from typing import List
from models import Ticket

class TrackDAG:
    def __init__(self, tickets: List[Ticket]):
        self.tickets = tickets
        self.ticket_map = {t.id: t for t in tickets}

    def get_ready_tasks(self) -> List[Ticket]:
        """Returns tickets that are 'todo' and whose dependencies are all 'completed'."""
        ready = []
        for ticket in self.tickets:
            if ticket.status == 'todo':
                # Check if all dependencies exist and are completed
                all_done = True
                for dep_id in ticket.depends_on:
                    dep = self.ticket_map.get(dep_id)
                    if not dep or dep.status != 'completed':
                        all_done = False
                        break
                if all_done:
                    ready.append(ticket)
        return ready

    def has_cycle(self) -> bool:
        """Returns True if there's a dependency cycle."""
        visited = set()
        rec_stack = set()

        def is_cyclic(ticket_id):
            if ticket_id in rec_stack:
                return True
            if ticket_id in visited:
                return False

            visited.add(ticket_id)
            rec_stack.add(ticket_id)

            ticket = self.ticket_map.get(ticket_id)
            if ticket:
                for neighbor in ticket.depends_on:
                    if is_cyclic(neighbor):
                        return True

            rec_stack.remove(ticket_id)
            return False

        for ticket in self.tickets:
            if ticket.id not in visited:
                if is_cyclic(ticket.id):
                    return True
        return False