"""
Design:

1. Services each have (named) graphs, which they patch as things
   change. PatchableGraph is an object for holding this graph.
2. You can http GET that graph, or ...
3. You can http GET/SSE that graph and hear about modifications to it
4. The client that got the graph holds and maintains a copy. The
   client may merge together multiple graphs.
5. Client queries its graph with low-level APIs or client-side sparql.
6. When the graph changes, the client knows and can update itself at
   low or high granularity.


See also:
* http://iswc2007.semanticweb.org/papers/533.pdf RDFSync: efficient remote synchronization of RDF
models
* https://www.w3.org/2009/12/rdf-ws/papers/ws07 Supporting Change Propagation in RDF
* https://www.w3.org/DesignIssues/lncs04/Diff.pdf Delta: an ontology for the distribution of
differences between RDF graphs

"""
import html
import itertools
import json
import logging
from typing import Callable, List, Optional, cast

import cyclone.sse
import cyclone.web
from cycloneerr import PrettyErrorHandler
from prometheus_client import Counter, Gauge, Summary
from rdfdb.grapheditapi import GraphEditApi
from rdfdb.patch import Patch
from rdfdb.rdflibpatch import inGraph, patchQuads
from rdflib import ConjunctiveGraph
from rdflib.namespace import NamespaceManager
from rdflib.parser import StringInputSource
from rdflib.plugins.serializers.jsonld import from_rdf

from . import patch_cyclone

patch_cyclone.patch_sse()
log = logging.getLogger('patchablegraph')

SERIALIZE_CALLS = Summary('serialize_calls', 'PatchableGraph.serialize calls', labelnames=['graph'])
PATCH_CALLS = Summary('patch_calls', 'PatchableGraph.patch calls', labelnames=['graph'])
STATEMENT_COUNT = Gauge('statement_count', 'current PatchableGraph graph size', labelnames=['graph'])
OBSERVERS_CURRENT = Gauge('observers_current', 'current observer count', labelnames=['graph'])
OBSERVERS_ADDED = Counter('observers_added', 'observers added', labelnames=['graph'])


# forked from /my/proj/light9/light9/rdfdb/rdflibpatch.py
def _graphFromQuads2(q):
    g = ConjunctiveGraph()
    #g.addN(q) # no effect on nquad output
    for s, p, o, c in q:
        g.get_context(c).add((s, p, o))  # kind of works with broken rdflib nquad serializer code
        #g.store.add((s,p,o), c) # no effect on nquad output
    return g


def jsonFromPatch(p: Patch) -> str:
    return json.dumps(
        {'patch': {
            'adds': from_rdf(_graphFromQuads2(p.addQuads)),
            'deletes': from_rdf(_graphFromQuads2(p.delQuads)),
        }})


patchAsJson = jsonFromPatch  # deprecated name


def patchFromJson(j: str) -> Patch:
    body = json.loads(j)['patch']
    a = ConjunctiveGraph()
    a.parse(StringInputSource(json.dumps(body['adds']).encode('utf8')), format='json-ld')
    d = ConjunctiveGraph()
    d.parse(StringInputSource(json.dumps(body['deletes']).encode('utf8')), format='json-ld')
    return Patch(addGraph=a, delGraph=d)


def graphAsJson(g: ConjunctiveGraph) -> str:
    # This is not the same as g.serialize(format='json-ld')! That
    # version omits literal datatypes.
    return json.dumps(from_rdf(g))


_graphsInProcess = itertools.count()


class PatchableGraph(GraphEditApi):
    """
    Master graph that you modify with self.patch, and we get the
    updates to all current listeners.
    """

    def __init__(self, label: Optional[str] = None):
        self._graph = ConjunctiveGraph()
        self._observers: List[Callable[[str], None]] = []
        if label is None:
            label = f'patchableGraph{next(_graphsInProcess)}'
        self.label = label

    def serialize(self, *arg, **kw) -> bytes:
        with SERIALIZE_CALLS.labels(graph=self.label).time():
            return cast(bytes, self._graph.serialize(*arg, **kw))

    def patch(self, p: Patch):
        with PATCH_CALLS.labels(graph=self.label).time():
            # assuming no stmt is both in p.addQuads and p.delQuads.
            dels = set([q for q in p.delQuads if inGraph(q, self._graph)])
            adds = set([q for q in p.addQuads if not inGraph(q, self._graph)])
            minimizedP = Patch(addQuads=adds, delQuads=dels)
            if minimizedP.isNoop():
                return
            patchQuads(self._graph, deleteQuads=dels, addQuads=adds, perfect=False)  # true?
            for ob in self._observers:
                ob(patchAsJson(p))
            STATEMENT_COUNT.labels(graph=self.label).set(len(self._graph))

    def asJsonLd(self) -> str:
        return graphAsJson(self._graph)

    def addObserver(self, onPatch: Callable[[str], None]):
        self._observers.append(onPatch)
        OBSERVERS_CURRENT.labels(graph=self.label).set(len(self._observers))
        OBSERVERS_ADDED.labels(graph=self.label).inc()

    def removeObserver(self, onPatch: Callable[[str], None]):
        try:
            self._observers.remove(onPatch)
        except ValueError:
            pass
        self._currentObservers = len(self._observers)

    def setToGraph(self, newGraph: ConjunctiveGraph):
        self.patch(Patch.fromDiff(self._graph, newGraph))


SEND_SIMPLE_GRAPH = Summary('send_simple_graph', 'calls to _writeGraphResponse')


class CycloneGraphHandler(PrettyErrorHandler, cyclone.web.RequestHandler):

    def initialize(self, masterGraph: PatchableGraph):
        self.masterGraph = masterGraph

    def get(self):
        with SEND_SIMPLE_GRAPH.time():
            self._writeGraphResponse()

    def _writeGraphResponse(self):
        acceptHeader = self.request.headers.get(
            'Accept',
            # see https://github.com/fiorix/cyclone/issues/20
            self.request.headers.get('accept', ''))

        if acceptHeader == 'application/nquads':
            self.set_header('Content-type', 'application/nquads')
            self.masterGraph.serialize(self, format='nquads')
        elif acceptHeader == 'application/ld+json':
            self.set_header('Content-type', 'application/ld+json')
            self.masterGraph.serialize(self, format='json-ld', indent=2)
        else:
            if acceptHeader.startswith('text/html'):
                self._writeGraphForBrowser()
                return
            self.set_header('Content-type', 'application/x-trig')
            self.masterGraph.serialize(self, format='trig')

    def _writeGraphForBrowser(self):
        # We think this is a browser, so respond with a live graph view
        # (todo)
        self.set_header('Content-type', 'text/html')

        self.write(b'''
        <html><body><pre>''')

        ns = NamespaceManager(self.masterGraph._graph)
        # maybe these could be on the PatchableGraph instance
        ns.bind('ex', 'http://example.com/')
        ns.bind('', 'http://projects.bigasterisk.com/room/')
        ns.bind("rdf", "http://www.w3.org/1999/02/22-rdf-syntax-ns#")
        ns.bind("xsd", "http://www.w3.org/2001/XMLSchema#")

        for s, p, o, g in sorted(self.masterGraph._graph.quads()):
            g = g.identifier
            nquadLine = f'{s.n3(ns)} {p.n3(ns)} {o.n3(ns)} {g.n3(ns)} .\n'
            self.write(html.escape(nquadLine).encode('utf8'))

        self.write(b'''
        </pre>
        <p>
          <a href="#">[refresh]</a>
          <label><input type="checkbox"> Auto-refresh</label>
        </p>
        <script>

        if (new URL(window.location).searchParams.get('autorefresh') == 'on') {
          document.querySelector("input").checked = true;
          setTimeout(() => {
            requestAnimationFrame(() => {
              window.location.replace(window.location.href);
            });
          }, 2000);
        }

        document.querySelector("a").addEventListener("click", (ev) => {
          ev.preventDefault();
          window.location.replace(window.location.href);

        });
        document.querySelector("input").addEventListener("change", (ev) => {
          if (document.querySelector("input").checked) {
             const u = new URL(window.location);
             u.searchParams.set('autorefresh', 'on');
             window.location.replace(u.href);
          } else {
             const u = new URL(window.location);
             u.searchParams.delete('autorefresh');
             window.location.replace(u.href);
          }
        });

        </script>
        </body></html>
        ''')


SEND_FULL_GRAPH = Summary('send_full_graph', 'fullGraph SSE events')
SEND_PATCH = Summary('send_patch', 'patch SSE events')


class CycloneGraphEventsHandler(cyclone.sse.SSEHandler):
    """
    One session with one client.

    returns current graph plus future patches to keep remote version
    in sync with ours.

    intsead of turning off buffering all over, it may work for this
    response to send 'x-accel-buffering: no', per
    http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_buffering
    """

    def __init__(self, application, request, masterGraph):
        cyclone.sse.SSEHandler.__init__(self, application, request)
        self.masterGraph = masterGraph

    def bind(self):
        with SEND_FULL_GRAPH.time():
            graphJson = self.masterGraph.asJsonLd()
            log.debug("send fullGraph event: %s", graphJson)
            self.sendEvent(message=graphJson, event=b'fullGraph')
            self.masterGraph.addObserver(self.onPatch)

    def onPatch(self, patchJson):
        with SEND_PATCH.time():
            # throttle and combine patches here- ideally we could see how
            # long the latency to the client is to make a better rate choice
            self.sendEvent(message=patchJson, event=b'patch')

    def unbind(self):
        self.masterGraph.removeObserver(self.onPatch)

    def flush(self):
        if getattr(self.settings, 'allowOrigin'):
            allow = self.settings.allowOrigin
            if allow != b'*':
                raise NotImplementedError()
            self.set_header(b"Access-Control-Allow-Origin", allow)
        return CycloneGraphEventsHandler.flush(self)