"""
E2E test klíčového požadavku v5: ZMĚNA NASTAVENÍ ZA BĚHU BEZ RESTARTU.

Scénář:
1. Aplikace běží, engine načte model A (mock vLLM subprocess).
2. Passthrough /v1/chat/completions odpovídá přes model A.
3. POST /admin/settings změní model na B => engine se reloadne NA POZADÍ.
4. Aplikace (/health) zůstává dostupná PO CELOU DOBU reloadu.
5. Po reloadu odpovídá model B; aplikace se nikdy nerestartovala.
"""

import time

from fastapi.testclient import TestClient


def _wait_ready(engine, timeout=20):
    deadline = time.time() + timeout
    while time.time() < deadline:
        if engine.is_ready:
            return True
        if engine.status_dict()["state"] == "error":
            raise AssertionError(f"Engine error: {engine.status_dict()}")
        time.sleep(0.1)
    return False


def test_hot_swap_without_app_restart(app_module, auth):
    c = TestClient(app_module.app)
    eng = app_module.ENGINE

    # 1) start s modelem A
    r = c.post("/admin/settings", json={"model": "org/model-A"}, headers=auth)
    assert r.json()["engine_reload_started"] is True
    assert _wait_ready(eng), eng.status_dict()
    assert eng.current_model == "org/model-A"

    # 2) inference přes model A (passthrough bez agentní smyčky)
    r = c.post("/v1/chat/completions", headers=auth,
               json={"model": "code-agent-llm",
                     "messages": [{"role": "user", "content": "ping"}]})
    assert r.status_code == 200
    assert r.json()["choices"][0]["message"]["content"] == "mock:org/model-A:ping"

    # 3) hot-swap na model B
    r = c.post("/admin/settings", json={"model": "org/model-B"}, headers=auth)
    data = r.json()
    assert data["applied"] == {"model": "org/model-B"}
    assert data["engine_reload_started"] is True

    # 4) BĚHEM reloadu aplikace žije a hlásí stav
    saw_loading = False
    deadline = time.time() + 20
    while time.time() < deadline:
        h = c.get("/health")
        assert h.status_code == 200          # aplikace se nikdy nerestartovala
        state = h.json()["engine"]["state"]
        if state == "starting":
            saw_loading = True
        if state == "ready" and eng.current_model == "org/model-B":
            break
        time.sleep(0.1)
    assert eng.is_ready, eng.status_dict()
    assert saw_loading, "očekával jsem přechodný stav 'starting' během reloadu"

    # 5) inference už jede přes model B
    r = c.post("/v1/chat/completions", headers=auth,
               json={"model": "code-agent-llm",
                     "messages": [{"role": "user", "content": "pong"}]})
    assert r.json()["choices"][0]["message"]["content"] == "mock:org/model-B:pong"

    # instant změna během provozu nezpůsobí reload
    rev = app_module.SETTINGS.revision
    r = c.post("/admin/settings", json={"max_steps": 33}, headers=auth)
    assert r.json()["engine_reload_started"] is False
    assert app_module.SETTINGS.revision == rev + 1
    assert eng.current_model == "org/model-B"   # engine nedotčen


def test_engine_reload_endpoint(app_module, auth):
    c = TestClient(app_module.app)
    eng = app_module.ENGINE
    c.post("/admin/settings", json={"model": "org/model-C"}, headers=auth)
    assert _wait_ready(eng)

    r = c.post("/admin/engine/reload", headers=auth)
    assert r.json()["status"] == "reload_started"
    assert _wait_ready(eng)
    assert eng.current_model == "org/model-C"

    r = c.post("/admin/engine/stop", headers=auth)
    assert r.json()["status"] == "stopped"
    assert eng.status_dict()["state"] == "stopped"