#
#
#            Nimrod's Runtime Library
#        (c) Copyright 2012 Andreas Rumpf
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

## This module provides the standard Nimrod command line parser.
## It supports one convenience iterator over all command line options and some
## lower-level features.
##
## Supported syntax:
##
## 1. short options - ``-abcd``, where a, b, c, d are names
## 2. long option - ``--foo:bar``, ``--foo=bar`` or ``--foo``
## 3. argument - everything else

{.push debugger: off.}

include "system/inclrtl"

import
  os, strutils

type
  TCmdLineKind* = enum        ## the detected command line token
    cmdEnd,                   ## end of command line reached
    cmdArgument,              ## argument detected
    cmdLongOption,            ## a long option ``--option`` detected
    cmdShortOption            ## a short option ``-c`` detected
  TOptParser* =
      object of TObject ## this object implements the command line parser
    cmd: seq[string]
    pos: int
    remainingShortOptions: string
    kind*: TCmdLineKind       ## the dected command line token
    key*, val*: TaintedString ## key and value pair; ``key`` is the option
                              ## or the argument, ``value`` is not "" if
                              ## the option was given a value

proc initOptParser*(cmdline: seq[string]): TOptParser {.rtl.} =
  ## Initalizes option parses with cmdline. cmdline should not contain
  ## argument 0 - program name.
  ## If cmdline == nil default to current command line arguments.
  result.remainingShortOptions = ""
  when not defined(createNimRtl):
    if cmdline == nil:
      result.cmd = commandLineParams()
      return
  else:
    assert cmdline != nil, "Cannot determine command line arguments."

  result.cmd = @cmdline

proc initOptParser*(cmdline: string): TOptParser {.rtl, deprecated.} =
  ## Initalizes option parses with cmdline. Splits cmdline in on spaces
  ## and calls initOptParser(openarray[string])
  ## Do not use.
  if cmdline == "": # backward compatibilty
    return initOptParser(seq[string](nil))
  else:
    return initOptParser(cmdline.split)

when not defined(createNimRtl):
  proc initOptParser*(): TOptParser =
    ## Initializes option parser from current command line arguments.
    return initOptParser(commandLineParams())

proc next*(p: var TOptParser) {.rtl, extern: "npo$1".}

proc nextOption(p: var TOptParser, token: string, allowEmpty: bool) =
  for splitchar in [':', '=']:
    if splitchar in token:
      let pos = token.find(splitchar)
      p.key = token[0..pos-1]
      p.val = token[pos+1..token.len-1]
      return

  p.key = token
  if allowEmpty:
    p.val = ""
  else:
    p.remainingShortOptions = token[0..token.len-1]
    p.next()

proc next(p: var TOptParser) =
  if p.remainingShortOptions.len != 0:
    p.kind = cmdShortOption
    p.key = TaintedString(p.remainingShortOptions[0..0])
    p.val = ""
    p.remainingShortOptions = p.remainingShortOptions[1..p.remainingShortOptions.len-1]
    return

  if p.pos >= p.cmd.len:
    p.kind = cmdEnd
    return

  let token = p.cmd[p.pos]
  p.pos += 1

  if token.startswith("--"):
    p.kind = cmdLongOption
    nextOption(p, token[2..token.len-1], allowEmpty=true)
  elif token.startswith("-"):
    p.kind = cmdShortOption
    nextOption(p, token[1..token.len-1], allowEmpty=true)
  else:
    p.kind = cmdArgument
    p.key = token
    p.val = ""

proc cmdLineRest*(p: TOptParser): TaintedString {.rtl, extern: "npo$1", deprecated.} =
  ## Returns part of command line string that has not been parsed yet.
  ## Do not use - does not correctly handle whitespace.
  return p.cmd[p.pos..p.cmd.len-1].join(" ")

type
  TGetoptResult* = tuple[kind: TCmdLineKind, key, val: TaintedString]

when defined(paramCount):
  iterator getopt*(): TGetoptResult =
    ## This is an convenience iterator for iterating over the command line.
    ## This uses the TOptParser object. Example:
    ##
    ## .. code-block:: nimrod
    ##   var
    ##     filename = ""
    ##   for kind, key, val in getopt():
    ##     case kind
    ##     of cmdArgument:
    ##       filename = key
    ##     of cmdLongOption, cmdShortOption:
    ##       case key
    ##       of "help", "h": writeHelp()
    ##       of "version", "v": writeVersion()
    ##     of cmdEnd: assert(false) # cannot happen
    ##   if filename == "":
    ##     # no filename has been given, so we show the help:
    ##     writeHelp()
    var p = initOptParser()
    while true:
      next(p)
      if p.kind == cmdEnd: break
      yield (p.kind, p.key, p.val)

{.pop.}