from django.db import models

# Represents an authenticated reviewer or reader of reviews.
class User(models.Model):
	# A non-unique name for the user.
	name = models.CharField(max_length=64)
	# The user's birth date.
	birth_date = models.DateField()

	# Returns the name as the string representation of the user.
	def __str__(self):
		return self.name

# Represents any object for which reviews can be made. (Universities, Professors, etc.)
class RateableEntity(models.Model):
	# Constants defined for types of rateable entities.
	UNIVERSITY = 0
	COURSE = 1
	PROFESSOR = 2
	TYPE_CHOICES = (
		(UNIVERSITY, 'University'),
		(COURSE, 'Course'),
		(PROFESSOR, 'Professor')
	)

	# The human-readable name of this entity.
	name = models.CharField(max_length=256)
	# The date and time at which this entity was created.
	created_date = models.DateTimeField(auto_now_add=True)
	# The type of entity this is.
	entity_type = models.SmallIntegerField(choices=TYPE_CHOICES)

	# Gets the average of all the reviews.
	def getAverageRating(self):
		reviews = self.review_set.select_related()
		rating_sum = 0
		for review in reviews:
			rating_sum += review.rating
		if reviews.count() == 0:
			return None
		return rating_sum / reviews.count()

	# Simply returns the name as the string representation.
	def __str__(self):
		return self.name

# A review represents any single data entry to the database.
class Review(models.Model):
	# An integer rating in the domain [1, 5]
	rating = models.IntegerField(default=1)
	# A title for the review (brief summary of sentiment)
	title = models.CharField(max_length=128)
	# The textual content of the review.
	content = models.TextField()
	# A foreign key referencing the entity for which this review was made.
	rateable_entity = models.ForeignKey('postings.RateableEntity', on_delete=models.CASCADE)
	# The date and time at which this review was published.
	created_date = models.DateTimeField(auto_now_add=True)
	# The date and time at which the last modification to this review was published.
	last_updated_date = models.DateTimeField(auto_now=True)
	# A reference to the person who created this review.
	author = models.ForeignKey('postings.User', on_delete=models.PROTECT, null=True, blank=True)

	# Gets the total number of votes which marked this review as 'helpful'.
	def getHelpfulVoteCount(self):
		return ReviewHelpfulVote.objects.filter(pk=self.pk, helpful=True).count()

	# Gets the total number of votes which marked this review as 'unhelpful'.
	def getUnhelpfulVoteCount(self):
		return ReviewHelpfulVote.objects.filter(pk=self.pk, helpful=False).count()

# A vote for a review as either positive or negative.
class ReviewHelpfulVote(models.Model):
	# A reference to the review that this vote is for.
	review = models.ForeignKey('postings.Review', on_delete=models.CASCADE)
	# Whether or not the referenced review was helpful.
	helpful = models.BooleanField()
	# The user who made this vote.
	user = models.ForeignKey('postings.User', on_delete=models.CASCADE)

# A RateableEntity for universities.
class University(RateableEntity):
	# A string referring to the URL of the university. Every single university should have one.
	website_url = models.URLField()
	# A string referring to the location of the university.
	location = models.CharField(max_length=256)

# A RateableEntity for professors, who belong to one or more university.
class Professor(RateableEntity):
	# The universities that this professor teaches or has taught at.
	universities = models.ManyToManyField('postings.University')

# A RateableEntity for courses, which belong to a university, and have one or more professors.
class Course(RateableEntity):
	# The university that this course belongs to.
	taught_at_university = models.ForeignKey('postings.University', on_delete=models.CASCADE)
	# A list of professors that teach this course.
	professors = models.ManyToManyField('postings.Professor')

# Create your models here.
class UniversityReview(models.Model):
	university_name = models.CharField(max_length=200)
	username = models.CharField(max_length=200)
	rating = models.IntegerField(default=1)
	title = models.CharField(max_length=200)
	date_published = models.DateTimeField(auto_now_add=True)
	content = models.CharField(max_length=200)