import pytest
from models import Ticket
from dag_engine import TrackDAG

def test_get_ready_tasks_linear():
    t1 = Ticket(id="T1", description="Task 1", status="completed", assigned_to="worker")
    t2 = Ticket(id="T2", description="Task 2", status="todo", assigned_to="worker", depends_on=["T1"])
    t3 = Ticket(id="T3", description="Task 3", status="todo", assigned_to="worker", depends_on=["T2"])
    
    dag = TrackDAG([t1, t2, t3])
    ready = dag.get_ready_tasks()
    assert len(ready) == 1
    assert ready[0].id == "T2"

def test_get_ready_tasks_branching():
    t1 = Ticket(id="T1", description="Task 1", status="completed", assigned_to="worker")
    t2 = Ticket(id="T2", description="Task 2", status="todo", assigned_to="worker", depends_on=["T1"])
    t3 = Ticket(id="T3", description="Task 3", status="todo", assigned_to="worker", depends_on=["T1"])
    
    dag = TrackDAG([t1, t2, t3])
    ready = dag.get_ready_tasks()
    assert len(ready) == 2
    ready_ids = {t.id for t in ready}
    assert ready_ids == {"T2", "T3"}

def test_has_cycle_no_cycle():
    t1 = Ticket(id="T1", description="Task 1", status="todo", assigned_to="worker")
    t2 = Ticket(id="T2", description="Task 2", status="todo", assigned_to="worker", depends_on=["T1"])
    
    dag = TrackDAG([t1, t2])
    assert not dag.has_cycle()

def test_has_cycle_direct_cycle():
    t1 = Ticket(id="T1", description="Task 1", status="todo", assigned_to="worker", depends_on=["T2"])
    t2 = Ticket(id="T2", description="Task 2", status="todo", assigned_to="worker", depends_on=["T1"])
    
    dag = TrackDAG([t1, t2])
    assert dag.has_cycle()

def test_has_cycle_indirect_cycle():
    t1 = Ticket(id="T1", description="Task 1", status="todo", assigned_to="worker", depends_on=["T2"])
    t2 = Ticket(id="T2", description="Task 2", status="todo", assigned_to="worker", depends_on=["T3"])
    t3 = Ticket(id="T3", description="Task 3", status="todo", assigned_to="worker", depends_on=["T1"])
    
    dag = TrackDAG([t1, t2, t3])
    assert dag.has_cycle()

def test_has_cycle_complex_no_cycle():
    # T1 -> T2, T1 -> T3, T2 -> T4, T3 -> T4
    t1 = Ticket(id="T1", description="T1", status="todo", assigned_to="worker", depends_on=["T2", "T3"])
    t2 = Ticket(id="T2", description="T2", status="todo", assigned_to="worker", depends_on=["T4"])
    t3 = Ticket(id="T3", description="T3", status="todo", assigned_to="worker", depends_on=["T4"])
    t4 = Ticket(id="T4", description="T4", status="todo", assigned_to="worker")
    
    dag = TrackDAG([t1, t2, t3, t4])
    assert not dag.has_cycle()

def test_get_ready_tasks_multiple_deps():
    t1 = Ticket(id="T1", description="T1", status="completed", assigned_to="worker")
    t2 = Ticket(id="T2", description="T2", status="completed", assigned_to="worker")
    t3 = Ticket(id="T3", description="T3", status="todo", assigned_to="worker", depends_on=["T1", "T2"])
    
    dag = TrackDAG([t1, t2, t3])
    assert [t.id for t in dag.get_ready_tasks()] == ["T3"]
    
    t2.status = "todo"
    assert [t.id for t in dag.get_ready_tasks()] == ["T2"]

def test_topological_sort():
    t1 = Ticket(id="T1", description="T1", status="todo", assigned_to="worker")
    t2 = Ticket(id="T2", description="T2", status="todo", assigned_to="worker", depends_on=["T1"])
    t3 = Ticket(id="T3", description="T3", status="todo", assigned_to="worker", depends_on=["T2"])
    
    dag = TrackDAG([t1, t2, t3])
    sort = dag.topological_sort()
    assert sort == ["T1", "T2", "T3"]

def test_topological_sort_cycle():
    t1 = Ticket(id="T1", description="T1", status="todo", assigned_to="worker", depends_on=["T2"])
    t2 = Ticket(id="T2", description="T2", status="todo", assigned_to="worker", depends_on=["T1"])
    
    dag = TrackDAG([t1, t2])
    with pytest.raises(ValueError, match="Dependency cycle detected"):
        dag.topological_sort()