path

path.nim

import strutils, os

type PathToken = enum
  ptParentDir
  ptCurrentDir
  ptExtraSep
  ptNone

proc parsePathToken(s: string, offset: int): PathToken =
  result = ptNone
  echo "Trying to parse token at ", offset
  if (offset + parDir.len) < s.len() and s.continuesWith(parDir, offset):
    if (offset + parDir.len) == s.len() or
       s[offset + (parDir.len)] in {altSep, dirSep}:
      result = ptParentDir
  elif s[offset] == curDir:
    if (offset + 1) == s.len() or s[offset + 1] in {altSep, dirSep}:
      result = ptCurrentDir
  elif (offset + 1) != s.len() and s[offset] in {dirSep, altSep}:
    result = ptExtraSep

proc simplifyPath(path: string): string =
  ## Simplify a path, removing redundant path seperators and current directory
  ## tokens, and applying parent directory tokens, 

  result = path
  var
    bounds = newSeq[int]()
    writePos, readPos = 0
  while readPos < path.len:
    echo("Writing '$#' at $# to '$#' at $#".format(path[readPos], readPos, result[writePos], writePos))
    if path[readPos] in {altSep, dirSep}: # Handle possible meta-paths and junk
        while true:
          case parsePathToken(path, readPos+1)
          of ptParentDir:
            echo("Got ptParentDir")
            writePos = bounds.pop()
            echo "Popping boundary to writePos: ", writePos
            readPos.inc(3)
            echo "readPos incremented to ", readPos
          of ptCurrentDir:
            echo("Got ptCurrentDir")
            readPos.inc(2)
            echo "readPos incremented to ", readPos
          of ptExtraSep:
            echo("Got ptExtraSep")
            readPos.inc(1)
            echo "readPos incremented to ", readPos
          else:
            echo("Got ptNone")
            break
        echo "Adding bound at ", readPos
        bounds.add(readPos)
    result[writePos] = path[readPos]
    writePos.inc
    readPos.inc
  echo readPos, ' ', writePos
  result.setLen(writePos)

echo simplifyPath(r"\User\..\Clay\..\Ben")
##
## "/User/Clay/../Ben/../../"
## 
## "                        "
## 
## "/User/Clay/../Ben/../../"