import options, os, strutils
import leveldb/raw

type
  LevelDb* = ref object
    path*: string
    db: ptr leveldb_t
    cache: ptr leveldb_cache_t
    readOptions: ptr leveldb_readoptions_t
    syncWriteOptions: ptr leveldb_writeoptions_t
    asyncWriteOptions: ptr leveldb_writeoptions_t

  LevelDbWriteBatch* = ref object
    batch: ptr leveldb_writebatch_t

  CompressionType* = enum
    ctNoCompression = leveldb_no_compression,
    ctSnappyCompression = leveldb_snappy_compression

  LevelDbException* = object of Exception

const
  version* = block:
    const configFile = "leveldb.nimble"
    const sourcePath = currentSourcePath()
    const parentConfig = sourcePath.parentDir.parentDir / configFile
    const localConfig = sourcePath.parentDir / configFile
    var content: string
    if fileExists(parentConfig):
      content = staticRead(parentConfig)
    else:
      content = staticRead(localConfig)
    var version_line: string
    for line in content.split("\L"):
      if line.startsWith("version"):
        version_line = line
        break
    let raw = version_line.split("=", maxsplit = 1)[1]
    raw.strip().strip(chars = {'"'})

  levelDbTrue = uint8(1)
  levelDbFalse = uint8(0)

proc free(p: pointer) {.importc.}

proc checkError(errPtr: cstring) =
  if errPtr != nil:
    defer: free(errPtr)
    raise newException(LevelDbException, $errPtr)

proc getLibVersion*(): (int, int) =
  result[0] = leveldb_major_version()
  result[1] = leveldb_minor_version()

proc close*(self: LevelDb) =
  if self.db == nil:
    return
  leveldb_close(self.db)
  leveldb_writeoptions_destroy(self.syncWriteOptions)
  leveldb_writeoptions_destroy(self.asyncWriteOptions)
  leveldb_readoptions_destroy(self.readOptions)
  if self.cache != nil:
    leveldb_cache_destroy(self.cache)
    self.cache = nil
  self.db = nil

proc open*(path: string, create = true, reuse = true, paranoidChecks = true,
    compressionType = ctSnappyCompression,
    cacheCapacity = 0, blockSize = 4 * 1024, writeBufferSize = 4*1024*1024,
    maxOpenFiles = 1000, maxFileSize = 2 * 1024 * 1024,
    blockRestartInterval = 16): LevelDb =
  new(result, close)

  let options = leveldb_options_create()
  defer: leveldb_options_destroy(options)

  result.syncWriteOptions = leveldb_writeoptions_create()
  leveldb_writeoptions_set_sync(result.syncWriteOptions, levelDbTrue)
  result.asyncWriteOptions = leveldb_writeoptions_create()
  leveldb_writeoptions_set_sync(result.asyncWriteOptions, levelDbFalse)
  result.readOptions = leveldb_readoptions_create()

  if create:
    leveldb_options_set_create_if_missing(options, levelDbTrue)
  else:
    leveldb_options_set_create_if_missing(options, levelDbFalse)
  if reuse:
    leveldb_options_set_error_if_exists(options, levelDbFalse)
  else:
    leveldb_options_set_error_if_exists(options, levelDbTrue)
  if paranoidChecks:
    leveldb_options_set_paranoid_checks(options, levelDbTrue)
  else:
    leveldb_options_set_paranoid_checks(options, levelDbFalse)

  leveldb_options_set_write_buffer_size(options, writeBufferSize)
  leveldb_options_set_block_size(options, blockSize)
  leveldb_options_set_max_open_files(options, cast[cint](maxOpenFiles))
  leveldb_options_set_max_file_size(options, maxFileSize)
  leveldb_options_set_block_restart_interval(options,
                                             cast[cint](blockRestartInterval))
  leveldb_options_set_compression(options, cast[cint](compressionType.ord))

  if cacheCapacity > 0:
    let cache = leveldb_cache_create_lru(cacheCapacity)
    leveldb_options_set_cache(options, cache)
    result.cache = cache

  var errPtr: cstring = nil
  result.path = path
  result.db = leveldb_open(options, path, addr errPtr)
  checkError(errPtr)

proc put*(self: LevelDb, key: string, value: string, sync = true) =
  assert self.db != nil
  var errPtr: cstring = nil
  let writeOptions = if sync: self.syncWriteOptions else: self.asyncWriteOptions
  leveldb_put(self.db, writeOptions,
              key, key.len.csize, value, value.len.csize, addr errPtr)
  checkError(errPtr)

proc newString(cstr: cstring, length: csize): string =
  if length > 0:
    result = newString(length)
    copyMem(unsafeAddr result[0], cstr, length)
  else:
    result = ""

proc get*(self: LevelDb, key: string): Option[string] =
  var size: csize
  var errPtr: cstring = nil
  let s = leveldb_get(self.db, self.readOptions, key, key.len, addr size, addr errPtr)
  checkError(errPtr)

  if s == nil:
    result = none(string)
  else:
    result = some(newString(s, size))
    free(s)

proc getOrDefault*(self: LevelDb, key: string, default = ""): string =
  runnableExamples:
    let db = leveldb.open("/tmp/test")
    doAssert db.getOrDefault("what?", "nothing") == "nothing"
    db.close()

  let val = self.get(key)
  if val.isNone():
    result = default
  else:
    result = val.get()

proc delete*(self: LevelDb, key: string, sync = true) =
  var errPtr: cstring = nil
  let writeOptions = if sync: self.syncWriteOptions else: self.asyncWriteOptions
  leveldb_delete(self.db, writeOptions, key, key.len, addr errPtr)
  checkError(errPtr)

proc destroy*(self: LevelDbWriteBatch) =
  if self.batch == nil:
    return
  leveldb_writebatch_destroy(self.batch)
  self.batch = nil

proc newBatch*(): LevelDbWriteBatch =
  new(result, destroy)
  result.batch = leveldb_writebatch_create()

proc put*(self: LevelDbWriteBatch, key: string, value: string, sync = true) =
  leveldb_writebatch_put(self.batch, key, key.len.csize, value, value.len.csize)

proc append*(self, source: LevelDbWriteBatch) =
  leveldb_writebatch_append(self.batch, source.batch)

proc delete*(self: LevelDbWriteBatch, key: string) =
  leveldb_writebatch_delete(self.batch, key, key.len.csize)

proc clear*(self: LevelDbWriteBatch) =
  leveldb_writebatch_clear(self.batch)

proc write*(self: LevelDb, batch: LevelDbWriteBatch) =
  var errPtr: cstring = nil
  leveldb_write(self.db, self.syncWriteOptions, batch.batch, addr errPtr)
  checkError(errPtr)

proc getIterData(iterPtr: ptr leveldb_iterator_t): (string, string) =
  var len: csize
  var str: cstring

  str = leveldb_iter_key(iterPtr, addr len)
  result[0] = newString(str, len)

  str = leveldb_iter_value(iterPtr, addr len)
  result[1] = newString(str, len)

iterator iter*(self: LevelDb, seek: string = "", reverse: bool = false): (
    string, string) =
  var iterPtr = leveldb_create_iterator(self.db, self.readOptions)
  defer: leveldb_iter_destroy(iterPtr)

  if seek.len > 0:
    leveldb_iter_seek(iterPtr, seek, seek.len)
  else:
    if reverse:
      leveldb_iter_seek_to_last(iterPtr)
    else:
      leveldb_iter_seek_to_first(iterPtr)

  while true:
    if leveldb_iter_valid(iterPtr) == levelDbFalse:
      break

    var (key, value) = getIterData(iterPtr)
    var err: cstring = nil
    leveldb_iter_get_error(iterPtr, addr err)
    checkError(err)
    yield (key, value)

    if reverse:
      leveldb_iter_prev(iterPtr)
    else:
      leveldb_iter_next(iterPtr)

iterator iterPrefix*(self: LevelDb, prefix: string): (string, string) =
  for key, value in iter(self, prefix, reverse = false):
    if key.startsWith(prefix):
      yield (key, value)
    else:
      break

iterator iterRange*(self: LevelDb, start, limit: string): (string, string) =
  let reverse: bool = limit < start
  for key, value in iter(self, start, reverse = reverse):
    if reverse:
      if key < limit:
        break
    else:
      if key > limit:
        break
    yield (key, value)

proc removeDb*(name: string) =
  var err: cstring = nil
  let options = leveldb_options_create()
  leveldb_destroy_db(options, name, addr err)
  checkError(err)

proc repairDb*(name: string) =
  let options = leveldb_options_create()
  leveldb_options_set_create_if_missing(options, levelDbFalse)
  leveldb_options_set_error_if_exists(options, levelDbFalse)
  var errPtr: cstring = nil
  leveldb_repair_db(options, name, addr errPtr)
  checkError(errPtr)