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Never hard code your urls again. Boomboom them all!


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

Still β stage...


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

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.


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:

  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):

  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
    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:

  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):

  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:

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:

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:

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

Is equivalent of this:

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

Now we can use this value and serialize it:

serialize boomboom v

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


Applicative API

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

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:


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


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


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

  • Initial design of diverging instances was inspired by this @sebastiaanvisser answer.

  • Name loosely inspired by this @notcome gist.