# vim: set sw=4 sts=4 et :
# Copyright: 2008-2009 Gentoo Foundation
# Author(s): Nirbheek Chauhan <nirbheek.chauhan@gmail.com>
# License: GPL-3
#

import subprocess, os
from .. import config

class Crypto(object):
    """
    Data Encrypter/Decrypter
    """

    def __init__(self, gpghome=config.GPGHOME):
        """
        @param gpghome: Home directory for GPG
        @type gpghome: string
        """
        self.gpghome = gpghome
        self.gpgcmd = 'gpg -a --keyid-format long --trust-model always '
        self.gpgcmd += '--homedir="%s" ' % self.gpghome

    def _validate_gpghome(self):
        try:
            gpghome = open(self.gpghome+'/secring.gpg')
        except (IOError, OSError):
            raise Exception('"%s": Unable to use GPG homedir' % self.gpghome)
        finally:
            gpghome.close()

    def _get_fp_from_keyid(self, keyid):
        gpg_args = '--with-colons --fingerprint --list-keys "%s"' % keyid
        process = subprocess.Popen(self.gpgcmd+gpg_args, shell=True,
                                   stdout=subprocess.PIPE)
        output = process.stdout.readlines()
        process.wait()
        for line in output:
            # Fingerprint line
            if line.startswith('fpr'):
                # Fingerprint
                return line.split(':')[-2]

    def export_pubkey(self, file, which):
        self._validate_gpghome()
        gpg_args = '--export "%s" > "%s"' % (which, file)
        print self.gpgcmd+gpg_args
        subprocess.check_call(self.gpgcmd+gpg_args, shell=True)

    def import_pubkey(self, pubkey):
        self._validate_gpghome()
        gpg_args = '--import <<<"%s"' % pubkey
        subprocess.check_call(self.gpgcmd+gpg_args, shell=True)

    def init_gpghome(self, name='Test AutotuA Slave', email='test_slave@test.org',
                     expire='5y', length='4096'):
        """
        Initialize a GnuPG home by generating keys
        """
        params = (('Key-Type', 'DSA'),
                  ('Key-Length', '1024'),
                  ('Subkey-Type', 'ELG-E'),
                  ('Subkey-Length', length),
                  ('Name-Real', name),
                  ('Name-Email', email),
                  ('Expire-Date', expire),)
        # Batch mode
        gpg_args = '--batch --gen-key <<<"'
        gpg_args += '%echo Generating keys.. [Worship the gods of randomness :p]'
        for param in params:
            gpg_args += '\n%s: %s' % param
        gpg_args += '"'
        subprocess.check_call(self.gpgcmd+gpg_args, shell=True)
        print 'Done.'

    def encrypt(self, data, recipient='Autotua Master'):
        """
        @param data: Data to be encrypted
        @type data: string

        @param recipient: Recipient for the data
        @type recipient: string

        returns: encrypted_data
        """
        self._validate_gpghome()
        gpg_args = '--encrypt --sign --recipient "%s" <<<"%s"' % (recipient, data)
        process = subprocess.Popen(self.gpgcmd+gpg_args, shell=True,
                                   stdout=subprocess.PIPE)
        data = process.stdout.read()
        process.wait()
        if process.returncode < 0:
            raise Exception('Unable to encrypt, something went wrong :(')
        return data

    def decrypt(self, data):
        """
        @param data: Data to be encrypted
        @type data: string

        returns: (decrypted_data, sender)
        """
        self._validate_gpghome()
        gpg_args = '--decrypt <<<"%s"' % data
        process = subprocess.Popen(self.gpgcmd+gpg_args, shell=True,
                                   stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        ddata = process.stdout.read()[:-1] # Extra \n at the end :-/
        # Get the output to stderr
        gpg_out = process.stderr.readlines()
        process.wait()
        if process.returncode < 0 or not ddata:
            raise Exception('Unable to decrypt, something went wrong')
        # Get the line with the DSA long key ID
        for line in gpg_out:
            if line.find('using DSA key') != -1:
                # Get the long key ID
                gpg_out = line.split()[-1]
                break
        # Get the fingerprint
        sender = self._get_fp_from_keyid(gpg_out)
        return (ddata, sender)