# -*- coding: utf-8 -*-
"""
Third-Party Tarballs
"""

#*****************************************************************************
#       Copyright (C) 2015 Volker Braun <vbraun.name@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.
#                  http://www.gnu.org/licenses/
#*****************************************************************************

import os
import logging
log = logging.getLogger()

from sage_bootstrap.env import SAGE_DISTFILES
from sage_bootstrap.download import Download, MirrorList
from sage_bootstrap.package import Package


class ChecksumError(Exception):
    """
    Exception raised when the checksum of the tarball does not match
    """
    pass


class FileNotMirroredError(Exception):
    """
    Exception raised when the tarball cannot be downloaded from the mirrors
    """
    pass


class Tarball(object):
    
    def __init__(self, tarball_name, package=None):
        """
        A (third-party downloadable) tarball

        Note that the tarball might also be a different kind of
        archive format that is supported, it does not necessarily have
        to be tar.

        INPUT:

        - ``tarball_name`` - string. The full filename (``foo-1.3.tar.bz2``)
          of a tarball on the Sage mirror network.
        """
        self.__filename = tarball_name
        if package is None:
            self.__package = None
            for pkg in Package.all():
                if pkg.tarball_filename == tarball_name:
                    self.__package = pkg.tarball_package
            if self.package is None:
                error = 'tarball {0} is not referenced by any Sage package'.format(tarball_name)
                log.error(error)
                raise ValueError(error)
        else:
            self.__package = package
            if package.tarball_filename != tarball_name:
                error = 'tarball {0} is not referenced by the {1} package'.format(tarball_name, package.name)
                log.error(error)
                raise ValueError(error)

    def __repr__(self):
        return 'Tarball {0}'.format(self.filename)
            
    @property
    def filename(self):
        """
        Return the tarball filename

        OUTPUT:

        String. The full filename (``foo-1.3.tar.bz2``) of the
        tarball.
        """
        return self.__filename
        
    @property
    def package(self):
        """
        Return the package that the tarball belongs to

        OUTPUT:

        Instance of :class:`sage_bootstrap.package.Package`
        """
        return self.__package
        
    @property
    def upstream_fqn(self):
        """
        The fully-qualified (including directory) file name in the upstream directory.
        """
        return os.path.join(SAGE_DISTFILES, self.filename)

    def __eq__(self, other):
        return self.filename == other.filename
        
    def _compute_hash(self, algorithm):
        with open(self.upstream_fqn, 'rb') as f:
            while True:
                buf = f.read(0x100000)
                if not buf:
                    break
                algorithm.update(buf)
        return algorithm.hexdigest()

    def _compute_sha1(self):
        import hashlib
        return self._compute_hash(hashlib.sha1())

    def _compute_md5(self):
        import hashlib
        return self._compute_hash(hashlib.md5())
    
    def _compute_cksum(self):
        from sage_bootstrap.cksum import CksumAlgorithm
        return self._compute_hash(CksumAlgorithm())
    
    def checksum_verifies(self):
        """
        Test whether the checksum of the downloaded file is correct.
        """
        sha1 = self._compute_sha1()
        return sha1 == self.package.sha1

    def is_distributable(self):
        return not 'do-not-distribute' in self.filename

    def download(self, allow_upstream=False):
        """
        Download the tarball to the upstream directory.

        If allow_upstream is False and the package cannot be found
        on the sage mirrors, fall back to downloading it from
        the upstream URL if the package has one.
        """
        if not self.filename:
            raise ValueError('non-normal package does define a tarball, so cannot download')
        destination = self.upstream_fqn
        if os.path.isfile(destination):
            if self.checksum_verifies():
                log.info('Using cached file {destination}'.format(destination=destination))
                return
            else:
                # Garbage in the upstream directory? Ignore it.
                # Don't delete it because maybe somebody just forgot to
                # update the checksum (Trac #23972).
                log.warning('Invalid checksum; ignoring cached file {destination}'
                            .format(destination=destination))
        successful_download = False
        log.info('Attempting to download package {0} from mirrors'.format(self.filename))
        for mirror in MirrorList():
            url = mirror + '/'.join(['spkg', 'upstream', self.package.name, self.filename])
            log.info(url)
            try:
                Download(url, destination).run()
                successful_download = True
                break
            except IOError:
                log.debug('File not on mirror')
        if not successful_download:
            url = self.package.tarball_upstream_url
            if allow_upstream and url:
                log.info('Attempting to download from {}'.format(url))
                try:
                    Download(url, destination).run()
                    successful_download = True
                except IOError:
                    raise FileNotMirroredError('tarball does not exist on mirror network and neither at the upstream URL')
            else:
                raise FileNotMirroredError('tarball does not exist on mirror network')
        if not self.checksum_verifies():
            raise ChecksumError('checksum does not match')

    def save_as(self, destination):
        """
        Save the tarball as a new file
        """
        import shutil
        shutil.copy(self.upstream_fqn, destination)

