from datetime import datetime

from django.conf import settings
from django.contrib import admin
from django.contrib.auth.models import User, Group
try:
    from django.core.urlresolvers import reverse
except ImportError:
    from django.urls import reverse
from django.templatetags.static import static
from django.utils.safestring import mark_safe
from django.utils.html import format_html, format_html_join

from .models import Correspondent, Tag, Document, Log


class MonthListFilter(admin.SimpleListFilter):

    title = "Month"

    # Parameter for the filter that will be used in the URL query.
    parameter_name = "month"

    def lookups(self, request, model_admin):
        r = []
        for document in Document.objects.all():
            r.append((
                document.created.strftime("%Y-%m"),
                document.created.strftime("%B %Y")
            ))
        return sorted(set(r), key=lambda x: x[0], reverse=True)

    def queryset(self, request, queryset):

        if not self.value():
            return None

        year, month = self.value().split("-")
        return queryset.filter(created__year=year, created__month=month)


class FinancialYearFilter(admin.SimpleListFilter):

    title = "Financial Year"
    parameter_name = "fy"
    _fy_wraps = None

    def _fy_start(self, year):
        """Return date of the start of financial year for the given year."""
        fy_start = "{}-{}".format(str(year), settings.FY_START)
        return datetime.strptime(fy_start, "%Y-%m-%d").date()

    def _fy_end(self, year):
        """Return date of the end of financial year for the given year."""
        fy_end = "{}-{}".format(str(year), settings.FY_END)
        return datetime.strptime(fy_end, "%Y-%m-%d").date()

    def _fy_does_wrap(self):
        """Return whether the financial year spans across two years."""
        if self._fy_wraps is None:
            start = "{}".format(settings.FY_START)
            start = datetime.strptime(start, "%m-%d").date()
            end = "{}".format(settings.FY_END)
            end = datetime.strptime(end, "%m-%d").date()
            self._fy_wraps = end < start

        return self._fy_wraps

    def _determine_fy(self, date):
        """Return a (query, display) financial year tuple of the given date."""
        if self._fy_does_wrap():
            fy_start = self._fy_start(date.year)

            if date.date() >= fy_start:
                query = "{}-{}".format(date.year, date.year + 1)
            else:
                query = "{}-{}".format(date.year - 1, date.year)

            # To keep it simple we use the same string for both
            # query parameter and the display.
            return (query, query)

        else:
            query = "{0}-{0}".format(date.year)
            display = "{}".format(date.year)
            return (query, display)

    def lookups(self, request, model_admin):
        if not settings.FY_START or not settings.FY_END:
            return None

        r = []
        for document in Document.objects.all():
            r.append(self._determine_fy(document.created))

        return sorted(set(r), key=lambda x: x[0], reverse=True)

    def queryset(self, request, queryset):
        if not self.value() or not settings.FY_START or not settings.FY_END:
            return None

        start, end = self.value().split("-")
        return queryset.filter(created__gte=self._fy_start(start),
                               created__lte=self._fy_end(end))


class CommonAdmin(admin.ModelAdmin):
    list_per_page = settings.PAPERLESS_LIST_PER_PAGE


class CorrespondentAdmin(CommonAdmin):

    list_display = ("name", "match", "matching_algorithm", "document_count")
    list_filter = ("matching_algorithm",)
    list_editable = ("match", "matching_algorithm")

    def document_count(self, obj):
        return obj.documents.count()


class TagAdmin(CommonAdmin):

    list_display = ("name", "colour", "match", "matching_algorithm",
                    "document_count")
    list_filter = ("colour", "matching_algorithm")
    list_editable = ("colour", "match", "matching_algorithm")

    def document_count(self, obj):
        return obj.documents.count()


class DocumentAdmin(CommonAdmin):

    class Media:
        css = {
            "all": ("paperless.css",)
        }

    search_fields = ("correspondent__name", "title", "content", "tags__name")
    readonly_fields = ("added",)
    list_display = ("title", "created", "added", "thumbnail", "correspondent",
                    "tags_")
    list_filter = ("tags", "correspondent", FinancialYearFilter,
                   MonthListFilter)

    ordering = ["-created", "correspondent"]

    def has_add_permission(self, request):
        return False

    def created_(self, obj):
        return obj.created.date().strftime("%Y-%m-%d")
    created_.short_description = "Created"

    def thumbnail(self, obj):
        return self._html_tag(
            "a",
            self._html_tag(
                "img",
                src=reverse("fetch", kwargs={"kind": "thumb", "pk": obj.pk}),
                width=180,
                alt="Thumbnail of {}".format(obj.file_name),
                title=obj.file_name
            ),
            href=obj.download_url
        )
    thumbnail.allow_tags = True

    def tags_(self, obj):
        r = ""
        for tag in obj.tags.all():
            colour = tag.get_colour_display()
            r += self._html_tag(
                "a",
                tag.slug,
                **{
                    "class": "tag",
                    "style": "background-color: {};".format(colour),
                    "href": "{}?tags__id__exact={}".format(
                        reverse("admin:documents_document_changelist"),
                        tag.pk
                    )
                }
            )
        return mark_safe(r)
    tags_.allow_tags = True

    def document(self, obj):
        return self._html_tag(
            "a",
            self._html_tag(
                "img",
                src=static("documents/img/{}.png".format(obj.file_type)),
                width=22,
                height=22,
                alt=obj.file_type,
                title=obj.file_name
            ),
            href=obj.download_url
        )
    document.allow_tags = True

    @staticmethod
    def _html_tag(kind, inside=None, **kwargs):
        attributes = format_html_join(' ', '{}="{}"', kwargs.items())

        if inside is not None:
            return format_html("<{kind} {attributes}>{inside}</{kind}>",
                               kind=kind, attributes=attributes, inside=inside)

        return format_html("<{} {}/>", kind, attributes)


class LogAdmin(CommonAdmin):

    list_display = ("created", "message", "level",)
    list_filter = ("level", "created",)


admin.site.register(Correspondent, CorrespondentAdmin)
admin.site.register(Tag, TagAdmin)
admin.site.register(Document, DocumentAdmin)
admin.site.register(Log, LogAdmin)


# Unless we implement multi-user, these default registrations don't make sense.
admin.site.unregister(Group)
admin.site.unregister(User)