"""Stopping a flow takes it off the engine; pausing holds its nodes."""

from pathlib import Path
from typing import Any

from fastapi import FastAPI
from fastapi.testclient import TestClient

from app.api.deps import get_current_user
from app.api.routes.flows import router
from app.flow.messages import DType, MessageSpec
from app.flow.nodes import Node
from app.flow.pipeline import Pipeline
from app.flow.schemas import FlowDef
from app.flow.store import FlowStore


def spec(name: str) -> MessageSpec:
    return MessageSpec(name=name, dtype=DType.FLOAT)


def make_node(node_id: str, flow: str, f, requires=(), provides=()) -> Node:
    node = Node(f=f, requires=list(requires), provides=list(provides), name=node_id)
    node.assign_flow(flow, node_id)
    return node


def a_chain(flow: str, ran: list[str]) -> list[Node]:
    """source → middle: two nodes, so stepping has somewhere to stop."""

    def source(params):
        ran.append(f"{flow}.source")
        return {"temp": 20.0}

    def middle(temp, params):
        ran.append(f"{flow}.middle")
        return {"warm": temp > 10}

    return [
        make_node("source", flow, source, provides=[spec("temp")]),
        make_node(
            "middle",
            flow,
            middle,
            requires=[spec("temp")],
            provides=[MessageSpec(name="warm", dtype=DType.BOOL)],
        ),
    ]


def test_a_stopped_flow_runs_nothing_and_its_neighbours_carry_on():
    ran: list[str] = []
    pipeline = Pipeline(
        nodes=a_chain("stopped", ran) + a_chain("running", ran),
        disabled_flows={"stopped"},
    )

    pipeline.run({})

    assert not any(name.startswith("stopped.") for name in ran)
    assert {"running.source", "running.middle"} <= set(ran)


def test_a_stopped_flow_ignores_a_trigger_from_its_own_nodes():
    ran: list[str] = []
    nodes = a_chain("stopped", ran)
    pipeline = Pipeline(nodes=nodes, disabled_flows={"stopped"})

    # What an MQTT subscription or a webhook would do.
    nodes[0].inject({"temp": 20.0})

    assert ran == []
    assert "stopped.temp" not in pipeline.state


def test_a_paused_flow_still_takes_values_but_acts_on_none_of_them():
    ran: list[str] = []
    nodes = a_chain("demo", ran)
    pipeline = Pipeline(nodes=nodes)

    pipeline.pause("demo")
    nodes[0].inject({"temp": 20.0})

    # The value is there to look at; nothing downstream of it ran.
    assert pipeline.state["demo.temp"] == 20.0
    assert ran == []


def test_resuming_runs_what_was_held_back():
    ran: list[str] = []
    pipeline = Pipeline(nodes=a_chain("demo", ran))

    pipeline.pause("demo")
    pipeline.run({})
    assert ran == []

    pipeline.resume("demo")
    assert ran == ["demo.source", "demo.middle"]
    assert pipeline.paused_flows() == []


def test_stopped_survives_a_restart(tmp_path: Path):
    store = FlowStore(tmp_path / "flows")
    assert store.read_enabled("heating") is True

    store.write_enabled("heating", False)
    assert store.read_enabled("heating") is False

    # A second store over the same directory is what a restart looks like.
    assert FlowStore(tmp_path / "flows").read_enabled("heating") is False


class _StubController:
    """Only what the step route touches: the store, and the step itself."""

    def __init__(self, store: FlowStore, stepped: str | None) -> None:
        self.store = store
        self.stepped = stepped
        self.calls: list[str] = []

    def step_flow(self, flow: str) -> str | None:
        self.calls.append(flow)
        return self.stepped


def _stub(tmp_path: Path, stepped: str | None) -> _StubController:
    """A controller over a store holding one flow, called 'heating'."""
    store = FlowStore(tmp_path / "flows")
    store.write_flow(FlowDef(name="heating"))
    return _StubController(store, stepped)


def _client(controller: Any) -> TestClient:
    app = FastAPI()
    app.include_router(router, prefix="/api/v1")
    app.state.flow_controller = controller
    app.dependency_overrides[get_current_user] = lambda: None
    return TestClient(app)


def test_the_step_endpoint_reports_what_it_ran(tmp_path: Path):
    controller = _stub(tmp_path, "heating.sensor")

    response = _client(controller).post("/api/v1/flows/heating/step")

    assert response.status_code == 200
    assert response.json() == {"message": "Stepped 'heating.sensor'"}
    assert controller.calls == ["heating"]


def test_stepping_a_flow_with_nothing_parked_answers_plainly(tmp_path: Path):
    """A button pressed once too often is not an error."""
    controller = _stub(tmp_path, None)

    response = _client(controller).post("/api/v1/flows/heating/step")

    assert response.status_code == 200
    assert response.json() == {"message": "Nothing held back in flow 'heating'"}


def test_stepping_an_unknown_flow_is_a_404(tmp_path: Path):
    controller = _stub(tmp_path, None)

    response = _client(controller).post("/api/v1/flows/nosuchflow/step")

    assert response.status_code == 404
    assert controller.calls == []