{-# LANGUAGE RecordWildCards, OverloadedStrings #-}
-- | To use this package you need to construct a Presentation tree using the types and constructors
--   from the 'Slides.Common' module (re-exported from this one). Then call one of the functions
--   bellow.
--   The generated HTML will not look like a presentation when you open it up in a browser, but
--   it has CSS guides in place that will split it up into pages properly when you print it.
--   Good default settings are A3-Landscape. You can just print to PDF to get the actual presentation.
--
--   Here's an example
--
-- @
-- sample :: 'Presentation'
-- sample =
--     'Presentation' [
--         'Slide' [
--             'Header' 2 \"Title\",
--             'Sequence' 'Immediate' [
--                 'UnfoldConcatList' 'Delay' [
--                     'Header' 3 \"Example\",
--                     'UnfoldList' 'Immediate' [
--                         \"These lines will unfold one by one.\",
--                         \"You can use some markdown in these strings like _this_ or *this* \\
--                         \\or \__this__ or **this**.\"
--                     ],
--                     'Diagram' 200 someDiagram
--                 ],
--                 'List' [
--                     \"This list will be shown in place of the previous title-list-diagram.\",
--                     \"This item will be shown immediately with the last one.\"
--                 ]
--             ] -- note that the above title \"Title\" will remain there during the sequence.
--         ],
--         'Slide' [
--             'Header' 2 \"Another slide\",
--             'List' [
--                 \"Some text describing stuff.\",
--                 \"More text.\"
--             ],
--             'Sequence' 'Delay' [
--                 'Diagram' 200 a,
--                 'Diagram' 200 sequence,
--                 'Diagram' 200 of,
--                 'Diagram' 300 diagrams
--             ]
--         ]
--     ]
 --
 -- main :: IO ()
 -- main = writeToFile \"index.html\" sample
-- @
module Slides.Presentation
    ( renderPresentation, writeToFile, module Slides.Common
    ) where

import Data.Colour (Colour)
import qualified Data.Colour.SRGB as Colour
import Data.Maybe (catMaybes)
import qualified Text.RegexPR as Regex
import Data.String (IsString(..))
import Data.List (groupBy)
import Slides.Common
import Slides.Sequencing
import Slides.Internal
import qualified System.IO.UTF8 as UTF8

class Renderable a where
    render :: a -> String

instance Renderable Presentation where
    render Presentation{..} = html "head" h ++ html "body" b
        where h = baseHead ++ render style
              b = concatMap render slides

instance Renderable Slide where
    render Slide{..} = concatMap (htmlClass "div" "slide") sequences
        where sequences = stepsToStrings $ mergeSequences $ map (simplify . sequenceContent) nodes

instance Renderable Style where
    render Style{..} = html "style" (baseCss ++ "\n" ++ concatMap renderSelector selectors)
        where renderSelector (k, v) =  render k ++ " { " ++ render v ++ " }\n"

instance Renderable Selector where
    render (HeaderSelector h) = "h" ++ show h
    render UniversalSelector  = "*"
    render TextSelector       = "p"
    render SlideSelector      = ".slide"

($>) :: Functor f => f a -> (a -> b) -> f b
($>) = flip fmap

instance Renderable ElementStyle where
    render ElementStyle{..} = concat $ catMaybes
        [ backgroundColor $> \col -> "background-color: " ++ Colour.sRGB24show col ++ ";\n"
        , fontFamily $> \ff -> "font-family: " ++ ff ++ ";\n"
        , fontSize $> \fs -> "font-size: " ++ show fs ++ ";" ]

inlineMarkdown :: String -> ContentNode
inlineMarkdown = Text . Regex.gsubRegexPR "\\*(.+?)\\*" "<i>\\1</i>"
                      . Regex.gsubRegexPR "_(.+?)_" "<i>\\1</i>"
                      . Regex.gsubRegexPR "\\*\\*(.+?)\\*\\*" "<b>\\1</b>"
                      . Regex.gsubRegexPR "__(.+?)__" "<b>\\1</b>"

instance IsString ContentNode where
    fromString = inlineMarkdown

-- | Render the Presentation to an HTML string.
renderPresentation :: Presentation -> String
renderPresentation = render

-- | Render a Presentation to an HTML file with UTF8 encoding.
writeToFile :: FilePath -> Presentation -> IO ()
writeToFile path = UTF8.writeFile path . render