//! Shared, credential-safe engine for Responses WebSocket compatibility probes.
//!
//! Provider profiles own their environment variables and handshake headers.
//! This module owns the common Responses WebSocket contract: two sequential
//! `response.create` warmups, continuation with `previous_response_id`, safe
//! event observation, and a redacted JSON report.

use std::env;
use std::time::{Duration, Instant};

use http::{HeaderMap, HeaderValue};
use serde::Serialize;
use serde_json::{json, Value};
use url::Url;
use wreq::ws::message::Message as WreqWsMessage;

const MAX_FRAME_SIZE: usize = 1 << 20;
const MAX_EVENTS_PER_TURN: usize = 16;

pub(crate) struct ProbeArgs {
    pub(crate) url: Option<String>,
    pub(crate) timeout_secs: u64,
}

pub(crate) struct ProbeConfig {
    url: Url,
    model: String,
    turn_timeout: Duration,
    handshake_headers: HeaderMap,
    sent_header_names: Vec<&'static str>,
}

impl ProbeConfig {
    pub(crate) fn new(
        url: Url,
        model: String,
        turn_timeout: Duration,
        handshake_headers: HeaderMap,
        sent_header_names: Vec<&'static str>,
    ) -> Self {
        Self {
            url,
            model,
            turn_timeout,
            handshake_headers,
            sent_header_names,
        }
    }
}

/// A profile retains provider-specific authentication and configuration while
/// reusing one Responses protocol probe engine.
pub(crate) trait ResponsesWebSocketProbeProfile {
    fn build_config(args: &ProbeArgs) -> Result<ProbeConfig, ProbeFailure>;
    fn sent_header_names() -> Vec<&'static str>;
}

#[derive(Debug, Clone, Copy)]
pub(crate) enum ProbeFailure {
    MissingConfiguration,
    InvalidEndpoint,
    ClientBuild,
    Handshake,
    Upgrade,
    Send,
    ReceiveTimeout,
    Receive,
    RemoteError,
    MissingResponseId,
    UnexpectedFrame,
}

impl ProbeFailure {
    const fn code(self) -> &'static str {
        match self {
            Self::MissingConfiguration => "missing_configuration",
            Self::InvalidEndpoint => "invalid_endpoint",
            Self::ClientBuild => "client_build_failed",
            Self::Handshake => "handshake_failed",
            Self::Upgrade => "upgrade_failed",
            Self::Send => "send_failed",
            Self::ReceiveTimeout => "receive_timeout",
            Self::Receive => "receive_failed",
            Self::RemoteError => "upstream_error_event",
            Self::MissingResponseId => "response_id_not_observed",
            Self::UnexpectedFrame => "unexpected_frame",
        }
    }
}

#[derive(Serialize)]
struct ProbeReport {
    status: &'static str,
    target_host: Option<String>,
    handshake_status: Option<u16>,
    sent_header_names: Vec<&'static str>,
    received_header_names: Vec<String>,
    observed_event_types: Vec<String>,
    continuation_confirmed: bool,
    elapsed_ms: u64,
    error: Option<&'static str>,
}

impl ProbeReport {
    fn failed(
        config: Option<&ProbeConfig>,
        sent_header_names: Vec<&'static str>,
        started_at: Instant,
        error: ProbeFailure,
    ) -> Self {
        Self {
            status: "failed",
            target_host: config.and_then(target_host),
            handshake_status: None,
            sent_header_names,
            received_header_names: Vec::new(),
            observed_event_types: Vec::new(),
            continuation_confirmed: false,
            elapsed_ms: started_at.elapsed().as_millis() as u64,
            error: Some(error.code()),
        }
    }
}

/// Runs a profile and returns the process exit code after emitting exactly one
/// credential-safe JSON report.
pub(crate) async fn run_profile_probe<P: ResponsesWebSocketProbeProfile>(args: ProbeArgs) -> i32 {
    let started_at = Instant::now();
    let config = match P::build_config(&args) {
        Ok(config) => config,
        Err(error) => {
            print_report(&ProbeReport::failed(
                None,
                P::sent_header_names(),
                started_at,
                error,
            ));
            return 2;
        }
    };

    match run_probe(&config, started_at).await {
        Ok(report) => {
            print_report(&report);
            0
        }
        Err(error) => {
            print_report(&ProbeReport::failed(
                Some(&config),
                config.sent_header_names.clone(),
                started_at,
                error,
            ));
            1
        }
    }
}

pub(crate) fn required_env(name: &str) -> Result<String, ProbeFailure> {
    env::var(name)
        .ok()
        .map(|value| value.trim().to_string())
        .filter(|value| !value.is_empty())
        .ok_or(ProbeFailure::MissingConfiguration)
}

pub(crate) fn resolve_probe_url(
    args: &ProbeArgs,
    url_env: &str,
    default_url: Option<&str>,
) -> Result<Url, ProbeFailure> {
    let raw_url = args
        .url
        .as_deref()
        .map(str::to_owned)
        .or_else(|| env::var(url_env).ok())
        .or_else(|| default_url.map(str::to_owned));
    let Some(raw_url) = raw_url
        .as_deref()
        .map(str::trim)
        .filter(|value| !value.is_empty())
    else {
        return Err(ProbeFailure::MissingConfiguration);
    };
    parse_probe_url(raw_url)
}

pub(crate) fn parse_probe_url(raw: &str) -> Result<Url, ProbeFailure> {
    let url = Url::parse(raw).map_err(|_| ProbeFailure::InvalidEndpoint)?;
    if !matches!(url.scheme(), "ws" | "wss")
        || url.host_str().is_none()
        || !url.username().is_empty()
        || url.password().is_some()
        || url.query().is_some()
        || url.fragment().is_some()
        || (url.scheme() == "ws" && !aether_http::url_has_literal_loopback_host(&url))
    {
        return Err(ProbeFailure::InvalidEndpoint);
    }
    Ok(url)
}

pub(crate) fn bearer_authorization_value(token: &str) -> Result<HeaderValue, ProbeFailure> {
    HeaderValue::from_str(format!("Bearer {token}").as_str())
        .map_err(|_| ProbeFailure::MissingConfiguration)
}

pub(crate) const fn turn_timeout(args: &ProbeArgs) -> Duration {
    Duration::from_secs(args.timeout_secs)
}

async fn run_probe(config: &ProbeConfig, started_at: Instant) -> Result<ProbeReport, ProbeFailure> {
    let client = wreq::Client::builder()
        .no_proxy()
        .connect_timeout(config.turn_timeout)
        .timeout(config.turn_timeout)
        .build()
        .map_err(|_| ProbeFailure::ClientBuild)?;
    let response = client
        .websocket(config.url.as_str())
        .headers(config.handshake_headers.clone())
        .max_frame_size(MAX_FRAME_SIZE)
        .max_message_size(MAX_FRAME_SIZE)
        .send()
        .await
        .map_err(|_| ProbeFailure::Handshake)?;
    let handshake_status = response.status().as_u16();
    let received_header_names = response
        .headers()
        .keys()
        .map(|name| name.as_str().to_string())
        .collect();
    let mut socket = response
        .into_websocket()
        .await
        .map_err(|_| ProbeFailure::Upgrade)?;
    let mut observed_event_types = Vec::new();

    send_warmup(&mut socket, &config.model, None).await?;
    let first_response_id =
        receive_completed_response_id(&mut socket, config.turn_timeout, &mut observed_event_types)
            .await?;

    send_warmup(&mut socket, &config.model, Some(&first_response_id)).await?;
    let _second_response_id =
        receive_completed_response_id(&mut socket, config.turn_timeout, &mut observed_event_types)
            .await?;

    Ok(ProbeReport {
        status: "passed",
        target_host: target_host(config),
        handshake_status: Some(handshake_status),
        sent_header_names: config.sent_header_names.clone(),
        received_header_names,
        observed_event_types,
        continuation_confirmed: true,
        elapsed_ms: started_at.elapsed().as_millis() as u64,
        error: None,
    })
}

fn target_host(config: &ProbeConfig) -> Option<String> {
    config.url.host_str().map(|host| match config.url.port() {
        Some(port) => format!("{host}:{port}"),
        None => host.to_string(),
    })
}

async fn send_warmup(
    socket: &mut wreq::ws::WebSocket,
    model: &str,
    previous_response_id: Option<&str>,
) -> Result<(), ProbeFailure> {
    let mut event = json!({
        "type": "response.create",
        "model": model,
        "store": false,
        "generate": false,
        "input": [],
        "tools": [],
    });
    if let Some(previous_response_id) = previous_response_id {
        event["previous_response_id"] = Value::String(previous_response_id.to_string());
    }
    socket
        .send(WreqWsMessage::text(event.to_string()))
        .await
        .map_err(|_| ProbeFailure::Send)
}

async fn receive_completed_response_id(
    socket: &mut wreq::ws::WebSocket,
    timeout: Duration,
    observed_event_types: &mut Vec<String>,
) -> Result<String, ProbeFailure> {
    let mut response_id = None;
    for _ in 0..MAX_EVENTS_PER_TURN {
        let message = tokio::time::timeout(timeout, socket.recv())
            .await
            .map_err(|_| ProbeFailure::ReceiveTimeout)?
            .ok_or(ProbeFailure::MissingResponseId)?
            .map_err(|_| ProbeFailure::Receive)?;
        match message {
            WreqWsMessage::Text(text) => {
                let event: Value = serde_json::from_str(text.as_str())
                    .map_err(|_| ProbeFailure::UnexpectedFrame)?;
                let event_type = event
                    .get("type")
                    .and_then(Value::as_str)
                    .map(safe_event_label)
                    .unwrap_or_else(|| "unknown".to_string());
                let is_remote_error = event_type == "error";
                let is_completed = event_type == "response.completed";
                observed_event_types.push(event_type);
                if is_remote_error {
                    return Err(ProbeFailure::RemoteError);
                }
                if let Some(observed_response_id) = event
                    .pointer("/response/id")
                    .and_then(Value::as_str)
                    .map(str::trim)
                    .filter(|value| !value.is_empty())
                {
                    response_id = Some(observed_response_id.to_string());
                }
                if is_completed {
                    return response_id.ok_or(ProbeFailure::MissingResponseId);
                }
            }
            WreqWsMessage::Ping(_) | WreqWsMessage::Pong(_) => continue,
            WreqWsMessage::Close(_) => return Err(ProbeFailure::MissingResponseId),
            _ => return Err(ProbeFailure::UnexpectedFrame),
        }
    }
    Err(ProbeFailure::MissingResponseId)
}

fn safe_event_label(value: &str) -> String {
    let trimmed = value.trim();
    if trimmed.is_empty()
        || trimmed.len() > 80
        || !trimmed
            .bytes()
            .all(|byte| byte.is_ascii_alphanumeric() || matches!(byte, b'.' | b'_' | b'-'))
    {
        return "unknown".to_string();
    }
    trimmed.to_string()
}

fn print_report(report: &ProbeReport) {
    match serde_json::to_string(report) {
        Ok(json) => println!("{json}"),
        Err(_) => println!("{{\"status\":\"failed\",\"error\":\"report_serialization_failed\"}}"),
    }
}

#[cfg(test)]
mod tests {
    use std::sync::Arc;
    use std::time::{Duration, Instant};

    use axum::extract::ws::{Message, WebSocket, WebSocketUpgrade};
    use axum::extract::State;
    use axum::http::header::AUTHORIZATION;
    use axum::http::{HeaderMap, HeaderValue};
    use axum::response::IntoResponse;
    use axum::routing::get;
    use axum::Router;
    use futures_util::{SinkExt, StreamExt};
    use serde_json::Value;
    use tokio::sync::{oneshot, Mutex};

    use super::{parse_probe_url, run_probe, ProbeConfig};

    #[derive(Default)]
    struct MockState {
        observed: Mutex<Option<oneshot::Sender<ObservedClientMessages>>>,
    }

    struct ObservedClientMessages {
        authorization_present: bool,
        profile_header_present: bool,
        second_before_first_completion: bool,
        first: Value,
        second: Value,
    }

    #[tokio::test]
    async fn probe_confirms_sequential_response_continuation_without_exposing_values() {
        let (url, observed, server) = spawn_mock_server().await;
        let mut headers = HeaderMap::new();
        headers.insert(
            AUTHORIZATION,
            HeaderValue::from_static("Bearer test-token-that-must-not-be-reported"),
        );
        headers.insert(
            "x-aether-probe-profile",
            HeaderValue::from_static("test-profile-id"),
        );
        let config = ProbeConfig::new(
            parse_probe_url(url.as_str()).expect("mock URL should be valid"),
            "gpt-test".to_string(),
            Duration::from_secs(2),
            headers,
            vec!["authorization", "x-aether-probe-profile"],
        );

        let report = run_probe(&config, Instant::now())
            .await
            .expect("probe should complete against mock server");
        let client_messages = observed.await.expect("mock should observe client messages");
        server.abort();

        assert_eq!(report.status, "passed");
        assert!(report.continuation_confirmed);
        assert!(report
            .observed_event_types
            .contains(&"response.created".to_string()));
        assert!(report
            .observed_event_types
            .contains(&"response.completed".to_string()));
        assert!(client_messages.authorization_present);
        assert!(client_messages.profile_header_present);
        assert!(!client_messages.second_before_first_completion);
        assert_eq!(client_messages.first["type"], "response.create");
        assert_eq!(client_messages.first["generate"], false);
        assert_eq!(client_messages.first["store"], false);
        assert_eq!(client_messages.second["previous_response_id"], "resp-first");
        let report_json = serde_json::to_string(&report).expect("report should serialize");
        assert!(!report_json.contains("test-token-that-must-not-be-reported"));
        assert!(!report_json.contains("test-profile-id"));
        assert!(!report_json.contains("resp-first"));
    }

    #[test]
    fn probe_url_rejects_credentials_and_query_strings() {
        assert!(parse_probe_url("wss://example.test/v1/responses").is_ok());
        assert!(parse_probe_url("ws://localhost:8080/v1/responses").is_ok());
        assert!(parse_probe_url("ws://127.42.0.1:8080/v1/responses").is_ok());
        assert!(parse_probe_url("ws://[::1]:8080/v1/responses").is_ok());
        assert!(parse_probe_url("https://example.test/v1/responses").is_err());
        assert!(parse_probe_url("ws://example.test/v1/responses").is_err());
        assert!(parse_probe_url("ws://10.0.0.1/v1/responses").is_err());
        assert!(parse_probe_url("ws://0.0.0.0:8080/v1/responses").is_err());
        assert!(parse_probe_url("ws://[::ffff:127.0.0.1]:8080/v1/responses").is_err());
        assert!(parse_probe_url("wss://token@example.test/v1/responses").is_err());
        assert!(parse_probe_url("wss://example.test/v1/responses?token=secret").is_err());
    }

    async fn spawn_mock_server() -> (
        String,
        oneshot::Receiver<ObservedClientMessages>,
        tokio::task::JoinHandle<()>,
    ) {
        let (observed_tx, observed_rx) = oneshot::channel();
        let state = Arc::new(MockState {
            observed: Mutex::new(Some(observed_tx)),
        });
        let app = Router::new()
            .route("/v1/responses", get(mock_websocket))
            .with_state(state);
        let listener = tokio::net::TcpListener::bind("127.0.0.1:0")
            .await
            .expect("mock listener should bind");
        let address = listener
            .local_addr()
            .expect("mock listener should expose address");
        let server = tokio::spawn(async move {
            axum::serve(listener, app)
                .await
                .expect("mock server should run");
        });
        (format!("ws://{address}/v1/responses"), observed_rx, server)
    }

    async fn mock_websocket(
        ws: WebSocketUpgrade,
        State(state): State<Arc<MockState>>,
        headers: HeaderMap,
    ) -> impl IntoResponse {
        let authorization_present = headers
            .get(AUTHORIZATION)
            .and_then(|value| value.to_str().ok())
            .is_some_and(|value| value.starts_with("Bearer "));
        let profile_header_present = headers.contains_key("x-aether-probe-profile");
        ws.on_upgrade(move |socket| async move {
            serve_mock_socket(socket, state, authorization_present, profile_header_present).await;
        })
    }

    async fn serve_mock_socket(
        socket: WebSocket,
        state: Arc<MockState>,
        authorization_present: bool,
        profile_header_present: bool,
    ) {
        let (mut sender, mut receiver) = socket.split();
        let first = receive_json(&mut receiver).await;
        let _ = sender
            .send(Message::Text(
                serde_json::json!({
                    "type": "response.created",
                    "response": {"id": "resp-first"}
                })
                .to_string()
                .into(),
            ))
            .await;
        let early_second = tokio::select! {
            message = receiver.next() => Some(message),
            _ = tokio::time::sleep(Duration::from_millis(50)) => None,
        };
        let second_before_first_completion = early_second.is_some();
        let _ = sender
            .send(Message::Text(
                serde_json::json!({
                    "type": "response.completed",
                    "response": {"id": "resp-first", "status": "completed"}
                })
                .to_string()
                .into(),
            ))
            .await;
        let second = match early_second {
            Some(Some(Ok(Message::Text(text)))) => {
                serde_json::from_str(text.as_str()).expect("early client message should be JSON")
            }
            Some(Some(Ok(_))) => panic!("expected text continuation message"),
            Some(Some(Err(error))) => panic!("client message should be valid: {error}"),
            Some(None) => panic!("client closed before continuation"),
            None => receive_json(&mut receiver).await,
        };
        let _ = sender
            .send(Message::Text(
                serde_json::json!({
                    "type": "response.created",
                    "response": {"id": "resp-second"}
                })
                .to_string()
                .into(),
            ))
            .await;
        let _ = sender
            .send(Message::Text(
                serde_json::json!({
                    "type": "response.completed",
                    "response": {"id": "resp-second", "status": "completed"}
                })
                .to_string()
                .into(),
            ))
            .await;
        if let Some(observed) = state.observed.lock().await.take() {
            let _ = observed.send(ObservedClientMessages {
                authorization_present,
                profile_header_present,
                second_before_first_completion,
                first,
                second,
            });
        }
    }

    async fn receive_json(receiver: &mut futures_util::stream::SplitStream<WebSocket>) -> Value {
        let message = receiver
            .next()
            .await
            .expect("client should send a message")
            .expect("client message should be valid");
        let Message::Text(text) = message else {
            panic!("expected text message");
        };
        serde_json::from_str(text.as_str()).expect("client message should be JSON")
    }
}