README.md

Dashdo

A framework for writing web-based analytics dashboards in Haskell, inspired by Shiny.

Dashdo dashboards are defined over a Haskell type which specify the state of the dashboard. Form elements are tied to lenses into the state value, and the displayed content is calculated from the state. Dashboards are defined in as single record type that can be interpreted in multiple different ways.

{-
            +------------------- the state of the dashboard
            |
            |          +-------- the state is augmented
            |          |          with information fetched in `IO`
            |          |
            v          v             -}
data Dashdo t = forall b. Dashdo
  { initial :: t                    -- the initial state
  , fetch :: t -> IO b              -- fetch more data
  , render :: t -> b -> SHtml t ()  -- render the dashboard
  }  {-                  /|\
                          |
                          +-------- generate HTML, and keep track
                                      of how form elements bind
                                      lenses into state
     -}

SHtml is a Lucid monad transformer and you can use all the usual Lucid combinators.

Run your dashdo dashboard with Dashdo.Serve.runDashdo.

Examples

For a simple example, we will just ask for the users name. We need a simple state containing that name. We could just use a Text value as the state and the identity lens, but a record is a more realistic starting point for when you want to add functionality.

data Example = Example
 { _name :: Text
 }

makeLenses ''Example

We then need to show the dashboard as a function of the state, together with the form element (here an <input>) to change the state.

myRender :: Example -> SHtml Example ()
myRender s = do
  h2_ "Testing Dashdo"
  textInput name
  br_ []
  "Hello " <> (toHtml $ s ^. name)

Since we are not making use of the functionality to fetch extra information in the IO monad, we can use the pureDashdo function to generate our Dashdo.

main = runDashdo $ pureDashdo "George" myRender

For more examples, see the dashdo-examples directory.

To re-run on file changes

git ls-files | entr -r stack build --exec test-dashdo

or

find . -name '*.hs' ! -path '*stack-work*' | entr -r stack build --exec test-dashdo