module Options

import Quox.Pretty
import System
import System.Console.GetOpt
import System.File
import System.Term
import Derive.Prelude

%default total
%language ElabReflection

public export
data OutFile = File String | Console | None
%name OutFile f
%runElab derive "OutFile" [Eq, Ord, Show]

public export
data Phase = Parse | Check | Erase | Scheme
%name Phase p
%runElab derive "Phase" [Eq, Ord, Show]

||| a list of all `Phase`s
public export %inline
allPhases : List Phase
allPhases = %runElab do
  -- as a script so it stays up to date
  cs <- getCons $ fst !(lookupName "Phase")
  traverse (check . var) cs

public export
record Options where
  constructor MkOpts
  color   : Bool
  outFile : OutFile
  until   : Maybe Phase
  flavor  : Pretty.Flavor
  width   : Nat
  include : List String
%name Options opts
%runElab derive "Options" [Show]

export
defaultWidth : IO Nat
defaultWidth = do
  w <- cast {to = Nat} <$> getTermCols
  pure $ if w == 0 then 80 else w

export
defaultOpts : IO Options
defaultOpts = pure $ MkOpts {
  color   = True,
  outFile = Console,
  until   = Nothing,
  flavor  = Unicode,
  width   = !defaultWidth,
  include = ["."]
}

private
data HelpType = Common | All

private
data OptAction = ShowHelp HelpType | Err String | Ok (Options -> Options)
%name OptAction act

private
toOutFile : String -> OptAction
toOutFile ""  = Ok {outFile := None}
toOutFile "-" = Ok {outFile := Console}
toOutFile f   = Ok {outFile := File f}

private
toPhase : String -> OptAction
toPhase str =
  let lstr = toLower str in
  case find (\p => toLower (show p) == lstr) allPhases of
    Just p  => Ok {until := Just p}
    Nothing => Err "unknown phase name \{show str}\nphases: \{phaseNames}"
where phaseNames = joinBy ", " $ map (toLower . show) allPhases

private
toWidth : String -> OptAction
toWidth s = case parsePositive s of
  Just n  => Ok {width := n}
  Nothing => Err "invalid width: \{show s}"

private
commonOptDescrs' : List (OptDescr OptAction)
commonOptDescrs' = [
  MkOpt ['i'] ["include"] (ReqArg (\i => Ok {include $= (i ::)}) "<dir>")
    "add a directory to look for source files",
  MkOpt ['o'] ["output"] (ReqArg toOutFile "<file>")
    "output file (\"-\" for stdout, \"\" for no output)",
  MkOpt ['P'] ["phase"] (ReqArg toPhase "<phase>")
    "phase to stop at (by default go as far as exists)"
]

private
extraOptDescrs : List (OptDescr OptAction)
extraOptDescrs = [
  MkOpt [] ["unicode"] (NoArg $ Ok {flavor := Unicode})
    "use unicode syntax when printing (default)",
  MkOpt [] ["ascii"] (NoArg $ Ok {flavor := Ascii})
    "use ascii syntax when printing",
  MkOpt [] ["width"] (ReqArg toWidth "<width>")
    "max output width (defaults to terminal width)",
  MkOpt [] ["color", "colour"] (NoArg $ Ok {color := True})
    "use colour output (default)",
  MkOpt [] ["no-color", "no-colour"] (NoArg $ Ok {color := False})
    "don't use colour output"
]

private
helpOptDescrs : List (OptDescr OptAction)
helpOptDescrs = [
  MkOpt ['h'] ["help"]     (NoArg $ ShowHelp Common) "show common options",
  MkOpt []    ["help-all"] (NoArg $ ShowHelp All)    "show all options"
]

commonOptDescrs = commonOptDescrs' ++ helpOptDescrs
allOptDescrs    = commonOptDescrs' ++ extraOptDescrs ++ helpOptDescrs

export
usageHeader : String
usageHeader = joinBy "\n" [
  "quox [options] [file.quox ...]",
  "rawr"
]

export
usage : List (OptDescr _) -> IO a
usage ds = do
  ignore $ fPutStr stderr $ usageInfo usageHeader ds
  exitSuccess

private
applyAction : Options -> OptAction -> IO Options
applyAction opts (ShowHelp Common) = usage commonOptDescrs
applyAction opts (ShowHelp All)    = usage allOptDescrs
applyAction opts (Err err)         = die err
applyAction opts (Ok f)            = pure $ f opts

private
finalise : Options -> Options
finalise = {include $= reverse}

export
options : IO (String, Options, List String)
options = do
  app :: args <- getArgs
    | [] => die "couldn't get command line arguments"
  let res = getOpt Permute allOptDescrs args
  unless (null res.errors) $
    die $ trim $ concat res.errors
  unless (null res.unrecognized) $
    die "unrecognised options: \{joinBy ", " res.unrecognized}"
  opts <- foldlM applyAction !defaultOpts res.options
  pure (app, finalise opts, res.nonOptions)