//! Kimi Code device-code login (PRD F1).
//!
//! Two-phase API mirroring kimi-cli's `login_kimi_code`:
//!   1. [`crate::auth::kimi_oauth::request_device_authorization`] — get a
//!      user code + verification URL from the OAuth host
//!   2. [`complete_device_code_login`] — poll the token endpoint until
//!      approved, then persist the token set via the `AuthManager`
//!
//! Poll semantics: the server-provided interval (default 5s, floored at 1s)
//! paces the loop; `slow_down` bumps it by 5s; `expired_token` restarts the
//! whole device authorization (fresh user code); every other non-200 outcome
//! (`authorization_pending`, unknown errors) waits and continues.

use std::sync::Arc;

use kigi_models::OAuthConfig;

use crate::auth::kimi_oauth::{DeviceAuthorization, DevicePollResult};
use crate::auth::{AuthChannels, AuthManager, AuthUrlInfo, AuthUrlMode, KimiAuth};

/// Extra wait added to the poll interval when the server answers `slow_down`
/// (OAuth-standard device-flow backpressure).
const SLOW_DOWN_INCREMENT_SECS: u64 = 5;

/// The wire behind a device-code login. The `Kimi` arm calls the bespoke Kimi
/// Code wire (X-Msh headers, `/api/oauth/*`) verbatim — byte-identical to the
/// pre-generalization path; the `Generic` arm drives a registry
/// [`OAuthConfig`] provider (xai-grok) through [`crate::auth::oauth_device`].
enum DeviceFlowBackend<'a> {
    Kimi {
        host: &'a str,
    },
    Generic(&'a OAuthConfig),
    /// GitHub Copilot two-stage flow: the device authorization is the generic
    /// one, but the token POLL reads GitHub's 200-body errors, and login
    /// FINALIZES the durable github token into a copilot session token via the
    /// Stage-2 exchange (see [`DeviceFlowBackend::finalize`]).
    GithubCopilot(&'a OAuthConfig),
}

impl DeviceFlowBackend<'_> {
    async fn request(&self) -> anyhow::Result<DeviceAuthorization> {
        match self {
            Self::Kimi { host } => {
                crate::auth::kimi_oauth::request_device_authorization(host).await
            }
            Self::Generic(cfg) | Self::GithubCopilot(cfg) => {
                crate::auth::oauth_device::request_device_authorization(cfg).await
            }
        }
    }
    async fn poll(&self, device_code: &str) -> anyhow::Result<DevicePollResult> {
        match self {
            Self::Kimi { host } => {
                crate::auth::kimi_oauth::poll_device_token(host, device_code).await
            }
            Self::Generic(cfg) => {
                crate::auth::oauth_device::poll_device_token(cfg, device_code).await
            }
            Self::GithubCopilot(cfg) => {
                crate::auth::github_copilot::poll_github_device_token(cfg, device_code).await
            }
        }
    }
    /// Transform the device-grant credential before it is persisted. The Kimi
    /// and generic flows persist the poll result verbatim; the GitHub Copilot
    /// flow exchanges the durable github token (in `auth.key`) for the
    /// short-lived copilot token, persisting BOTH (copilot as `key`, github as
    /// `refresh_token`).
    async fn finalize(&self, auth: KimiAuth) -> anyhow::Result<KimiAuth> {
        match self {
            Self::Kimi { .. } | Self::Generic(_) => Ok(auth),
            Self::GithubCopilot(cfg) => {
                crate::auth::github_copilot::exchange_copilot_token(cfg, &auth.key).await
            }
        }
    }
}

/// Outcome of one full poll loop over a single device authorization.
enum PollLoopOutcome {
    /// Access token issued.
    Done(Box<KimiAuth>),
    /// The device code expired before the user approved — request a fresh
    /// authorization and start over.
    Restart,
}

/// Device-code login shared by the TUI and CLI.
///
/// With `channels` (TUI) the verification URL goes to `url_tx` and the
/// browser opens automatically. Without `channels` (CLI) the URL + code are
/// printed to stderr. The caller reports success (`✓ Signed in`).
pub async fn run_device_code_login_channels(
    host: &str,
    auth_manager: &Arc<AuthManager>,
    channels: &mut Option<AuthChannels>,
) -> anyhow::Result<(KimiAuth, bool)> {
    run_device_code_login_backend(DeviceFlowBackend::Kimi { host }, auth_manager, channels).await
}

/// Device-code login for a GENERIC [`OAuthConfig`] provider (xai-grok). Same
/// TUI/CLI presentation as the Kimi login; only the wire differs.
pub async fn run_device_code_login_generic(
    oauth: &OAuthConfig,
    auth_manager: &Arc<AuthManager>,
    channels: &mut Option<AuthChannels>,
) -> anyhow::Result<(KimiAuth, bool)> {
    run_device_code_login_backend(DeviceFlowBackend::Generic(oauth), auth_manager, channels).await
}

/// GitHub Copilot two-stage login (github-copilot): the same device-flow
/// presentation as the generic path, but the token poll reads GitHub's 200-body
/// errors and the minted github token is finalized into a copilot session token
/// before it is persisted (see [`DeviceFlowBackend::finalize`]).
pub async fn run_device_code_login_github_copilot(
    oauth: &OAuthConfig,
    auth_manager: &Arc<AuthManager>,
    channels: &mut Option<AuthChannels>,
) -> anyhow::Result<(KimiAuth, bool)> {
    run_device_code_login_backend(
        DeviceFlowBackend::GithubCopilot(oauth),
        auth_manager,
        channels,
    )
    .await
}

async fn run_device_code_login_backend(
    backend: DeviceFlowBackend<'_>,
    auth_manager: &Arc<AuthManager>,
    channels: &mut Option<AuthChannels>,
) -> anyhow::Result<(KimiAuth, bool)> {
    let interactive_tui = channels.is_some();
    let mut channels = channels.take();
    loop {
        let device_auth = backend.request().await?;
        let display_uri = device_auth.verification_uri_complete.clone();

        if interactive_tui {
            // TUI: push the URL through the channel BEFORE opening the
            // browser, so the UI isn't blocked on a slow/hanging browser
            // launch (e.g. SSH/headless).
            if let Some(tx) = channels.as_mut().and_then(|c| c.url_tx.take()) {
                let _ = tx.send(AuthUrlInfo {
                    url: display_uri.clone(),
                    mode: AuthUrlMode::Device,
                });
            }
            open_browser_detached(&display_uri).await;
        } else {
            prompt_on_stderr(&device_auth).await;
        }

        match complete_device_code_login(&backend, &device_auth).await? {
            PollLoopOutcome::Done(auth) => {
                // Finalize before persisting: the GitHub Copilot flow exchanges
                // the durable github token for the short-lived copilot token
                // here; the Kimi / generic flows pass the credential through.
                let auth = backend.finalize(*auth).await?;
                let auth = auth_manager
                    .update(auth)
                    .await
                    .map_err(|e| anyhow::anyhow!("Failed to save credentials: {e}"))?;
                return Ok((auth, true));
            }
            PollLoopOutcome::Restart => {
                tracing::info!("auth: device code expired, restarting device authorization");
                if !interactive_tui {
                    eprintln!("Device code expired — requesting a new one...");
                }
                // The TUI already consumed url_tx; the restarted flow can
                // only reach the user via the (re-)opened browser page.
                continue;
            }
        }
    }
}

/// Print the verification URL + user code to stderr and open the browser.
async fn prompt_on_stderr(device_auth: &DeviceAuthorization) {
    let display_uri = &device_auth.verification_uri_complete;
    eprintln!();
    eprintln!("To sign in, open this URL in your browser:");
    eprintln!();
    eprintln!("  {display_uri}");
    eprintln!();
    if !open_browser_detached(display_uri).await {
        eprintln!("  (Could not open browser automatically — open the URL above manually.)");
        eprintln!();
    }
    // Show the code so the user can confirm it matches the browser
    // (anti-phishing): the complete URL pre-fills it.
    eprintln!("Confirm this code in your browser:");
    eprintln!();
    eprintln!("  {}", device_auth.user_code);
    eprintln!();
    eprintln!(
        "\x1b[90mOnly continue with a code you requested. \
         Don't share it with anyone.\x1b[0m"
    );
    eprintln!();
    eprintln!("Waiting for authorization...");
}

/// Poll the token endpoint until the user approves, the device code expires
/// (→ [`PollLoopOutcome::Restart`]), or the wire fails.
async fn complete_device_code_login(
    backend: &DeviceFlowBackend<'_>,
    device_auth: &DeviceAuthorization,
) -> anyhow::Result<PollLoopOutcome> {
    let mut poll_interval = std::time::Duration::from_secs(device_auth.interval.max(1) as u64);
    loop {
        // Sleep first: an immediate poll on a fresh code only returns
        // authorization_pending (and risks slow_down).
        tokio::time::sleep(poll_interval).await;
        match backend.poll(&device_auth.device_code).await? {
            DevicePollResult::Success(auth) => {
                tracing::info!("auth: device login authorized");
                return Ok(PollLoopOutcome::Done(auth));
            }
            DevicePollResult::Expired => return Ok(PollLoopOutcome::Restart),
            DevicePollResult::Pending { error, description } => {
                if error == "slow_down" {
                    poll_interval += std::time::Duration::from_secs(SLOW_DOWN_INCREMENT_SECS);
                    tracing::info!(
                        new_interval_secs = poll_interval.as_secs(),
                        "auth: server asked to slow down device polling"
                    );
                } else {
                    tracing::debug!(
                        error = %error,
                        description = ?description,
                        "auth: device authorization pending"
                    );
                }
            }
        }
    }
}

/// Open `url` in the browser off-thread: `webbrowser::open` is synchronous and
/// would stall the single-threaded TUI loop. Returns `true` on success so the
/// caller can decide how to notify the user (eprintln on CLI, nothing on TUI
/// where the URL is already rendered in the widget). Shared with the PKCE flow.
pub(super) async fn open_browser_detached(url: &str) -> bool {
    // Unit tests drive the full login flow against mock servers — their
    // fixture URLs must never reach a real browser.
    if cfg!(test) {
        return false;
    }
    let url = url.to_owned();
    match tokio::task::spawn_blocking(move || webbrowser::open(&url)).await {
        Ok(Ok(())) => true,
        Ok(Err(e)) => {
            tracing::info!(error = %e, "device auth: could not open browser automatically");
            false
        }
        Err(e) => {
            tracing::info!(error = %e, "device auth: browser-open task failed");
            false
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::auth::KimiCodeConfig;
    use wiremock::matchers::{body_string_contains, method, path};
    use wiremock::{Mock, MockServer, ResponseTemplate};

    /// Fixture mirroring the live `device_authorization` payload (verified
    /// against auth.kimi.com): verification URLs are passed through verbatim
    /// by the login flow, so they use the real shape.
    fn device_auth_json(code: &str) -> serde_json::Value {
        serde_json::json!({
            "user_code": "WXYZ-6789",
            "device_code": code,
            "verification_uri": "https://www.kimi.com/code/authorize_device",
            "verification_uri_complete": "https://www.kimi.com/code/authorize_device?user_code=WXYZ-6789",
            "expires_in": 1800,
            "interval": 0, // floored to 1s by the poll loop
        })
    }

    fn token_json(access: &str) -> serde_json::Value {
        serde_json::json!({
            "access_token": access,
            "refresh_token": "rt-1",
            "expires_in": 3600,
            "scope": "kimi-code",
            "token_type": "bearer",
        })
    }

    fn auth_manager(dir: &tempfile::TempDir) -> Arc<AuthManager> {
        Arc::new(AuthManager::new(dir.path(), KimiCodeConfig::default()))
    }

    /// End-to-end (mock server): authorization → pending → token, persisting
    /// via the AuthManager.
    #[tokio::test]
    async fn device_login_persists_token_after_pending() {
        let server = MockServer::start().await;
        Mock::given(method("POST"))
            .and(path("/api/oauth/device_authorization"))
            .respond_with(ResponseTemplate::new(200).set_body_json(device_auth_json("dev-1")))
            .expect(1)
            .mount(&server)
            .await;
        Mock::given(method("POST"))
            .and(path("/api/oauth/token"))
            .respond_with(
                ResponseTemplate::new(400)
                    .set_body_json(serde_json::json!({ "error": "authorization_pending" })),
            )
            .up_to_n_times(1)
            .mount(&server)
            .await;
        Mock::given(method("POST"))
            .and(path("/api/oauth/token"))
            .and(body_string_contains("device_code=dev-1"))
            .respond_with(ResponseTemplate::new(200).set_body_json(token_json("at-done")))
            .mount(&server)
            .await;

        let dir = tempfile::tempdir().unwrap();
        let mgr = auth_manager(&dir);
        let mut channels = None;
        let (auth, is_new) = run_device_code_login_channels(&server.uri(), &mgr, &mut channels)
            .await
            .unwrap();
        assert!(is_new);
        assert_eq!(auth.key, "at-done");
        assert_eq!(
            mgr.current_or_expired().map(|a| a.key),
            Some("at-done".into()),
            "login must land in the manager cache"
        );
        assert!(
            dir.path().join("auth.json").exists(),
            "login must persist to the fallback file store"
        );
    }

    /// `expired_token` during polling restarts the whole device
    /// authorization (fresh device code), then completes.
    #[tokio::test]
    async fn expired_token_restarts_device_authorization() {
        let server = MockServer::start().await;
        // First authorization issues dev-1; second issues dev-2.
        Mock::given(method("POST"))
            .and(path("/api/oauth/device_authorization"))
            .respond_with(ResponseTemplate::new(200).set_body_json(device_auth_json("dev-1")))
            .up_to_n_times(1)
            .expect(1)
            .mount(&server)
            .await;
        Mock::given(method("POST"))
            .and(path("/api/oauth/device_authorization"))
            .respond_with(ResponseTemplate::new(200).set_body_json(device_auth_json("dev-2")))
            .expect(1)
            .mount(&server)
            .await;
        // dev-1 polls expire; dev-2 polls succeed.
        Mock::given(method("POST"))
            .and(path("/api/oauth/token"))
            .and(body_string_contains("device_code=dev-1"))
            .respond_with(
                ResponseTemplate::new(400)
                    .set_body_json(serde_json::json!({ "error": "expired_token" })),
            )
            .expect(1)
            .mount(&server)
            .await;
        Mock::given(method("POST"))
            .and(path("/api/oauth/token"))
            .and(body_string_contains("device_code=dev-2"))
            .respond_with(ResponseTemplate::new(200).set_body_json(token_json("at-restarted")))
            .expect(1)
            .mount(&server)
            .await;

        let dir = tempfile::tempdir().unwrap();
        let mgr = auth_manager(&dir);
        let mut channels = None;
        let (auth, _) = run_device_code_login_channels(&server.uri(), &mgr, &mut channels)
            .await
            .unwrap();
        assert_eq!(auth.key, "at-restarted");
    }

    /// `slow_down` is wait-and-continue (interval bumped), never fatal.
    /// Unknown-error continuation is covered at the wire level by
    /// `kimi_oauth::tests::poll_maps_pending_and_unknown_errors_to_pending`.
    #[tokio::test]
    async fn slow_down_keeps_polling_then_succeeds() {
        let server = MockServer::start().await;
        Mock::given(method("POST"))
            .and(path("/api/oauth/device_authorization"))
            .respond_with(ResponseTemplate::new(200).set_body_json(device_auth_json("dev-1")))
            .mount(&server)
            .await;
        Mock::given(method("POST"))
            .and(path("/api/oauth/token"))
            .respond_with(
                ResponseTemplate::new(400)
                    .set_body_json(serde_json::json!({ "error": "slow_down" })),
            )
            .up_to_n_times(1)
            .mount(&server)
            .await;
        Mock::given(method("POST"))
            .and(path("/api/oauth/token"))
            .respond_with(ResponseTemplate::new(200).set_body_json(token_json("at-patient")))
            .expect(1)
            .mount(&server)
            .await;

        let dir = tempfile::tempdir().unwrap();
        let mgr = auth_manager(&dir);
        let mut channels = None;
        let started = std::time::Instant::now();
        let (auth, _) = run_device_code_login_channels(&server.uri(), &mgr, &mut channels)
            .await
            .unwrap();
        assert_eq!(auth.key, "at-patient");
        assert!(
            started.elapsed() >= std::time::Duration::from_secs(6),
            "slow_down must bump the poll interval by {SLOW_DOWN_INCREMENT_SECS}s"
        );
    }

    /// GitHub Copilot two-stage login e2e (mock wire): device authorization →
    /// poll (pending → github token) → Stage-2 copilot-token exchange (Bearer
    /// github token + editor headers → copilot token + expiry). The persisted
    /// credential keys the COPILOT token, keeps the GITHUB token as
    /// `refresh_token`, and carries the copilot expiry.
    #[tokio::test]
    async fn github_copilot_two_stage_login_persists_copilot_and_github() {
        let server = MockServer::start().await;
        let host: &'static str = Box::leak(server.uri().into_boxed_str());
        let cfg = OAuthConfig {
            auth_host: host,
            token_host: host,
            copilot_exchange: Some((host, "/copilot_internal/v2/token")),
            ..kigi_models::COPILOT_OAUTH_CONFIG
        };
        // Stage 1a: device authorization (github.com/login/device/code).
        Mock::given(method("POST"))
            .and(path("/login/device/code"))
            .and(body_string_contains("client_id=Iv1.b507a08c87ecfe98"))
            .and(body_string_contains("scope=read"))
            .respond_with(ResponseTemplate::new(200).set_body_json(serde_json::json!({
                "device_code": "gh-dev-1",
                "user_code": "WDJB-MJHT",
                "verification_uri": "https://github.com/login/device",
                "expires_in": 900,
                "interval": 0,
            })))
            .mount(&server)
            .await;
        // Stage 1b: token poll — GitHub returns errors AND success in a 200 body.
        Mock::given(method("POST"))
            .and(path("/login/oauth/access_token"))
            .respond_with(
                ResponseTemplate::new(200)
                    .set_body_json(serde_json::json!({ "error": "authorization_pending" })),
            )
            .up_to_n_times(1)
            .mount(&server)
            .await;
        Mock::given(method("POST"))
            .and(path("/login/oauth/access_token"))
            .and(body_string_contains("device_code=gh-dev-1"))
            .respond_with(
                ResponseTemplate::new(200)
                    .set_body_json(serde_json::json!({ "access_token": "gho_github_tok" })),
            )
            .mount(&server)
            .await;
        // Stage 2: copilot-token exchange (Bearer github token + editor headers).
        let future = (chrono::Utc::now() + chrono::Duration::minutes(30)).timestamp();
        Mock::given(method("GET"))
            .and(path("/copilot_internal/v2/token"))
            .and(wiremock::matchers::header(
                "Authorization",
                "Bearer gho_github_tok",
            ))
            .and(wiremock::matchers::header(
                "Editor-Plugin-Version",
                "copilot-chat/0.35.0",
            ))
            .respond_with(ResponseTemplate::new(200).set_body_json(
                serde_json::json!({ "token": "copilot-session-tok", "expires_at": future }),
            ))
            .expect(1)
            .mount(&server)
            .await;

        let dir = tempfile::tempdir().unwrap();
        let mgr = auth_manager(&dir);
        let mut channels = None;
        let (auth, is_new) = run_device_code_login_github_copilot(&cfg, &mgr, &mut channels)
            .await
            .unwrap();
        assert!(is_new);
        assert_eq!(
            auth.key, "copilot-session-tok",
            "key = copilot session token"
        );
        assert_eq!(
            auth.refresh_token.as_deref(),
            Some("gho_github_tok"),
            "the durable github token is persisted as refresh_token"
        );
        assert!(
            auth.expires_at.is_some_and(|e| e > chrono::Utc::now()),
            "the copilot expiry must be persisted"
        );
        assert_eq!(
            mgr.current_or_expired().map(|a| a.key),
            Some("copilot-session-tok".into()),
            "login must land the copilot token in the manager cache"
        );
    }

    /// A 5xx from the token endpoint is a hard error (kimi-cli parity).
    #[tokio::test]
    async fn server_error_during_poll_fails_login() {
        let server = MockServer::start().await;
        Mock::given(method("POST"))
            .and(path("/api/oauth/device_authorization"))
            .respond_with(ResponseTemplate::new(200).set_body_json(device_auth_json("dev-1")))
            .mount(&server)
            .await;
        Mock::given(method("POST"))
            .and(path("/api/oauth/token"))
            .respond_with(ResponseTemplate::new(500))
            .mount(&server)
            .await;

        let dir = tempfile::tempdir().unwrap();
        let mgr = auth_manager(&dir);
        let mut channels = None;
        let err = run_device_code_login_channels(&server.uri(), &mgr, &mut channels)
            .await
            .unwrap_err();
        assert!(err.to_string().contains("server error"), "{err}");
        assert!(
            mgr.current_or_expired().is_none(),
            "failed login must not persist credentials"
        );
    }
}