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

import asyncio
from pathlib import Path
from typing import Any

import pytest
from fastapi import FastAPI
from fastapi.testclient import TestClient

from fluksio.api.deps import get_current_user
from fluksio.api.routes.flows import router
from fluksio.flow.controller import FlowController, LoadedNode
from fluksio.flow.messages import DType, MessageSpec
from fluksio.flow.nodes import Node
from fluksio.flow.pipeline import Pipeline
from fluksio.flow.schemas import FlowDef
from fluksio.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 == []


def test_a_node_that_will_not_stop_does_not_wedge_the_rebuild(
    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
):
    """A node closing a connection nobody answers used to hold the lock forever.

    Everything that deploys rebuilds, so the next publish, start or stop then
    waited on a lock that was never given back.
    """
    monkeypatch.setattr("fluksio.flow.controller.NODE_STOP_TIMEOUT", 0.05)

    class NeverStops(Node):
        async def stop(self, app: FastAPI | None = None) -> None:
            await asyncio.Event().wait()

    node = NeverStops(f=lambda params: None, name="stuck")
    node.assign_flow("heating", "stuck")
    engine = FlowController(FlowStore(tmp_path / "flows"))
    engine.loaded = {
        "heating.stuck": LoadedNode(id="heating.stuck", flow="heating", node=node)
    }

    async def scenario() -> None:
        # The first rebuild gives up on the node it cannot stop, and the second
        # is not left queueing behind a lock the first never released.
        await engine.reload()
        await engine.reload()

    asyncio.run(asyncio.wait_for(scenario(), timeout=5))