{-# LANGUAGE OverloadedStrings #-}
module Main where

import Prelude hiding (id)
import Control.Arrow
import Control.Category (id)
import Control.Monad
import Data.Function (on)
import Data.List hiding (group)
import Data.Maybe
import Data.Monoid (mempty, mconcat)

import System.FilePath (takeFileName)
import System.Locale (defaultTimeLocale, TimeLocale)
import Data.Time.Calendar
import Data.Time.Clock (UTCTime (..))
import Data.Time.Format (parseTime, formatTime)

import Text.Printf

import Hakyll hiding (chronological, recentFirst)

main :: IO ()
main = hakyll $ do
  -- Compress CSS
  match "css/*" $ do
    route   idRoute
    compile compressCssCompiler

  -- Images
  match "images/**" $ do
    route   idRoute
    compile copyFileCompiler

  -- Render posts
  group "posts" $ do
    match (inPostGroup "posts/*") $ do
      route   $ setExtension ".html"
      compile $ pageCompiler
        >>> addDate
        >>> addTagCloud
        >>> addArchiveLinks
        >>> renderTagsField "prettytags" (fromCapture "tags/*")
        >>> applyTemplateCompiler "templates/post.html"
        >>> addTopnav
        >>> applyTemplateCompiler "templates/default.html"
        >>> relativizeUrlsCompiler

  -- Index
  match "index*" $ route $ setExtension ".html"
  metaCompile $ requireAllA allPosts $ arr (recentFirst . snd)
    >>> (constA ("Home", "index*") &&& id)
    >>> paginatePosts

  match "posts/*" $ compile $ pageCompiler
    >>> (id &&& arr (getField "path"))
    >>> setFieldA "url" (arr (Identifier postGroup) >>> getRouteFor >>> arr (fromMaybe "" . fmap toUrl))
    
  -- Tags
  create "tags" $
    requireAll_ allPosts >>> arr readTags

  match "tags/*" $ route $ setExtension ".html"
  metaCompile $ require_ "tags"
    >>> arr tagsMap
    >>> arr (map $ second recentFirst)
    >>> mapCompiler (((arr (\tag -> "Posts tagged ‘" ++ tag ++ "’") &&& arr (parseGlob . (++ "*") . identifierPath . tagIdentifier)) *** id)
                     >>> paginatePosts
                    )
    >>> arr concat

  -- Archive
  create "archive" $
    requireAll_ allPosts >>> arr (Tags . groupTuples . reverse . sortBy (compare `on` fst) . catMaybes . map (\page -> getDate page >>= (\date -> return (date, page))))
  
  match "archive/**" $ route $ setExtension ".html"
  metaCompile $ require_ "archive"
    >>> arr tagsMap
    >>> arr (map $ second recentFirst)
    >>> mapCompiler (((arr (\month -> "Archive for " ++ prettyMonth month) &&& arr (parseGlob . (++ "*") . identifierPath . archiveIdentifier)) *** id)
                     >>> paginatePosts
                    )
    >>> arr concat

  -- Render RSS feed
  match "rss.xml" $ route idRoute
  create "rss.xml" $ requireAll_ allPosts
    >>> mapCompiler (arr $ copyBodyToField "description")
    >>> renderRss feedConfiguration

  -- Read templates
  match "templates/*" $ compile templateCompiler
  where
    postGroup = Just "posts"

    inPostGroup :: Pattern a -> Pattern a
    inPostGroup p = patternIntersection [inGroup postGroup, p]

    notInPostGroup :: Pattern a -> Pattern a
    notInPostGroup p = patternIntersection [complement $ inGroup postGroup, p]

    allPosts :: Pattern (Page String)
    allPosts = notInPostGroup "posts/*"

    addTopnav :: Compiler (Page a) (Page a)
    addTopnav = arr (id &&& const ()) >>> setFieldA "topnav" topnav

    topnav :: Compiler () String
    topnav = constA topLinks >>> mapCompiler topnavLink >>> arr (concat . catMaybes)
      where
        topnavLink = second (id &&& (getRouteFor >>> arr (fmap toUrl)) >>> arr pullSnd)
                     >>> arr pullSnd
                     >>> (getIdentifier &&& id)
                     >>> arr pullSnd
                     >>> arr (fmap (\(cur, (text, (link, url))) -> "<li><a href=\"" ++ url ++ "\"" ++ cl cur link ++ "><span>" ++ escapeHtml text ++ "</span></a></li>"))

        cl cur link = if cur == link then " class=\"s\"" else ""

    maybeGetRouteFor :: Compiler (Maybe (Identifier (Page String))) (Maybe FilePath)
    maybeGetRouteFor = arr maybeToEither >>> (constA Nothing ||| getRouteFor)
      where
        maybeToEither Nothing = Left ()
        maybeToEither (Just a) = Right a

    addPagenav :: Compiler (Page a, (Maybe (Identifier (Page String)), Maybe (Identifier (Page String)))) (Page a)
    addPagenav = setFieldA "pagenav" $ (maybeGetRouteFor *** maybeGetRouteFor) >>> arr pagenav

    pagenav (prev, next) = pagenavPrev prev ++ pagenavNext next

    pagenavPrev Nothing = "<span class=\"newer\">&nbsp;</span>"
    pagenavPrev (Just url) = "<span class=\"newer\"><a href=\"" ++ url ++ "\" rel=\"prev\">&laquo; Newer Entries</a></span>"

    pagenavNext Nothing = "<span class=\"older\">&nbsp;</span>"
    pagenavNext (Just url) = "<span class=\"older\"><a href=\"" ++ url ++ "\" rel=\"next\">Older Entries &raquo;</a></span>"

    pageTitle 0 = ""
    pageTitle i = " &ndash; Page " ++ show (i+1)

    paginatePosts :: Compiler ((String, Pattern (Page String)), [Page String]) [(Identifier (Page String), Compiler () (Page String))]
    paginatePosts = paginate 5
                    (arr (\(title, prev, next, i, pages) -> (((mempty, (prev, next)), (title, i)), pages))
                     >>> first (first (first (addTagCloud >>> addArchiveLinks)
                                       >>> addPagenav)
                                >>> arr (\(page, (title, i)) -> setField "title" (title ++ pageTitle i) page)
                               )
                     >>> addPosts
                     >>> applyTemplateCompiler "templates/index.html"
                     >>> addTopnav
                     >>> applyTemplateCompiler "templates/default.html"
                     >>> relativizeUrlsCompiler
                    )


topLinks :: [(String, Identifier (Page String))]
topLinks = [("Home", "index")
           ]


pullSnd :: Functor m => (a, m b) -> m (a, b)
pullSnd (a, b) = fmap (const a &&& id) b


patternIntersection :: [Pattern a] -> Pattern a
patternIntersection patterns = predicate $ flip all patterns . flip matches


getUTCMaybe :: Page a         -- ^ Input page
            -> Maybe UTCTime  -- ^ Parsed UTCTime
getUTCMaybe page = msum
    [ fromPublished "%a, %d %b %Y %H:%M:%S UT"
    , fromPublished "%Y-%m-%dT%H:%M:%SZ"
    , fromPublished "%B %e, %Y %l:%M %p"
    , fromPublished "%B %e, %Y"
    , getFieldMaybe "path" page >>= parseTime' "%Y-%m-%d" .
        intercalate "-" . take 3 . splitAll "-" . takeFileName
    ]
  where
    fromPublished f  = getFieldMaybe "published" page >>= parseTime' f
    parseTime' f str = parseTime defaultTimeLocale f str

getDate :: Page a -> Maybe String
getDate = liftM ((\(y, m, _) -> printf "%04d/%02d" y m) . toGregorian . utctDay) . getUTCMaybe

chronological :: [Page a] -> [Page a]
chronological = sortBy (compare `on` getUTCMaybe)

recentFirst :: [Page a] -> [Page a]
recentFirst = reverse . chronological

groupTuples :: Eq a => [(a, b)] -> [(a, [b])]
groupTuples = map (fst . head &&& map snd) . groupBy ((==) `on` fst)

paginate :: Int -> Compiler (a, Maybe (Identifier (Page String)), Maybe (Identifier (Page String)), Int, [Page String]) (Page String) -> Compiler ((a, Pattern (Page String)), [Page String]) [(Identifier (Page String), Compiler () (Page String))]
paginate perPage c = arr $ \((a, pattern), posts) -> renderPages a pattern 0 (n posts) posts
  where
    renderPages _ _ _ _ [] = []
    renderPages a pattern i n posts = (name i, constA (a, prev i, next i n, i, cur) >>> c):(renderPages a pattern (i+1) n rest)
      where
        (cur, rest) = splitAt perPage posts

        prev 0 = Nothing
        prev i = Just . name $ i-1

        next i n = if i == (n-1) then Nothing else Just . name $ i+1

        name 0 = fromCapture pattern ""
        name i = fromCapture pattern $ show i

    n posts = (length posts + perPage - 1) `div` perPage


addPosts :: Compiler (Page String, [Page String]) (Page String)
addPosts = setFieldA "posts" $
              mapCompiler (addDate
                           >>> addTagCloud
                           >>> renderTagsField "prettytags" (fromCapture "tags/*")
                           >>> applyTemplateCompiler "templates/post.html")
              >>> arr mconcat
              >>> arr pageBody

addDate = arr $ renderDateField "date" "<span class=\"data\"><span class=\"j\">%e</span>%b/%y</span>" ""

addTagCloud = requireA "tags" (setFieldA "tagcloud" renderTagCloud')
  where
    renderTagCloud' :: Compiler (Tags String) String
    renderTagCloud' = renderTagCloud tagIdentifier 100 300

addArchiveLinks = requireA "archive" (setFieldA "archive" renderArchive)
  where
    renderArchive :: Compiler (Tags String) String
    renderArchive = arr tagsMap
                    >>> arr (map (\(s, p) -> "<li><a href=\"/archive/" ++ s ++ ".html\">" ++ prettyMonth s ++ "</a>&nbsp;(" ++ show (length p) ++ ")</li>"))
                    >>> arr mconcat

prettyMonth :: String -> String
prettyMonth s = month ++ " " ++ year
  where
    year = take 4 s
    month = case (drop 5 s) of
      "01" -> "January"
      "02" -> "February"
      "03" -> "March"
      "04" -> "April"
      "05" -> "May"
      "06" -> "June"
      "07" -> "July"
      "08" -> "August"
      "09" -> "September"
      "10" -> "October"
      "11" -> "November"
      "12" -> "December"
      _ -> "Unknown"


tagIdentifier :: String -> Identifier (Page String)
tagIdentifier = fromCapture "tags/*"

archiveIdentifier :: String -> Identifier (Page String)
archiveIdentifier = fromCapture "archive/*"

feedConfiguration :: FeedConfiguration
feedConfiguration = FeedConfiguration
    { feedTitle       = "Universe Factory"
    , feedDescription = "Because one universe is not enough"
    , feedAuthorName  = "NeoRaider"
    , feedRoot        = "http://blog.universe-factory.net"
    }