[![Build Status](https://travis-ci.org/amarpotghan/crjdt-haskell.svg?branch=master)](https://travis-ci.org/amarpotghan/haskell-crjdt)

# A Conflict-Free Replicated JSON Datatype for Haskell

*crjdt-haskell* provides high level interface to CRDT which is formalised in the [paper](https://arxiv.org/pdf/1608.03960v1.pdf) by Martin Kleppmann and Alastair R. Beresford.

## Documentation

See [haddocks](https://hackage.haskell.org/package/crjdt-haskell).

## Example

```haskell

{-# LANGUAGE OverloadedStrings #-}
module Main where

import Data.Crjdt as C

-- Original state
original :: Command ()
original = (doc .> key "key") =: "A"

-- First replica updates doc["key"] to "B"
replica1 :: Command ()
replica1 = do
  original
  (doc .> key "key") =: "B"

-- Second replica updates doc["key"] to "C"
replica2 :: Command ()
replica2 = do
  original
  (doc .> key "key") =: "C"

main :: IO ()
main = do
  -- Sync first and second replica
  let Right (r1, r2) = sync (1, replica1) (2, replica2)

  let replica1' = execEval 1 r1
      replica2' = execEval 2 r2

  -- Both replicas converge to: {"key": {"B", "C"}}
  print (document replica1' == document replica2') -- True

```

## Future work

* Improve documentation
* Aeson support
* Simplify API as described in [second version](https://arxiv.org/abs/1608.03960) of the paper

## LICENSE

Copyright © 2017 Amar Potghan

Distributed under BSD License.