import pytest

from app.algorithms.demand_allocation import allocate_demand_by_pipe_length


def test_allocate_demand_by_incident_pipe_length():
    nodes = {
        "J1": {"type": "junction", "links": ["P1"]},
        "J2": {"type": "junction", "links": ["P1", "P2"]},
        "R1": {"type": "reservoir", "links": ["P2"]},
    }
    links = {"P1": {"length": 100.0}, "P2": {"length": 300.0}}

    result = allocate_demand_by_pipe_length(80.0, nodes, links)

    assert result == {"J1": pytest.approx(10.0), "J2": pytest.approx(40.0)}


def test_allocate_demand_returns_empty_for_zero_length_topology():
    result = allocate_demand_by_pipe_length(
        80.0,
        {"J1": {"type": "junction", "links": ["P1"]}},
        {"P1": {"length": 0.0}},
    )

    assert result == {}