module Utilities where

import Config
import Data.Aeson (Result (Error, Success))
import qualified Data.Aeson as A
import Data.Maybe (fromMaybe)
import Data.Text (Text)
import qualified Data.Text as T
import Data.Time
import Data.Yaml.Aeson
import Development.Shake (Action)
import qualified Development.Shake as Shake
import Development.Shake.FilePath ((<.>), (</>))
import qualified Development.Shake.FilePath as Shake
import Text.Pandoc (Block (Plain), Meta (..), MetaValue (..), Pandoc (..))
import qualified Text.Pandoc as Pandoc
import Types

indexHtmlOutputPath :: FilePath -> FilePath
indexHtmlOutputPath srcPath =
  outputDir </> Shake.dropExtension srcPath </> "index.html"

-- were applicative shenanigans necessary? no
-- but using them felt cool
indexHtmlSourcePaths :: FilePath -> [FilePath]
indexHtmlSourcePaths path = [indexHtmlTypstSourcePath, indexHtmlMarkdownSourcePath] <*> [path]

indexHtmlTypstSourcePath :: FilePath -> FilePath
indexHtmlTypstSourcePath =
  Shake.dropDirectory1
    . (<.> "typ")
    . Shake.dropTrailingPathSeparator
    . Shake.dropFileName

indexHtmlMarkdownSourcePath :: FilePath -> FilePath
indexHtmlMarkdownSourcePath =
  Shake.dropDirectory1
    . (<.> "md")
    . Shake.dropTrailingPathSeparator
    . Shake.dropFileName

indexHtmlTypstMetaPath :: FilePath -> FilePath
indexHtmlTypstMetaPath = typstMetaPath . indexHtmlTypstSourcePath

typstMetaPath :: FilePath -> FilePath
typstMetaPath typstPath = Shake.dropExtension typstPath <.> "yaml"

typstToHtml :: FilePath -> Action Text
typstToHtml filePath = do
  content <- Shake.readFile' filePath
  Shake.quietly . Shake.traced "Typst to HTML" $ do
    doc <- runPandoc . Pandoc.readTypst readerOptions . T.pack $ content
    html <- runPandoc . Pandoc.writeHtml5String writerOptions $ doc
    return html
  where
    readerOptions =
      Pandoc.def {Pandoc.readerExtensions = Pandoc.pandocExtensions}
    writerOptions =
      Pandoc.def {Pandoc.writerExtensions = Pandoc.pandocExtensions}

markdownToHtml :: (FromJSON a) => FilePath -> Action (a, Text)
markdownToHtml filePath = do
  content <- Shake.readFile' filePath
  Shake.quietly . Shake.traced "Markdown to HTML" $ do
    pandoc@(Pandoc meta _) <-
      runPandoc . Pandoc.readMarkdown readerOptions . T.pack $ content
    -- WARNING markdown needs to have no whitespace before/after dashes
    -- print meta
    meta' <- fromMeta meta
    html <- runPandoc . Pandoc.writeHtml5String writerOptions $ pandoc
    return (meta', html)
  where
    readerOptions =
      Pandoc.def
        { Pandoc.readerStandalone = True,
          Pandoc.readerExtensions = Pandoc.enableExtension Pandoc.Ext_yaml_metadata_block Pandoc.pandocExtensions
        }
    writerOptions =
      Pandoc.def {Pandoc.writerExtensions = Pandoc.pandocExtensions}
    fromMeta (Meta meta) =
      A.fromJSON . A.toJSON <$> traverse metaValueToJSON meta >>= \case
        Success res -> pure res
        Error err -> fail $ "json conversion error:" <> err
    metaValueToJSON = \case
      MetaMap m -> A.toJSON <$> traverse metaValueToJSON m
      MetaList m -> A.toJSONList <$> traverse metaValueToJSON m
      MetaBool m -> pure $ A.toJSON m
      MetaString m -> pure $ A.toJSON $ T.strip m
      MetaInlines m -> metaValueToJSON $ MetaBlocks [Plain m]
      MetaBlocks m ->
        fmap (A.toJSON . T.strip)
          . runPandoc
          . Pandoc.writePlain Pandoc.def
          $ Pandoc mempty m

runPandoc :: Pandoc.PandocIO b -> IO b
runPandoc action =
  Pandoc.runIO (Pandoc.setVerbosity Pandoc.ERROR >> action)
    >>= either (fail . show) return

yamlToPost :: FilePath -> Action Post
yamlToPost path = do
  post <- decodeFileThrow path
  let post' = dateTransform post
  return $ fromMaybe post post'
  where
    dateTransform post@(Post {postDate}) = do
      postDate' <- postDate
      let postDate'' = dateStrTransform $ T.unpack postDate'
      Just
        post
          { postDate = postDate''
          }
    dateStrTransform date = do
      date' <- parseTimeM False defaultTimeLocale "%Y-%-m-%-d" date
      Just $ T.pack $ formatTime @UTCTime defaultTimeLocale "%b %e, %Y" date'

isTypstPost :: FilePath -> Bool
isTypstPost path = Shake.takeExtension path == ".typ"

isMarkdownPost :: FilePath -> Bool
isMarkdownPost path = Shake.takeExtension path == ".md"