from debian import deb822

from dedup.hashing import hash_file

def pkgname_from_dict(entry):
    """Given an entry dictionary obtained from deb822, return the package
    name.
    @rtype: bytes
    """
    name = entry[u"name"]
    # deb822 currently returns :any dependencies raw. see #670679
    name = name.split(u':', 1)[0]
    return name.encode("ascii")


def process_control(control_contents):
    """Parses the contents of a control file from a control.tar.gz of a Debian
    package and returns a dictionary containing the fields relevant to dedup.
    @type control_contents: bytes
    @rtype: {str: object}
    """
    control = deb822.Packages(control_contents)
    package = control["package"].encode("ascii")
    try:
        source = control["source"].encode("ascii").split()[0]
    except KeyError:
        source = package
    version = control["version"].encode("ascii")
    architecture = control["architecture"].encode("ascii")
    depends = set(pkgname_from_dict(dep[0])
                  for dep in control.relations.get("depends", ())
                  if len(dep) == 1)
    conflicts = set(pkgname_from_dict(ent)
                    for group in control.relations.get("conflicts", ())
                    for ent in group)
    conflicts.update(set(pkgname_from_dict(ent)
                         for group in control.relations.get("replaces", ())
                         for ent in group))
    provides = set(pkgname_from_dict(ent)
                   for group in control.relations.get("provides", ())
                   for ent in group)
    return dict(package=package, source=source, version=version,
                architecture=architecture, depends=depends,
                conflicts=conflicts, provides=provides)

class MultiHash(object):
    def __init__(self, *hashes):
        self.hashes = hashes

    def update(self, data):
        for hasher in self.hashes:
            hasher.update(data)

def get_tar_hashes(tar, hash_functions):
    """Given a TarFile read all regular files and compute all of the given hash
    functions on each file.
    @type tar: tarfile.TarFile
    @param hash_functions: a sequence of parameter-less functions each creating a
            new hashlib-like object
    @rtype: gen((str, int, {str: str}}
    @returns: an iterable of (filename, filesize, hashes) tuples where
            hashes is a dict mapping hash function names to hash values
    """

    for elem in tar:
        if not elem.isreg(): # excludes hard links as well
            continue
        hasher = MultiHash(*[func() for func in hash_functions])
        hasher = hash_file(hasher, tar.extractfile(elem))
        hashes = {}
        for hashobj in hasher.hashes:
            hashvalue = hashobj.hexdigest()
            if hashvalue:
                hashes[hashobj.name] = hashvalue
        yield (elem.name, elem.size, hashes)