Data.Mergeless

A way to synchronise items without merge conflicts.

This concept has a few requirements:

• Items must be immutable.
• Items must allow for a centrally unique identifier.
• Identifiers for items must be generatable in such a way that they are certainly unique.

Should mutation be a requirement, then it can be build such that it entails deleting the old version and creating a new version that is the modification of the old version.

There are a few obvious candidates for identifiers:

• incremental identifiers
• universally unique identifiers (recommended).

The typical setup is as follows:

• A central server is set up to synchronise with
• Each client synchronises with the central server, but never with eachother

A central server should operate as follows:

• The server accepts a SyncRequest.
• The server performs operations according to the functionality of processSync.
• The server respons with a SyncResponse.

A client should operate as follows:

• The client produces a SyncRequest with makeSyncRequest.
• The client sends that request to the central server and gets a SyncResponse.
• The client then updates its local store with mergeSyncResponse.

Documentation

newtype Store i a

A client-side store of items with Id's of type i and values of type a

Constructors

Store

Fields

• storeItems :: Set (StoreItem i a)

Instances

(Eq a, Eq i) => Eq (Store i a)

Methods

(==) :: Store i a -> Store i a -> Bool

(/=) :: Store i a -> Store i a -> Bool

(Ord a, Ord i) => Ord (Store i a)

Methods

compare :: Store i a -> Store i a -> Ordering

(<) :: Store i a -> Store i a -> Bool

(<=) :: Store i a -> Store i a -> Bool

(>) :: Store i a -> Store i a -> Bool

(>=) :: Store i a -> Store i a -> Bool

max :: Store i a -> Store i a -> Store i a

min :: Store i a -> Store i a -> Store i a

(Show a, Show i) => Show (Store i a)

Methods

showsPrec :: Int -> Store i a -> ShowS

show :: Store i a -> String

showList :: [Store i a] -> ShowS

Generic (Store i a)

Associated Types

type Rep (Store i a) :: * -> *

Methods

from :: Store i a -> Rep (Store i a) x

to :: Rep (Store i a) x -> Store i a

(ToJSON a, ToJSON i) => ToJSON (Store i a)

Methods

toJSON :: Store i a -> Value

toEncoding :: Store i a -> Encoding

toJSONList :: [Store i a] -> Value

toEncodingList :: [Store i a] -> Encoding

(FromJSON a, FromJSON i, Ord a, Ord i) => FromJSON (Store i a)

Methods

parseJSON :: Value -> Parser (Store i a)

parseJSONList :: Value -> Parser [Store i a]

(Validity i, Validity a, Ord i, Ord a) => Validity (Store i a)

Methods

validate :: Store i a -> Validation

type Rep (Store i a)

type Rep (Store i a) = D1 * (MetaData "Store" "Data.Mergeless" "mergeless-0.0.0.0-3ukUmlP02EMDeV1JFeafyp" True) (C1 * (MetaCons "Store" PrefixI True) (S1 * (MetaSel (Just Symbol "storeItems") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * (Set (StoreItem i a)))))

data StoreItem i a

A store item with an Id of type i and a value of type a

Constructors

UnsyncedItem !(Added a)

A local item that has not been synchronised to the central store yet

SyncedItem !(Synced i a)

A local item that has been synchronised to the central store already

UndeletedItem i

An item that has been synchronised to the central store, was subsequently deleted locally but this deletion has not been synchronised to the central store yet.

Instances

(Eq i, Eq a) => Eq (StoreItem i a)

Methods

(==) :: StoreItem i a -> StoreItem i a -> Bool

(/=) :: StoreItem i a -> StoreItem i a -> Bool

(Ord i, Ord a) => Ord (StoreItem i a)

Methods

compare :: StoreItem i a -> StoreItem i a -> Ordering

(<) :: StoreItem i a -> StoreItem i a -> Bool

(<=) :: StoreItem i a -> StoreItem i a -> Bool

(>) :: StoreItem i a -> StoreItem i a -> Bool

(>=) :: StoreItem i a -> StoreItem i a -> Bool

max :: StoreItem i a -> StoreItem i a -> StoreItem i a

min :: StoreItem i a -> StoreItem i a -> StoreItem i a

(Show i, Show a) => Show (StoreItem i a)

Methods

showsPrec :: Int -> StoreItem i a -> ShowS

show :: StoreItem i a -> String

showList :: [StoreItem i a] -> ShowS

Generic (StoreItem i a)

Associated Types

type Rep (StoreItem i a) :: * -> *

Methods

from :: StoreItem i a -> Rep (StoreItem i a) x

to :: Rep (StoreItem i a) x -> StoreItem i a

(ToJSON i, ToJSON a) => ToJSON (StoreItem i a)

Methods

toJSON :: StoreItem i a -> Value

toEncoding :: StoreItem i a -> Encoding

toJSONList :: [StoreItem i a] -> Value

toEncodingList :: [StoreItem i a] -> Encoding

(FromJSON i, FromJSON a) => FromJSON (StoreItem i a)

Methods

parseJSON :: Value -> Parser (StoreItem i a)

parseJSONList :: Value -> Parser [StoreItem i a]

(Validity i, Validity a) => Validity (StoreItem i a)

Methods

validate :: StoreItem i a -> Validation

type Rep (StoreItem i a)

type Rep (StoreItem i a) = D1 * (MetaData "StoreItem" "Data.Mergeless" "mergeless-0.0.0.0-3ukUmlP02EMDeV1JFeafyp" False) ((:+:) * (C1 * (MetaCons "UnsyncedItem" PrefixI False) (S1 * (MetaSel (Nothing Symbol) NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * (Added a)))) ((:+:) * (C1 * (MetaCons "SyncedItem" PrefixI False) (S1 * (MetaSel (Nothing Symbol) NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * (Synced i a)))) (C1 * (MetaCons "UndeletedItem" PrefixI False) (S1 * (MetaSel (Nothing Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * i)))))

data Added a

A local item of type a that has been added but not synchronised yet

Constructors

Added

Fields

• addedValue :: !a
• addedCreated :: !UTCTime

Instances

Eq a => Eq (Added a)

Methods

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

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

Ord a => Ord (Added a)

Methods

compare :: Added a -> Added a -> Ordering

(<) :: Added a -> Added a -> Bool

(<=) :: Added a -> Added a -> Bool

(>) :: Added a -> Added a -> Bool

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

max :: Added a -> Added a -> Added a

min :: Added a -> Added a -> Added a

Show a => Show (Added a)

Methods

showsPrec :: Int -> Added a -> ShowS

show :: Added a -> String

showList :: [Added a] -> ShowS

Generic (Added a)

Associated Types

type Rep (Added a) :: * -> *

Methods

from :: Added a -> Rep (Added a) x

to :: Rep (Added a) x -> Added a

ToJSON a => ToJSON (Added a)

Methods

toJSON :: Added a -> Value

toEncoding :: Added a -> Encoding

toJSONList :: [Added a] -> Value

toEncodingList :: [Added a] -> Encoding

FromJSON a => FromJSON (Added a)

Methods

parseJSON :: Value -> Parser (Added a)

parseJSONList :: Value -> Parser [Added a]

Validity a => Validity (Added a)

Methods

validate :: Added a -> Validation

type Rep (Added a)

type Rep (Added a) = D1 * (MetaData "Added" "Data.Mergeless" "mergeless-0.0.0.0-3ukUmlP02EMDeV1JFeafyp" False) (C1 * (MetaCons "Added" PrefixI True) ((:*:) * (S1 * (MetaSel (Just Symbol "addedValue") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * a)) (S1 * (MetaSel (Just Symbol "addedCreated") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * UTCTime))))

data Synced i a

A local item of type a with an identifier of type a that has been synchronised

Constructors

Synced

Fields

• syncedUuid :: i
• syncedValue :: !a
• syncedCreated :: !UTCTime
• syncedSynced :: !UTCTime

Instances

(Eq a, Eq i) => Eq (Synced i a)

Methods

(==) :: Synced i a -> Synced i a -> Bool

(/=) :: Synced i a -> Synced i a -> Bool

(Ord a, Ord i) => Ord (Synced i a)

Methods

compare :: Synced i a -> Synced i a -> Ordering

(<) :: Synced i a -> Synced i a -> Bool

(<=) :: Synced i a -> Synced i a -> Bool

(>) :: Synced i a -> Synced i a -> Bool

(>=) :: Synced i a -> Synced i a -> Bool

max :: Synced i a -> Synced i a -> Synced i a

min :: Synced i a -> Synced i a -> Synced i a

(Show a, Show i) => Show (Synced i a)

Methods

showsPrec :: Int -> Synced i a -> ShowS

show :: Synced i a -> String

showList :: [Synced i a] -> ShowS

Generic (Synced i a)

Associated Types

type Rep (Synced i a) :: * -> *

Methods

from :: Synced i a -> Rep (Synced i a) x

to :: Rep (Synced i a) x -> Synced i a

(ToJSON i, ToJSON a) => ToJSON (Synced i a)

Methods

toJSON :: Synced i a -> Value

toEncoding :: Synced i a -> Encoding

toJSONList :: [Synced i a] -> Value

toEncodingList :: [Synced i a] -> Encoding

(FromJSON i, FromJSON a) => FromJSON (Synced i a)

Methods

parseJSON :: Value -> Parser (Synced i a)

parseJSONList :: Value -> Parser [Synced i a]

(Validity i, Validity a) => Validity (Synced i a)

Methods

validate :: Synced i a -> Validation

type Rep (Synced i a)

type Rep (Synced i a) = D1 * (MetaData "Synced" "Data.Mergeless" "mergeless-0.0.0.0-3ukUmlP02EMDeV1JFeafyp" False) (C1 * (MetaCons "Synced" PrefixI True) ((:*:) * ((:*:) * (S1 * (MetaSel (Just Symbol "syncedUuid") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * i)) (S1 * (MetaSel (Just Symbol "syncedValue") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * a))) ((:*:) * (S1 * (MetaSel (Just Symbol "syncedCreated") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * UTCTime)) (S1 * (MetaSel (Just Symbol "syncedSynced") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * UTCTime)))))

data SyncRequest i a

A synchronisation request for items with identifiers of type i and values of type a

Constructors

SyncRequest

Fields

• syncRequestAddedItems :: !(Set (Added a))
• syncRequestSyncedItems :: !(Set i)
• syncRequestUndeletedItems :: !(Set i)

Instances

(Eq i, Eq a) => Eq (SyncRequest i a)

Methods

(==) :: SyncRequest i a -> SyncRequest i a -> Bool

(/=) :: SyncRequest i a -> SyncRequest i a -> Bool

(Ord i, Ord a) => Ord (SyncRequest i a)

Methods

compare :: SyncRequest i a -> SyncRequest i a -> Ordering

(<) :: SyncRequest i a -> SyncRequest i a -> Bool

(<=) :: SyncRequest i a -> SyncRequest i a -> Bool

(>) :: SyncRequest i a -> SyncRequest i a -> Bool

(>=) :: SyncRequest i a -> SyncRequest i a -> Bool

max :: SyncRequest i a -> SyncRequest i a -> SyncRequest i a

min :: SyncRequest i a -> SyncRequest i a -> SyncRequest i a

(Show i, Show a) => Show (SyncRequest i a)

Methods

showsPrec :: Int -> SyncRequest i a -> ShowS

show :: SyncRequest i a -> String

showList :: [SyncRequest i a] -> ShowS

Generic (SyncRequest i a)

Associated Types

type Rep (SyncRequest i a) :: * -> *

Methods

from :: SyncRequest i a -> Rep (SyncRequest i a) x

to :: Rep (SyncRequest i a) x -> SyncRequest i a

(ToJSON i, ToJSON a) => ToJSON (SyncRequest i a)

Methods

toJSON :: SyncRequest i a -> Value

toEncoding :: SyncRequest i a -> Encoding

toJSONList :: [SyncRequest i a] -> Value

toEncodingList :: [SyncRequest i a] -> Encoding

(FromJSON i, FromJSON a, Ord i, Ord a) => FromJSON (SyncRequest i a)

Methods

parseJSON :: Value -> Parser (SyncRequest i a)

parseJSONList :: Value -> Parser [SyncRequest i a]

(Validity i, Validity a, Ord i, Ord a) => Validity (SyncRequest i a)

Methods

validate :: SyncRequest i a -> Validation

type Rep (SyncRequest i a)

type Rep (SyncRequest i a) = D1 * (MetaData "SyncRequest" "Data.Mergeless" "mergeless-0.0.0.0-3ukUmlP02EMDeV1JFeafyp" False) (C1 * (MetaCons "SyncRequest" PrefixI True) ((:*:) * (S1 * (MetaSel (Just Symbol "syncRequestAddedItems") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * (Set (Added a)))) ((:*:) * (S1 * (MetaSel (Just Symbol "syncRequestSyncedItems") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * (Set i))) (S1 * (MetaSel (Just Symbol "syncRequestUndeletedItems") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * (Set i))))))

makeSyncRequest :: (Ord i, Ord a) => Store i a -> SyncRequest i a

Produce a synchronisation request for a client-side store.

This request can then be sent to a central store for synchronisation.

data SyncResponse i a

A synchronisation response for items with identifiers of type i and values of type a

Constructors

SyncResponse

Fields

• syncResponseAddedItems :: !(Set (Synced i a))
• syncResponseNewRemoteItems :: !(Set (Synced i a))
• syncResponseItemsToBeDeletedLocally :: !(Set i)

Instances

(Eq i, Eq a) => Eq (SyncResponse i a)

Methods

(==) :: SyncResponse i a -> SyncResponse i a -> Bool

(/=) :: SyncResponse i a -> SyncResponse i a -> Bool

(Ord i, Ord a) => Ord (SyncResponse i a)

Methods

compare :: SyncResponse i a -> SyncResponse i a -> Ordering

(<) :: SyncResponse i a -> SyncResponse i a -> Bool

(<=) :: SyncResponse i a -> SyncResponse i a -> Bool

(>) :: SyncResponse i a -> SyncResponse i a -> Bool

(>=) :: SyncResponse i a -> SyncResponse i a -> Bool

max :: SyncResponse i a -> SyncResponse i a -> SyncResponse i a

min :: SyncResponse i a -> SyncResponse i a -> SyncResponse i a

(Show i, Show a) => Show (SyncResponse i a)

Methods

showsPrec :: Int -> SyncResponse i a -> ShowS

show :: SyncResponse i a -> String

showList :: [SyncResponse i a] -> ShowS

Generic (SyncResponse i a)

Associated Types

type Rep (SyncResponse i a) :: * -> *

Methods

from :: SyncResponse i a -> Rep (SyncResponse i a) x

to :: Rep (SyncResponse i a) x -> SyncResponse i a

(ToJSON i, ToJSON a) => ToJSON (SyncResponse i a)

Methods

toJSON :: SyncResponse i a -> Value

toEncoding :: SyncResponse i a -> Encoding

toJSONList :: [SyncResponse i a] -> Value

toEncodingList :: [SyncResponse i a] -> Encoding

(FromJSON i, FromJSON a, Ord i, Ord a) => FromJSON (SyncResponse i a)

Methods

parseJSON :: Value -> Parser (SyncResponse i a)

parseJSONList :: Value -> Parser [SyncResponse i a]

(Validity i, Validity a, Ord i, Ord a) => Validity (SyncResponse i a)

Methods

validate :: SyncResponse i a -> Validation

type Rep (SyncResponse i a)

type Rep (SyncResponse i a) = D1 * (MetaData "SyncResponse" "Data.Mergeless" "mergeless-0.0.0.0-3ukUmlP02EMDeV1JFeafyp" False) (C1 * (MetaCons "SyncResponse" PrefixI True) ((:*:) * (S1 * (MetaSel (Just Symbol "syncResponseAddedItems") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * (Set (Synced i a)))) ((:*:) * (S1 * (MetaSel (Just Symbol "syncResponseNewRemoteItems") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * (Set (Synced i a)))) (S1 * (MetaSel (Just Symbol "syncResponseItemsToBeDeletedLocally") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * (Set i))))))

mergeSyncResponse :: (Ord i, Ord a) => Store i a -> SyncResponse i a -> Store i a

Merge a synchronisation response back into a client-side store.

newtype CentralStore i a

A central store of items with identifiers of type i and values of type a

Constructors

CentralStore

Fields

• centralStoreItems :: Map i (CentralItem a)

Instances

(Eq a, Eq i) => Eq (CentralStore i a)

Methods

(==) :: CentralStore i a -> CentralStore i a -> Bool

(/=) :: CentralStore i a -> CentralStore i a -> Bool

(Ord a, Ord i) => Ord (CentralStore i a)

Methods

compare :: CentralStore i a -> CentralStore i a -> Ordering

(<) :: CentralStore i a -> CentralStore i a -> Bool

(<=) :: CentralStore i a -> CentralStore i a -> Bool

(>) :: CentralStore i a -> CentralStore i a -> Bool

(>=) :: CentralStore i a -> CentralStore i a -> Bool

max :: CentralStore i a -> CentralStore i a -> CentralStore i a

min :: CentralStore i a -> CentralStore i a -> CentralStore i a

(Show a, Show i) => Show (CentralStore i a)

Methods

showsPrec :: Int -> CentralStore i a -> ShowS

show :: CentralStore i a -> String

showList :: [CentralStore i a] -> ShowS

Generic (CentralStore i a)

Associated Types

type Rep (CentralStore i a) :: * -> *

Methods

from :: CentralStore i a -> Rep (CentralStore i a) x

to :: Rep (CentralStore i a) x -> CentralStore i a

(ToJSONKey i, ToJSON a) => ToJSON (CentralStore i a)

Methods

toJSON :: CentralStore i a -> Value

toEncoding :: CentralStore i a -> Encoding

toJSONList :: [CentralStore i a] -> Value

toEncodingList :: [CentralStore i a] -> Encoding

(FromJSON a, Ord i, FromJSONKey i) => FromJSON (CentralStore i a)

Methods

parseJSON :: Value -> Parser (CentralStore i a)

parseJSONList :: Value -> Parser [CentralStore i a]

(Validity i, Validity a, Ord i, Ord a) => Validity (CentralStore i a)

Methods

validate :: CentralStore i a -> Validation

type Rep (CentralStore i a)

type Rep (CentralStore i a) = D1 * (MetaData "CentralStore" "Data.Mergeless" "mergeless-0.0.0.0-3ukUmlP02EMDeV1JFeafyp" True) (C1 * (MetaCons "CentralStore" PrefixI True) (S1 * (MetaSel (Just Symbol "centralStoreItems") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * (Map i (CentralItem a)))))

data CentralItem a

An item in a central store with a value of type a

Constructors

CentralItem

Fields

• centralValue :: !a
• centralSynced :: !UTCTime
• centralCreated :: !UTCTime

Instances

Eq a => Eq (CentralItem a)

Methods

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

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

Ord a => Ord (CentralItem a)

Methods

compare :: CentralItem a -> CentralItem a -> Ordering

(<) :: CentralItem a -> CentralItem a -> Bool

(<=) :: CentralItem a -> CentralItem a -> Bool

(>) :: CentralItem a -> CentralItem a -> Bool

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

max :: CentralItem a -> CentralItem a -> CentralItem a

min :: CentralItem a -> CentralItem a -> CentralItem a

Show a => Show (CentralItem a)

Methods

showsPrec :: Int -> CentralItem a -> ShowS

show :: CentralItem a -> String

showList :: [CentralItem a] -> ShowS

Generic (CentralItem a)

Associated Types

type Rep (CentralItem a) :: * -> *

Methods

from :: CentralItem a -> Rep (CentralItem a) x

to :: Rep (CentralItem a) x -> CentralItem a

ToJSON a => ToJSON (CentralItem a)

Methods

toJSON :: CentralItem a -> Value

toEncoding :: CentralItem a -> Encoding

toJSONList :: [CentralItem a] -> Value

toEncodingList :: [CentralItem a] -> Encoding

FromJSON a => FromJSON (CentralItem a)

Methods

parseJSON :: Value -> Parser (CentralItem a)

parseJSONList :: Value -> Parser [CentralItem a]

Validity a => Validity (CentralItem a)

Methods

validate :: CentralItem a -> Validation

type Rep (CentralItem a)

type Rep (CentralItem a) = D1 * (MetaData "CentralItem" "Data.Mergeless" "mergeless-0.0.0.0-3ukUmlP02EMDeV1JFeafyp" False) (C1 * (MetaCons "CentralItem" PrefixI True) ((:*:) * (S1 * (MetaSel (Just Symbol "centralValue") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * a)) ((:*:) * (S1 * (MetaSel (Just Symbol "centralSynced") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * UTCTime)) (S1 * (MetaSel (Just Symbol "centralCreated") NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 * UTCTime)))))

processSync :: (Ord i, Ord a, MonadIO m) => m i -> CentralStore i a -> SyncRequest i a -> m (SyncResponse i a, CentralStore i a)

Process a server-side synchronisation request using getCurrentTime

processSyncWith :: forall i a m. (Ord i, Ord a, Monad m) => m i -> UTCTime -> CentralStore i a -> SyncRequest i a -> m (SyncResponse i a, CentralStore i a)

Process a server-side synchronisation request using a time of syncing, and an identifier generation function.

WARNING: The identifier generation function must produce newly unique identifiers such that each new item gets a unique identifier.

You can use this function with deterministically-random identifiers or incrementing identifiers.