"""
requesting /graph/foo returns an SSE patch stream that's the
result of fetching multiple other SSE patch streams. The result stream
may include new statements injected by this service.

Future:
- filter out unneeded stmts from the sources
- give a time resolution and concatenate any patches that come faster than that res
"""
import logging, collections, json, time
from twisted.internet import reactor, defer
import cyclone.web, cyclone.sse
from rdflib import URIRef, Namespace
from docopt import docopt
from greplin import scales
from greplin.scales.cyclonehandler import StatsHandler
from logsetup import log, enableTwistedLog
from patchablegraph import jsonFromPatch
from rdfdb.patch import Patch
from typing import Callable, Dict, NewType

# workaround for broken import in twisted_sse_demo/eventsourcee.py
import sys; sys.path.append('twisted_sse_demo')
from patchsource import ReconnectingPatchSource

from sse_collector_config import config

SourceUri = NewType('SourceUri', URIRef)


ROOM = Namespace("http://projects.bigasterisk.com/room/")
COLLECTOR = URIRef('http://bigasterisk.com/sse_collector/')

STATS = scales.collection('/root',
                          scales.PmfStat('getState'),
                          scales.PmfStat('localStatementsPatch'),
                          scales.PmfStat('makeSyncPatch'),
                          scales.PmfStat('onPatch'),
                          scales.PmfStat('sendUpdatePatch'),
                          scales.PmfStat('replaceSourceStatements'),
)

class LocalStatements(object):
    """
    functions that make statements originating from sse_collector itself
    """
    def __init__(self, applyPatch: Callable[[Patch], None]):
        self.applyPatch = applyPatch
        self._sourceState: Dict[SourceUri, URIRef] = {} # source: state URIRef

    @STATS.localStatementsPatch.time()
    def setSourceState(self, source, state):
        """
        add a patch to the COLLECTOR graph about the state of this
        source. state=None to remove the source.
        """
        oldState = self._sourceState.get(source, None)
        if state == oldState:
            return
        log.info('source state %s -> %s', source, state)
        if oldState is None:
            self._sourceState[source] = state
            self.applyPatch(COLLECTOR, Patch(addQuads=[
                (COLLECTOR, ROOM['source'], source, COLLECTOR),
                (source, ROOM['state'], state, COLLECTOR),
            ]))
        elif state is None:
            del self._sourceState[source]
            self.applyPatch(COLLECTOR, Patch(delQuads=[
                (COLLECTOR, ROOM['source'], source, COLLECTOR),
                (source, ROOM['state'], oldState, COLLECTOR),
            ]))
        else:
            self._sourceState[source] = state
            self.applyPatch(COLLECTOR, Patch(
                addQuads=[
                (source, ROOM['state'], state, COLLECTOR),
                ],
                delQuads=[
                    (source, ROOM['state'], oldState, COLLECTOR),
                ]))

def abbrevTerm(t):
    if isinstance(t, URIRef):
        return (t.replace('http://projects.bigasterisk.com/room/', 'room:')
                .replace('http://projects.bigasterisk.com/device/', 'dev:')
                .replace('http://bigasterisk.com/sse_collector/', 'sc:'))
    return t

def abbrevStmt(stmt):
    return '(%s %s %s %s)' % tuple(map(abbrevTerm, stmt))
    
class ActiveStatements(object):
    def __init__(self):
        # This table holds statements asserted by any of our sources
        # plus local statements that we introduce (source is
        # http://bigasterisk.com/sse_collector/).
        self.statements = collections.defaultdict(lambda: (set(), set())) # (s,p,o,c): (sourceUrls, handlers)

    def state(self):
        return {
            'len': len(self.statements),
            }
        
    def _postDeleteStatements(self):
        statements = self.statements
        class PostDeleter(object):
            def __enter__(self):
                self._garbage = []
                return self
            def add(self, stmt):
                self._garbage.append(stmt)
            def __exit__(self, type, value, traceback):
                if type is not None:
                    raise
                for stmt in self._garbage:
                    del statements[stmt]
        return PostDeleter()
        
    def pprintTable(self):
        for i, (stmt, (sources, handlers)) in enumerate(sorted(self.statements.items())):
            print("%03d. %-80s from %s to %s" % (
                i,
                abbrevStmt(stmt),
                [abbrevTerm(s) for s in sources],
                handlers))

    @STATS.makeSyncPatch.time()
    def makeSyncPatch(self, handler, sources):
        # todo: this could run all handlers at once, which is how we use it anyway
        adds = []
        dels = []

        sources_set = set(sources)
        with self._postDeleteStatements() as garbage:
            for stmt, (stmtSources, handlers) in self.statements.items():
                belongsInHandler = not sources_set.isdisjoint(stmtSources)
                handlerHasIt = handler in handlers
                log.debug("%s %s %s", abbrevStmt(stmt), belongsInHandler, handlerHasIt)
                if belongsInHandler and not handlerHasIt:
                    adds.append(stmt)
                    handlers.add(handler)
                elif not belongsInHandler and handlerHasIt:
                    dels.append(stmt)
                    handlers.remove(handler)
                    if not handlers and not stmtSources:
                        garbage.add(stmt)

        return Patch(addQuads=adds, delQuads=dels)
        
    def applySourcePatch(self, source, p):
        for stmt in p.addQuads:
            sourceUrls, handlers = self.statements[stmt]
            if source in sourceUrls:
                raise ValueError("%s added stmt that it already had: %s" %
                                 (source, abbrevStmt(stmt)))
            sourceUrls.add(source)
            
        with self._postDeleteStatements() as garbage:
            for stmt in p.delQuads:
                sourceUrls, handlers = self.statements[stmt]
                if source not in sourceUrls:
                    raise ValueError("%s deleting stmt that it didn't have: %s" %
                                     (source, abbrevStmt(stmt)))
                sourceUrls.remove(source)
                # this is rare, since some handler probably still has
                # the stmt we're deleting, but it can happen e.g. when
                # a handler was just deleted
                if not sourceUrls and not handlers:
                    garbage.add(stmt)

    @STATS.replaceSourceStatements.time()
    def replaceSourceStatements(self, source, stmts):
        log.debug('replaceSourceStatements with %s stmts', len(stmts))
        newStmts = set(stmts)

        with self._postDeleteStatements() as garbage:
            for stmt, (sources, handlers) in self.statements.items():
                if source in sources:
                    if stmt not in stmts:
                        sources.remove(source)
                        if not sources and not handlers:
                            garbage.add(stmt)
                else:
                    if stmt in stmts:
                        sources.add(source)
                newStmts.discard(stmt)

        self.applySourcePatch(source, Patch(addQuads=newStmts, delQuads=[]))

    def discardHandler(self, handler):
        with self._postDeleteStatements() as garbage:
            for stmt, (sources, handlers) in self.statements.items():
                handlers.discard(handler)
                if not sources and not handlers:
                    garbage.add(stmt)

    def discardSource(self, source):
        with self._postDeleteStatements() as garbage:
            for stmt, (sources, handlers) in self.statements.items():
                sources.discard(source)
                if not sources and not handlers:
                    garbage.add(stmt)
                    
class GraphClients(object):
    """
    All the active PatchSources and SSEHandlers

    To handle all the overlapping-statement cases, we store a set of
    true statements along with the sources that are currently
    asserting them and the requesters who currently know them. As
    statements come and go, we make patches to send to requesters.
    """
    def __init__(self):
        self.clients = {}  # url: PatchSource (COLLECTOR is not listed)
        self.handlers = set()  # handler
        self.statements = ActiveStatements()
        
        self._localStatements = LocalStatements(self._onPatch)

    def state(self):
        return {
            'clients': [ps.state() for ps in self.clients.values()],
            'sseHandlers': [h.state() for h in self.handlers],
            'statements': self.statements.state(),
        }

    def _sourcesForHandler(self, handler):
        streamId = handler.streamId
        matches = [s for s in config['streams'] if s['id'] == streamId]
        if len(matches) != 1:
            raise ValueError("%s matches for %r" % (len(matches), streamId))
        return list(map(URIRef, matches[0]['sources'])) + [COLLECTOR]

    @STATS.onPatch.time()
    def _onPatch(self, source, p, fullGraph=False):
        if fullGraph:
            # a reconnect may need to resend the full graph even
            # though we've already sent some statements
            self.statements.replaceSourceStatements(source, p.addQuads)
        else:
            self.statements.applySourcePatch(source, p)

        self._sendUpdatePatch()

        if log.isEnabledFor(logging.DEBUG):
            self.statements.pprintTable()

        if source != COLLECTOR:
            self._localStatements.setSourceState(
                source,
                ROOM['fullGraphReceived'] if fullGraph else
                ROOM['patchesReceived'])

    @STATS.sendUpdatePatch.time()
    def _sendUpdatePatch(self, handler=None):
        """
        send a patch event out this handler to bring it up to date with
        self.statements
        """
        now = time.time()
        # reduce loops here- prepare all patches at once
        for h in (self.handlers if handler is None else [handler]):
            period = 1
            if 'Raspbian' in h.request.headers.get('user-agent', ''):
                period = 5
            if h.lastPatchSentTime > now - period:
                continue
            p = self.statements.makeSyncPatch(h, self._sourcesForHandler(h))
            log.debug('makeSyncPatch for %r: %r', h, p.jsonRepr)
            if not p.isNoop():
                log.debug("send patch %s to %s", p.shortSummary(), h)
                # This can be a giant line, which was a problem once. Might be 
                # nice for this service to try to break it up into multiple sends,
                # although there's no guarantee at all since any single stmt 
                # could be any length.
                h.sendEvent(message=jsonFromPatch(p).encode('utf8'), event=b'patch')
                h.lastPatchSentTime = now
            else:
                log.debug('nothing to send to %s', h)
                
    def addSseHandler(self, handler):
        log.info('addSseHandler %r %r', handler, handler.streamId)

        # fail early if id doesn't match
        sources = self._sourcesForHandler(handler)

        self.handlers.add(handler)
        
        for source in sources:
            if source not in self.clients and source != COLLECTOR:
                log.debug('connect to patch source %s', source)
                self._localStatements.setSourceState(source, ROOM['connect'])
                self.clients[source] = ReconnectingPatchSource(
                    source,
                    listener=lambda p, fullGraph, source=source: self._onPatch(
                        source, p, fullGraph),
                    reconnectSecs=10)
        log.debug('bring new client up to date')
        handler.sendEvent(message='hello', event='greets')

        self._sendUpdatePatch(handler)
        
    def removeSseHandler(self, handler):
        log.info('removeSseHandler %r', handler)
        self.statements.discardHandler(handler)
        for source in self._sourcesForHandler(handler):
            for otherHandler in self.handlers:
                if (otherHandler != handler and
                    source in self._sourcesForHandler(otherHandler)):
                    break
            else:
                self._stopClient(source)
            
        self.handlers.remove(handler)

    def _stopClient(self, url):
        if url == COLLECTOR:
            return
            
        self.clients[url].stop()

        self.statements.discardSource(url)
        
        self._localStatements.setSourceState(url, None)
        if url in self.clients:
            del self.clients[url]
        

class SomeGraph(cyclone.sse.SSEHandler):
    _handlerSerial = 0
    def __init__(self, application, request):
        cyclone.sse.SSEHandler.__init__(self, application, request)
        self.bound = False
        self.created = time.time()
        self.graphClients = self.settings.graphClients
        
        self._serial = SomeGraph._handlerSerial
        SomeGraph._handlerSerial += 1
        self.lastPatchSentTime = 0

    def __repr__(self):
        return '<Handler #%s>' % self._serial

    def state(self):
        return {
            'created': round(self.created, 2),
            'ageHours': round((time.time() - self.created) / 3600, 2),
            'streamId': self.streamId,
            'remoteIp': self.request.remote_ip,
            'userAgent': self.request.headers.get('user-agent'),
        }
        
    def bind(self, graphPath):
        self.streamId = graphPath

        self.graphClients.addSseHandler(self)
        # If something goes wrong with addSseHandler, I don't want to
        # try removeSseHandler.
        self.bound = True
        
    def unbind(self):
        if self.bound:
            self.graphClients.removeSseHandler(self)

class State(cyclone.web.RequestHandler):
    @STATS.getState.time()
    def get(self):
        try:
            state = self.settings.graphClients.state()
        except:
            import traceback; traceback.print_exc()
            raise
        
        self.write(json.dumps({'graphClients': state}, indent=2))

class Root(cyclone.web.RequestHandler):
    def get(self):
        self.write('<html><body>sse_collector</body></html>')
        
if __name__ == '__main__':
    arg = docopt("""
    Usage: sse_collector.py [options]

    -v   Verbose
    """)
    
    if arg['-v']:
        enableTwistedLog()
        log.setLevel(logging.DEBUG)
        defer.setDebugging(True)


    graphClients = GraphClients()
    #exporter = InfluxExporter(... to export some stats values
    
    reactor.listenTCP(
        19072,
        cyclone.web.Application(
            handlers=[
                (r'/', Root),
                (r'/state', State),
                (r'/graph/(.*)', SomeGraph),
                (r'/stats/(.*)', StatsHandler, {'serverName': 'collector'}),
            ],
            graphClients=graphClients),
        interface='::')
    reactor.run()