from django.db import models

# Utils function to truncate my string when it's too long (use in to string method)
def truncate_string(text):
    if len(text) > 15:
        return text[:15] + "..."
    else:
        return text

class Course(models.Model):
    # Defining choices for the course level
    BEGINNER = "B"
    INTERMEDIATE = "I"
    ADVANCED = "A"
    LEVELS_CHOICES = [
        (BEGINNER, "Beginner"),
        (INTERMEDIATE, "Intermediate"),
        (ADVANCED, "Advanced"),
    ]

    # Defining our attributes which equal the Course table's columns
    title = models.CharField(max_length=200)
    summary = models.CharField(max_length=1000)
    level = models.CharField(choices=LEVELS_CHOICES, default=BEGINNER, max_length=12)
    places = models.IntegerField(default=0)
    teacher = models.ForeignKey('Person', on_delete=models.CASCADE, related_name='teacher', limit_choices_to={'role': 'Teacher'})
    students = models.ManyToManyField('Person', blank=True, related_name='students', limit_choices_to={'role': 'Student'})

    # Utils function
    def __str__(self):
        return self.title + " " + truncate_string(self.summary)
    
    def getLevel(self):
        if (self.level == "B"):
            return "Beginner"
        if (self.level == "I"):
            return "Intermediate"
        return "Advanced"

# Student or teacher, what differs? For teachers, courses will be the courses taught, and for students, the courses followed.
# However, this only deferrs into a 'role'. If it's a teacher, then the courses are taught, else they are followed.
# All the logic can be simplified with the role attribute. Later, we'll also be able to check permission with this attribute.
class Person(models.Model):
    # Defining choices for the course level
    STUDENT = "Student"
    TEACHER = "Teacher"
    ROLE_CHOICES = [
        (STUDENT, "Student"),
        (TEACHER, "Teacher"),
    ]

    # Defining our attributes which equal the Course table's columns
    name = models.CharField(max_length=200)
    role = models.CharField(choices=ROLE_CHOICES, default=STUDENT, max_length=7)

    # Return the courses list for the Person 
    # If it's a teacher, returns all courses he teaches
    # If it's a student, returns all courses he follows
    @property
    def courses(self):
        if (self.role == "Student"):
            return [course for course in Course.objects.all() if self in course.students.all()]
        return Course.objects.filter(teacher=self)

    # Utils function
    def __str__(self):
        return self.name + " is a " + self.role