from django.contrib.gis.db import models
from django.contrib.gis import geos
from django.db import transaction

# Create your models here.
from django.contrib.auth.models import User


class TrackManager(models.Manager):
    def get_or_create_from_gpx(cls, obj, user):
        # Get some Meta data from the gpx file.
        metadata = obj['metadata']
        start_time = metadata['time']
        # Get the the track and segments from the gpx file.
        tracks = obj['trk']
        name = tracks['name']
        segments = tracks['trkseg']

        track, created = cls.model.objects.get_or_create(
            user=user,
            start=start_time,
            name=name)
        if created:
            with transaction.atomic():
                points = segments['trkpt']
                segment = Segment(
                    track=track,
                    time=points[0]['time'])
                segment.save()
                for pt in points:
                    lon = float(pt['@lon'])
                    lat = float(pt['@lat'])

                    Point.objects.create(
                        segment=segment,
                        time=pt['time'],
                        elevation=pt['ele'],
                        point=geos.Point(lon, lat))
        return created, track


class Track(models.Model):
    user = models.ForeignKey(User, blank=False)
    start = models.DateTimeField()
    name = models.CharField(max_length=1024, blank=False)
    description = models.TextField(blank=True)
    objects = TrackManager()

    @property
    def finish(self):
        return self.segment_set.order_by("-time")[0].finish

    def __str__(self):
        return "[{user}] '{name}' from {start} to {finish}".format(
            user=self.user.username,
            name=self.name,
            start=self.start,
            finish=self.finish)


class Segment(models.Model):
    track = models.ForeignKey(Track)
    time = models.DateTimeField()
    number = models.IntegerField(default=1)

    @property
    def finish(self):
        return self.point_set.order_by("-time")[0].time

    def __str__(self):
        return "'{name}' Segment #{number} at {tme}".format(
            name=self.track.name,
            number=self.number,
            tme=self.time)


class Point(models.Model):
    time = models.DateTimeField()
    elevation = models.DecimalField(max_digits=20, decimal_places=2)
    segment = models.ForeignKey(Segment)

    # GeoDjango-specific: a geometry field (MultiPolygonField), and
    # overriding the default manager with a GeoManager instance.
    point = models.PointField()
    objects = models.GeoManager()

    def __str__(self):
        return "'{name}' ({lat},{lon}) -> {alt} on {time}".format(
            lat=self.point.x,
            lon=self.point.y,
            alt=self.elevation,
            time=self.time,
            name=self.segment.track.name)