Headroom.IO.KVStore

This is really simple key-value persistent store that uses SQLite as a backend. Main goal is to provide type-safe way how to define value keys, that can be later used to set/put the actual value into the store.

Type Aliases

type GetValueFn m

Arguments

 = forall a. ValueCodec a

=> ValueKey a

key for the value

-> m (Maybe a)

value (if found)

Gets the value for given ValueKey from the store.

type PutValueFn m

Arguments

 = forall a. ValueCodec a

=> ValueKey a

key for the value

-> a

value to put into store

-> m ()

operation result

Puts the value for given ValueKey into the store.

data KVStore m

Polymorphic record composed of key-value store operations, allowing to abstract over concrete implementation without (ab)using type classes.

Constructors

KVStore

Fields

• kvGetValue :: GetValueFn m
• kvPutValue :: PutValueFn m

Type Classes

class ValueCodec a where

Represents way how to encode/decode concrete types into textual representation used by the store to hold values.

Methods

encodeValue

Arguments

:: a

value to encode

-> Text

textual representation

Encodes value into textual representation.

decodeValue

Arguments

:: Text

value to decode

-> Maybe a

decoded value (if available)

Decodes value from textual representation.

Instances

ValueCodec Text

Defined in Headroom.IO.KVStore

Methods

encodeValue :: Text -> Text

decodeValue :: Text -> Maybe Text

ValueCodec UTCTime

Defined in Headroom.IO.KVStore

Methods

encodeValue :: UTCTime -> Text

decodeValue :: Text -> Maybe UTCTime

Data Types

newtype ValueKey a

Type-safe representation of the key for specific value.

Constructors

ValueKey Text

Instances

Eq (ValueKey a)

Defined in Headroom.IO.KVStore

Methods

(==) :: ValueKey a -> ValueKey a -> Bool

(/=) :: ValueKey a -> ValueKey a -> Bool

Show (ValueKey a)

Defined in Headroom.IO.KVStore

Methods

showsPrec :: Int -> ValueKey a -> ShowS

show :: ValueKey a -> String

showList :: [ValueKey a] -> ShowS

newtype StorePath

Path to the store (e.g. path of the SQLite database on filesystem).

Constructors

StorePath Text

Instances

Eq StorePath

Defined in Headroom.IO.KVStore

Methods

(==) :: StorePath -> StorePath -> Bool

(/=) :: StorePath -> StorePath -> Bool

Show StorePath

Defined in Headroom.IO.KVStore

Methods

showsPrec :: Int -> StorePath -> ShowS

show :: StorePath -> String

showList :: [StorePath] -> ShowS

Public Functions

inMemoryKVStore :: MonadIO m => m (KVStore m)

Constructs non-persistent in-memory instance of KVStore.

sqliteKVStore

Arguments

:: MonadIO m

=> StorePath

path of the store location

-> KVStore m

store instance

Constructs persistent instance of KVStore that uses SQLite as a backend.

valueKey :: Text -> ValueKey a

Constructor function for ValueKey.