import uuid
import re
from typing import List, Optional
from sqlalchemy.orm import Session

from app.models import User, Notification, Task, Comment, Mention


class NotificationService:
    """Service for creating and managing notifications."""

    MAX_MENTIONS_PER_COMMENT = 10

    @staticmethod
    def create_notification(
        db: Session,
        user_id: str,
        notification_type: str,
        reference_type: str,
        reference_id: str,
        title: str,
        message: Optional[str] = None,
    ) -> Notification:
        """Create a notification for a user."""
        notification = Notification(
            id=str(uuid.uuid4()),
            user_id=user_id,
            type=notification_type,
            reference_type=reference_type,
            reference_id=reference_id,
            title=title,
            message=message,
        )
        db.add(notification)
        return notification

    @staticmethod
    def notify_task_assignment(
        db: Session,
        task: Task,
        assigned_by: User,
    ) -> Optional[Notification]:
        """Notify user when they are assigned to a task."""
        if not task.assignee_id or task.assignee_id == assigned_by.id:
            return None

        return NotificationService.create_notification(
            db=db,
            user_id=task.assignee_id,
            notification_type="assignment",
            reference_type="task",
            reference_id=task.id,
            title=f"You've been assigned to: {task.title}",
            message=f"Assigned by {assigned_by.name}",
        )

    @staticmethod
    def notify_blocker(
        db: Session,
        task: Task,
        reported_by: User,
        reason: str,
    ) -> List[Notification]:
        """Notify project owner when a task is blocked."""
        notifications = []

        # Notify project owner
        project = task.project
        if project and project.owner_id and project.owner_id != reported_by.id:
            notification = NotificationService.create_notification(
                db=db,
                user_id=project.owner_id,
                notification_type="blocker",
                reference_type="task",
                reference_id=task.id,
                title=f"Task blocked: {task.title}",
                message=f"Reported by {reported_by.name}: {reason[:100]}...",
            )
            notifications.append(notification)

        return notifications

    @staticmethod
    def notify_blocker_resolved(
        db: Session,
        task: Task,
        resolved_by: User,
        reporter_id: str,
    ) -> Optional[Notification]:
        """Notify the original reporter when a blocker is resolved."""
        if reporter_id == resolved_by.id:
            return None

        return NotificationService.create_notification(
            db=db,
            user_id=reporter_id,
            notification_type="blocker_resolved",
            reference_type="task",
            reference_id=task.id,
            title=f"Blocker resolved: {task.title}",
            message=f"Resolved by {resolved_by.name}",
        )

    @staticmethod
    def count_mentions(content: str) -> int:
        """Count the number of @mentions in content."""
        pattern = r'@([a-zA-Z0-9._-]+(?:@[a-zA-Z0-9.-]+)?)'
        matches = re.findall(pattern, content)
        return len(matches)

    @staticmethod
    def parse_mentions(content: str) -> List[str]:
        """Extract @mentions from comment content. Returns list of email usernames."""
        # Match @username patterns (alphanumeric and common email chars before @domain)
        pattern = r'@([a-zA-Z0-9._-]+(?:@[a-zA-Z0-9.-]+)?)'
        matches = re.findall(pattern, content)
        return matches[:NotificationService.MAX_MENTIONS_PER_COMMENT]

    @staticmethod
    def process_mentions(
        db: Session,
        comment: Comment,
        task: Task,
        author: User,
    ) -> List[Notification]:
        """Process mentions in a comment and create notifications."""
        notifications = []
        mentioned_usernames = NotificationService.parse_mentions(comment.content)

        if not mentioned_usernames:
            return notifications

        # Find users by email or name
        for username in mentioned_usernames:
            # Try to find user by email first
            user = db.query(User).filter(
                (User.email.ilike(f"{username}%")) | (User.name.ilike(f"%{username}%"))
            ).first()

            if user and user.id != author.id:
                # Create mention record
                mention = Mention(
                    id=str(uuid.uuid4()),
                    comment_id=comment.id,
                    mentioned_user_id=user.id,
                )
                db.add(mention)

                # Create notification
                notification = NotificationService.create_notification(
                    db=db,
                    user_id=user.id,
                    notification_type="mention",
                    reference_type="comment",
                    reference_id=comment.id,
                    title=f"{author.name} mentioned you in: {task.title}",
                    message=comment.content[:100] + ("..." if len(comment.content) > 100 else ""),
                )
                notifications.append(notification)

        return notifications

    @staticmethod
    def notify_comment_reply(
        db: Session,
        comment: Comment,
        task: Task,
        author: User,
        parent_author_id: str,
    ) -> Optional[Notification]:
        """Notify original commenter when someone replies."""
        if parent_author_id == author.id:
            return None

        return NotificationService.create_notification(
            db=db,
            user_id=parent_author_id,
            notification_type="comment",
            reference_type="comment",
            reference_id=comment.id,
            title=f"{author.name} replied to your comment on: {task.title}",
            message=comment.content[:100] + ("..." if len(comment.content) > 100 else ""),
        )