def manifest_to_file_list(manifest_fn):
    """
    open a manifest file and read it into a list

    manifest_fn -- the manifest file to read
    """
    image_manifest_list = []
    with open(manifest_fn) as image:
        image_manifest_list = image.read().splitlines()

    return image_manifest_list


def delta_contents(difflist):
    """
    Generate a list of files which exist in the bundle image but not the base
    image

    '- ' - line unique to lhs
    '+ ' - line unique to rhs
    '  ' - line common
    '? ' - line not present in either

    returns a list containing the items which are unique in the rhs

    difflist --- a list containing the output of difflib.Differ.compare
          where the lhs (left-hand-side) was the base image and the rhs
          (right-hand-side) was base image + extras (the bundle image).
    """
    cont = []
    for ln in difflist:
        if ln[0] == '+':
            cont.append(ln[3:])
    return cont


def unique_contents(base_manifest_fn, image_manifest_fn):
    """
    Get a list of files unique to the bundle image

    Compare the bundle image manifest to the base image manifest and return
    a list of files unique to the bundle image.

    base_manifest_fn -- the base image manifest
    image_manifest_fn -- the bundle image manifest
    """
    import difflib
    differ = difflib.Differ()

    base_manifest_list = []
    with open(base_manifest_fn) as base:
        base_manifest_list = base.read().splitlines()

    image_manifest_list = []
    with open(image_manifest_fn) as image:
        image_manifest_list = image.read().splitlines()

    delta = list(differ.compare(base_manifest_list, image_manifest_list))

    return delta_contents(delta)


# FIXME: Mariano proposed a similar method to OE-Core for package_manager
def get_package_manager(d, dest):
    """
    Instantiate an instance of the PM object for the image's package manager

    d -- the bitbake datastore
    dest -- the target / of any package manager operations
    """
    from oe.package_manager import RpmPM
    from oe.package_manager import OpkgPM
    from oe.package_manager import DpkgPM

    ptype = d.getVar('IMAGE_PKGTYPE', True)
    pm = None

    if ptype == 'rpm':
        pm = RpmPM(d, dest,
                   d.getVar('TARGET_VENDOR', True))
    elif ptype == 'ipk':
        pm = OpkgPM(d, dest,
                    d.getVar('IPKGCONF_TARGET', True),
                    d.getVar('ALL_MULTILIB_PACKAGE_ARCHS', True))
    elif ptype == 'deb':
        pm = DpkgPM(d, dest,
                    d.getVar('PACKAGE_ARCHS', True),
                    d.getVar('DPKG_ARCH', True))

    pm.write_index()
    pm.update()

    return pm