-- |
-- Module      :  Distribution.Client.Manpage
-- Copyright   :  (c) Maciek Makowski 2015
-- License     :  BSD-like
--
-- Maintainer  :  cabal-devel@haskell.org
-- Stability   :  provisional
-- Portability :  portable
--
-- Functions for building the manual page.
module Distribution.Client.Manpage
  ( -- * Manual page generation
    manpage
  , manpageCmd
  , ManpageFlags
  , defaultManpageFlags
  , manpageOptions
  ) where

import qualified Data.List.NonEmpty as List1
import Distribution.Client.Compat.Prelude
import Prelude ()

import Distribution.Client.Errors
import Distribution.Client.Init.Utils (trim)
import Distribution.Client.ManpageFlags
import Distribution.Client.Setup (globalCommand)
import Distribution.Compat.Process (proc)
import Distribution.Simple.Command
import Distribution.Simple.Flag (fromFlag, fromFlagOrDefault)
import Distribution.Simple.Utils
  ( IOData (..)
  , IODataMode (..)
  , dieWithException
  , fromCreatePipe
  , ignoreSigPipe
  , rawSystemProcAction
  , rawSystemStdInOut
  )
import System.Environment (lookupEnv)
import System.IO (hClose, hPutStr)
import qualified System.Process as Process

data FileInfo
  = -- | path, description
    FileInfo String String

-------------------------------------------------------------------------------
--
-------------------------------------------------------------------------------

-- | A list of files that should be documented in the manual page.
files :: [FileInfo]
files =
  [ (FileInfo "~/.config/cabal/config" "The defaults that can be overridden with command-line options.")
  ]

manpageCmd :: String -> [CommandSpec a] -> ManpageFlags -> IO ()
manpageCmd pname commands flags
  | fromFlagOrDefault False (manpageRaw flags) =
      putStrLn contents
  | otherwise =
      ignoreSigPipe $ do
        -- 2021-10-08, issue #7714
        -- @cabal man --raw | man -l -@ does not work on macOS/BSD,
        -- because BSD-man does not support option @-l@, rather would
        -- accept directly a file argument, e.g. @man /dev/stdin@.
        -- The following works both on macOS and Linux
        -- (but not on Windows out-of-the-box):
        --
        --   cabal man --raw | nroff -man /dev/stdin | less
        --
        -- So let us simulate this!

        -- Feed contents into @nroff -man /dev/stdin@
        (formatted, _errors, ec1) <-
          rawSystemStdInOut
            verbosity
            "nroff"
            ["-man", "/dev/stdin"]
            Nothing -- Inherit working directory
            Nothing -- Inherit environment
            (Just $ IODataText contents)
            IODataModeText

        unless (ec1 == ExitSuccess) $ exitWith ec1

        pagerAndArgs <- fromMaybe "less -R" <$> lookupEnv "PAGER"
        -- 'less' is borked with color sequences otherwise, hence -R
        (pager, pagerArgs) <- case words pagerAndArgs of
          [] -> dieWithException verbosity EmptyValuePagerEnvVariable
          (p : pa) -> pure (p, pa)
        -- Pipe output of @nroff@ into @less@
        (ec2, _) <- rawSystemProcAction
          verbosity
          (proc pager pagerArgs){Process.std_in = Process.CreatePipe}
          $ \mIn _ _ -> do
            let wIn = fromCreatePipe mIn
            hPutStr wIn formatted
            hClose wIn
        exitWith ec2
  where
    contents :: String
    contents = manpage pname commands
    verbosity = fromFlag $ manpageVerbosity flags

-- | Produces a manual page with @troff@ markup.
manpage :: String -> [CommandSpec a] -> String
manpage pname commands =
  unlines $
    [ ".TH " ++ map toUpper pname ++ " 1"
    , ".SH NAME"
    , pname ++ " \\- a system for building and packaging Haskell libraries and programs"
    , ".SH SYNOPSIS"
    , ".B " ++ pname
    , ".I command"
    , ".RI < arguments |[ options ]>..."
    , ""
    , "Where the"
    , ".I commands"
    , "are"
    , ""
    ]
      ++ concatMap (commandSynopsisLines pname) commands
      ++ [ ".SH DESCRIPTION"
         , "Cabal is the standard package system for Haskell software. It helps people to configure, "
         , "build and install Haskell software and to distribute it easily to other users and developers."
         , ""
         , "The command line " ++ pname ++ " tool (also referred to as cabal-install) helps with "
         , "installing existing packages and developing new packages. "
         , "It can be used to work with local packages or to install packages from online package archives, "
         , "including automatically installing dependencies. By default it is configured to use Hackage, "
         , "which is Haskell's central package archive that contains thousands of libraries and applications "
         , "in the Cabal package format."
         , ".SH OPTIONS"
         , "Global options:"
         , ""
         ]
      ++ optionsLines (globalCommand [])
      ++ [ ".SH COMMANDS"
         ]
      ++ concatMap (commandDetailsLines pname) commands
      ++ [ ".SH FILES"
         ]
      ++ concatMap fileLines files
      ++ [ ".SH BUGS"
         , "To browse the list of known issues or report a new one please see "
         , "https://github.com/haskell/cabal/labels/cabal-install."
         ]

commandSynopsisLines :: String -> CommandSpec action -> [String]
commandSynopsisLines pname (CommandSpec ui _ NormalCommand) =
  [ ".B " ++ pname ++ " " ++ (commandName ui)
  , "- " ++ commandSynopsis ui
  , ".br"
  ]
commandSynopsisLines _ (CommandSpec _ _ HiddenCommand) = []

commandDetailsLines :: String -> CommandSpec action -> [String]
commandDetailsLines pname (CommandSpec ui _ NormalCommand) =
  [ ".B " ++ pname ++ " " ++ (commandName ui)
  , ""
  , commandUsage ui pname
  , ""
  ]
    ++ optional removeLineBreaks commandDescription
    ++ optional id commandNotes
    ++ [ "Flags:"
       , ".RS"
       ]
    ++ optionsLines ui
    ++ [ ".RE"
       , ""
       ]
  where
    optional f field =
      case field ui of
        Just text -> [f $ text pname, ""]
        Nothing -> []
    -- 2021-10-12, https://github.com/haskell/cabal/issues/7714#issuecomment-940842905
    -- Line breaks just before e.g. 'new-build' cause weird @nroff@ warnings.
    -- Thus:
    -- Remove line breaks but preserve paragraph breaks.
    -- We group lines by empty/non-empty and then 'unwords'
    -- blocks consisting of non-empty lines.
    removeLineBreaks =
      unlines
        . concatMap unwordsNonEmpty
        . List1.groupWith null
        . map trim
        . lines
    unwordsNonEmpty :: List1.NonEmpty String -> [String]
    unwordsNonEmpty ls1 = if null (List1.head ls1) then ls else [unwords ls]
      where
        ls = List1.toList ls1
commandDetailsLines _ (CommandSpec _ _ HiddenCommand) = []

optionsLines :: CommandUI flags -> [String]
optionsLines command = concatMap optionLines (concatMap optionDescr (commandOptions command ParseArgs))

data ArgumentRequired = Optional | Required
type OptionArg = (ArgumentRequired, ArgPlaceHolder)

optionLines :: OptDescr flags -> [String]
optionLines (ReqArg description (optionChars, optionStrings) placeHolder _ _) =
  argOptionLines description optionChars optionStrings (Required, placeHolder)
optionLines (OptArg description (optionChars, optionStrings) placeHolder _ _ _) =
  argOptionLines description optionChars optionStrings (Optional, placeHolder)
optionLines (BoolOpt description (trueChars, trueStrings) (falseChars, falseStrings) _ _) =
  optionLinesIfPresent trueChars trueStrings
    ++ optionLinesIfPresent falseChars falseStrings
    ++ optionDescriptionLines description
optionLines (ChoiceOpt options) =
  concatMap choiceLines options
  where
    choiceLines (description, (optionChars, optionStrings), _, _) =
      [optionsLine optionChars optionStrings]
        ++ optionDescriptionLines description

argOptionLines :: String -> [Char] -> [String] -> OptionArg -> [String]
argOptionLines description optionChars optionStrings arg =
  [ optionsLine optionChars optionStrings
  , optionArgLine arg
  ]
    ++ optionDescriptionLines description

optionLinesIfPresent :: [Char] -> [String] -> [String]
optionLinesIfPresent optionChars optionStrings =
  if null optionChars && null optionStrings
    then []
    else [optionsLine optionChars optionStrings, ".br"]

optionDescriptionLines :: String -> [String]
optionDescriptionLines description =
  [ ".RS"
  , description
  , ".RE"
  , ""
  ]

optionsLine :: [Char] -> [String] -> String
optionsLine optionChars optionStrings =
  intercalate ", " (shortOptions optionChars ++ longOptions optionStrings)

shortOptions :: [Char] -> [String]
shortOptions = map (\c -> "\\-" ++ [c])

longOptions :: [String] -> [String]
longOptions = map (\s -> "\\-\\-" ++ s)

optionArgLine :: OptionArg -> String
optionArgLine (Required, placeHolder) = ".I " ++ placeHolder
optionArgLine (Optional, placeHolder) = ".RI [ " ++ placeHolder ++ " ]"

fileLines :: FileInfo -> [String]
fileLines (FileInfo path description) =
  [ path
  , ".RS"
  , description
  , ".RE"
  , ""
  ]
