import pytest
from src.models import Ticket
from src.dag_engine import TrackDAG

def test_get_ready_tasks_linear():
 t1 = Ticket(id="T1", description="desc", status="todo")
 t2 = Ticket(id="T2", description="desc", status="todo", depends_on=["T1"])
 dag = TrackDAG([t1, t2])
 ready = dag.get_ready_tasks()
 assert len(ready) == 1
 assert ready[0].id == "T1"

def test_get_ready_tasks_branching():
 t1 = Ticket(id="T1", description="desc", status="completed")
 t2 = Ticket(id="T2", description="desc", status="todo", depends_on=["T1"])
 t3 = Ticket(id="T3", description="desc", status="todo", depends_on=["T1"])
 dag = TrackDAG([t1, t2, t3])
 ready = dag.get_ready_tasks()
 assert len(ready) == 2
 ids = [t.id for t in ready]
 assert "T2" in ids
 assert "T3" in ids

def test_has_cycle_no_cycle():
 t1 = Ticket(id="T1", description="desc", status="todo")
 t2 = Ticket(id="T2", description="desc", status="todo", depends_on=["T1"])
 dag = TrackDAG([t1, t2])
 assert dag.has_cycle() is False

def test_has_cycle_direct_cycle():
 t1 = Ticket(id="T1", description="desc", status="todo", depends_on=["T2"])
 t2 = Ticket(id="T2", description="desc", status="todo", depends_on=["T1"])
 dag = TrackDAG([t1, t2])
 assert dag.has_cycle() is True

def test_has_cycle_indirect_cycle():
 t1 = Ticket(id="T1", description="desc", status="todo", depends_on=["T3"])
 t2 = Ticket(id="T2", description="desc", status="todo", depends_on=["T1"])
 t3 = Ticket(id="T3", description="desc", status="todo", depends_on=["T2"])
 dag = TrackDAG([t1, t2, t3])
 assert dag.has_cycle() is True

def test_has_cycle_complex_no_cycle():
 t1 = Ticket(id="T1", description="desc", status="todo")
 t2 = Ticket(id="T2", description="desc", status="todo", depends_on=["T1"])
 t3 = Ticket(id="T3", description="desc", status="todo", depends_on=["T1"])
 t4 = Ticket(id="T4", description="desc", status="todo", depends_on=["T2", "T3"])
 dag = TrackDAG([t1, t2, t3, t4])
 assert dag.has_cycle() is False

def test_get_ready_tasks_multiple_deps():
 t1 = Ticket(id="T1", description="desc", status="completed")
 t2 = Ticket(id="T2", description="desc", status="todo")
 t3 = Ticket(id="T3", description="desc", status="todo", depends_on=["T1", "T2"])
 dag = TrackDAG([t1, t2, t3])
 # Only T2 is ready because T3 depends on T2 (todo)
 ready = dag.get_ready_tasks()
 assert len(ready) == 1
 assert ready[0].id == "T2"

def test_topological_sort():
 t1 = Ticket(id="T1", description="desc", status="todo")
 t2 = Ticket(id="T2", description="desc", status="todo", depends_on=["T1"])
 dag = TrackDAG([t2, t1]) # Out of order input
 sorted_tasks = dag.topological_sort()
 assert [t.id for t in sorted_tasks] == ["T1", "T2"]

def test_topological_sort_cycle():
 t1 = Ticket(id="T1", description="desc", status="todo", depends_on=["T2"])
 t2 = Ticket(id="T2", description="desc", status="todo", depends_on=["T1"])
 dag = TrackDAG([t1, t2])
 with pytest.raises(ValueError, match="DAG Validation Error: Cycle detected"):
  dag.topological_sort()