from django.conf import settings
from django.db import models
from django.utils.translation import gettext_lazy as _
from apps.profiles.models.institution import Institution


class ChatRoom(models.Model):
    class RoomType(models.TextChoices):
        DIRECT = 'direct', _('Direct Message')
        GROUP = 'group', _('Group Conversation')

    room_type = models.CharField(
        max_length=20,
        choices=RoomType.choices,
        default=RoomType.DIRECT,
        verbose_name=_('Room Type')
    )
    title = models.CharField(
        max_length=255,
        blank=True,
        null=True,
        verbose_name=_('Conversation Title')
    )
    participant_users = models.ManyToManyField(
        settings.AUTH_USER_MODEL,
        blank=True,
        related_name='chat_rooms',
        verbose_name=_('Participant Users')
    )
    participant_institutions = models.ManyToManyField(
        Institution,
        blank=True,
        related_name='chat_rooms',
        verbose_name=_('Participant Institutions')
    )
    created_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='created_chat_rooms',
        verbose_name=_('Created By')
    )
    created_at = models.DateTimeField(
        auto_now_add=True,
        verbose_name=_('Created At')
    )
    updated_at = models.DateTimeField(
        auto_now=True,
        verbose_name=_('Last Activity')
    )

    class Meta:
        ordering = ('-updated_at',)
        verbose_name = _('Chat Room')
        verbose_name_plural = _('Chat Rooms')

    def __str__(self):
        return self.title or f"Chat Room #{self.id} ({self.room_type})"

    @property
    def centrifugo_channel(self) -> str:
        return f"chat:room_{self.id}"

    def is_participant(self, user) -> bool:
        if not user or not user.is_authenticated:
            return False
        if getattr(user, 'is_super_admin', False) or getattr(user, 'is_regional_admin', False):
            return True
        if self.participant_users.filter(id=user.id).exists():
            return True
        # Check if user belongs to any participant institution
        user_inst_ids = user.institution_memberships.values_list('institution_id', flat=True)
        if self.participant_institutions.filter(id__in=user_inst_ids).exists():
            return True
        return False

    def get_last_message(self):
        return self.messages.all().select_related('sender', 'sender_institution').order_by('-created_at', '-id').first()

    def get_unread_count(self, user) -> int:
        if not user or not user.is_authenticated:
            return 0
        return self.messages.exclude(sender=user).exclude(read_by=user).count()

    def get_display_title(self, current_user=None) -> str:
        if self.title:
            return self.title
        if self.room_type == self.RoomType.DIRECT and current_user:
            other_user = self.participant_users.exclude(id=current_user.id).first()
            if other_user:
                return other_user.fullname or other_user.email
            other_inst = self.participant_institutions.first()
            if other_inst:
                return other_inst.name
        return f"Conversation #{self.id}"


class ChatMessage(models.Model):
    room = models.ForeignKey(
        ChatRoom,
        on_delete=models.CASCADE,
        related_name='messages',
        verbose_name=_('Chat Room')
    )
    sender = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name='sent_chat_messages',
        verbose_name=_('Sender')
    )
    sender_institution = models.ForeignKey(
        Institution,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='institution_chat_messages',
        verbose_name=_('Sender Institution Affiliation')
    )
    content = models.TextField(
        blank=True,
        null=True,
        verbose_name=_('Message Text')
    )
    attachment = models.FileField(
        upload_to='chat/attachments/%Y/%m/',
        blank=True,
        null=True,
        verbose_name=_('Attachment File')
    )
    attachment_name = models.CharField(
        max_length=255,
        blank=True,
        null=True,
        verbose_name=_('Attachment Filename')
    )
    read_by = models.ManyToManyField(
        settings.AUTH_USER_MODEL,
        blank=True,
        related_name='read_chat_messages',
        verbose_name=_('Read Receipts')
    )
    created_at = models.DateTimeField(
        auto_now_add=True,
        verbose_name=_('Timestamp')
    )

    class Meta:
        ordering = ('created_at',)
        verbose_name = _('Chat Message')
        verbose_name_plural = _('Chat Messages')

    def __str__(self):
        return f"[{self.room.id}] {self.sender.fullname or self.sender.email}: {self.content[:30] if self.content else 'Attachment'}"

    def save(self, *args, **kwargs):
        is_new = self.pk is None
        if self.attachment and not self.attachment_name:
            self.attachment_name = self.attachment.name.split('/')[-1]
        super().save(*args, **kwargs)

        if is_new:
            # Mark as read by sender immediately
            self.read_by.add(self.sender)
            # Update room activity timestamp
            ChatRoom.objects.filter(id=self.room_id).update(updated_at=self.created_at)