"""
This module provides the functionality to download the latest primary.xml
database from koji on the rawhide repo.
Decompress that xml file (which are downloaded compressed).
Read its content and build a dictionary with the package names as keys
and their summaries as values.

This code can then be used to create an in-memory cache of this information
which can then later be re-used in other places.
This prevents relying on remote services such as mdapi (of which a lot of
code here is coming from) when needing to access the summary of a lot of
packages.
"""
import contextlib
import hashlib
import logging
import os
import time
from xml.etree.ElementTree import ParseError

from defusedxml import cElementTree as etree
import requests


KOJI_REPO = "https://kojipkgs.fedoraproject.org/repos/"

repomd_xml_namespace = {
    "repo": "http://linux.duke.edu/metadata/repo",
    "rpm": "http://linux.duke.edu/metadata/rpm",
}

log = logging.getLogger(__name__)


def download_db(name, repomd_url, archive):
    log.info("%-12s Downloading file: %s to %s", name, repomd_url, archive)
    response = requests.get(repomd_url, verify=True)
    with open(archive, "wb") as stream:
        stream.write(response.content)


def decompress_db(name, archive, location):
    """ Decompress the given archive at the specified location. """
    log.info("%-12s Extracting %s to %s", name, archive, location)
    if archive.endswith(".xz"):
        import lzma

        with contextlib.closing(lzma.LZMAFile(archive)) as stream_xz:
            data = stream_xz.read()
        with open(location, "wb") as stream:
            stream.write(data)
    elif archive.endswith(".tar.gz"):
        import tarfile

        with tarfile.open(archive) as tar:
            tar.extractall(path=location)
    elif archive.endswith(".gz"):
        import gzip

        with open(location, "wb") as out:
            with gzip.open(archive, "rb") as inp:
                out.write(inp.read())
    elif archive.endswith(".bz2"):
        import bz2

        with open(location, "wb") as out:
            bzar = bz2.BZ2File(archive)
            out.write(bzar.read())
            bzar.close()
    else:
        raise NotImplementedError(archive)


def needs_update(local_file, remote_sha, sha_type):
    """ Compare hash of a local and remote file.
    Return True if our local file needs to be updated.
    """

    if not os.path.isfile(local_file):
        # If we have never downloaded this before, then obviously it has
        # "changed"
        return True

    # Old epel5 doesn't even know which sha it is using...
    if sha_type == "sha":
        sha_type = "sha1"

    hashobj = getattr(hashlib, sha_type)()
    with open(local_file, "rb") as f:
        hashobj.update(f.read())

    local_sha = hashobj.hexdigest()
    if local_sha != remote_sha:
        return True

    return False


def get_primary_xml(destfolder, url, name):
    """ Retrieve the repo metadata at the given url and store them using
    the provided name.
    """
    repomd_url = url + "/repomd.xml"
    response = requests.get(repomd_url, verify=True)
    if not bool(response):
        log.warning("%-12s !! Failed to get %s %s", name, repomd_url, response)
        return

    try:
        root = etree.fromstring(response.text)
    except ParseError:
        log.warning("%-12s !! Failed to parse %s %s", name, repomd_url, response)
        return

    data_nodes = list(root.findall('repo:data[@type="primary"]', repomd_xml_namespace))
    if not data_nodes:
        log.debug("No primary.xml could be found in %s", url)
        return
    elif len(data_nodes) > 1:
        log.debug("More than one primary.xml could be found in %s", url)
        return

    primary_node = data_nodes[0]

    location_node = primary_node.find("repo:location", repomd_xml_namespace)
    if location_node is None or "href" not in location_node.attrib:
        log.debug("No valid location found for primary.xml in %s", url)
        return

    cksuminfo_node = primary_node.find("repo:open-checksum", repomd_xml_namespace)
    if cksuminfo_node is None or "type" not in cksuminfo_node.attrib:
        log.debug("No valid checksum information found for primary.xml in %s", url)
        return

    filename = location_node.attrib["href"].replace("repodata/", "")
    hash_digest = cksuminfo_node.text
    hash_type = cksuminfo_node.attrib["type"]

    repomd_url = url + "/" + filename

    # First, determine if the file has changed by comparing hash
    db = "distgit-bugzilla-sync-primary.xml"

    # Have we downloaded this before?  Did it change?
    destfile = os.path.join(destfolder, db)
    if not needs_update(destfile, hash_digest, hash_type):
        log.debug("%s No change of %s", name.ljust(12), repomd_url)
    else:
        # If it has changed, then download it and move it into place.
        archive = os.path.join(destfolder, filename)

        download_db(name, repomd_url, archive)
        decompress_db(name, archive, destfile)

    return destfile


def get_package_summaries():
    summaries = {}

    start = time.time()

    primary_xml = get_primary_xml(
        "/var/tmp", KOJI_REPO + "rawhide/latest/x86_64/repodata", "koji",
    )

    context = etree.iterparse(primary_xml, events=("start", "end"))

    root = None

    # iterate over the rest of the primary.xml tree
    for event, elem in context:
        if not root:
            root = elem
            continue

        if (
            event == "end"
            and elem.tag == "package"
            and elem.get("type", "rpm") == "rpm"
        ):
            name = elem.findtext("name")
            summary = elem.findtext("summary")
            if name is not None and summary is not None:
                summaries[name] = summary
            # remove package child from root element to keep memory consumption low
            root.clear()

    delta = time.time() - start
    log.info(f"Parsed in {delta} seconds -- ie: {delta/60} minutes")

    return summaries


if __name__ == "__main__":
    logging.basicConfig(level=logging.DEBUG)
    db = get_package_summaries()
    print(f"guake: {db.get('guake')}")
    print(f"geany: {db.get('geany')}")
    print(f"kernel: {db.get('kernel')}")