import uuid
from django.db import models
from django.conf import settings
from django.utils import timezone
from cryptography.fernet import Fernet
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
import base64
import os

class EncryptionManager:
    def __init__(self):
        self.fernet = self._get_fernet()
    
    def _get_fernet_key(self):
        key = getattr(settings, 'ENCRYPTION_KEY', None) or os.environ.get('ENCRYPTION_KEY')
        if not key:
            key = Fernet.generate_key().decode()
        key = key.encode()
        return key
    
    def _get_fernet(self):
        key = self._get_fernet_key()
        return Fernet(key)
    
    def encrypt_value(self, value):
        if value is None or value == "":
            return value
        encrypted_value = self.fernet.encrypt(value.encode())
        return base64.urlsafe_b64encode(encrypted_value).decode()
    
    def decrypt_value(self, encrypted_value):
        if encrypted_value is None or encrypted_value == "":
            return encrypted_value
        try:
            encrypted_bytes = base64.urlsafe_b64decode(encrypted_value.encode())
            decrypted_value = self.fernet.decrypt(encrypted_bytes)
            return decrypted_value.decode()
        except Exception as e:
            print(f"Decryption error: {e}")
            return encrypted_value

encryption_manager = EncryptionManager()

class EncryptedCharField(models.CharField):
    def from_db_value(self, value, expression, connection):
        if value is None:
            return value
        return encryption_manager.decrypt_value(value)
    
    def get_prep_value(self, value):
        if value is None:
            return value
        return encryption_manager.encrypt_value(value)

class EncryptedEmailField(EncryptedCharField):
    def __init__(self, *args, **kwargs):
        kwargs['max_length'] = 254
        super().__init__(*args, **kwargs)
        
    def from_db_value(self, value, expression, connection):
        if value is None:
            return value
        return encryption_manager.decrypt_value(value)
    
    def get_prep_value(self, value):
        if value is None:
            return value
        return encryption_manager.encrypt_value(value)

class EncryptedTextField(models.TextField):
    def from_db_value(self, value, expression, connection):
        if value is None:
            return value
        return encryption_manager.decrypt_value(value)
    
    def get_prep_value(self, value):
        if value is None:
            return value
        return encryption_manager.encrypt_value(value)

class AdminWeeklyAvailability(models.Model):
    DAYS_OF_WEEK = [
        (0, 'Monday'),
        (1, 'Tuesday'),
        (2, 'Wednesday'),
        (3, 'Thursday'),
        (4, 'Friday'),
        (5, 'Saturday'),
        (6, 'Sunday'),
    ]
    
    available_days = models.JSONField(
        default=list,
        help_text="List of weekdays (0-6) when appointments are accepted"
    )
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    
    class Meta:
        verbose_name = 'Admin Weekly Availability'
        verbose_name_plural = 'Admin Weekly Availability'
    
    def __str__(self):
        days = [self.DAYS_OF_WEEK[day][1] for day in self.available_days]
        return f"Available: {', '.join(days)}"

class AppointmentRequest(models.Model):
    STATUS_CHOICES = [
        ('pending_review', 'Pending Review'),
        ('scheduled', 'Scheduled'),
        ('rejected', 'Rejected'),
        ('completed', 'Completed'),
        ('cancelled', 'Cancelled'),
    ]
    
    TIME_SLOT_CHOICES = [
        ('morning', 'Morning (9AM - 12PM)'),
        ('afternoon', 'Afternoon (1PM - 5PM)'),
        ('evening', 'Evening (6PM - 9PM)'),
    ]

    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    first_name = EncryptedCharField(max_length=100)
    last_name = EncryptedCharField(max_length=100)
    email = EncryptedEmailField()
    phone = EncryptedCharField(max_length=20, blank=True)
    reason = EncryptedTextField(blank=True)
    
    preferred_dates = models.JSONField(
        help_text="List of preferred dates (YYYY-MM-DD format)"
    )
    preferred_time_slots = models.JSONField(
        help_text="List of preferred time slots (morning/afternoon/evening)"
    )
    
    status = models.CharField(
        max_length=20, 
        choices=STATUS_CHOICES, 
        default='pending_review'
    )
    
    scheduled_datetime = models.DateTimeField(null=True, blank=True)
    scheduled_duration = models.PositiveIntegerField(
        default=60,
        help_text="Duration in minutes"
    )
    rejection_reason = EncryptedTextField(blank=True)
    
    jitsi_meet_url = models.URLField(blank=True, help_text="Jitsi Meet URL for the video session")
    jitsi_room_id = models.CharField(max_length=100, unique=True, blank=True, help_text="Jitsi room ID")
    
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    
    class Meta:
        ordering = ['-created_at']
        verbose_name = 'Appointment Request'
        verbose_name_plural = 'Appointment Requests'
        indexes = [
            models.Index(fields=['status', 'scheduled_datetime']),
            models.Index(fields=['email', 'created_at']),
        ]

    @property
    def full_name(self):
        return f"{self.first_name} {self.last_name}"

    @property
    def formatted_created_at(self):
        return self.created_at.strftime("%B %d, %Y at %I:%M %p")

    @property
    def formatted_scheduled_datetime(self):
        if self.scheduled_datetime:
            return self.scheduled_datetime.strftime("%B %d, %Y at %I:%M %p")
        return None

    @property
    def has_jitsi_meeting(self):
        return bool(self.jitsi_meet_url and self.jitsi_room_id)

    @property
    def meeting_in_future(self):
        if not self.scheduled_datetime:
            return False
        return self.scheduled_datetime > timezone.now()

    @property
    def meeting_duration_display(self):
        hours = self.scheduled_duration // 60
        minutes = self.scheduled_duration % 60
        if hours > 0:
            return f"{hours}h {minutes}m"
        return f"{minutes}m"

    def get_preferred_dates_display(self):
        try:
            dates = [timezone.datetime.strptime(date, '%Y-%m-%d').strftime('%b %d, %Y') 
                    for date in self.preferred_dates]
            return ', '.join(dates)
        except:
            return ', '.join(self.preferred_dates)

    def get_preferred_time_slots_display(self):
        slot_display = {
            'morning': 'Morning',
            'afternoon': 'Afternoon', 
            'evening': 'Evening'
        }
        return ', '.join([slot_display.get(slot, slot) for slot in self.preferred_time_slots])

    def generate_jitsi_room_id(self):
        if not self.jitsi_room_id:
            self.jitsi_room_id = f"therapy_session_{self.id.hex[:16]}"
        return self.jitsi_room_id

    def create_jitsi_meeting(self):
        if not self.jitsi_room_id:
            self.generate_jitsi_room_id()
        
        jitsi_base_url = getattr(settings, 'JITSI_BASE_URL', 'https://meet.jit.si')
        self.jitsi_meet_url = f"{jitsi_base_url}/{self.jitsi_room_id}"
        return self.jitsi_meet_url

    def get_jitsi_join_info(self):
        if not self.has_jitsi_meeting:
            return None
        
        return {
            'meeting_url': self.jitsi_meet_url,
            'room_id': self.jitsi_room_id,
            'scheduled_time': self.formatted_scheduled_datetime,
            'duration': self.meeting_duration_display,
            'join_instructions': 'Click the meeting URL to join the video session. No password required.'
        }

    def schedule_appointment(self, datetime_obj, duration=60, commit=True):
        self.status = 'scheduled'
        self.scheduled_datetime = datetime_obj
        self.scheduled_duration = duration
        self.rejection_reason = ''
        
        self.create_jitsi_meeting()
        
        if commit:
            self.save()

    def reject_appointment(self, reason='', commit=True):
        self.status = 'rejected'
        self.rejection_reason = reason
        self.scheduled_datetime = None
        self.jitsi_meet_url = ''
        self.jitsi_room_id = ''
        if commit:
            self.save()

    def cancel_appointment(self, reason='', commit=True):
        self.status = 'cancelled'
        self.rejection_reason = reason
        if commit:
            self.save()

    def complete_appointment(self, commit=True):
        self.status = 'completed'
        if commit:
            self.save()

    def can_join_meeting(self):
        if not self.scheduled_datetime or not self.has_jitsi_meeting:
            return False
        
        if self.status != 'scheduled':
            return False
        
        now = timezone.now()
        meeting_start = self.scheduled_datetime
        meeting_end = meeting_start + timezone.timedelta(minutes=self.scheduled_duration + 15)  # 15 min buffer
        
        return meeting_start - timezone.timedelta(minutes=10) <= now <= meeting_end

    def get_meeting_status(self):
        if not self.scheduled_datetime:
            return "Not scheduled"
        
        now = timezone.now()
        meeting_start = self.scheduled_datetime
        
        if now < meeting_start - timezone.timedelta(minutes=10):
            return "Scheduled"
        elif self.can_join_meeting():
            return "Ready to join"
        elif now > meeting_start + timezone.timedelta(minutes=self.scheduled_duration):
            return "Completed"
        else:
            return "Ended"

    def __str__(self):
        return f"{self.full_name} - {self.get_status_display()} - {self.created_at.strftime('%Y-%m-%d')}"