#! /usr/bin/gawk -f
# Last edited on 2012-04-30 01:18:34 by stolfi

# Usage: "make-fix-rel-link-command.gawk -v link={LINK} -v target={TARGET}"
# Given a symbolic link pathname and its target pathname,
# both relative to the same root directory.
# outputs the command that creates a relative symbolic link using "../"
# If data is invalid, complains to {stderr} and outputs nothing.

BEGIN {
  if (link ~ /^[/]/) { printf "invalid link\n" > "/dev/stderr"; }
  if (target ~ /^[/]/) { printf "invalid target\n" > "/dev/stderr"; }
  dir="";
  tdir = ""; 
  while (1)
    { match(link, /[/]/);   ap = RSTART;
      match(target, /[/]/); bp = RSTART;
      if (ap == 0)
        { printf "cd %s && ln -s %s%s %s \n", dir, tdir, target, link; exit(0); }
      link_head = substr(link,1,ap);
      if (link_head == "./") 
        { link = substr(link,ap+1); }
      else if (link_head == "../")
        { printf "invalid link\n" > "/dev/stderr"; }
      else 
        { dir = (dir link_head); 
          link = substr(link,ap+1); 
          target_head = substr(target,1,bp);
          if (target_head == "./") 
            { target = substr(target,bp+1); }
          else if (target_head == "../")
            { printf "invalid target\n" > "/dev/stderr"; }
          else
            { if (link_head == target_head)
                { target = substr(target,bp+1); }
              else
                { tdir = (tdir "../"); }
            }
        }
    }
}