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https://github.com/paluh/purescript-boomboom

Never hard code your urls again. Boomboom them all!
https://github.com/paluh/purescript-boomboom

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Never hard code your urls again. Boomboom them all!

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# purescript-boomboom



## Disclaimer



Never hard code your urls again. ~~Boomboom~~ [routing-duplex](https://github.com/natefaubion/purescript-routing-duplex) them all!



It was quite a nice coding challange and experiment for me, but I feel that `routing-duplex` exposes much cleaner and user friendly API at this moment. Please check it first!



## Description



Bidirectional routing library with principled plumbing which provides easy to use generic sugar for variants and records.



Still β stage...



## `BoomBoom`



The core type of this library is `BoomBoom.BoomBoom` which translates really to this simple record:



```purescript

newtype BoomBoom tok a = BoomBoom { prs ∷ tok → Maybe { a ∷ a, tok ∷ tok }, ser ∷ a → tok }

```



So our `BoomBoom tok a` is a simple parser from `tok` to `a` and also a total serializer function in opposite direction. Composability of this type requires usually that `tok` has a `Semigroup` instance. For details check `BoomBoom.BoomBoom` module docs.



## Usage



### Basic generic helpers



Please note that more user friendly API is described in the next section.



These are tests fragments (`test/BoomBoom/Generic.purs`) which use basic generic helpers:



* `tok` in this case is an `Array String`



* `int` is `BoomBoom (Array String) Int`



* `record` is a helper which builds `BoomBoom` for a give record of `BoomBooms`



* `R` is a record wrapper which provides `Eq` ;-)



Record `BoomBoom` generation and usage:



```purescript

let

  recordB = BoomBoom.Generic.record { x: int, y: int, z: int }

Test.Unit.suite "simple record boomboom" $ do



  test "serializes correctly" $ do

    equal ("1":"2":"3":Nil) (serialize recordB { x: 1, y: 2, z: 3 })



  test "parses correctly" $ do

    equal (Just $ R { x: 1, y: 2, z: 3 }) (R <$> parse recordB ("1":"2":"3":Nil))

```



Variant `BoomBoom` generation and usage (with `variant` helper):



```purescript

let

  variantB = variant

    { zero: BoomBoom $ pure unit

    , one: int

    -- | Here we are wrapping our record in `R`

    -- | it is only required because we want

    -- | to perform `eq`...

    , two: BoomBoom $ R <$> unwrap >- recordB

    }

Test.Unit.suite "simple variant boomboom" $ do

  let

    wrong = ("wrong":"8":Nil)

    zi = ("zero":Nil)

    oi = ("one":"1":Nil)

    ti = ("two":"2":"3":"4":Nil)

    zv = inj (SProxy ∷ SProxy "zero") unit

    ov = inj (SProxy ∷ SProxy "one") 1

    tv = inj (SProxy ∷ SProxy "two") (R {x: 2, y: 3, z: 4})

  test "serializes correctly" $ do

    equal zi (serialize variantB zv)

    equal oi (serialize variantB ov)

    equal ti (serialize variantB tv)

  test "parses correctly" $ do

    equal Nothing (parse variantB wrong)

    equal (Just zv) (parse variantB zi)

    equal (Just ov) (parse variantB oi)

    equal (Just tv) (parse variantB ti)

```



Of course you can compose and mix these `BoomBooms` and build arbitrarly large routers/serializers:



```purescript

let

  nestedB = variant

    { p1: variant

        -- | Here again our R which is here just for `eq`

        { sp1: ((xrap $ record { x: int, y: int, z: int }) ∷ BoomBoom _ R)

        , sp2: int

        }

    , p2: int

    }

  i = ("p1":"sp1":"1":"2":"3":Nil)

  iv = inj (SProxy ∷ SProxy "p1") (inj (SProxy ∷ SProxy "sp1") (R {x: 1, y: 2, z: 3}))

test "serializes correctly" $ do

  equal i (serialize nestedB iv)

test "parses correctly" $ do

  equal (Just iv) (parse nestedB i)

```



### Typelevel interpretation and helpers



Let's assume that we have routes from previous example and want to produce this serialization `p1/sp1/1/2/3` result. To do this we have to build our variant by hand (as in previous example):



```purescript

  serialize $ inj (SProxy ∷ SProxy "p1") (inj (SProxy ∷ SProxy "sp1") {x: 1, y: 2, z: 3})

```



This API is not really readable and easy to use as we have to nest all these `inj` functions with `SProxy` constructors.



In `BoomBoom.Generic.Interpret` you can find "type level interpreters" which are able to produce `BoomBooms` but also easy to use builders of values (variants/records) from "records tree".

Instead of building `BoomBooms` directly you should define your tree using provided constructors:



```purescript

import BoomBoom.Generic.Interpret (V, R, B)

import BoomBoom.Strings (int)



desc = V

  { p1: V

      { sp1: R { x: B int, y: B int, z: B int }

      , sp2: B int

      }

  , p2: B int

  }

```



Now you can produce your `BoomBoom` value but also a `builder`:



```purescript

import BoomBoom.Generic.Interpret (interpret)

import Type.Prelude (SProxy(..))



-- | Generate a builder

builder = interpret (SProxy ∷ SProxy "builder") desc



-- | Generate a BoomBoom

boomboom = interpret (SProxy ∷ SProxy "boomboom") desc



```



This `builder` is a record (for variants build up) or function (for records build up) which helps us build values ready for serialization. So for example this:



```purescript

v = builder.p1.sp1 {x: 1, y: 2, z: 3}

```



Is equivalent of this:



```purescript

v = inj (SProxy ∷ SProxy "p1") (inj (SProxy ∷ SProxy "sp1") {x: 1, y: 2, z: 3})

```



Now we can use this value and serialize it:



```purescript

serialize boomboom v

```



Output (in case of `BoomBoom.Strings` serialization) value:



```purescript

("p1":"sp1":"1":"2":"3":Nil)

```



### `Applicative` API



And here is completely different approach which uses `apply` and `BoomBoom.diverge` (aka `(>-)`):



```purescript

path :: BoomBoom String { x :: Int, y :: Int }

path = BoomBoom $

  { x: _, y: _ }

    <$> _.x >- int

    <* lit "test"

    <*> _.y >- int



main :: forall e. Eff (console :: CONSOLE | e) Unit

main = do

  log $ unsafeStringify (parse path ("8080":"test":"200":Nil))



  log (serialize path { x: 300, y: 800 })

```



Output values:



```shell

{"value0":{"x":8080,"y":200}}



-- | I've replaced here `Cons` with (:) to simplify reading

("300":"test":"800":Nil)

```



## TODO



There is ongoing work for "API interpreters" which would generate records clients and server helpers but also docs etc.



## Credits



* A lot of inspirations and crucial suggestions I received from @MonoidMusician. Thanks!



* Initial design of diverging instances was inspired by this @sebastiaanvisser [answer](https://www.reddit.com/r/haskell/comments/38o0f7/a_mixture_of_applicative_and_divisible/#thing_t1_crwh6le).



* Name loosely inspired by this @notcome [gist](https://gist.github.com/notcome/c9d4c750985230d7e346).