{-# LANGUAGE OverloadedStrings #-}

-- | Lists the package page similar to Hackage.

module Handler.Package
    ( getPackageR
    , getPackageSnapshotsR
    , packagePage
    ) where

import           Data.Char
import           Data.Slug
import           Data.Tag
import qualified Data.Text as T
import qualified Data.Text.Encoding as T
import qualified Data.Text.Lazy as LT

import           Database.Esqueleto ((^.))
import qualified Database.Esqueleto as E
import qualified Database.Persist as P
import           Formatting
import           Import
import qualified Text.Blaze.Html.Renderer.Text as LT
import           Text.Email.Validate
import Stackage.Database

-- | Page metadata package.
getPackageR :: PackageName -> Handler Html
getPackageR = packagePage Nothing

packagePage :: Maybe (SnapName, Version)
            -> PackageName
            -> Handler Html
packagePage mversion pname = do
    let pname' = toPathPiece pname
    (deprecated, inFavourOf) <- getDeprecated pname'
    latests <- getLatests pname'
    deps' <- getDeps pname'
    revdeps' <- getRevDeps pname'
    Entity _ package <- getPackage pname' >>= maybe notFound return

    mdocs <-
        case mversion of
            Just (sname, version) -> do
                ms <- getPackageModules sname pname'
                return $ Just (sname, toPathPiece version, ms)
            Nothing ->
                case latests of
                    li:_ -> do
                        ms <- getPackageModules (liSnapName li) pname'
                        return $ Just (liSnapName li, liVersion li, ms)
                    [] -> return Nothing

    let ixInFavourOf = zip [0::Int ..] inFavourOf
        displayedVersion = maybe (packageLatest package) (toPathPiece . snd) mversion

    let homepage = case T.strip (packageHomepage package) of
                     x | null x -> Nothing
                       | otherwise -> Just x
        synopsis = packageSynopsis package
        deps = enumerate deps'
        revdeps = enumerate revdeps'
        authors = enumerate (parseIdentitiesLiberally (packageAuthor package))
        maintainers = let ms = enumerate (parseIdentitiesLiberally (packageMaintainer package))
                      in if ms == authors
                            then []
                            else ms
    defaultLayout $ do
        setTitle $ toHtml pname
        $(combineScripts 'StaticR
                          [ js_highlight_js
                          ])
        $(combineStylesheets 'StaticR
            [ css_font_awesome_min_css
            , css_highlight_github_css
            ])
        let pn = pname
            toPkgVer x y = concat [x, "-", y]
        $(widgetFile "package")
  where enumerate = zip [0::Int ..]

-- | An identifier specified in a package. Because this field has
-- quite liberal requirements, we often encounter various forms. A
-- name, a name and email, just an email, or maybe nothing at all.
data Identifier
  = EmailOnly !EmailAddress -- ^ An email only e.g. jones@example.com
  | Contact !Text
            !EmailAddress -- ^ A contact syntax, e.g. Dave Jones <jones@example.com>
  | PlainText !Text -- ^ Couldn't parse anything sensible, leaving as-is.
  deriving (Show,Eq)

-- | An author/maintainer field may contain a comma-separated list of
-- identifiers. It may be the case that a person's name is written as
-- "Einstein, Albert", but we only parse commas when there's an
-- accompanying email, so that would be:
--
--  Einstein, Albert <emc2@gmail.com>, Isaac Newton <falling@apple.com>
--
-- Whereas
--
-- Einstein, Albert, Isaac Newton
--
-- Will just be left alone. It's an imprecise parsing because the
-- input is wide open, but it's better than nothing:
--
-- λ> parseIdentitiesLiberally "Chris Done, Dave Jones <chrisdone@gmail.com>, Einstein, Albert, Isaac Newton, Michael Snoyman <michael@snoyman.com>"
-- [PlainText "Chris Done"
-- ,Contact "Dave Jones" "chrisdone@gmail.com"
-- ,PlainText "Einstein, Albert, Isaac Newton"
-- ,Contact "Michael Snoyman" "michael@snoyman.com"]
--
-- I think that is quite a predictable and reasonable result.
--
parseIdentitiesLiberally :: Text -> [Identifier]
parseIdentitiesLiberally =
  filter (not . empty) .
  map strip .
  concatPlains .
  map parseChunk .
  T.split (== ',')
  where empty (PlainText e) = T.null e
        empty _ = False
        strip (PlainText t) = PlainText (T.strip t)
        strip x = x
        concatPlains = go
          where go (PlainText x:PlainText y:xs) =
                  go (PlainText (x <> "," <> y) :
                      xs)
                go (x:xs) = x : go xs
                go [] = []

-- | Try to parse a chunk into an identifier.
--
-- 1. First tries to parse an \"email@domain.com\".
-- 2. Then tries to parse a \"Foo <email@domain.com>\".
-- 3. Finally gives up and returns a plain text.
--
-- λ> parseChunk "foo@example.com"
-- EmailOnly "foo@example.com"
-- λ> parseChunk "Dave Jones <dave@jones.com>"
-- Contact "Dave Jones" "dave@jones.com"
-- λ> parseChunk "<x>"
-- PlainText "<x>"
-- λ> parseChunk "Hello!"
-- PlainText "Hello!"
--
parseChunk :: Text -> Identifier
parseChunk chunk =
  case emailAddress (T.encodeUtf8 (T.strip chunk)) of
    Just email -> EmailOnly email
    Nothing ->
      case T.stripPrefix
             ">"
             (T.dropWhile isSpace
                          (T.reverse chunk)) of
        Just rest ->
          case T.span (/= '<') rest of
            (T.reverse -> emailStr,this) ->
              case T.stripPrefix "< " this of
                Just (T.reverse -> name) ->
                  case emailAddress (T.encodeUtf8 (T.strip emailStr)) of
                    Just email ->
                      Contact (T.strip name) email
                    _ -> plain
                _ -> plain
        _ -> plain
  where plain = PlainText chunk

-- | Render email to text.
renderEmail :: EmailAddress -> Text
renderEmail = T.decodeUtf8 . toByteString

getPackageSnapshotsR :: PackageName -> Handler Html
getPackageSnapshotsR pn =
  do snapshots <- getSnapshotsForPackage $ toPathPiece pn
     defaultLayout
       (do setTitle ("Packages for " >> toHtml pn)
           $(combineStylesheets 'StaticR
                                [css_font_awesome_min_css])
           $(widgetFile "package-snapshots"))