import binascii
import logging

from twisted.internet import defer

log = logging.getLogger(__name__)


class DummyPeerFinder:
    """This class finds peers which have announced to the DHT that they have certain blobs"""

    def find_peers_for_blob(self, blob_hash, timeout=None, filter_self=True):
        return defer.succeed([])


class DHTPeerFinder(DummyPeerFinder):
    """This class finds peers which have announced to the DHT that they have certain blobs"""
    #implements(IPeerFinder)

    def __init__(self, component_manager):
        """
        component_manager - an instance of ComponentManager
        """
        self.component_manager = component_manager
        self.peer_manager = component_manager.peer_manager
        self.peers = {}
        self._ongoing_searchs = {}

    def find_peers_for_blob(self, blob_hash, timeout=None, filter_self=True):
        """
        Find peers for blob in the DHT
        blob_hash (str): blob hash to look for
        timeout (int): seconds to timeout after
        filter_self (bool): if True, and if a peer for a blob is itself, filter it
                from the result

        Returns:
        list of peers for the blob
        """
        if "dht" in self.component_manager.skip_components:
            return defer.succeed([])
        if not self.component_manager.all_components_running("dht"):
            return defer.succeed([])
        dht_node = self.component_manager.get_component("dht")

        self.peers.setdefault(blob_hash, {(dht_node.externalIP, dht_node.peerPort,)})
        if not blob_hash in self._ongoing_searchs or self._ongoing_searchs[blob_hash].called:
            self._ongoing_searchs[blob_hash] = self._execute_peer_search(dht_node, blob_hash, timeout)

        def _filter_self(blob_hash):
            my_host, my_port = dht_node.externalIP, dht_node.peerPort
            return {(host, port) for host, port in self.peers[blob_hash] if (host, port) != (my_host, my_port)}

        peers = set(_filter_self(blob_hash) if filter_self else self.peers[blob_hash])
        return defer.succeed([self.peer_manager.get_peer(*peer) for peer in peers])

    @defer.inlineCallbacks
    def _execute_peer_search(self, dht_node, blob_hash, timeout):
        bin_hash = binascii.unhexlify(blob_hash)
        finished_deferred = dht_node.iterativeFindValue(bin_hash, exclude=self.peers[blob_hash])
        timeout = timeout or self.component_manager.conf.peer_search_timeout
        if timeout:
            finished_deferred.addTimeout(timeout, dht_node.clock)
        try:
            peer_list = yield finished_deferred
            self.peers[blob_hash].update({(host, port) for _, host, port in peer_list})
        except defer.TimeoutError:
            log.debug("DHT timed out while looking peers for blob %s after %s seconds", blob_hash, timeout)
        finally:
            del self._ongoing_searchs[blob_hash]