#!/usr/bin/env python
"""
Usage:
Shut down your registry service to avoid race conditions and possible data loss
and then run the command with an image repo like this:
delete_docker_registry_image.py --image awesomeimage --dry-run
"""

import argparse
import json
import logging
import os
import sys
import shutil
import glob

logger = logging.getLogger(__name__)


def del_empty_dirs(s_dir, top_level):
    """recursively delete empty directories"""
    b_empty = True

    for s_target in os.listdir(s_dir):
        s_path = os.path.join(s_dir, s_target)
        if os.path.isdir(s_path):
            if not del_empty_dirs(s_path, False):
                b_empty = False
        else:
            b_empty = False

    if b_empty:
        logger.debug("Deleting empty directory '%s'", s_dir)
        if not top_level:
            os.rmdir(s_dir)

    return b_empty


def get_layers_from_blob(path):
    """parse json blob and get set of layer digests"""
    try:
        with open(path, "r") as blob:
            data_raw = blob.read()
            data = json.loads(data_raw)
            if data["schemaVersion"] == 1:
                result = set([entry["blobSum"].split(":")[1] for entry in data["fsLayers"]])
            else:
                result = set([entry["digest"].split(":")[1] for entry in data["layers"]])
                if "config" in data:
                    result.add(data["config"]["digest"].split(":")[1])
            return result
    except Exception as error:
        logger.critical("Failed to read layers from blob:%s", error)
        return set()


def get_digest_from_blob(path):
    """parse file and get digest"""
    try:
        with open(path, "r") as blob:
            return blob.read().split(":")[1]
    except Exception as error:
        logger.critical("Failed to read digest from blob:%s", error)
        return ""


def get_links(path, _filter=None):
    """recursively walk `path` and parse every link inside"""
    result = []
    for root, _, files in os.walk(path):
        for each in files:
            if each == "link":
                filepath = os.path.join(root, each)
                if not _filter or _filter in filepath:
                    result.append(get_digest_from_blob(filepath))
    return result


class RegistryCleanerError(Exception):
    pass


class RegistryCleaner(object):
    """Clean registry"""

    def __init__(self, registry_data_dir, dry_run=False):
        self.registry_data_dir = registry_data_dir
        if not os.path.isdir(self.registry_data_dir):
            raise RegistryCleanerError("No repositories directory found inside " \
                                       "REGISTRY_DATA_DIR '{0}'.".
                                       format(self.registry_data_dir))
        self.dry_run = dry_run

    def _delete_layer(self, repo, digest):
        """remove blob directory from filesystem"""
        path = os.path.join(self.registry_data_dir, "repositories", repo, "_layers/sha256", digest)
        self._delete_dir(path)

    def _delete_blob(self, digest):
        """remove blob directory from filesystem"""
        path = os.path.join(self.registry_data_dir, "blobs/sha256", digest[0:2], digest)
        self._delete_dir(path)

    def _blob_path_for_revision(self, digest):
        """where we can find the blob that contains the json describing this digest"""
        return os.path.join(self.registry_data_dir, "blobs/sha256",
                            digest[0:2], digest, "data")

    def _blob_path_for_revision_is_missing(self, digest):
        """for each revision, there should be a blob describing it"""
        return not os.path.isfile(self._blob_path_for_revision(digest))

    def _get_layers_from_blob(self, digest):
        """get layers from blob by digest"""
        return get_layers_from_blob(self._blob_path_for_revision(digest))

    def _delete_dir(self, path):
        """remove directory from filesystem"""
        if self.dry_run:
            logger.info("DRY_RUN: would have deleted %s", path)
        else:
            logger.info("Deleting %s", path)
            try:
                shutil.rmtree(path)
            except Exception as error:
                logger.critical("Failed to delete directory:%s", error)

    def _delete_from_tag_index_for_revision(self, repo, digest):
        """delete revision from tag indexes"""
        paths = glob.glob(
            os.path.join(self.registry_data_dir, "repositories", repo,
                         "_manifests/tags/*/index/sha256", digest)
        )
        for path in paths:
            self._delete_dir(path)

    def _delete_revisions(self, repo, revisions, blobs_to_keep=None):
        """delete revisions from list of directories"""
        if blobs_to_keep is None:
            blobs_to_keep = []
        for revision_dir in revisions:
            digests = get_links(revision_dir)
            for digest in digests:
                self._delete_from_tag_index_for_revision(repo, digest)
                if digest not in blobs_to_keep:
                    self._delete_blob(digest)

            self._delete_dir(revision_dir)

    def _get_tags(self, repo):
        """get all tags for given repository"""
        path = os.path.join(self.registry_data_dir, "repositories", repo, "_manifests/tags")
        if not os.path.isdir(path):
            logger.critical("No repository '%s' found in repositories directory %s",
                             repo, self.registry_data_dir)
            return None
        result = []
        for each in os.listdir(path):
            filepath = os.path.join(path, each)
            if os.path.isdir(filepath):
                result.append(each)
        return result

    def _get_repositories(self):
        """get all repository repos"""
        result = []
        root = os.path.join(self.registry_data_dir, "repositories")
        for each in os.listdir(root):
            filepath = os.path.join(root, each)
            if os.path.isdir(filepath):
                inside = os.listdir(filepath)
                if "_layers" in inside:
                    result.append(each)
                else:
                    for inner in inside:
                        result.append(os.path.join(each, inner))
        return result

    def _get_all_links(self, except_repo=""):
        """get links for every repository"""
        result = []
        repositories = self._get_repositories()
        for repo in [r for r in repositories if r != except_repo]:
            path = os.path.join(self.registry_data_dir, "repositories", repo)
            for link in get_links(path):
                result.append(link)
        return result

    def prune(self):
        """delete all empty directories in registry_data_dir"""
        del_empty_dirs(self.registry_data_dir, True)

    def _layer_in_same_repo(self, repo, tag, layer):
        """check if layer is found in other tags of same repository"""
        for other_tag in [t for t in self._get_tags(repo) if t != tag]:
            path = os.path.join(self.registry_data_dir, "repositories", repo,
                                "_manifests/tags", other_tag, "current/link")
            manifest = get_digest_from_blob(path)
            try:
                layers = self._get_layers_from_blob(manifest)
                if layer in layers:
                    return True
            except IOError:
                if self._blob_path_for_revision_is_missing(manifest):
                    logger.warn("Blob for digest %s does not exist. Deleting tag manifest: %s", manifest, other_tag)
                    tag_dir = os.path.join(self.registry_data_dir, "repositories", repo,
                                           "_manifests/tags", other_tag)
                    self._delete_dir(tag_dir)
                else:
                    raise
        return False

    def _manifest_in_same_repo(self, repo, tag, manifest):
        """check if manifest is found in other tags of same repository"""
        for other_tag in [t for t in self._get_tags(repo) if t != tag]:
            path = os.path.join(self.registry_data_dir, "repositories", repo,
                                "_manifests/tags", other_tag, "current/link")
            other_manifest = get_digest_from_blob(path)
            if other_manifest == manifest:
                return True

        return False

    def delete_entire_repository(self, repo):
        """delete all blobs for given repository repo"""
        logger.debug("Deleting entire repository '%s'", repo)
        repo_dir = os.path.join(self.registry_data_dir, "repositories", repo)
        if not os.path.isdir(repo_dir):
            raise RegistryCleanerError("No repository '{0}' found in repositories "
                                       "directory {1}/repositories".
                                       format(repo, self.registry_data_dir))
        links = set(get_links(repo_dir))
        all_links_but_current = set(self._get_all_links(except_repo=repo))
        for layer in links:
            if layer in all_links_but_current:
                logger.debug("Blob found in another repository. Not deleting: %s", layer)
            else:
                self._delete_blob(layer)
        self._delete_dir(repo_dir)

    def delete_repository_tag(self, repo, tag):
        """delete all blobs only for given tag of repository"""
        logger.debug("Deleting repository '%s' with tag '%s'", repo, tag)
        tag_dir = os.path.join(self.registry_data_dir, "repositories", repo, "_manifests/tags", tag)
        if not os.path.isdir(tag_dir):
            raise RegistryCleanerError("No repository '{0}' tag '{1}' found in repositories "
                                       "directory {2}/repositories".
                                       format(repo, tag, self.registry_data_dir))
        manifests_for_tag = set(get_links(tag_dir))
        revisions_to_delete = []
        blobs_to_keep = []
        layers = []
        all_links_not_in_current_repo = set(self._get_all_links(except_repo=repo))
        for manifest in manifests_for_tag:
            logger.debug("Looking up filesystem layers for manifest digest %s", manifest)

            if self._manifest_in_same_repo(repo, tag, manifest):
                logger.debug("Not deleting since we found another tag using manifest: %s", manifest)
                continue
            else:
                revisions_to_delete.append(
                    os.path.join(self.registry_data_dir, "repositories", repo,
                                 "_manifests/revisions/sha256", manifest)
                )
                if manifest in all_links_not_in_current_repo:
                    logger.debug("Not deleting the blob data since we found another repo using manifest: %s", manifest)
                    blobs_to_keep.append(manifest)

                layers.extend(self._get_layers_from_blob(manifest))

        layers_uniq = set(layers)
        for layer in layers_uniq:
            if self._layer_in_same_repo(repo, tag, layer):
                logger.debug("Not deleting since we found another tag using digest: %s", layer)
                continue

            self._delete_layer(repo, layer)
            if layer in all_links_not_in_current_repo:
                logger.debug("Blob found in another repository. Not deleting: %s", layer)
            else:
                self._delete_blob(layer)

        self._delete_revisions(repo, revisions_to_delete, blobs_to_keep)
        self._delete_dir(tag_dir)

    def delete_untagged(self, repo):
        """delete all untagged data from repo"""
        logger.debug("Deleting utagged data from repository '%s'", repo)
        repositories_dir = os.path.join(self.registry_data_dir, "repositories")
        repo_dir = os.path.join(repositories_dir, repo)
        if not os.path.isdir(repo_dir):
            raise RegistryCleanerError("No repository '{0}' found in repositories "
                                       "directory {1}/repositories".
                                       format(repo, self.registry_data_dir))
        tagged_links = set(get_links(repositories_dir, _filter="current"))
        layers_to_protect = []
        for link in tagged_links:
            layers_to_protect.extend(self._get_layers_from_blob(link))

        unique_layers_to_protect = set(layers_to_protect)
        for layer in unique_layers_to_protect:
            logger.debug("layer_to_protect: %s", layer)

        tagged_revisions = set(get_links(repo_dir, _filter="current"))

        revisions_to_delete = []
        layers_to_delete = []

        dir_for_revisions = os.path.join(repo_dir, "_manifests/revisions/sha256")
        for rev in os.listdir(dir_for_revisions):
            if rev not in tagged_revisions:
                revisions_to_delete.append(os.path.join(dir_for_revisions, rev))
                for layer in self._get_layers_from_blob(rev):
                    if layer not in unique_layers_to_protect:
                        layers_to_delete.append(layer)

        unique_layers_to_delete = set(layers_to_delete)

        self._delete_revisions(repo, revisions_to_delete)
        for layer in unique_layers_to_delete:
            self._delete_blob(layer)
            self._delete_layer(repo, layer)


    def get_tag_count(self, repo):
        logger.debug("Get tag count of repository '%s'", repo)
        repo_dir = os.path.join(self.registry_data_dir, "repositories", repo)
        tags_dir = os.path.join(repo_dir, "_manifests/tags")

        if os.path.isdir(tags_dir):
            tags = os.listdir(tags_dir)
            return len(tags)
        else:
            logger.info("Tags directory does not exist: '%s'", tags_dir)
            return -1

def main():
    """cli entrypoint"""
    parser = argparse.ArgumentParser(description="Cleanup docker registry")
    parser.add_argument("-i", "--image",
                        dest="image",
                        required=True,
                        help="Docker image to cleanup")
    parser.add_argument("-v", "--verbose",
                        dest="verbose",
                        action="store_true",
                        help="verbose")
    parser.add_argument("-n", "--dry-run",
                        dest="dry_run",
                        action="store_true",
                        help="Dry run")
    parser.add_argument("-f", "--force",
                        dest="force",
                        action="store_true",
                        help="Force delete (deprecated)")
    parser.add_argument("-p", "--prune",
                        dest="prune",
                        action="store_true",
                        help="Prune")
    parser.add_argument("-u", "--untagged",
                        dest="untagged",
                        action="store_true",
                        help="Delete all untagged blobs for image")
    args = parser.parse_args()


    handler = logging.StreamHandler()
    handler.setFormatter(logging.Formatter(u'%(levelname)-8s [%(asctime)s]  %(message)s'))
    logger.addHandler(handler)

    if args.verbose:
        logger.setLevel(logging.DEBUG)
    else:
        logger.setLevel(logging.INFO)


    # make sure not to log before logging is setup. that'll hose your logging config.
    if args.force:
        logger.info(
            "You supplied the force switch, which is deprecated. It has no effect now, and the script defaults to doing what used to be only happen when force was true")

    splitted = args.image.split(":")
    if len(splitted) == 2:
        image = splitted[0]
        tag = splitted[1]
    else:
        image = args.image
        tag = None

    if 'REGISTRY_DATA_DIR' in os.environ:
        registry_data_dir = os.environ['REGISTRY_DATA_DIR']
    else:
        registry_data_dir = "/opt/registry_data/docker/registry/v2"

    try:
        cleaner = RegistryCleaner(registry_data_dir, dry_run=args.dry_run)
        if args.untagged:
            cleaner.delete_untagged(image)
        else:
            if tag:
                tag_count = cleaner.get_tag_count(image)
                if tag_count == 1:
                    cleaner.delete_entire_repository(image)
                else:
                    cleaner.delete_repository_tag(image, tag)
            else:
                cleaner.delete_entire_repository(image)

        if args.prune:
            cleaner.prune()
    except RegistryCleanerError as error:
        logger.fatal(error)
        sys.exit(1)


if __name__ == "__main__":
    main()