    value*: bool      # Flag to indicate if data should be returned
    limit*: int       # Max items to return - not available in all backends
    offset*: int      # Offset from which to start querying - not available in all backends
    sort*: SortOrder  # Sort order - not available in all backends

  KeyId* = object
    ## serialized Key ID, equivalent to `key.id()`
    data*: DataBuffer

  DbKey* = string | KeyId
  DbVal* = seq[byte] | DataBuffer

  DbBatchEntry*[K, V] = tuple[key: K, data: V]

  DbQueryHandle*[K, V, T] = object
    query*: DbQuery[K]
    cancel*: bool
    closed*: bool
    env*: T

proc dbQuery*[K](
    key: K,
    value = false,
    sort = SortOrder.Ascending,
    offset = 0,
    limit = -1
): DbQuery[K] =
  DbQuery[K](key: key, value: value, sort: sort, offset: offset, limit: limit)

proc `$`*(id: KeyId): string = $(id.data)

proc toKey*(tp: typedesc[KeyId], id: cstring): KeyId = KeyId.new(id)
proc toKey*(tp: typedesc[string], id: cstring): string = $(id)

template toVal*(tp: typedesc[DataBuffer], id: openArray[byte]): DataBuffer = DataBuffer.new(id)
template toVal*(tp: typedesc[seq[byte]], id: openArray[byte]): seq[byte] = @(id)

proc new*(tp: typedesc[KeyId], id: cstring): KeyId =
  KeyId(data: DataBuffer.new(id.toOpenArray(0, id.len()-1)))

proc new*(tp: typedesc[KeyId], id: string): KeyId =
  KeyId(data: DataBuffer.new(id))

template toOpenArray*(x: DbKey): openArray[char] =
  x.data.toOpenArray(char)