{-# LANGUAGE OverloadedStrings, RankNTypes, StandaloneDeriving, FlexibleInstances #-}

import Hakyll

import Data.Monoid (Monoid(..), mconcat, (<>))
import Control.Monad (liftM)
import Data.Char (toLower, isSpace, isAlphaNum)
import Data.Maybe (mapMaybe, fromMaybe)
import Data.Map (Map)
import qualified Data.Map as Map
import Data.List (take, reverse)
import Data.Default
import Text.Pandoc.Options (WriterOptions(..), ObfuscationMethod(..))
import Control.Applicative (Alternative(..), Applicative(..))

import System.FilePath (takeBaseName, (</>), (<.>))

main :: IO ()
main = hakyllWith config $ do
  match "templates/*" $ compile templateCompiler

  match "css/*" $ do
    route idRoute
    compile copyFileCompiler

  match "posts/*" $ do
    route $ setExtension ".html"
    compile $ do
      getResourceBody >>= saveSnapshot "content"
      pandocCompiler
        >>= loadAndApplyTemplate "templates/default.html" defaultContext
        >>= relativizeUrls

  tags <- buildTags "posts/*" tagTranslation' >>= addTag "All Posts" "posts/*"

  tagsRules tags $ \tag pattern -> do
    route idRoute
    compile $ do
      let ctx = mconcat [ constField "title" tag
                        , listField "posts" defaultContext $ chronological =<< loadAll pattern
                        , constField "rss" $ "/rss" </> tagTranslation tag <.> "rss"
                        , defaultContext
                        ]
      makeItem ""
        >>= loadAndApplyTemplate "templates/post-list.html" ctx
        >>= loadAndApplyTemplate "templates/default.html" ctx
        >>= relativizeUrls

  let
    tags' = tags { tagsMakeId = fromFilePath . (\b -> "rss" </> b <.> "rss") . takeBaseName . toFilePath . tagsMakeId tags}

  tagsRules tags' $ \tag pattern -> do
    route idRoute
    compile $ do
      let
        feedCtx = mconcat [ bodyField "description"
                          , defaultContext
                          ]
      renderRss (feedConfig tag) feedCtx =<< loadAllSnapshots pattern "content"

  match "index.md" $ rulesExtraDependencies [tagsDependency tags] $ do
    route $ setExtension ".html"
    compile $ do
      let ctx = mconcat [ listField "tags" defaultContext $ mapM (\(k, _) -> renderTag k tags) $ tagsMap tags
                        , constField "title" "Index"
                        , constField "rss" "/rss/all-posts.rss"
                        , defaultContext
                        ]
      item <- getResourceBody
      pandocCompilerWith def (def { writerEmailObfuscation = NoObfuscation })
        >>= loadAndApplyTemplate "templates/index.html" ctx
        >>= loadAndApplyTemplate "templates/default.html" ctx
        >>= relativizeUrls

deriving instance Eq (Item String)

feedConfig :: String -> FeedConfiguration
feedConfig tagName = FeedConfiguration { feedTitle = "dirty-haskell.org: " ++ tagName
                                       , feedDescription = "dirty-haskell.org — A Blog."
                                       , feedAuthorName = "G. Kleen"
                                       , feedAuthorEmail = "blog@dirty-haskell.org"
                                       , feedRoot = "https://dirty-haskell.org"
                                       }

renderTag :: String -- ^ Tag name
          -> Tags
          -> Compiler (Item String)
renderTag tag tags = do
  ellipsisItem <- makeItem ""
  let
    ids = fromMaybe [] $ lookup tag $ tagsMap tags
    postCtx = mconcat [ listField "posts" (ellipsisContext ellipsisItem) $ liftM (withEllipsis ellipsisItem) $ chronological =<< mapM load ids
                      , constField "title" tag
                      , constField "rss" ("rss" </> tagTranslation tag <.> "rss")
                      , constField "url" ("tags" </> tagTranslation tag <.> "html")
                      , defaultContext
                      ]
  makeItem ""
    >>= loadAndApplyTemplate "templates/post-list.html" postCtx
    >>= loadAndApplyTemplate "templates/tag.html" postCtx
  where
    ellipsisContext item = mconcat [ boolField "ellipsis" (== item)
                                   , defaultContext
                                   ]
    boolField name f = field name (\i -> if f i
                                         then pure (error $ unwords ["no string value for bool field:",name])
                                         else empty)
    withEllipsis ellipsisItem xs
      | length xs > max = ellipsisItem : takeEnd (max - 1) xs
      | otherwise = xs
    takeEnd i = reverse . take i . reverse
    max = 4

tagTranslation' :: String -> Identifier
tagTranslation' = fromCapture "tags/*.html" . tagTranslation

tagTranslation :: String -> String
tagTranslation = mapMaybe charTrans
  where
    charTrans c
      | isSpace c = Just '-'
      | isAlphaNum c = Just $ toLower c
      | otherwise = Nothing

addTag :: MonadMetadata m => String -> Pattern -> Tags -> m Tags
addTag name pattern tags = do
  ids <- getMatches pattern
  return $ tags { tagsMap = tagsMap tags ++ [(name, ids)] }

config :: Configuration
config = defaultConfiguration { providerDirectory = "provider"
                              , deployCommand = "rsync -av --progress -c --delete-delay -m  _site/ gkleen@surtr.yggdrasil.li:/var/www/dirty-haskell.org/"
                              }