{-| Table building library for yesod

    This library is intended to be brought in by a qualified import
    along with type import as follows:

> import qualified Yesod.Table as Table
> import Yesod.Table (Table)

    There are two types in this module: 'Table' and 'Column'. Roughly, a 
    'Table' is just a list of 'Column's. Except in the case of rendering
    a 'Table', you should not need to use the data constructors of 
    either of these types. (In fact, you should not need to refer to 
    the type 'Column' either). Instead, you should use the functions
    'singleton', 'text', 'int', etc. to build singleton 'Table's
    (a 'Table' with only one 'Column') and use monoidal concatenation
    to combine these.

    If you want to define your own table rendering function (and it's
    likely that you will), then you will need the aforementioned data 
    constructors. You can look at the source of 'buildBootstrap' for 
    an example of how to do this.
-}
module Yesod.Table 
  ( Table(..)
  , Column(..)
  , buildBootstrap
  , singleton
  , widget
  , text
  , int
  , linked
  ) where

import Prelude hiding (mapM_)
import Yesod.Core
import Yesod.Core.Widget
import Data.Functor.Contravariant
import Data.Sequence (Seq)
import qualified Data.Sequence as Seq
import Data.Text (Text)
import qualified Data.Text as Text

-- import Control.Monad
import Data.Foldable (forM_, mapM_)
import Data.Monoid

newtype Table site a = Table (Seq (Column site a))
  deriving (Monoid)

data Column site a = Column
  { header :: !(WidgetT site IO ())
  , cell :: !(a -> WidgetT site IO ()) 
  }

instance Contravariant (Column site) where
  contramap g (Column h c) = Column h (c . g)

instance Contravariant (Table site) where
  contramap g (Table cols) = Table (fmap (contramap g) cols)

-- | This is the most primitive and essential operation for building a 'Table'.
--   All other table-building functions (such as 'widget', 'text', and 'linked')
--   build on top of 'singleton'. One common trend in the convenience functions 
--   is that they accept 'Text' as the table header. This is done because I have 
--   found that it is uncommon to need the full power of HTML in the header.
--   Just know that if you need it, this function is the only way to get it.
--   The first argument is a widget that is
--   content to be displayed in the table header. The second argument is the
--   a function that consumes a value to produce the content shown in a row of the
--   table body. 
singleton :: WidgetT site IO () -> (a -> WidgetT site IO ()) -> Table site a
singleton c h = Table (Seq.singleton (Column c h))

-- | This is the same as 'singleton', with the convenience of accepting 
--   the table header as 'Text'.
widget :: Text -> (a -> WidgetT site IO ()) -> Table site a
widget h c = singleton (textToWidget h) c

text :: Text -> (a -> Text) -> Table site a
text h c = singleton (textToWidget h) (textToWidget . c)

int :: Text -> (a -> Int) -> Table site a
int h c = singleton (textToWidget h) (textToWidget . Text.pack . show . c)

linked :: Text -> (a -> Text) -> (a -> Route site) -> Table site a
linked h propFunc routeFunc = singleton (textToWidget h) render
  where render a = [whamlet|<a href=@{routeFunc a}>#{propFunc a}|]

buildBootstrap :: Table site a -> [a] -> WidgetT site IO ()
buildBootstrap (Table cols) vals = table $ do
  thead $ mapM_ (td . header) cols
  tbody $ forM_ vals $ \val -> tr $ forM_ cols $ \col -> td $ cell col val
  where table b  = [whamlet|
                     <table.table.table-striped>^{b}
                   |]
        thead b  = [whamlet|
                     <thead>
                       <tr>
                         ^{b}
                   |]
        td b     = [whamlet|
                     <td>^{b}
                   |]
        tbody b  = [whamlet|
                     <tbody>^{b}
                   |]
        tr b     = [whamlet|
                     <tr>^{b}
                   |]

textToWidget :: Text -> WidgetT site IO ()
textToWidget = toWidget . toHtml