log = require 'iced-logger'
{E} = require './err'
{make_esc} = require 'iced-error'
{Lock} = require 'iced-lock'

##=======================================================================

exports.Base = class Base

  constructor : () ->
    @lock = new Lock

  #========================

  unimplemented : (n, cb) -> cb new E.UnimplementedError "BaseKvStore::#{n}: unimplemented"

  #========================

  # Base classes need to implement these...
  open : (opts, cb) -> @unimplemented('open', cb)
  nuke : (opts, cb) -> @unimplemented('nuke', cb)
  close : (opts, cb) -> @unimplemented('close', cb)
  _put : ({key,value},cb) -> @unimplemented('_put', cb)
  _get : ({key}, cb) -> @unimplemented("_get", cb)
  _resolve : ({name}, cb) -> @unimplemented("_resolve", cb)
  _link : ({name,key}, cb) -> @unimplemented('_link', cb)
  _unlink : ({name}, cb) -> @unimplemented('_unlink', cb)
  _unlink_all : ({key}, cb) -> @unimplemented('_unlink_all', cb)
  _remove : ({key}, cb) -> @unimplemented('_remove', cb)

  #=========================

  make_kvstore_key : ( {type, key } ) ->
    type or= key[-2...]
    [ type, key ].join(":").toLowerCase()
  make_lookup_name : ( {type, name} ) -> [ type, name ].join(":").toLowerCase()

  unmake_kvstore_key : ( {key}) ->
    parts = key.split(":")
    { type : parts[0], key : parts[1...].join(":") }

  can_unlink : () -> true

  #=========================

  link : ({type, name, key}, cb) ->
    @_link {
      name : @make_lookup_name({ type, name }),
      key : @make_kvstore_key({ key, type })
    }, cb
  unlink : ({type, name}, cb) -> @_unlink { name : @make_lookup_name({ type, name }) }, cb
  unlink_all : ({type, key}, cb) -> @_unlink_all { key : @make_kvstore_key({type, key}) }, cb
  get : ({type,key}, cb) -> @_get { key : @make_kvstore_key({type, key}) }, cb
  resolve : ({type, name}, cb) ->
    await @_resolve { name : @make_lookup_name({type,name})}, defer err, key
    if not err? and key?
      { key } = @unmake_kvstore_key { key }
    cb err, key

  #=========================

  put : ({type, key, value, name, names}, cb) ->
    esc = make_esc cb, "BaseKvStore::put"
    kvsk = @make_kvstore_key {type,key}
    log.debug "+ KvStore::put #{key}/#{kvsk}"
    await @_put { key : kvsk, value }, esc defer()
    names = [ name ] if name? and not names?
    if names and names.length
      for name in names
        log.debug "| KvStore::link #{name} -> #{key}"
        await @link { type, name, key }, esc defer()
    log.debug "- KvStore::put #{key} -> ok"
    cb null

  #-----

  remove : ({type, key, optional}, cb) ->
    k = @make_kvstore_key { type, key }
    await @lock.acquire defer()

    log.debug "+ DB remove #{key}/#{k}"

    await @_remove { key : k }, defer err
    if err? and (err instanceof E.NotFoundError) and optional
      log.debug "| No object found for #{k}"
      err = null
    else if not err?
      await @_unlink_all { type, key : k }, defer err

    log.debug "- DB remove #{key}/#{k} -> #{if err? then 'ok' else #{err.message}}"
    @lock.release()

    cb err

  #-----

  lookup : ({type, name}, cb) ->
    esc = make_esc cb, "BaseKvStore::lookup"
    await @resolve { name, type }, esc defer key
    await @get { type, key }, esc defer value
    cb null, value

##=======================================================================

# Use this interface if you want to store objects in a Flat key-value store,
# without secondary indices.  In this case, "linking" multiple names to one
# value is just a @_put{} link any other, and there is no ability to _unlink_all.
# This layout is what we used for the original node client.
exports.Flat = class Flat extends Base

  make_kvstore_key : ({type,key}) ->
    "kv:" + super { type, key }

  make_lookup_name : ({type,name}) ->
    "lo:" + super { type, name }

  unmake_kvstore_key : ( {key}) ->
    parts = key.split(":")
    { type : parts[1], key : parts[2...].join(":") }

  _link : ({key, name}, cb) ->
    await @_put { key : name, value : key }, defer err
    cb err

  _unlink : ({name}, cb) ->
    await @_remove { key : name }, defer err
    cb err

  _unlink_all : ({key}, cb) ->
    log.debug "| Can't _unlink_all names for #{key} in flat kvstore"
    cb null

  _resolve : ({name}, cb) ->
    await @_get { key : name }, defer err, value
    if err? and (err instanceof E.NotFoundError)
      err = new E.LookupNotFoundError "No lookup available for #{name}"
    cb err, value

  can_unlink : () -> false

##=======================================================================

# A memory-backed store, mainly for testing...
exports.Memory = class Memory extends Base

  constructor : () ->
    super
    @data =
      lookup : {}
      rlookup : {}
      kv : {}

  open : (opts, cb) -> cb null
  nuke : (opts, cb) -> cb null
  close : (opts, cb) -> cb null

  _put : ({key, value}, cb) ->
    @data.kv[key] = value
    cb null

  _get : ({key}, cb) ->
    err = null
    if (val = @data.kv[key]) is undefined
      err = new E.NotFoundError "key not found: '#{key}'"
    cb err, val

  _resolve : ({name}, cb) ->
    err = null
    unless (key = @data.lookup[name])?
      err = new E.LookupNotFoundError "name not found: '#{name}'"
    cb err, key

  _link : ({key, name}, cb) ->
    @data.lookup[name] = key
    @data.rlookup[key] = set = {} unless (set = @data.rlookup[key])?
    set[name] = true
    cb null

  _unlink : ({name}, cb) ->
    if (key = @data.lookup[name])?
      delete d[name] if (d = @data.rlookup[key])?
      delete @data.lookup[name]
      err = null
    else
      err = new E.LookupNotFoundError "cannot unlink '#{name}'"
    cb err

  _remove : ({key}, cb) ->
    err = null
    unless (v = @data.kv[key])?
      err = new E.NotFoundError "key not found: '#{key}'"
    else
      delete @data.kv[key]
    cb err

  _unlink_all : ({key}, cb) ->
    if (d = @data.rlookup[key])?
      for name,_ of d
        delete @data.lookup[name]
      delete @data.rlookup[key]
      err = null
    else
      err = new E.LookupNotFoundError "cannot find names for key '#{key}'"
    cb err

##=======================================================================

# for testing, an in-memory flat store, that stores lookups and kv-pairs
# in the same table, and doesn't have the ability to "unlink_all"
exports.FlatMemory = class FlatMemory extends Flat

  constructor : () ->
    super
    @kv = {}

  open : (opts, cb) -> cb null
  nuke : (opts, cb) -> cb null
  close : (opts, cb) -> cb null

  _put : ({key, value}, cb) ->
    @kv[key] = value
    cb null

  _get : ({key}, cb) ->
    err = null
    if (val = @kv[key]) is undefined
      err = new E.NotFoundError "key not found: '#{key}'"
    cb err, val

  _remove : ({key}, cb) ->
    err = null
    unless (v = @kv[key])?
      err = new E.NotFoundError "key not found: '#{key}'"
    else
      delete @kv[key]
    cb err

##=======================================================================