use anyhow::Result;
use codex_core::TurnInputRequest;
use codex_core::TurnInputSubmission;
use codex_core::config::Config;
use codex_extension_api::ConfigContributor;
use codex_extension_api::ExtensionData;
use codex_extension_api::ExtensionRegistryBuilder;
use codex_protocol::protocol::EventMsg;
use codex_protocol::protocol::Op;
use codex_protocol::protocol::ThreadSettingsOverrides;
use codex_protocol::user_input::UserInput;
use core_test_support::responses;
use core_test_support::skip_if_no_network;
use core_test_support::test_codex::test_codex;
use core_test_support::wait_for_event;
use pretty_assertions::assert_eq;
use std::sync::Arc;
use std::sync::Mutex;
use std::sync::mpsc;
use std::time::Duration;
use test_case::test_case;
use tokio::sync::oneshot;
use tokio::time::timeout;

const INITIAL_MODEL: &str = "gpt-5.4";
const COMMITTED_MODEL: &str = "gpt-5.2";
const TIMEOUT: Duration = Duration::from_secs(10);

struct PauseAfterCommit {
    gate: Mutex<Option<(oneshot::Sender<()>, mpsc::Receiver<()>)>>,
}

impl ConfigContributor<Config> for PauseAfterCommit {
    fn on_config_changed(
        &self,
        _session_store: &ExtensionData,
        _thread_store: &ExtensionData,
        _previous_config: &Config,
        new_config: &Config,
    ) {
        if new_config.model.as_deref() != Some(COMMITTED_MODEL) {
            return;
        }
        let Some((entered, release)) = self.gate.lock().expect("commit gate lock").take() else {
            return;
        };
        entered.send(()).expect("test is waiting for the commit");
        // The callback is synchronous, so this test uses a second runtime worker.
        release
            .recv_timeout(TIMEOUT)
            .expect("test releases the committed update");
    }
}

#[derive(Clone, Copy)]
enum SettingsOperation {
    TurnStart,
    Standalone,
}

#[test_case(SettingsOperation::TurnStart; "turn start retains its committed settings and notification")]
#[test_case(SettingsOperation::Standalone; "standalone notification retains its committed settings")]
#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
async fn settings_notifications_keep_their_commit_across_postcommit_work(
    operation: SettingsOperation,
) -> Result<()> {
    skip_if_no_network!(Ok(()));

    let server = responses::start_mock_server().await;
    let response = responses::mount_sse_once(
        &server,
        responses::sse(vec![
            responses::ev_response_created("response"),
            responses::ev_completed("response"),
        ]),
    )
    .await;
    let (entered_tx, entered_rx) = oneshot::channel();
    let (release_tx, release_rx) = mpsc::channel();
    let mut extensions = ExtensionRegistryBuilder::<Config>::new();
    extensions.config_contributor(Arc::new(PauseAfterCommit {
        gate: Mutex::new(Some((entered_tx, release_rx))),
    }));
    let test = test_codex()
        .with_model(INITIAL_MODEL)
        .with_extensions(Arc::new(extensions.build()))
        .build_with_auto_env(&server)
        .await?;
    let initial = test.codex.restorable_thread_settings().await;
    let thread_settings = ThreadSettingsOverrides {
        model: Some(COMMITTED_MODEL.to_string()),
        ..Default::default()
    };
    let submission = tokio::spawn({
        let codex = Arc::clone(&test.codex);
        async move {
            match operation {
                SettingsOperation::TurnStart => {
                    let result = codex
                        .start_or_steer_turn(
                            TurnInputRequest::user_input(vec![UserInput::Text {
                                text: "use the committed model".to_string(),
                                text_elements: Vec::new(),
                            }])
                            .with_thread_settings(thread_settings),
                        )
                        .await?;
                    let TurnInputSubmission::Started { turn_id } = result else {
                        panic!("expected a new turn, got {result:?}");
                    };
                    Ok(turn_id)
                }
                SettingsOperation::Standalone => {
                    codex.submit(Op::ThreadSettings { thread_settings }).await
                }
            }
        }
    });

    timeout(TIMEOUT, entered_rx).await??;
    let expected = test.codex.thread_settings_snapshot().await;
    assert_eq!(expected.model, COMMITTED_MODEL);
    // Submitted operations are serialized. Runtime restoration is an existing
    // direct writer, so it can overlap the first operation's post-commit work.
    timeout(TIMEOUT, test.codex.restore_thread_settings(initial)).await??;
    let restored = test.codex.thread_settings_snapshot().await;
    assert_eq!(restored.model, INITIAL_MODEL);
    release_tx.send(())?;
    let submission_id = timeout(TIMEOUT, submission).await???;

    let applied = timeout(TIMEOUT, async {
        loop {
            let event = test.codex.next_event().await?;
            match event.msg {
                EventMsg::ThreadSettingsApplied(applied) if event.id == submission_id => {
                    return Ok::<_, anyhow::Error>(applied.thread_settings);
                }
                EventMsg::Error(error) => {
                    anyhow::bail!("settings update failed: {}", error.message)
                }
                _ => {}
            }
        }
    })
    .await??;
    assert_eq!(applied, expected);

    let expected_request_model = match operation {
        SettingsOperation::TurnStart => COMMITTED_MODEL,
        SettingsOperation::Standalone => {
            assert!(response.requests().is_empty());
            test.codex
                .start_or_steer_turn(TurnInputRequest::user_input(vec![UserInput::Text {
                    text: "use the restored settings".to_string(),
                    text_elements: Vec::new(),
                }]))
                .await?;
            INITIAL_MODEL
        }
    };
    wait_for_event(&test.codex, |event| {
        matches!(event, EventMsg::TurnComplete(_))
    })
    .await;
    assert_eq!(
        response.single_request().body_json()["model"],
        expected_request_model
    );
    assert_eq!(test.codex.thread_settings_snapshot().await, restored);
    Ok(())
}