/*  
  GRAPHS - graph theory package for Maxima
  Copyright (C) 2007-2011 Andrej Vodopivec <andrej.vodopivec@gmail.com>

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or	 
  (at your option) any later version. 

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA

*/

dimacs_export(gr, file, [comments]) := block(
  [fl, str],
  str: apply(dimacs_export_string, cons(gr, comments)),
  fl:openw(file),
  printf(fl, str),
  close(fl))$

dimacs_export_string(gr, [comments]) := block(
  [str:"", names:hash_table(), i:1],
  if not(is_graph_or_digraph(gr)) then error("dimacs_export: first argument is not a graph:", gr),
  for v in sort(vertices(gr)) do (
    set_hash(v, names, i),
    i:i+1),
  str : sconcat(str, printf(false, "c graph exported from MAXIMA~%")),
  for c in comments do (
    str: sconcat(str, printf(false, "c ~a~%", c))),
  if is_graph(gr) then
    str: sconcat(str, printf(false, "p edge ~a ~a~%", graph_order(gr), graph_size(gr)))
  else
    str: sconcat(str, printf(false, "p arc ~a ~a~%", graph_order(gr), graph_size(gr))),
  for v in vertices(gr) do (
    if get_vertex_label(v, gr)#false then
      str: sconcat(str, printf(false, "n ~a ~a~%", get_hash(v, names), get_vertex_label(v, gr)))),
  for e in edges(gr) do block(
    [u:get_hash(first(e), names), v:get_hash(second(e), names), u1, v1],
    if is_graph(gr) then
      [u1,v1] : [min(u,v), max(u,v)]
    else
      [u1,v1] : [u, v],
    if get_edge_weight(e, gr)=1 then
      str: sconcat(str, printf(false, "e ~a ~a~%", u1, v1))
    else
      str: sconcat(str, printf(false, "e ~a ~a ~a~%", u1, v1, get_edge_weight(e, gr)))),
  str)$

dimacs_import(file, [mv]) := block(
  [n, fl, line, elist:[], t, e, v_labels:[], g, dir:false],
  if length(mv)=1 and integerp(mv[1]) then mv:mv[1]
  else mv:1,
  fl:openr(file),
  l:readline(fl),
  while l#false do (
    t:tokens(l),
    if length(t) > 0 then (
      if t[1]="p" then (
        n:read_string(third(t)),
        dir:second(t),
        if dir="edges" or dir="edge" then dir:false
        else dir:true)
      else if t[1]="n" and length(t)>=3 then
        v_labels:cons([read_string(second(t))-mv, third(t)], v_labels)
      else if t[1]="e" then (
        e : map(lambda([u], read_string(u)-mv), [second(t), third(t)]),
        if length(t)=3 then
          elist:cons(e, elist)
        else
          elist:cons([e, read_string(fourth(t))], elist))
      else if t[1]#"c" then error("import_dimacs: wrong file format")),
    l:readline(fl)),
  close(fl),
  if not(integerp(n)) then error("import_dimacs: wrong file format"),
  g : create_graph(n,elist,'directed=dir),
  for v in v_labels do set_vertex_label(v[1], v[2], g),
  g)$
