from decimal import Decimal, getcontext
from urllib.parse import urljoin

getcontext().prec = 2  # use 2 significant figures for decimal calculations

from django.db import models
from django.urls import reverse

import settings

"""This file declares TroggleModel which inherits from django.db.models.Model 
All TroggleModel and models.Model subclasses inherit persistence in the django relational database. This is known as
the django Object Relational Mapping (ORM).
There are more subclasses defined in models/caves.py models/survex.py etc.
"""


class TroggleModel(models.Model):
    """This class is for adding fields and methods which all of our models will have."""

    new_since_parsing = models.BooleanField(default=False, editable=False)
    non_public = models.BooleanField(default=False)

    def object_name(self):
        return self._meta.object_name

    def get_admin_url(self):
        # we do not use URL_ROOT any more.
        return urljoin("/admin/core/" + self.object_name().lower() + "/" + str(self.pk))

    class Meta:
        abstract = True


class DataIssue(TroggleModel):
    """When importing cave data any validation problems produce a message which is
    recorded as a DataIssue. The django admin system automatically produces a page listing
    these at /admin/core/dataissue/
    This is a use of the NOTIFICATION pattern:
    https://martinfowler.com/eaaDev/Notification.html

    We have replaced all assertions in the code with messages and local fix-ups or skips:
    https://martinfowler.com/articles/replaceThrowWithNotification.html

    See also the use of stash_data_issue() & store_data_issues() in parsers/survex.py which defer writing to the database until the end of the import.
    """

    date = models.DateTimeField(auto_now_add=True, blank=True)
    parser = models.CharField(max_length=50, blank=True, null=True)
    # message = models.CharField(max_length=800, blank=True, null=True) # causes extremely obscure error message
    message = models.TextField(blank=True, null=True)
    url = models.CharField(max_length=300, blank=True, null=True)  # link to offending object

    class Meta:
        ordering = ["date"]

    def __str__(self):
        return f"{self.parser} - {self.message}"

#
# single Expedition, usually seen by year
#
class Expedition(TroggleModel):
    year = models.CharField(max_length=20, unique=True)
    name = models.CharField(max_length=100)
    logbookfile = models.CharField(max_length=100, blank=True, null=True)

    def __str__(self):
        return self.year

    class Meta:
        ordering = ("-year",)
        get_latest_by = "year"

    def get_absolute_url(self):
        # we do not use URL_ROOT any more.
        return reverse("expedition", args=[self.year])

class Person(TroggleModel):
    """single Person, can go on many years"""

    first_name = models.CharField(max_length=100)
    last_name = models.CharField(max_length=100)
    fullname = models.CharField(max_length=200) # display name, but should not be used for lookups
    nickname = models.CharField(max_length=200)
    slug = models.SlugField(max_length=50, blank=True, null=True) # unique, enforced in code not in db

    is_vfho = models.BooleanField(
        help_text="VFHO is the Vereines für Höhlenkunde in Obersteier, a nearby Austrian caving club.",
        default=False,
    )
    is_guest = models.BooleanField(default=False) # This is per-Person, not per-PersonExpedition
    mug_shot = models.CharField(max_length=100, blank=True, null=True)
    blurb = models.TextField(blank=True, null=True)
    orderref = models.CharField(max_length=200)  # for alphabetic

    def get_absolute_url(self):
        # we do not use URL_ROOT any more.
        return reverse("person", kwargs={"slug": self.slug})
        return reverse("person", kwargs={"first_name": self.first_name, "last_name": self.last_name})

    class Meta:
        verbose_name_plural = "People"
        ordering = ("orderref",)  # "Wookey" makes too complex for: ('last_name', 'first_name')

    def __str__(self):
        return self.slug
        if self.last_name:
            return f"{self.first_name} {self.last_name}"
        return self.first_name

    def notability(self):
        """This is actually recency: all recent cavers, weighted by number of expos"""
        notability = Decimal(0)
        max_expo_val = 0

        max_expo_year = Expedition.objects.all().aggregate(models.Max("year"))
        max_expo_val = int(max_expo_year["year__max"]) + 1

        for personexpedition in self.personexpedition_set.all():
             notability += Decimal(1) / (max_expo_val - int(personexpedition.expedition.year))
        return notability

    def bisnotable(self):
        """Boolean: is this person notable?"""
        return self.notability() > Decimal(1) / Decimal(3)

    def surveyedleglength(self):
        return sum([personexpedition.surveyedleglength() for personexpedition in self.personexpedition_set.all()])

    def first(self):
        return self.personexpedition_set.order_by("-expedition")[0]

    def last(self):
        return self.personexpedition_set.order_by("expedition")[0]

    # moved from personexpedition
    def name(self):
        if self.nickname:
            return f"{self.first_name} ({self.nickname}) {self.last_name}"
        if self.last_name:
            return f"{self.first_name} {self.last_name}"
        return self.first_name


class PersonExpedition(TroggleModel):
    """Person's attendance to one Expo
    CASCADE means that if an expedition or a person is deleted, the PersonExpedition
    is deleted too
    """

    expedition = models.ForeignKey(Expedition, on_delete=models.CASCADE)
    person = models.ForeignKey(Person, on_delete=models.CASCADE)
    slugfield = models.SlugField(max_length=50, blank=True, null=True)  # 2022 to be used in future

    # is_guest = models.BooleanField(default=False) # This is per-Person, not per-PersonExpedition

    class Meta:
        ordering = ("-expedition",)
        # order_with_respect_to = 'expedition'

    def __str__(self):
        return f"{self.person}: ({self.expedition})"


    def get_absolute_url(self):
        # we do not use URL_ROOT any more.
        return(f"/personexpedition/{self.person.slug}/{self.expedition.year}")
        # why does this hang the system ?
        return reverse(
            "personexpedition",
            kwargs={
                "slug": self.slug,
                "year": self.expedition.year,
            },
        )
        # old style, no longer used
        return reverse(
                "personexpedition",
                kwargs={
                    "first_name": self.person.first_name,
                    "last_name": self.person.last_name,
                    "year": self.expedition.year,
                },
            )

    def surveyedleglength(self):
        """Survey length for this person on all survex trips on this expedition"""
        survexblocks = [personrole.survexblock for personrole in self.survexpersonrole_set.all()]
        return sum([survexblock.legslength for survexblock in set(survexblocks)])