import uuid
from datetime import date
from types import SimpleNamespace

import pytest

from app.scheduling_service import calculate_schedule, check_for_cycle


def test_cycle_detection():
    id_a = uuid.uuid4()
    id_b = uuid.uuid4()
    id_c = uuid.uuid4()

    edges = [
        (id_a, id_b),
        (id_b, id_c),
    ]

    # Adding C -> A should detect cycle
    assert check_for_cycle(edges, id_c, id_a) is True

    # Adding A -> A (self-loop) should detect cycle
    assert check_for_cycle(edges, id_a, id_a) is True

    # Adding C -> D (new node) should not detect cycle
    id_d = uuid.uuid4()
    assert check_for_cycle(edges, id_c, id_d) is False


def test_cpm_forward_and_backward_pass():
    id_a = uuid.uuid4()
    id_b = uuid.uuid4()
    id_c = uuid.uuid4()

    t_a = SimpleNamespace(id=id_a, duration=3, planned_start=date(2026, 1, 1), parent_id=None, progress=0)
    t_b = SimpleNamespace(id=id_b, duration=4, planned_start=None, parent_id=None, progress=0)
    t_c = SimpleNamespace(id=id_c, duration=2, planned_start=None, parent_id=None, progress=0)

    # A (3d) -[FS + 1 lag]-> B (4d) -[FS + 0 lag]-> C (2d)
    rel_ab = SimpleNamespace(from_task_id=id_a, to_task_id=id_b, relation_type="FS", lag_days=1)
    rel_bc = SimpleNamespace(from_task_id=id_b, to_task_id=id_c, relation_type="FS", lag_days=0)

    res = calculate_schedule([t_a, t_b, t_c], [rel_ab, rel_bc], project_start=date(2026, 1, 1))

    sched = res["tasks_schedule"]

    # Task A: 2026-01-01, duration 3 is a gap -> ends 2026-01-04
    assert sched[id_a]["planned_start"] == date(2026, 1, 1)
    assert sched[id_a]["planned_end"] == date(2026, 1, 4)

    # Task B starts right after A finishes (Jan 4) plus 1 lag day = Jan 5
    assert sched[id_b]["planned_start"] == date(2026, 1, 5)
    # B: duration 4 gap -> Jan 5 + 4 = Jan 9
    assert sched[id_b]["planned_end"] == date(2026, 1, 9)

    # Task C starts Jan 9, duration 2 gap -> ends Jan 11
    assert sched[id_c]["planned_start"] == date(2026, 1, 9)
    assert sched[id_c]["planned_end"] == date(2026, 1, 11)

    # All three are on critical path
    assert id_a in res["critical_path"]
    assert id_b in res["critical_path"]
    assert id_c in res["critical_path"]