{-| Conventions used for common shakebook projects, lenses, enrichments, affixes.
-}

module Shakebook.Conventions (
  -- * Lenses
  viewContent
, viewPostTime
, viewPostTimeRaw
, viewSrcPath
, viewTags
, viewTitle
, viewUrl
, viewAllPostTags
, viewAllPostTimes
, withBaseUrl
, withFullUrl
, withHighlighting
, withNext
, withPages
, withPrettyDate
, withPrevious
, withPosts
, withRecentPosts
, withSrcPath
, withSubsections
, withTagIndex
, withTagLinks
, withTeaser
, withTitle
, withUrl

  -- * Enrichment
, enrichFullUrl
, enrichPrettyDate
, enrichTagLinks
, enrichTeaser
, enrichTypicalUrl

  -- * Affixes
 
  -- * Extensions
, extendNext
, extendPrevious
, extendNextPrevious
, extendPageNeighbours

  -- * Generations
, genBlogNavbarData
, genLinkData
, genPageData
, genTocNavbarData

, dateSortPosts
, monthFilterPosts
, sameMonth
, tagFilterPosts
) where

import           Control.Comonad.Cofree
import           Control.Comonad.Store
import           Control.Comonad.Store.Zipper
import           Control.Lens                 hiding ((:<))
import           Control.Monad.Extra
import           Data.Aeson                   as A
import           Data.Aeson.Lens
import           Data.Text.Time
import           Development.Shake.FilePath
import           RIO                          hiding (view)
import           RIO.List
import           RIO.List.Partial
import qualified RIO.Text                     as T
import qualified RIO.Text.Partial             as T
import           RIO.Time
import qualified RIO.Vector                   as V
import           Shakebook.Aeson
import           Shakebook.Zipper
import           Text.Pandoc.Highlighting


-- View the "content" field of a JSON Value.
viewContent :: Value -> Text
viewContent = view (key "content" . _String)

-- View the "date" field of a JSON Value as a UTCTime.
viewPostTime :: Value -> UTCTime
viewPostTime = parseISODateTime . view (key "date" . _String)

-- View the "date" field of a JSON Value as Text.
viewPostTimeRaw :: Value -> Text
viewPostTimeRaw = view (key "date" . _String)

-- View the "srcPath" field of a JSON Value.
viewSrcPath :: Value -> Text
viewSrcPath = view (key "srcPath" . _String)

-- View the "tags" field of a JSON Value as a list.
viewTags :: Value -> [Text]
viewTags = toListOf (key "tags" . values . _String)

-- View the "title" field of a JSON Value.
viewTitle :: Value -> Text
viewTitle = view (key "title" . _String)

-- View the "url" field of a JSON Value.
viewUrl :: Value -> Text
viewUrl = view (key "url" . _String)

-- View all post tags for a list of posts.
viewAllPostTags :: [Value] -> [Text]
viewAllPostTags = (>>= viewTags)

-- View all posts times for a list of posts.
viewAllPostTimes :: [Value] -> [UTCTime]
viewAllPostTimes = fmap viewPostTime

-- Add "baseUrl" field from input Text.
withBaseUrl :: Text -> Value -> Value
withBaseUrl = withStringField "baseUrl"

-- Add "fullUrl" field  from input Text.
withFullUrl :: Text -> Value -> Value
withFullUrl = withStringField "fullUrl"

-- Add "highlighting-css" field from input Style.
withHighlighting :: Style -> Value -> Value
withHighlighting = withStringField "highlighting-css" . T.pack . styleToCss

-- Add "next" field from input Value.
withNext :: Maybe Value -> (Value -> Value)
withNext = withObjectFieldMaybe "next"

-- Add "pages" field from input [Value].
withPages :: [Value] -> (Value -> Value)
withPages = withArrayField "pages"

-- Add "prettydate" field using input Text.
withPrettyDate :: Text -> Value -> Value
withPrettyDate = withStringField "prettydate"

-- Add "previous" field using input Value.
withPrevious :: Maybe Value -> (Value -> Value)
withPrevious = withObjectFieldMaybe "previous"

-- Add "posts" field based on input [Value].
withPosts :: [Value] -> Value -> Value
withPosts = withArrayField "posts"

-- Add "recentposts" field using input Value. 
withRecentPosts :: [Value] -> Value -> Value
withRecentPosts = withArrayField "recent-posts" 

-- Add "srcPath" field based on input Text.
withSrcPath :: Text -> Value -> Value
withSrcPath = withStringField "srcPath"

-- Add "subsections" field based on inpt [Value].
withSubsections :: [Value] -> (Value -> Value)
withSubsections = withArrayField "subsections"

-- Add "tagindex" field based on input [Value].
withTagIndex :: [Value] -> Value -> Value
withTagIndex = withArrayField "tagindex"

-- Add "taglinks" field based on input [Value].
withTagLinks :: [Value] -> Value -> Value
withTagLinks  = withArrayField "taglinks"

-- Add "teaser" field based on input Text.
withTeaser :: Text -> Value -> Value
withTeaser = withStringField "teaser"

-- Add "title" field based on input Text.
withTitle :: Text -> Value -> Value
withTitle = withStringField "title"

-- Add "url" field from input Text.
withUrl :: Text -> Value -> Value
withUrl = withStringField "url"

-- Add both "next" and "previous" fields using `withPostNext` and `withPostPrevious`
extendNextPrevious :: Zipper [] Value -> Zipper [] Value
extendNextPrevious  = extendPrevious . extendNext

-- Extend a Zipper of JSON Values to add "previous" objects.
extendPrevious :: Zipper [] Value -> Zipper [] Value
extendPrevious = extend (liftA2 withPrevious zipperPreviousMaybe extract)

-- Extend a Zipper of JSON Values to add "next" objects.
extendNext :: Zipper [] Value -> Zipper [] Value
extendNext = extend (liftA2 withNext zipperNextMaybe extract)

extendPageNeighbours :: Int -> Zipper [] Value -> Zipper [] Value
extendPageNeighbours r = extend (liftA2 withPages (zipperWithin r) extract)


-- Assuming a "url" field, enrich via a baseURL
enrichFullUrl :: Text -> Value -> Value
enrichFullUrl base v = withFullUrl (base <> viewUrl v) v

-- Assuming a "date" field, enrich using withPrettyDate and a format string.
enrichPrettyDate :: (UTCTime -> String) -> Value -> Value
enrichPrettyDate f v = withPrettyDate (T.pack . f . viewPostTime $ v) v

-- Assuming a "tags" field, enrich using withTagLinks.
enrichTagLinks :: (Text -> Text) -> Value -> Value
enrichTagLinks f v = withTagLinks ((`genLinkData` f) <$> viewTags v) v

-- Assuming a "content" field with a spitter section, enrich using withTeaser
enrichTeaser :: Text -> Value -> Value
enrichTeaser s v = withTeaser (head (T.splitOn s (viewContent v))) v

-- Assuming a 'srcPath' field, enrich using withUrl using a typicalHTMLUrl
enrichTypicalUrl :: Value -> Value
enrichTypicalUrl v = withUrl (typicalHTMLUrl (viewSrcPath v)) v

-- Typical Markdown to HTML path transformation, by dropping a directory and
-- changing the extension.
typicalHTMLPath :: String -> String
typicalHTMLPath = dropDirectory1 . (-<.> "html")

-- Typical URL transformation, dropping the first directory, chagnging the
-- extension to "html", and adding a preslash.
typicalHTMLUrl :: Text -> Text
typicalHTMLUrl = T.pack . ("/" <>) . typicalHTMLPath . T.unpack

-- Create link data object with fields "id" and "url" using an id and a function
-- transforming an id into a url.
genLinkData :: Text -> (Text -> Text) -> Value
genLinkData id f = object ["id" A..= String id, "url" A..= String (f id)]

-- Filter a lists of posts by tag.
tagFilterPosts :: Text -> [Value] -> [Value]
tagFilterPosts tag = filter (elem tag . viewTags)

-- Sort a lists of posts by date.
dateSortPosts :: [Value] -> [Value]
dateSortPosts = sortOn (Down . viewPostTime)

-- Check whether two posts were posted in the same month.
sameMonth :: UTCTime -> UTCTime -> Bool
sameMonth a b = y1 == y2 && m1 == m2 where
  (y1, m1, _) = f a
  (y2, m2, _) = f b
  f = toGregorian . utctDay

monthFilterPosts :: UTCTime -> [Value] -> [Value]
monthFilterPosts time = filter (sameMonth time . viewPostTime)


-- Partition a list of posts by the month they were posted.
partitionToMonths :: [Value] -> [[Value]]
partitionToMonths = groupBy (on sameMonth viewPostTime) . dateSortPosts

-- Create a blog navbar object for a posts section, with layers "toc1", "toc2", and "toc3".
genBlogNavbarData :: Text -- "Top level title, e.g "Blog"
               -> Text -- Root page, e.g "/posts"
               -> (UTCTime -> Text) -- Formatting function to a UTCTime to a title.
               -> (UTCTime -> Text) -- Formatting function to convert a UTCTime to a URL link
               -> [Value]
               -> Value
genBlogNavbarData a b f g xs = object [ "toc1" A..= object [
                                        "title" A..= String a
                                      , "url"   A..= String b
                                      , "toc2"  A..= Array (V.fromList $ map toc2 (partitionToMonths xs)) ]
                                     ] where
       toc2 t@(x : _) = object [ "title" A..= String (f (viewPostTime x))
                               , "url"   A..= String (g (viewPostTime x))
                               , "toc3"  A..= Array (V.fromList t) ]

-- Create a toc navbar object for a docs section, with layers "toc1", "toc2" and "toc3".
genTocNavbarData :: Cofree [] Value -> Value
genTocNavbarData (x :< xs) =
  object ["toc1" A..= [_Object . at "toc2" ?~ Array (V.fromList $ map toc2 xs) $ x]] where
      toc2 (x :< xs) = (_Object . at "toc3" ?~ Array (V.fromList $ map extract xs)) x

genPageData :: Text -> (Text -> Text) -> Zipper [] [Value] -> Value 
genPageData t f xs = withTitle t
                   . withJSON (genLinkData (T.pack . show $ pos xs + 1) f)
                   . withPosts (extract xs) $ Object mempty