# copyright 2003-2011 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of logilab-common.
#
# logilab-common is free software: you can redistribute it and/or modify it under
# the terms of the GNU Lesser General Public License as published by the Free
# Software Foundation, either version 2.1 of the License, or (at your option) any
# later version.
#
# logilab-common 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 Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with logilab-common.  If not, see <http://www.gnu.org/licenses/>.
"""Manipulate pdf and fdf files (pdftk recommended).

Notes regarding pdftk, pdf forms and fdf files (form definition file)
fields names can be extracted with:

    pdftk orig.pdf generate_fdf output truc.fdf

to merge fdf and pdf:

    pdftk orig.pdf fill_form test.fdf output result.pdf [flatten]

without flatten, one could further edit the resulting form.
with flatten, everything is turned into text.


"""
__docformat__ = "restructuredtext en"
# XXX seems very unix specific
# TODO: check availability of pdftk at import


import os

HEAD="""%FDF-1.2
%\xE2\xE3\xCF\xD3
1 0 obj
<<
/FDF
<<
/Fields [
"""

TAIL="""]
>>
>>
endobj
trailer

<<
/Root 1 0 R
>>
%%EOF
"""

def output_field( f ):
    return "\xfe\xff" + "".join( [ "\x00"+c for c in f ] )

def extract_keys(lines):
    keys = []
    for line in lines:
        if line.startswith('/V'):
            pass #print 'value',line
        elif line.startswith('/T'):
            key = line[7:-2]
            key = ''.join(key.split('\x00'))
            keys.append( key )
    return keys

def write_field(out, key, value):
    out.write("<<\n")
    if value:
        out.write("/V (%s)\n" %value)
    else:
        out.write("/V /\n")
    out.write("/T (%s)\n" % output_field(key) )
    out.write(">> \n")

def write_fields(out, fields):
    out.write(HEAD)
    for (key, value, comment) in fields:
        write_field(out, key, value)
        write_field(out, key+"a", value) # pour copie-carbone sur autres pages
    out.write(TAIL)

def extract_keys_from_pdf(filename):
    # what about using 'pdftk filename dump_data_fields' and parsing the output ?
    os.system('pdftk %s generate_fdf output /tmp/toto.fdf' % filename)
    lines = file('/tmp/toto.fdf').readlines()
    return extract_keys(lines)


def fill_pdf(infile, outfile, fields):
    write_fields(file('/tmp/toto.fdf', 'w'), fields)
    os.system('pdftk %s fill_form /tmp/toto.fdf output %s flatten' % (infile, outfile))

def testfill_pdf(infile, outfile):
    keys = extract_keys_from_pdf(infile)
    fields = []
    for key in keys:
        fields.append( (key, key, '') )
    fill_pdf(infile, outfile, fields)