from collections import Counter
from datetime import timedelta as td
from itertools import tee

from django.conf import settings
from django.contrib.auth.decorators import login_required
from django.core.urlresolvers import reverse
from django.db.models import Count
from django.http import HttpResponseBadRequest, HttpResponseForbidden
from django.shortcuts import get_object_or_404, redirect, render
from django.utils import timezone
from django.utils.crypto import get_random_string
from django.utils.six.moves.urllib.parse import urlencode
from hc.api.decorators import uuid_or_400
from hc.api.models import Channel, Check, Ping, DEFAULT_TIMEOUT, DEFAULT_GRACE
from hc.front.forms import (AddChannelForm, AddWebhookForm, NameTagsForm,
                            TimeoutForm)


# from itertools recipes:
def pairwise(iterable):
    "s -> (s0,s1), (s1,s2), (s2, s3), ..."
    a, b = tee(iterable)
    next(b, None)
    return zip(a, b)


@login_required
def my_checks(request):
    q = Check.objects.filter(user=request.team.user).order_by("created")
    checks = list(q)

    counter = Counter()
    down_tags, grace_tags = set(), set()
    for check in checks:
        status = check.get_status()
        for tag in check.tags_list():
            if tag == "":
                continue

            counter[tag] += 1

            if status == "down":
                down_tags.add(tag)
            elif status == "grace":
                grace_tags.add(tag)

    ctx = {
        "page": "checks",
        "checks": checks,
        "now": timezone.now(),
        "tags": counter.most_common(),
        "down_tags": down_tags,
        "grace_tags": grace_tags
    }

    return render(request, "front/my_checks.html", ctx)


def _welcome_check(request):
    check = None
    if "welcome_code" in request.session:
        code = request.session["welcome_code"]
        check = Check.objects.filter(code=code).first()

    if check is None:
        check = Check()
        check.save()
        request.session["welcome_code"] = str(check.code)

    return check


def index(request):
    if request.user.is_authenticated():
        return redirect("hc-checks")

    check = _welcome_check(request)

    ctx = {
        "page": "welcome",
        "check": check,
        "ping_url": check.url(),
        "enable_pushover": settings.PUSHOVER_API_TOKEN is not None
    }

    return render(request, "front/welcome.html", ctx)


def docs(request):
    check = _welcome_check(request)

    ctx = {
        "page": "docs",
        "section": "home",
        "ping_endpoint": settings.PING_ENDPOINT,
        "check": check,
        "ping_url": check.url()
    }

    return render(request, "front/docs.html", ctx)


def docs_api(request):
    ctx = {
        "page": "docs",
        "section": "api",
        "SITE_ROOT": settings.SITE_ROOT,
        "PING_ENDPOINT": settings.PING_ENDPOINT,
        "default_timeout": int(DEFAULT_TIMEOUT.total_seconds()),
        "default_grace": int(DEFAULT_GRACE.total_seconds())
    }

    return render(request, "front/docs_api.html", ctx)


def about(request):
    return render(request, "front/about.html", {"page": "about"})


@login_required
def add_check(request):
    assert request.method == "POST"

    check = Check(user=request.team.user)
    check.save()

    check.assign_all_channels()

    return redirect("hc-checks")


@login_required
@uuid_or_400
def update_name(request, code):
    assert request.method == "POST"

    check = get_object_or_404(Check, code=code)
    if check.user_id != request.team.user.id:
        return HttpResponseForbidden()

    form = NameTagsForm(request.POST)
    if form.is_valid():
        check.name = form.cleaned_data["name"]
        check.tags = form.cleaned_data["tags"]
        check.save()

    return redirect("hc-checks")


@login_required
@uuid_or_400
def update_timeout(request, code):
    assert request.method == "POST"

    check = get_object_or_404(Check, code=code)
    if check.user != request.team.user:
        return HttpResponseForbidden()

    form = TimeoutForm(request.POST)
    if form.is_valid():
        check.timeout = td(seconds=form.cleaned_data["timeout"])
        check.grace = td(seconds=form.cleaned_data["grace"])
        check.save()

    return redirect("hc-checks")


@login_required
@uuid_or_400
def remove_check(request, code):
    assert request.method == "POST"

    check = get_object_or_404(Check, code=code)
    if check.user != request.team.user:
        return HttpResponseForbidden()

    check.delete()

    return redirect("hc-checks")


@login_required
@uuid_or_400
def log(request, code):
    check = get_object_or_404(Check, code=code)
    if check.user != request.team.user:
        return HttpResponseForbidden()

    limit = request.team.ping_log_limit
    pings = Ping.objects.filter(owner=check).order_by("-id")[:limit]

    pings = list(pings.iterator())
    # oldest-to-newest order will be more convenient for adding
    # "not received" placeholders:
    pings.reverse()

    # Add a dummy ping object at the end. We iterate over *pairs* of pings
    # and don't want to handle a special case of a check with a single ping.
    pings.append(Ping(created=timezone.now()))

    # Now go through pings, calculate time gaps, and decorate
    # the pings list for convenient use in template
    wrapped = []

    early = False
    for older, newer in pairwise(pings):
        wrapped.append({"ping": older, "early": early})

        # Fill in "missed ping" placeholders:
        expected_date = older.created + check.timeout
        n_blanks = 0
        while expected_date + check.grace < newer.created and n_blanks < 10:
            wrapped.append({"placeholder_date": expected_date})
            expected_date = expected_date + check.timeout
            n_blanks += 1

        # Prepare early flag for next ping to come
        early = older.created + check.timeout > newer.created + check.grace

    reached_limit = len(pings) > limit

    wrapped.reverse()
    ctx = {
        "check": check,
        "pings": wrapped,
        "num_pings": len(pings),
        "limit": limit,
        "show_limit_notice": reached_limit and settings.USE_PAYMENTS
    }

    return render(request, "front/log.html", ctx)


@login_required
def channels(request):
    if request.method == "POST":
        code = request.POST["channel"]
        try:
            channel = Channel.objects.get(code=code)
        except Channel.DoesNotExist:
            return HttpResponseBadRequest()
        if channel.user_id != request.team.user.id:
            return HttpResponseForbidden()

        new_checks = []
        for key in request.POST:
            if key.startswith("check-"):
                code = key[6:]
                try:
                    check = Check.objects.get(code=code)
                except Check.DoesNotExist:
                    return HttpResponseBadRequest()
                if check.user_id != request.team.user.id:
                    return HttpResponseForbidden()
                new_checks.append(check)

        channel.checks = new_checks
        return redirect("hc-channels")

    channels = Channel.objects.filter(user=request.team.user).order_by("created")
    channels = channels.annotate(n_checks=Count("checks"))

    num_checks = Check.objects.filter(user=request.team.user).count()

    ctx = {
        "page": "channels",
        "channels": channels,
        "num_checks": num_checks,
        "enable_pushover": settings.PUSHOVER_API_TOKEN is not None,
    }
    return render(request, "front/channels.html", ctx)


def do_add_channel(request, data):
    form = AddChannelForm(data)
    if form.is_valid():
        channel = form.save(commit=False)
        channel.user = request.team.user
        channel.save()

        channel.assign_all_checks()

        if channel.kind == "email":
            channel.send_verify_link()

        return redirect("hc-channels")
    else:
        return HttpResponseBadRequest()


@login_required
def add_channel(request):
    assert request.method == "POST"
    return do_add_channel(request, request.POST)


@login_required
@uuid_or_400
def channel_checks(request, code):
    channel = get_object_or_404(Channel, code=code)
    if channel.user_id != request.team.user.id:
        return HttpResponseForbidden()

    assigned = set(channel.checks.values_list('code', flat=True).distinct())
    checks = Check.objects.filter(user=request.team.user).order_by("created")

    ctx = {
        "checks": checks,
        "assigned": assigned,
        "channel": channel
    }

    return render(request, "front/channel_checks.html", ctx)


@uuid_or_400
def verify_email(request, code, token):
    channel = get_object_or_404(Channel, code=code)
    if channel.make_token() == token:
        channel.email_verified = True
        channel.save()
        return render(request, "front/verify_email_success.html")

    return render(request, "bad_link.html")


@login_required
@uuid_or_400
def remove_channel(request, code):
    assert request.method == "POST"

    # user may refresh the page during POST and cause two deletion attempts
    channel = Channel.objects.filter(code=code).first()
    if channel:
        if channel.user != request.team.user:
            return HttpResponseForbidden()
        channel.delete()

    return redirect("hc-channels")


@login_required
def add_email(request):
    ctx = {"page": "channels"}
    return render(request, "integrations/add_email.html", ctx)


@login_required
def add_webhook(request):
    if request.method == "POST":
        form = AddWebhookForm(request.POST)
        if form.is_valid():
            channel = Channel(user=request.team.user, kind="webhook")
            channel.value = form.get_value()
            channel.save()

            channel.assign_all_checks()
            return redirect("hc-channels")
    else:
        form = AddWebhookForm()

    ctx = {"page": "channels", "form": form}
    return render(request, "integrations/add_webhook.html", ctx)


@login_required
def add_pd(request):
    ctx = {"page": "channels"}
    return render(request, "integrations/add_pd.html", ctx)


@login_required
def add_slack(request):
    ctx = {"page": "channels"}
    return render(request, "integrations/add_slack.html", ctx)


@login_required
def add_hipchat(request):
    ctx = {"page": "channels"}
    return render(request, "integrations/add_hipchat.html", ctx)


@login_required
def add_pushover(request):
    if settings.PUSHOVER_API_TOKEN is None or settings.PUSHOVER_SUBSCRIPTION_URL is None:
        return HttpResponseForbidden()

    if request.method == "POST":
        # Initiate the subscription
        nonce = get_random_string()
        request.session["po_nonce"] = nonce

        failure_url = settings.SITE_ROOT + reverse("hc-channels")
        success_url = settings.SITE_ROOT + reverse("hc-add-pushover") + "?" + urlencode({
            "nonce": nonce,
            "prio": request.POST.get("po_priority", "0"),
        })
        subscription_url = settings.PUSHOVER_SUBSCRIPTION_URL + "?" + urlencode({
            "success": success_url,
            "failure": failure_url,
        })

        return redirect(subscription_url)

    # Handle successful subscriptions
    if "pushover_user_key" in request.GET:
        if "nonce" not in request.GET or "prio" not in request.GET:
            return HttpResponseBadRequest()

        # Validate nonce
        if request.GET["nonce"] != request.session.get("po_nonce"):
            return HttpResponseForbidden()

        # Validate priority
        if request.GET["prio"] not in ("-2", "-1", "0", "1", "2"):
            return HttpResponseBadRequest()

        # All looks well--
        del request.session["po_nonce"]

        if request.GET.get("pushover_unsubscribed") == "1":
            # Unsubscription: delete all Pushover channels for this user
            Channel.objects.filter(user=request.user, kind="po").delete()
            return redirect("hc-channels")
        else:
            # Subscription
            user_key = request.GET["pushover_user_key"]
            priority = int(request.GET["prio"])

            return do_add_channel(request, {
                "kind": "po",
                "value": "%s|%d" % (user_key, priority),
            })

    # Show Integration Settings form
    ctx = {
        "page": "channels",
        "po_retry_delay": td(seconds=settings.PUSHOVER_EMERGENCY_RETRY_DELAY),
        "po_expiration": td(seconds=settings.PUSHOVER_EMERGENCY_EXPIRATION),
    }
    return render(request, "integrations/add_pushover.html", ctx)


@login_required
def add_victorops(request):
    ctx = {"page": "channels"}
    return render(request, "integrations/add_victorops.html", ctx)


def privacy(request):
    return render(request, "front/privacy.html", {})