{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
module Text.PrettyPrint.GHCi.Value (
  prettyPrintValue, value2Doc,
  ValuePrintConf(..),
  defaultValueConf,
) where

import Text.PrettyPrint.GHCi.Value.Lexer
import Text.PrettyPrint.GHCi.Value.Parser
import System.Terminal.Utils

-- base
import Data.String       ( fromString )
import Control.Exception ( catch, ErrorCall )
import System.IO         ( stdout )
import qualified Data.List.NonEmpty as N

-- prettyprinter, prettyprinter-ansi-terminal
import Data.Text.Prettyprint.Doc
import Data.Text.Prettyprint.Doc.Render.Terminal

-- | Given a 'Show'-ed value, print that value out to the terminal, add helpful
-- indentation and colours whenever possible. If a structured value cannot be
-- parsed out, this falls back on 'print'.
--
-- The 'Bool' is to enable a slower but potentially smarter layout algorithm.
prettyPrintValue :: Bool -> String -> IO ()
prettyPrintValue smarter str = do
  termSize <- getTerminalSize
  let layoutOpts = LayoutOptions (AvailablePerLine (maybe 80 snd termSize) 1.0)
      layoutAlgo = if smarter then layoutSmart else layoutPretty
      rendered = layoutAlgo layoutOpts (value2Doc str)
  renderIO stdout rendered `catch` \(_ :: ErrorCall) -> putStr str

-- | Parse a shown value into a pretty 'Doc'. Can throw an error on outputs
-- that could not be parsed properly, but should not throw errors for inputs
-- which are the outputs of 'show' from derived 'Show' instances.
value2Doc :: String -> Doc AnsiStyle
value2Doc shown = case parseValue shown of
                    Just v -> renderValue defaultValueConf v <> hardline
                    Nothing -> renderTokens defaultValueConf tokens
  where
    tokens = lexTokens shown


-- | A Good Enough colour scheme
defaultValueConf :: ValuePrintConf
defaultValueConf = ValuePrintConf
  { vpc_number    = color Cyan 
  , vpc_character = color Blue
  , vpc_string    = color Green
  , vpc_control   = bold <> color Magenta
  , vpc_comma     = color Yellow
  , vpc_operator  = color White
  , vpc_field     = italicized <> colorDull Red 
  , vpc_indent    = 2
  }

-- | Options for how to colour the terminal output
data ValuePrintConf = ValuePrintConf
  { vpc_number :: AnsiStyle    -- ^ all sorts of numeric literals
  , vpc_character :: AnsiStyle -- ^ character literals
  , vpc_string :: AnsiStyle    -- ^ string literals
  , vpc_control :: AnsiStyle   -- ^ various control characters (ex: parens)
  , vpc_comma :: AnsiStyle     -- ^ commas
  , vpc_operator :: AnsiStyle  -- ^ general operators
  , vpc_field :: AnsiStyle     -- ^ field in a record
  , vpc_indent :: Int          -- ^ how many spaces is one indent?
  }


-- | Function for turning a 'Value' into a 'Doc'
renderValue :: ValuePrintConf -> Value -> Doc AnsiStyle
renderValue vpc = renderVal
  where
    renderVal v = case v of

      Num i -> num (fromString i)
      Char c -> char (fromString c)
      Str s -> string (fromString s)
      
      List vs  -> renderSeq (ctrl "[") (map (align . renderVal) vs) (ctrl "]")
      Tuple vs -> renderSeq (ctrl "(") (map (align . renderVal) vs) (ctrl ")")
      
      -- Either everything goes on one line or the constructor and args each
      -- start on a new line (with args indented)
      Prefix c [] -> fromString c
      Prefix c vs ->
        let args = map (align . renderVal) vs
        in fromString c <> group (nest n (line <> align (vsep args)))
     
      -- Either everything goes on one line, or each argument gets its own
      -- line with operators at the beginning of the lines
      Infix arg0 ops ->
        let tails = fmap (\(op,arg) -> optr (fromString op) <+> align (renderVal arg)) ops
        in renderVal arg0 <> group (nest n (line <> align (vsep (N.toList tails))))

      -- Either everything goes on one line or the constructor and fields each
      -- start on a new line (with fields indented)
      Record c vs ->
        let fields = zipWith (\l (f,x) -> hsep [ l, field (fromString f)
                                               , ctrl "=", align (renderVal x) ])
                             (ctrl "{" : repeat (coma ",")) (N.toList vs)
        in fromString c <> group (nest n (line <> align (vcat fields) <+> ctrl "}"))
      
      Paren x -> ctrl "(" <> align (renderVal x) <> ctrl ")"

    -- Haskell style formatting of sequence-like things, with the comma at the
    -- start of the line
    renderSeq :: Doc AnsiStyle -> [Doc AnsiStyle] -> Doc AnsiStyle -> Doc AnsiStyle
    renderSeq opn [] cls = opn <> cls
    renderSeq opn vs cls = align . group . encloseSep opn' cls' (coma ", ") $ vs
      where
        opn' = flatAlt (opn <> space) opn
        cls' = flatAlt (space <> cls) cls

    n = vpc_indent vpc

    -- Useful annotations
    num    = annotate (vpc_number    vpc)
    char   = annotate (vpc_character vpc)
    string = annotate (vpc_string    vpc)
    ctrl   = annotate (vpc_control   vpc)
    coma   = annotate (vpc_comma     vpc)
    optr   = annotate (vpc_operator  vpc)
    field  = annotate (vpc_field     vpc)


-- | Function for turning a list of 'Token's into a 'Doc'
renderTokens :: ValuePrintConf -> [Token] -> Doc AnsiStyle
renderTokens vpc = mconcat . map renderTok
  where
    renderTok tok = case tok of

      WhiteTok w -> renderWhite w

      NumberTok i -> num (fromString i)
      CharacterTok c -> char (fromString c)
      StringTok s -> string (fromString s)

      OpenBracket  -> ctrl "["
      CloseBracket -> ctrl "]"
      OpenParen    -> ctrl "("
      CloseParen   -> ctrl ")"
      OpenBrace    -> ctrl "{"
      CloseBrace   -> ctrl "}"
      Equal        -> ctrl "="

      OperatorTok op -> optr (fromString op)
      IdentifierTok c -> fromString c

      Comma -> coma ","

    -- Render whitespace (which might have newlines)
    renderWhite :: String -> Doc AnsiStyle
    renderWhite "" = mempty
    renderWhite str = let (ln, str') = span (/= '\n') str
                      in fromString ln <> hardline <> renderWhite (drop 1 str')

    -- Useful annotations
    num    = annotate (vpc_number    vpc)
    char   = annotate (vpc_character vpc)
    string = annotate (vpc_string    vpc)
    ctrl   = annotate (vpc_control   vpc)
    coma   = annotate (vpc_comma     vpc)
    optr   = annotate (vpc_operator  vpc)