normpath.nim

import strutils, os

proc simplifyPath(path: string): string =
  var segments: seq[string] = @[]

  var i = 0
  var curDir = ""
  while true:
    case path[i]
    of dirSep, altSep:
      if curDir != "" or i == 0:
        segments.add curDir
        curDir = ""
    of '.':
      if path[i+1] == '.' and path[i+2] in {dirSep, altSep, '\0'}:
        # Move up a dir.
        discard segments.pop()
        i.inc
      elif path[i+1] notin {dirSep, altSep, '\0'}:
        curDir.add path[i]
    of '~':
      if path[i+1] in {dirSep, altSep, '\0'}:
        segments.add getHomeDir()
    of '\0':
      if curDir != "":
        segments.add curDir
      break
    else:
      curDir.add path[i]
    i.inc
  result = segments.join($dirSep)

when isMainModule:
  when defined(windows):
    doAssert simplifyPath(r"\User\..\Clay\..\Ben") == r"\Ben"
    doAssert simplifyPath(r"C:\Test\..\Program Files\Nimrod") == r"C:\Program Files\Nimrod"
    doAssert simplifyPath(r"/Blah/./../Test/") == r"\Test"
    doAssert simplifyPath(r"/Blah/./foo.txt/..asf/../a..sd/") == r"\Blah\foo.txt\a..sd"
  else:
    doAssert simplifyPath(r"\User\..\Clay\..\Ben") == r"/Ben"
    doAssert simplifyPath(r"C:\Test\..\Program Files\Nimrod") == r"C:/Program Files/Nimrod"
    doAssert simplifyPath(r"/Blah/./../Test/") == r"/Test"
    doAssert simplifyPath(r"/Blah/./foo.txt/..asf/../a..sd/") == r"/Blah/foo.txt/a..sd"