qcs-api-client-common 0.21.1

//!
//! By default, all settings are loaded from files located under your home directory in the
//! `.qcs` folder. Within that folder:
//!
//! * `settings.toml` will be used to load general settings (e.g. which URLs to connect to).
//! * `secrets.toml` will be used to load tokens for authentication.
//!
//! Both files should contain profiles. Your settings should contain a `default_profile_name`
//! that determines which profile is loaded when no other profile is explicitly provided.
//!
//! If you don't have either of these files, see [the QCS credentials guide](https://docs.rigetti.com/qcs/guides/qcs-credentials) for details on how to obtain them.
//!
//! You can use environment variables to override values in your configuration:
//!
//! * [`SETTINGS_PATH_VAR`]: Set the path of the `settings.toml` file to load.
//! * [`SECRETS_PATH_VAR`]: Set the path of the `secrets.toml` file to load.
//! * [`SECRETS_READ_ONLY_VAR`]: Flag indicating whether to treat the `secrets.toml` file as read-only. Disabled by default.
//!     * Access token updates will _not_ be persisted to the secrets file, regardless of file permissions, for any of the following values (case insensitive): "true", "yes", "1".
//!     * Access token updates will be persisted to the secrets file if it is writeable for any other value or if unset.
//! * [`PROFILE_NAME_VAR`]: Override the profile that is loaded by default
//! * [`QUILC_URL_VAR`]: Override the URL used for requests to the quilc server.
//! * [`QVM_URL_VAR`]: Override the URL used for requests to the QVM server.
//! * [`API_URL_VAR`]: Override the URL used for requests to the QCS REST API server.
//! * [`GRPC_API_URL_VAR`]: Override the URL used for requests to the QCS gRPC API.
//!
//! Note that an externally-managed credential cannot be directly
//! configured by environmental variables - see [`ExternallyManagedCredential`][secrets::ExternallyManagedCredential].
//!
//! # Credentials
//!
//! A credential in `secrets.toml` works in three ways, by:
//!
//! 1. Storing tokens from a PKCE flow directly
//!
//! ```toml
//! [credentials.default.token_payload]
//! access_token = "..."
//! refresh_token = "..."
//! ```
//!
//! 2. Delegating completely to an external program which is expected to yield valid tokens
//!    NOTE: Please read the security notes in [`ExternallyManagedCredential`][secrets::ExternallyManagedCredential].
//!
//! ```toml
//! [credentials.coder.externally_managed]
//! command = "/usr/bin/coder"
//! args = ["external-auth", "access-token", "qcs"]
//! ```
//!
//! 3. Using an OAuth client ID + secret to exchange for access tokens, for service-to-service auth
//!
//! ```toml
//! [credentials.service.client_credentials]
//! client_id = "0oa..."
//! client_secret = "..."
//! ```
//!
//! The [`ClientConfiguration`] exposes an API for loading and accessing your
//! configuration.

use crate::configuration::{secrets::SecretAccessToken, tokens::insecure_validate_token_exp};
#[cfg(feature = "tracing-config")]
use crate::tracing_configuration::TracingConfiguration;
use derive_builder::Builder;
use std::{env, path::PathBuf};
use tokio_util::sync::CancellationToken;

#[cfg(feature = "stubs")]
use rigetti_pyo3::pyo3_stub_gen::derive::gen_stub_pyclass;

use self::{
    secrets::{Credential, Secrets, TokenPayload},
    settings::Settings,
};

pub(crate) mod error;
mod external_command;
pub mod fs;
mod login;
pub mod oidc;
mod pkce;
mod secret_string;
pub mod secrets;
pub mod settings;
pub mod tokens;

pub use error::{DiscoveryError, LoadError, TokenError};
pub use tokens::default_http_client;
#[cfg(feature = "python")]
pub(crate) mod py;

use pkce::RedirectBinding;
use settings::AuthServer;
use tokens::{
    AuthTokens, OAuthGrant, OAuthSession, RefreshToken, TokenDispatcher, persist_oauth_session,
};

/// Default profile name.
pub const DEFAULT_PROFILE_NAME: &str = "default";
/// Setting this environment variable will change which profile is used from the loaded config files
pub const PROFILE_NAME_VAR: &str = "QCS_PROFILE_NAME";
fn env_or_default_profile_name() -> String {
    env::var(PROFILE_NAME_VAR).unwrap_or_else(|_| DEFAULT_PROFILE_NAME.to_string())
}

/// Default URL to access the QCS API.
pub const DEFAULT_API_URL: &str = "https://api.qcs.rigetti.com";
/// Setting this environment variable will override the URL used to connect to the QCS REST API.
pub const API_URL_VAR: &str = "QCS_SETTINGS_APPLICATIONS_API_URL";
fn env_or_default_api_url() -> String {
    env::var(API_URL_VAR).unwrap_or_else(|_| DEFAULT_API_URL.to_string())
}

/// Default URL to access the gRPC API.
pub const DEFAULT_GRPC_API_URL: &str = "https://grpc.qcs.rigetti.com";
/// Setting this environment variable will override the URL used to connect to the GRPC server.
pub const GRPC_API_URL_VAR: &str = "QCS_SETTINGS_APPLICATIONS_GRPC_URL";
fn env_or_default_grpc_url() -> String {
    env::var(GRPC_API_URL_VAR).unwrap_or_else(|_| DEFAULT_GRPC_API_URL.to_string())
}

/// Default URL to access QVM.
pub const DEFAULT_QVM_URL: &str = "http://127.0.0.1:5000";
/// Setting this environment variable will override the URL used to access the QVM.
pub const QVM_URL_VAR: &str = "QCS_SETTINGS_APPLICATIONS_QVM_URL";
fn env_or_default_qvm_url() -> String {
    env::var(QVM_URL_VAR).unwrap_or_else(|_| DEFAULT_QVM_URL.to_string())
}

/// Default URL to access `quilc`.
pub const DEFAULT_QUILC_URL: &str = "tcp://127.0.0.1:5555";
/// Setting this environment variable will override the URL used to access quilc.
pub const QUILC_URL_VAR: &str = "QCS_SETTINGS_APPLICATIONS_QUILC_URL";
fn env_or_default_quilc_url() -> String {
    env::var(QUILC_URL_VAR).unwrap_or_else(|_| DEFAULT_QUILC_URL.to_string())
}

/// A configuration suitable for use as a QCS API Client.
///
/// This configuration can be constructed in a few ways.
///
/// The most common way is to use [`ClientConfiguration::load_default`]. This will load the
/// configuration associated with your default QCS profile.
///
/// When loading your config, any values set by environment variables will override the values in
/// your configuration files.
///
/// You can also build a configuration from scratch using [`ClientConfigurationBuilder`]. Using a
/// builder bypasses configuration files and environment overrides.
#[derive(Clone, Debug, Builder)]
#[cfg_attr(
    not(feature = "stubs"),
    builder_struct_attr(optipy::strip_pyo3(only_stubs)),
    optipy::strip_pyo3(only_stubs)
)]
#[cfg_attr(
    not(feature = "python"),
    builder_struct_attr(optipy::strip_pyo3),
    optipy::strip_pyo3
)]
#[cfg_attr(
    feature = "stubs",
    builder_struct_attr(gen_stub_pyclass),
    gen_stub_pyclass
)]
#[cfg_attr(
    feature = "python",
    builder_struct_attr(pyo3::pyclass(
        module = "qcs_api_client_common._qcs_api_client_common.configuration",
        from_py_object
    )),
    pyo3::pyclass(
        module = "qcs_api_client_common._qcs_api_client_common.configuration",
        frozen,
        from_py_object
    )
)]
pub struct ClientConfiguration {
    #[builder(private, default = "env_or_default_profile_name()")]
    #[builder_field_attr(gen_stub(skip))]
    profile: String,

    /// The key under `[credentials]` in `secrets.toml` that this profile's tokens are stored
    /// under. This is *not* necessarily the profile name: a profile declares its own
    /// `credentials_name`, and several profiles may share one credential entry. Tokens must be
    /// persisted under this name, otherwise a refresh writes to an entry nobody reads and the
    /// stale credential is retried forever.
    #[builder(private, default = "env_or_default_profile_name()")]
    #[builder_field_attr(gen_stub(skip))]
    credentials_name: String,

    #[doc = "The URL for the QCS REST API."]
    #[builder(default = "env_or_default_api_url()")]
    #[builder_field_attr(pyo3(get, set))]
    #[pyo3(get)]
    api_url: String,

    #[doc = "The URL for the QCS gRPC API."]
    #[builder(default = "env_or_default_grpc_url()")]
    #[builder_field_attr(pyo3(get, set))]
    #[pyo3(get)]
    grpc_api_url: String,

    #[doc = "The URL of the quilc server."]
    #[builder(default = "env_or_default_quilc_url()")]
    #[builder_field_attr(pyo3(get, set))]
    #[pyo3(get)]
    quilc_url: String,

    #[doc = "The URL of the QVM server."]
    #[builder(default = "env_or_default_qvm_url()")]
    #[builder_field_attr(pyo3(get, set))]
    #[pyo3(get)]
    qvm_url: String,

    /// Provides a single, semi-shared access to user credential tokens.
    ///
    /// Note that the tokens are *not* shared when the `ClientConfiguration` is created multiple
    /// times, e.g. through [`ClientConfiguration::load_default`].
    #[builder(default, setter(custom))]
    #[builder_field_attr(pyo3(get))]
    pub(crate) oauth_session: Option<TokenDispatcher>,

    #[builder(private, default = "ConfigSource::Builder")]
    #[builder_field_attr(gen_stub(skip))]
    source: ConfigSource,

    /// Configuration for tracing of network API calls. If `None`, tracing is disabled.
    #[cfg(feature = "tracing-config")]
    #[builder(default)]
    #[builder_field_attr(gen_stub(skip))]
    tracing_configuration: Option<TracingConfiguration>,
}

impl ClientConfigurationBuilder {
    /// The [`OAuthSession`] to use to authenticate with the QCS API.
    ///
    /// When set to [`None`], the configuration will not manage an OAuth Session, and access to the
    /// QCS API will be limited to unauthenticated routes.
    pub fn oauth_session(&mut self, oauth_session: Option<OAuthSession>) -> &mut Self {
        self.oauth_session = Some(oauth_session.map(Into::into));
        self
    }
}

/// The common context used to build a [`ClientConfiguration`].
struct ConfigurationContext {
    builder: ClientConfigurationBuilder,
    auth_server: AuthServer,
    credential: Option<Credential>,
    /// The [`ConfigSource`] the [`ClientConfigurationBuilder`] was configured with.
    ///
    /// Kept alongside the builder (rather than read back off of it) so that callers can persist
    /// freshly acquired tokens via [`tokens::persist_oauth_session`] before the final
    /// [`ClientConfiguration`] is built.
    source: ConfigSource,
    /// The credentials name the [`ClientConfigurationBuilder`] was configured with, i.e. the key
    /// the profile's tokens live under in `secrets.toml`. See [`Self::source`].
    credentials_name: String,
}

impl ConfigurationContext {
    fn from_profile(profile_name: Option<String>) -> Result<Self, LoadError> {
        #[cfg(feature = "tracing-config")]
        match profile_name.as_ref() {
            None => tracing::debug!("loading default QCS profile"),
            Some(profile) => {
                tracing::debug!("loading QCS profile {profile}")
            }
        }
        let settings = Settings::load()?;
        let secrets = Secrets::load()?;
        Self::from_sources(settings, secrets, profile_name)
    }

    fn from_sources(
        settings: Settings,
        mut secrets: Secrets,
        profile_name: Option<String>,
    ) -> Result<Self, LoadError> {
        let Settings {
            default_profile_name,
            mut profiles,
            mut auth_servers,
            file_path: settings_path,
        } = settings;
        let profile_name = profile_name
            .or_else(|| env::var(PROFILE_NAME_VAR).ok())
            .unwrap_or(default_profile_name);
        let profile = profiles
            .remove(&profile_name)
            .ok_or(LoadError::ProfileNotFound(profile_name.clone()))?;
        let auth_server = auth_servers
            .remove(&profile.auth_server_name)
            .ok_or_else(|| LoadError::AuthServerNotFound(profile.auth_server_name.clone()))?;

        let secrets_path = secrets.file_path;
        let credentials_name = profile.credentials_name;
        let credential = secrets.credentials.remove(&credentials_name);

        let api_url = env::var(API_URL_VAR)
            .unwrap_or(profile.api_url)
            .trim_end_matches('/')
            .to_string();
        let quilc_url = env::var(QUILC_URL_VAR).unwrap_or(profile.applications.pyquil.quilc_url);
        let qvm_url = env::var(QVM_URL_VAR).unwrap_or(profile.applications.pyquil.qvm_url);
        let grpc_api_url = env::var(GRPC_API_URL_VAR)
            .unwrap_or(profile.grpc_api_url)
            .trim_end_matches('/')
            .to_string();

        #[cfg(feature = "tracing-config")]
        let tracing_configuration =
            TracingConfiguration::from_env().map_err(LoadError::TracingFilterParseError)?;

        let source = match (settings_path, secrets_path) {
            (Some(settings_path), Some(secrets_path)) => ConfigSource::File {
                settings_path,
                secrets_path,
            },
            _ => ConfigSource::Default,
        };

        let mut builder = ClientConfiguration::builder();
        builder
            .profile(profile_name)
            .credentials_name(credentials_name.clone())
            .source(source.clone())
            .api_url(api_url)
            .quilc_url(quilc_url)
            .qvm_url(qvm_url)
            .grpc_api_url(grpc_api_url);

        #[cfg(feature = "tracing-config")]
        {
            builder.tracing_configuration(tracing_configuration);
        }

        Ok(Self {
            builder,
            auth_server,
            credential,
            source,
            credentials_name,
        })
    }
}

/// Persists `oauth_session` via [`persist_oauth_session`], logging a warning on failure instead of
/// returning an error. A session that was just successfully refreshed or logged in is still valid
/// and usable even if it can't be persisted, so a persistence failure shouldn't prevent returning
/// it to the caller (mirroring how [`TokenError::Write`] is handled elsewhere).
async fn persist_or_warn(
    oauth_session: &OAuthSession,
    source: &ConfigSource,
    credentials_name: &str,
) {
    if let Err(_error) = persist_oauth_session(oauth_session, source, credentials_name).await {
        #[cfg(feature = "tracing")]
        tracing::warn!(
            "Refreshed QCS credentials but failed to persist them to the secrets file: {_error}"
        );
    }
}

fn credential_to_oauth_session(
    credential: Option<Credential>,
    auth_server: AuthServer,
) -> Option<OAuthSession> {
    match credential? {
        Credential::TokenPayload(token_payload) => {
            let TokenPayload {
                access_token,
                refresh_token,
                ..
            } = token_payload;

            Some(OAuthSession::new(
                OAuthGrant::RefreshToken(RefreshToken::new(refresh_token.unwrap_or_default())),
                auth_server,
                access_token,
            ))
        }
        Credential::ExternallyManaged(externally_managed) => Some(OAuthSession::new(
            OAuthGrant::ExternallyManaged(externally_managed.into()),
            auth_server,
            None,
        )),
        Credential::ClientCredentials(client_credentials) => {
            let grant = OAuthGrant::ClientCredentials(client_credentials);
            Some(OAuthSession::new(grant, auth_server, None))
        }
    }
}

impl ClientConfiguration {
    #[cfg(test)]
    fn new(
        settings: Settings,
        secrets: Secrets,
        profile_name: Option<String>,
    ) -> Result<Self, LoadError> {
        let ConfigurationContext {
            mut builder,
            auth_server,
            credential,
            ..
        } = ConfigurationContext::from_sources(settings, secrets, profile_name)?;
        let oauth_session = credential_to_oauth_session(credential, auth_server);
        Ok(builder.oauth_session(oauth_session).build()?)
    }

    /// Attempts to load config files
    ///
    /// # Errors
    ///
    /// See [`LoadError`]
    pub fn load_default() -> Result<Self, LoadError> {
        let base_config = Self::load(None)?;
        Ok(base_config)
    }

    /// Attempts to load a QCS configuration and creates a [`ClientConfiguration`] using the
    /// specified profile.
    ///
    /// # Errors
    ///
    /// See [`LoadError`]
    pub fn load_profile(profile_name: String) -> Result<Self, LoadError> {
        Self::load(Some(profile_name))
    }

    /// Attempts to load a QCS configuration and creates a [`ClientConfiguration`] using the
    /// specified profile. If no `profile_name` is provided, then a default configuration is
    /// loaded. When stored OAuth credentials are unavailable, this method falls back to an
    /// interactive PKCE login flow.
    ///
    /// # Errors
    ///
    /// See [`LoadError`]
    pub async fn load_with_login(
        cancel_token: CancellationToken,
        profile_name: Option<String>,
    ) -> Result<Self, LoadError> {
        Self::load_with_login_with_redirect(cancel_token, profile_name, RedirectBinding::default())
            .await
    }

    /// See [`Self::load_with_login`].
    pub(crate) async fn load_with_login_with_redirect(
        cancel_token: CancellationToken,
        profile_name: Option<String>,
        redirect: RedirectBinding,
    ) -> Result<Self, LoadError> {
        let ConfigurationContext {
            mut builder,
            auth_server,
            credential,
            source,
            credentials_name,
        } = ConfigurationContext::from_profile(profile_name)?;

        match credential {
            // There's no possible logging in here, we expect the credentials to be valid.
            credential @ Some(
                Credential::ExternallyManaged(_) | Credential::ClientCredentials(_),
            ) => {
                let oauth_session = credential_to_oauth_session(credential, auth_server);
                return Ok(builder.oauth_session(oauth_session).build()?);
            }
            Some(Credential::TokenPayload(TokenPayload {
                access_token,
                refresh_token,
                ..
            })) => {
                if let Some(access_token) = access_token
                    && insecure_validate_token_exp(&access_token).is_ok()
                {
                    let refresh_token = refresh_token.clone().unwrap_or_default();
                    let oauth_session = OAuthSession::new(
                        OAuthGrant::RefreshToken(RefreshToken::new(refresh_token)),
                        auth_server,
                        Some(access_token),
                    );
                    return Ok(builder.oauth_session(Some(oauth_session)).build()?);
                }

                // The access token is invalid, try to refresh it
                if let Some(refresh_token) = refresh_token
                    && !refresh_token.is_empty()
                {
                    let mut refresh_token = RefreshToken::new(refresh_token);

                    // If the refresh token is valid, use it
                    if let Ok(access_token) = refresh_token.request_access_token(&auth_server).await
                    {
                        let oauth_session = OAuthSession::new(
                            OAuthGrant::RefreshToken(refresh_token),
                            auth_server,
                            Some(access_token),
                        );

                        // Requesting a new access token may have rotated the refresh token.
                        persist_or_warn(&oauth_session, &source, &credentials_name).await;

                        return Ok(builder.oauth_session(Some(oauth_session)).build()?);
                    }
                }

                #[cfg(feature = "tracing")]
                tracing::debug!("Stored credentials are invalid, falling back to login flow");
            }
            None => {
                #[cfg(feature = "tracing")]
                tracing::debug!("No stored credentials found, falling back to login flow",);
            }
        }

        // At this point the stored credentials are known to be invalid, so a login is required
        let login_tokens =
            AuthTokens::interactive_login_with_redirect(cancel_token, &auth_server, redirect)
                .await?;
        let access_token = login_tokens.access_token.clone();
        let oauth_session =
            OAuthSession::from_interactive_login(login_tokens, auth_server, Some(access_token));

        // Persist eagerly: without this, the freshly logged-in tokens are only saved once
        // something later triggers a dispatcher-managed refresh (e.g. the access token expiring
        // during a later call). If this process exits before that happens, the login is lost and
        // the next process is forced through the login flow again.
        persist_or_warn(&oauth_session, &source, &credentials_name).await;

        Ok(builder.oauth_session(Some(oauth_session)).build()?)
    }

    /// Attempts to load a QCS configuration and creates a [`ClientConfiguration`] using the
    /// specified profile. If no `profile_name` is provided, then a default configuration is
    /// loaded.
    ///
    /// # Errors
    ///
    /// See [`LoadError`]
    fn load(profile_name: Option<String>) -> Result<Self, LoadError> {
        let ConfigurationContext {
            mut builder,
            auth_server,
            credential,
            ..
        } = ConfigurationContext::from_profile(profile_name)?;
        let oauth_session = credential_to_oauth_session(credential, auth_server);
        Ok(builder.oauth_session(oauth_session).build()?)
    }

    /// Get a [`ClientConfigurationBuilder`]
    #[must_use]
    pub fn builder() -> ClientConfigurationBuilder {
        ClientConfigurationBuilder::default()
    }

    /// Get the name of the profile that was loaded, if any.
    #[must_use]
    pub fn profile(&self) -> &str {
        &self.profile
    }

    /// Get the name of the credential the loaded profile uses, i.e. the key its tokens are stored
    /// under in `secrets.toml`. This may differ from [`Self::profile`].
    #[must_use]
    pub fn credentials_name(&self) -> &str {
        &self.credentials_name
    }

    /// Get the URL of the QCS REST API.
    #[must_use]
    pub fn api_url(&self) -> &str {
        &self.api_url
    }

    /// Get the URL of the QCS gRPC API.
    #[must_use]
    pub fn grpc_api_url(&self) -> &str {
        &self.grpc_api_url
    }

    /// Get the URL of the quilc server.
    #[must_use]
    pub fn quilc_url(&self) -> &str {
        &self.quilc_url
    }

    /// Get the URL of the QVM server.
    #[must_use]
    pub fn qvm_url(&self) -> &str {
        &self.qvm_url
    }

    /// Get the [`TracingConfiguration`].
    #[cfg(feature = "tracing-config")]
    #[must_use]
    pub const fn tracing_configuration(&self) -> Option<&TracingConfiguration> {
        self.tracing_configuration.as_ref()
    }

    /// Get the source of the configuration.
    #[must_use]
    pub const fn source(&self) -> &ConfigSource {
        &self.source
    }

    /// Get a copy of the current [`OAuthSession`].
    ///
    /// Note: This is a _copy_, the contained tokens will become stale once they expire.
    ///
    /// # Errors
    ///
    /// See [`TokenError`]
    pub async fn oauth_session(&self) -> Result<OAuthSession, TokenError> {
        Ok(self
            .oauth_session
            .as_ref()
            .ok_or(TokenError::NoRefreshToken)?
            .tokens()
            .await)
    }

    /// Gets the `Bearer` access token, refreshing it if it is expired.
    ///
    /// # Errors
    ///
    /// See [`TokenError`].
    pub async fn get_bearer_access_token(&self) -> Result<SecretAccessToken, TokenError> {
        let dispatcher = self
            .oauth_session
            .as_ref()
            .ok_or_else(|| TokenError::NoCredentials)?;
        match dispatcher.validate().await {
            Ok(tokens) => Ok(tokens),
            #[allow(unused_variables)]
            Err(e) => {
                #[cfg(feature = "tracing-config")]
                tracing::debug!("Refreshing access token because current one is invalid: {e}");
                dispatcher
                    .refresh(self.source(), self.credentials_name())
                    .await
                    .map(|e| e.access_token().cloned())?
            }
        }
    }

    /// Refreshes the [`Tokens`] in use and returns the new bearer access token.
    ///
    /// # Errors
    ///
    /// See [`TokenError`]
    pub async fn refresh(&self) -> Result<OAuthSession, TokenError> {
        self.oauth_session
            .as_ref()
            .ok_or(TokenError::NoRefreshToken)?
            .refresh(self.source(), self.credentials_name())
            .await
    }
}

/// Describes how a [`ClientConfiguration`] was initialized.
#[derive(Clone, Debug)]
pub enum ConfigSource {
    /// A [`ClientConfiguration`] derived from a [`ClientConfigurationBuilder`]
    Builder,
    /// A [`ClientConfiguration`] derived from at least one file.
    File {
        /// The path to the QCS `settings.toml` file used to initialize the [`ClientConfiguration`].
        settings_path: PathBuf,
        /// The path to a QCS `secrets.toml` file used to initialize the [`ClientConfiguration`].
        secrets_path: PathBuf,
    },
    /// A [`ClientConfiguration`] derived from default values.
    Default,
}

fn expand_path_from_env_or_default(
    env_var_name: &str,
    default: &str,
) -> Result<PathBuf, LoadError> {
    match env::var(env_var_name) {
        Ok(path) => {
            let expanded_path = shellexpand::env(&path).map_err(LoadError::from)?;
            let path_buf: PathBuf = expanded_path.as_ref().into();
            if !path_buf.exists() {
                return Err(LoadError::Path {
                    path: path_buf,
                    message: format!("The given path does not exist: {path}"),
                });
            }
            Ok(path_buf)
        }
        Err(env::VarError::NotPresent) => {
            let expanded_path = shellexpand::tilde_with_context(default, || {
                env::home_dir().map(|path| path.display().to_string())
            });
            let path_buf: PathBuf = expanded_path.as_ref().into();
            if !path_buf.exists() {
                return Err(LoadError::Path {
                    path: path_buf,
                    message: format!(
                        "Could not find a QCS configuration at the default path: {default}"
                    ),
                });
            }
            Ok(path_buf)
        }
        Err(other_error) => Err(LoadError::EnvVar {
            variable_name: env_var_name.to_string(),
            message: other_error.to_string(),
        }),
    }
}

#[cfg(test)]
mod test {
    #![allow(clippy::result_large_err, reason = "happens in figment tests")]

    use httpmock::prelude::*;
    use jsonwebtoken::{EncodingKey, Header, encode};
    use serde::Serialize;
    use time::{Duration, OffsetDateTime};
    use tokio_util::sync::CancellationToken;

    use crate::configuration::{
        API_URL_VAR, AuthServer, ClientConfiguration, DEFAULT_QUILC_URL, GRPC_API_URL_VAR,
        OAuthGrant, OAuthSession, QUILC_URL_VAR, QVM_URL_VAR, RefreshToken,
        expand_path_from_env_or_default, oidc,
        pkce::{RedirectBinding, tests::PkceTestServerHarness},
        secrets::{
            Credential, SECRETS_PATH_VAR, SECRETS_READ_ONLY_VAR, SecretAccessToken,
            SecretRefreshToken, Secrets, TokenPayload,
        },
        settings::{SETTINGS_PATH_VAR, Settings},
        tokens::{ClientCredentialsResponse, RefreshTokenResponse, TokenRefresher},
    };

    use super::{settings::QCS_DEFAULT_AUTH_ISSUER_PRODUCTION, tokens::ClientCredentials};

    /// Unwrap a [`Credential`] into its [`TokenPayload`], panicking for any other credential kind.
    fn expect_token_payload(credential: Credential) -> TokenPayload {
        match credential {
            Credential::TokenPayload(payload) => payload,
            Credential::ExternallyManaged(_) | Credential::ClientCredentials(_) => {
                panic!("expected a token payload credential")
            }
        }
    }

    #[test]
    fn expands_env_var() {
        figment::Jail::expect_with(|jail| {
            let dir = jail.create_dir("~/blah/blah/")?;
            jail.create_file(dir.join("file.toml"), "")?;
            jail.set_env("SOME_PATH", "blah/blah");
            jail.set_env("SOME_VAR", "~/$SOME_PATH/file.toml");
            let secrets_path = expand_path_from_env_or_default("SOME_VAR", "default").unwrap();
            assert_eq!(secrets_path.to_str().unwrap(), "~/blah/blah/file.toml");

            Ok(())
        });
    }

    #[test]
    fn uses_env_var_overrides() {
        figment::Jail::expect_with(|jail| {
            let quilc_url = "tcp://quilc:5555";
            let qvm_url = "http://qvm:5000";
            let grpc_url = "http://grpc:80";
            let api_url = "http://api:80";

            jail.set_env(QUILC_URL_VAR, quilc_url);
            jail.set_env(QVM_URL_VAR, qvm_url);
            jail.set_env(API_URL_VAR, api_url);
            jail.set_env(GRPC_API_URL_VAR, grpc_url);

            let config = ClientConfiguration::new(
                Settings::default(),
                Secrets::default(),
                Some("default".to_string()),
            )
            .expect("Should be able to build default config.");

            assert_eq!(config.quilc_url, quilc_url);
            assert_eq!(config.qvm_url, qvm_url);
            assert_eq!(config.grpc_api_url, grpc_url);

            Ok(())
        });
    }

    #[tokio::test]
    async fn test_default_uses_env_var_overrides() {
        figment::Jail::expect_with(|jail| {
            let quilc_url = "quilc_url";
            let qvm_url = "qvm_url";
            let grpc_url = "grpc_url";
            let api_url = "api_url";

            jail.set_env(QUILC_URL_VAR, quilc_url);
            jail.set_env(QVM_URL_VAR, qvm_url);
            jail.set_env(GRPC_API_URL_VAR, grpc_url);
            jail.set_env(API_URL_VAR, api_url);

            let config = ClientConfiguration::load_default().unwrap();
            assert_eq!(config.quilc_url, quilc_url);
            assert_eq!(config.qvm_url, qvm_url);
            assert_eq!(config.grpc_api_url, grpc_url);
            assert_eq!(config.api_url, api_url);

            Ok(())
        });
    }

    #[test]
    fn test_default_loads_settings_with_partial_profile_applications() {
        figment::Jail::expect_with(|jail| {
            let directory = jail.directory();
            let settings_file_name = "settings.toml";
            let settings_file_path = directory.join(settings_file_name);

            let quilc_url_env_var = "env-var://quilc.url/after";

            let settings_file_contents = r#"
default_profile_name = "default"

[profiles]
[profiles.default]
api_url = ""
auth_server_name = "default"
credentials_name = "default"
applications = {}

[auth_servers]
[auth_servers.default]
client_id = ""
issuer = ""
"#;
            jail.create_file(settings_file_name, settings_file_contents)
                .expect("should create test settings.toml");

            jail.set_env(
                "QCS_SETTINGS_FILE_PATH",
                settings_file_path
                    .to_str()
                    .expect("settings file path should be a string"),
            );

            // before setting env var
            let config = ClientConfiguration::load_default().unwrap();
            assert_eq!(config.quilc_url, DEFAULT_QUILC_URL);

            jail.set_env("QCS_SETTINGS_APPLICATIONS_QUILC_URL", quilc_url_env_var);

            // after setting env var
            let config = ClientConfiguration::load_default().unwrap();
            assert_eq!(config.quilc_url, quilc_url_env_var);

            Ok(())
        });
    }

    #[test]
    fn test_default_loads_settings_with_partial_profile_applications_pyquil() {
        figment::Jail::expect_with(|jail| {
            let directory = jail.directory();
            let settings_file_name = "settings.toml";
            let settings_file_path = directory.join(settings_file_name);

            let quilc_url_settings_toml = "settings-toml://quilc.url";
            let quilc_url_env_var = "env-var://quilc.url/after";

            let settings_file_contents = format!(
                r#"
default_profile_name = "default"

[profiles]
[profiles.default]
api_url = ""
auth_server_name = "default"
credentials_name = "default"
applications.pyquil.quilc_url = "{quilc_url_settings_toml}"

[auth_servers]
[auth_servers.default]
client_id = ""
issuer = ""
"#
            );

            jail.create_file(settings_file_name, &settings_file_contents)
                .expect("should create test settings.toml");

            jail.set_env(
                "QCS_SETTINGS_FILE_PATH",
                settings_file_path
                    .to_str()
                    .expect("settings file path should be a string"),
            );

            // before setting env var
            let config = ClientConfiguration::load_default().unwrap();
            assert_eq!(config.quilc_url, quilc_url_settings_toml);

            jail.set_env("QCS_SETTINGS_APPLICATIONS_QUILC_URL", quilc_url_env_var);

            // after setting env var
            let config = ClientConfiguration::load_default().unwrap();
            assert_eq!(config.quilc_url, quilc_url_env_var);

            Ok(())
        });
    }

    #[tokio::test]
    async fn test_hydrate_access_token_on_load() {
        let mut config = ClientConfiguration::builder().build().unwrap();
        let access_token = "test_access_token";
        figment::Jail::expect_with(|jail| {
            let directory = jail.directory();
            let settings_file_name = "settings.toml";
            let settings_file_path = directory.join(settings_file_name);
            let secrets_file_name = "secrets.toml";
            let secrets_file_path = directory.join(secrets_file_name);

            let settings_file_contents = r#"
default_profile_name = "default"

[profiles]
[profiles.default]
api_url = ""
auth_server_name = "default"
credentials_name = "default"

[auth_servers]
[auth_servers.default]
client_id = ""
issuer = ""
"#;

            let secrets_file_contents = format!(
                r#"
[credentials]
[credentials.default]
[credentials.default.token_payload]
access_token = "{access_token}"
expires_in = 3600
id_token = "id_token"
refresh_token = "refresh_token"
scope = "offline_access openid profile email"
token_type = "Bearer"
"#
            );

            jail.create_file(settings_file_name, settings_file_contents)
                .expect("should create test settings.toml");
            jail.create_file(secrets_file_name, &secrets_file_contents)
                .expect("should create test settings.toml");

            jail.set_env(
                "QCS_SETTINGS_FILE_PATH",
                settings_file_path
                    .to_str()
                    .expect("settings file path should be a string"),
            );
            jail.set_env(
                "QCS_SECRETS_FILE_PATH",
                secrets_file_path
                    .to_str()
                    .expect("secrets file path should be a string"),
            );

            config = ClientConfiguration::load_default().unwrap();
            Ok(())
        });
        assert_eq!(
            config.get_access_token().await.unwrap().unwrap(),
            SecretAccessToken::from(access_token)
        );
    }

    #[derive(Clone, Debug, Serialize)]
    struct Claims {
        exp: i64,
        iss: String,
        sub: String,
    }

    impl Default for Claims {
        fn default() -> Self {
            Self {
                exp: 0,
                iss: QCS_DEFAULT_AUTH_ISSUER_PRODUCTION.to_string(),
                sub: "qcs@rigetti.com".to_string(),
            }
        }
    }

    impl Claims {
        fn new_valid() -> Self {
            Self {
                exp: (OffsetDateTime::now_utc() + Duration::seconds(100)).unix_timestamp(),
                ..Self::default()
            }
        }

        fn new_expired() -> Self {
            Self {
                exp: (OffsetDateTime::now_utc() - Duration::seconds(100)).unix_timestamp(),
                ..Self::default()
            }
        }

        fn to_encoded(&self) -> String {
            encode(&Header::default(), &self, &EncodingKey::from_secret(&[])).unwrap()
        }

        fn to_access_token(&self) -> SecretAccessToken {
            SecretAccessToken::from(self.to_encoded())
        }
    }

    #[test]
    fn test_valid_token() {
        let valid_token = Claims::new_valid().to_access_token();
        let tokens = OAuthSession::from_refresh_token(
            RefreshToken::new(SecretRefreshToken::from("unused")),
            AuthServer::default(),
            Some(valid_token.clone()),
        );
        assert_eq!(
            tokens
                .validate()
                .expect("Token should not fail validation."),
            valid_token
        );
    }

    #[test]
    fn test_expired_token() {
        let invalid_token = Claims::new_expired().to_access_token();
        let tokens = OAuthSession::from_refresh_token(
            RefreshToken::new(SecretRefreshToken::from("unused")),
            AuthServer::default(),
            Some(invalid_token),
        );
        assert!(tokens.validate().is_err());
    }

    #[test]
    fn test_client_credentials_without_access_token() {
        let tokens = OAuthSession::from_client_credentials(
            ClientCredentials::new("client_id", "client_secret"),
            AuthServer::default(),
            None,
        );
        assert!(tokens.validate().is_err());
    }

    #[tokio::test]
    async fn test_session_is_present_with_empty_refresh_token_and_valid_access_token() {
        let access_token = Claims::new_valid().to_encoded();
        let mut config = ClientConfiguration::builder().build().unwrap();
        figment::Jail::expect_with(|jail| {
            let directory = jail.directory();
            let settings_file_name = "settings.toml";
            let settings_file_path = directory.join(settings_file_name);
            let secrets_file_name = "secrets.toml";
            let secrets_file_path = directory.join(secrets_file_name);

            let settings_file_contents = r#"
default_profile_name = "default"

[profiles]
[profiles.default]
api_url = ""
auth_server_name = "default"
credentials_name = "default"

[auth_servers]
[auth_servers.default]
client_id = ""
issuer = ""
"#;

            // note this has no `refresh_token` property
            let secrets_file_contents = format!(
                r#"
[credentials]
[credentials.default]
[credentials.default.token_payload]
access_token = "{access_token}"
expires_in = 3600
id_token = "id_token"
scope = "offline_access openid profile email"
token_type = "Bearer"
"#
            );

            jail.create_file(settings_file_name, settings_file_contents)
                .expect("should create test settings.toml");
            jail.create_file(secrets_file_name, &secrets_file_contents)
                .expect("should create test secrets.toml");

            jail.set_env(
                "QCS_SETTINGS_FILE_PATH",
                settings_file_path
                    .to_str()
                    .expect("settings file path should be a string"),
            );
            jail.set_env(
                "QCS_SECRETS_FILE_PATH",
                secrets_file_path
                    .to_str()
                    .expect("secrets file path should be a string"),
            );

            config = ClientConfiguration::load_default().unwrap();
            Ok(())
        });

        assert_eq!(
            config.get_bearer_access_token().await.unwrap(),
            SecretAccessToken::from(access_token)
        );
    }

    /// Exercises the PKCE login flow end-to-end, ensuring that the token is persisted to the secrets file.
    #[test]
    fn test_pkce_flow_persists_token() {
        // Because we need to block on the runtime inside the jail function,
        // we have to create one manually here instead of relying on #[tokio::test].
        let runtime = tokio::runtime::Runtime::new().expect("should create runtime");

        let PkceTestServerHarness {
            server,
            client,
            discovery: _,
            redirect_listener,
        } = runtime.block_on(PkceTestServerHarness::new());

        let client_id = client.client_id;
        let issuer = server.issuer().to_string();

        figment::Jail::expect_with(move |jail| {
            // In CI, the secrets file is mounted as read-only,
            // but these tmp testing files should be writable.
            jail.set_env(SECRETS_READ_ONLY_VAR, "false");

            let directory = jail.directory();
            let settings_file_name = "settings.toml";
            let settings_file_path = directory.join(settings_file_name);

            let secrets_file_name = "secrets.toml";
            let secrets_file_path = directory.join(secrets_file_name);

            let settings_file_contents = format!(
                r#"
default_profile_name = "default"

[profiles]
[profiles.default]
api_url = ""
auth_server_name = "default"
credentials_name = "default"

[auth_servers]
[auth_servers.default]
client_id = "{client_id}"
issuer = "{issuer}"
"#
            );

            let secrets_file_contents = r#"
[credentials]
[credentials.default]
[credentials.default.token_payload]
access_token = ""
"#;

            jail.create_file(settings_file_name, &settings_file_contents)
                .expect("should create test settings.toml");

            jail.set_env(
                SETTINGS_PATH_VAR,
                settings_file_path
                    .to_str()
                    .expect("settings file path should be a string"),
            );

            jail.create_file(secrets_file_name, secrets_file_contents)
                .expect("should create test secrets.toml");

            jail.set_env(
                SECRETS_PATH_VAR,
                secrets_file_path
                    .to_str()
                    .expect("secrets file path should be a string"),
            );

            // should perform a login flow, which persists the token to the secrets file.
            runtime.block_on(async {
                let cancel_token = CancellationToken::new();
                // should load the configuration and perform a login flow
                let configuration = ClientConfiguration::load_with_login_with_redirect(
                    cancel_token,
                    None,
                    RedirectBinding::Bound(redirect_listener),
                )
                .await
                .expect("should load configuration");
                let oauth_session = configuration.refresh().await.expect("should refresh");
                let token = oauth_session.validate().expect("token should be valid");

                // now, the configuration should load without needing to perform a login flow
                let configuration =
                    ClientConfiguration::load_default().expect("should load configuration");

                let oauth_session = configuration
                    .oauth_session()
                    .await
                    .expect("should get oauth session");

                let token_payload = expect_token_payload(
                    Secrets::load_from_path(&secrets_file_path)
                        .expect("should load secrets")
                        .credentials
                        .remove("default")
                        .expect("should get default credentials"),
                );

                assert_eq!(
                    token,
                    oauth_session.validate().expect("should contain token"),
                    "session: {oauth_session:?}, token_payload: {token_payload:?}",
                );
                assert_eq!(
                    token_payload.access_token,
                    Some(token),
                    "session: {oauth_session:?}, token_payload: {token_payload:?}"
                );
                assert_ne!(
                    token_payload.refresh_token, None,
                    "session: {oauth_session:?}, token_payload: {token_payload:?}"
                );
            });

            Ok(())
        });

        drop(server);
    }

    /// Exercises the "no valid credential, perform an interactive login" branch of
    /// [`ClientConfiguration::load_with_login`], ensuring the resulting tokens are persisted to the
    /// secrets file immediately — unlike [`test_pkce_flow_persists_token`], this does NOT call
    /// `.refresh()` afterward. If `load_with_login` doesn't persist the login on its own, a process
    /// that exits before anything else triggers a dispatcher-managed refresh would lose the login
    /// entirely, forcing the next process back through an interactive login too.
    #[test]
    fn test_load_with_login_persists_login_flow_token_without_explicit_refresh() {
        // Because we need to block on the runtime inside the jail function,
        // we have to create one manually here instead of relying on #[tokio::test].
        let runtime = tokio::runtime::Runtime::new().expect("should create runtime");

        let PkceTestServerHarness {
            server,
            client,
            discovery: _,
            redirect_listener,
        } = runtime.block_on(PkceTestServerHarness::new());

        let client_id = client.client_id;
        let issuer = server.issuer().to_string();

        figment::Jail::expect_with(move |jail| {
            // In CI, the secrets file is mounted as read-only,
            // but these tmp testing files should be writable.
            jail.set_env(SECRETS_READ_ONLY_VAR, "false");

            let directory = jail.directory();
            let settings_file_name = "settings.toml";
            let settings_file_path = directory.join(settings_file_name);

            let secrets_file_name = "secrets.toml";
            let secrets_file_path = directory.join(secrets_file_name);

            let settings_file_contents = format!(
                r#"
default_profile_name = "default"

[profiles]
[profiles.default]
api_url = ""
auth_server_name = "default"
credentials_name = "default"

[auth_servers]
[auth_servers.default]
client_id = "{client_id}"
issuer = "{issuer}"
"#
            );

            let secrets_file_contents = r#"
[credentials]
[credentials.default]
[credentials.default.token_payload]
access_token = ""
"#;

            jail.create_file(settings_file_name, &settings_file_contents)
                .expect("should create test settings.toml");

            jail.set_env(
                SETTINGS_PATH_VAR,
                settings_file_path
                    .to_str()
                    .expect("settings file path should be a string"),
            );

            jail.create_file(secrets_file_name, secrets_file_contents)
                .expect("should create test secrets.toml");

            jail.set_env(
                SECRETS_PATH_VAR,
                secrets_file_path
                    .to_str()
                    .expect("secrets file path should be a string"),
            );

            runtime.block_on(async {
                let cancel_token = CancellationToken::new();

                // Deliberately do NOT call `.refresh()` afterward: `load_with_login` itself
                // should persist the freshly logged-in tokens.
                let configuration = ClientConfiguration::load_with_login_with_redirect(
                    cancel_token,
                    None,
                    RedirectBinding::Bound(redirect_listener),
                )
                .await
                .expect("should perform a login flow");

                let oauth_session = configuration
                    .oauth_session()
                    .await
                    .expect("should get oauth session");
                let token = oauth_session.validate().expect("token should be valid");

                let token_payload = expect_token_payload(
                    Secrets::load_from_path(&secrets_file_path)
                        .expect("should load secrets")
                        .credentials
                        .remove("default")
                        .expect("should get default credentials"),
                );

                assert_eq!(
                    token_payload.access_token,
                    Some(token),
                    "the access token from the login flow should be persisted without an \
                     explicit follow-up refresh"
                );
                assert!(
                    token_payload.refresh_token.is_some(),
                    "the refresh token from the login flow should be persisted without an \
                     explicit follow-up refresh"
                );
            });

            Ok(())
        });

        drop(server);
    }

    /// Exercises the "refresh the stored refresh token" branch of [`ClientConfiguration::load_with_login`],
    /// which is taken when the stored access token has expired but a refresh token is still on file.
    ///
    /// This ensures that a rotated refresh token returned by the auth server is (a) reflected in the
    /// in-memory [`OAuthSession`] and (b) persisted back to the secrets file. If the rotated refresh
    /// token is not persisted, the next process to load this profile will retry the stale, already-consumed
    /// refresh token, fail, and be forced into an interactive login flow every time.
    #[test]
    fn test_load_with_login_persists_rotated_refresh_token_on_refresh() {
        let runtime = tokio::runtime::Runtime::new().expect("should create runtime");

        let mock_server = runtime.block_on(MockServer::start_async());

        let new_access_token = Claims::new_valid().to_encoded();
        let rotated_refresh_token = "rotated_refresh_token".to_string();

        let oidc_mock = runtime.block_on(mock_server.mock_async(|when, then| {
            when.method(GET).path("/.well-known/openid-configuration");
            then.status(200)
                .json_body_obj(&oidc::Discovery::new_for_test(
                    mock_server.base_url().parse().unwrap(),
                ));
        }));

        let issuer_mock = runtime.block_on(mock_server.mock_async(|when, then| {
            when.method(POST).path("/v1/token");
            then.status(200).json_body_obj(&RefreshTokenResponse {
                access_token: SecretAccessToken::from(new_access_token.clone()),
                refresh_token: Some(SecretRefreshToken::from(rotated_refresh_token.clone())),
            });
        }));

        let client_id = "client_id";
        let issuer = mock_server.base_url();
        let initial_refresh_token = "initial_refresh_token";
        let expired_access_token = Claims::new_expired().to_encoded();

        figment::Jail::expect_with(|jail| {
            jail.set_env(SECRETS_READ_ONLY_VAR, "false");

            let directory = jail.directory();
            let settings_file_name = "settings.toml";
            let settings_file_path = directory.join(settings_file_name);

            let secrets_file_name = "secrets.toml";
            let secrets_file_path = directory.join(secrets_file_name);

            let settings_file_contents = format!(
                r#"
default_profile_name = "default"

[profiles]
[profiles.default]
api_url = ""
auth_server_name = "default"
credentials_name = "default"

[auth_servers]
[auth_servers.default]
client_id = "{client_id}"
issuer = "{issuer}"
"#
            );

            let secrets_file_contents = format!(
                r#"
[credentials]
[credentials.default]
[credentials.default.token_payload]
access_token = "{expired_access_token}"
refresh_token = "{initial_refresh_token}"
"#
            );

            jail.create_file(settings_file_name, &settings_file_contents)
                .expect("should create test settings.toml");
            jail.set_env(
                SETTINGS_PATH_VAR,
                settings_file_path
                    .to_str()
                    .expect("settings file path should be a string"),
            );

            jail.create_file(secrets_file_name, &secrets_file_contents)
                .expect("should create test secrets.toml");
            jail.set_env(
                SECRETS_PATH_VAR,
                secrets_file_path
                    .to_str()
                    .expect("secrets file path should be a string"),
            );

            runtime.block_on(async {
                let cancel_token = CancellationToken::new();

                // The expired access token should be refreshed using the stored refresh token,
                // without falling back to an interactive login flow.
                let configuration = ClientConfiguration::load_with_login(cancel_token, None)
                    .await
                    .expect("should refresh using the stored refresh token");

                oidc_mock.assert_async().await;
                issuer_mock.assert_async().await;

                let oauth_session = configuration
                    .oauth_session()
                    .await
                    .expect("should get oauth session");

                assert_eq!(
                    oauth_session.access_token().cloned().ok(),
                    Some(SecretAccessToken::from(new_access_token.clone())),
                    "in-memory access token should be the freshly refreshed one"
                );

                match oauth_session.payload() {
                    OAuthGrant::RefreshToken(payload) => {
                        assert_eq!(
                            payload.refresh_token,
                            SecretRefreshToken::from(rotated_refresh_token.clone()),
                            "in-memory refresh token should be updated to the rotated value"
                        );
                    }
                    other => panic!("expected a RefreshToken grant, got {other:?}"),
                }

                let token_payload = expect_token_payload(
                    Secrets::load_from_path(&secrets_file_path)
                        .expect("should load secrets")
                        .credentials
                        .remove("default")
                        .expect("should get default credentials"),
                );

                assert_eq!(
                    token_payload.access_token,
                    Some(SecretAccessToken::from(new_access_token.clone())),
                    "new access token should be persisted to the secrets file"
                );
                assert_eq!(
                    token_payload.refresh_token,
                    Some(SecretRefreshToken::from(rotated_refresh_token.clone())),
                    "rotated refresh token should be persisted to the secrets file, otherwise \
                     the next process to load this profile will retry the stale, \
                     already-consumed refresh token and be forced back into a login flow"
                );
            });

            Ok(())
        });
    }

    /// A profile's `credentials_name` may differ from the profile's own name, and several profiles
    /// may point at the same credential. Tokens are *read* from `credentials.<credentials_name>`,
    /// so they must also be *written* there.
    ///
    /// Persisting under the profile name instead means every refresh lands in an entry nobody
    /// reads, leaving the credential actually in use permanently stale: the profile works until
    /// the access token expires (~1 hour), then retries the same consumed refresh token forever.
    ///
    /// This exercises the runtime path taken by ordinary API calls
    /// ([`ClientConfiguration::get_bearer_access_token`] -> [`TokenDispatcher::refresh`]), not just
    /// the login path.
    #[test]
    fn test_refresh_persists_to_credentials_name_not_profile_name() {
        let runtime = tokio::runtime::Runtime::new().expect("should create runtime");

        let mock_server = runtime.block_on(MockServer::start_async());

        let new_access_token = Claims::new_valid().to_encoded();
        let rotated_refresh_token = "rotated_refresh_token".to_string();

        let oidc_mock = runtime.block_on(mock_server.mock_async(|when, then| {
            when.method(GET).path("/.well-known/openid-configuration");
            then.status(200)
                .json_body_obj(&oidc::Discovery::new_for_test(
                    mock_server.base_url().parse().unwrap(),
                ));
        }));

        let issuer_mock = runtime.block_on(mock_server.mock_async(|when, then| {
            when.method(POST).path("/v1/token");
            then.status(200).json_body_obj(&RefreshTokenResponse {
                access_token: SecretAccessToken::from(new_access_token.clone()),
                refresh_token: Some(SecretRefreshToken::from(rotated_refresh_token.clone())),
            });
        }));

        let client_id = "client_id";
        let issuer = mock_server.base_url();
        let initial_refresh_token = "initial_refresh_token";
        let expired_access_token = Claims::new_expired().to_encoded();

        // The profile and the credential it uses are deliberately named differently.
        let profile_name = "funnel";
        let credentials_name = "shared";

        figment::Jail::expect_with(|jail| {
            jail.set_env(SECRETS_READ_ONLY_VAR, "false");

            let directory = jail.directory();
            let settings_file_name = "settings.toml";
            let settings_file_path = directory.join(settings_file_name);

            let secrets_file_name = "secrets.toml";
            let secrets_file_path = directory.join(secrets_file_name);

            let settings_file_contents = format!(
                r#"
default_profile_name = "{profile_name}"

[profiles]
[profiles.{profile_name}]
api_url = ""
auth_server_name = "default"
credentials_name = "{credentials_name}"

[auth_servers]
[auth_servers.default]
client_id = "{client_id}"
issuer = "{issuer}"
"#
            );

            // A decoy credential named after the profile. Persisting by profile name would write
            // here, silently succeed, and leave `{credentials_name}` (the one actually loaded)
            // stale, which is exactly the failure this test guards against.
            let secrets_file_contents = format!(
                r#"
[credentials]
[credentials.{credentials_name}]
[credentials.{credentials_name}.token_payload]
access_token = "{expired_access_token}"
refresh_token = "{initial_refresh_token}"

[credentials.{profile_name}]
[credentials.{profile_name}.token_payload]
access_token = "decoy_access_token"
refresh_token = "decoy_refresh_token"
"#
            );

            jail.create_file(settings_file_name, &settings_file_contents)
                .expect("should create test settings.toml");
            jail.set_env(
                SETTINGS_PATH_VAR,
                settings_file_path
                    .to_str()
                    .expect("settings file path should be a string"),
            );

            jail.create_file(secrets_file_name, &secrets_file_contents)
                .expect("should create test secrets.toml");
            jail.set_env(
                SECRETS_PATH_VAR,
                secrets_file_path
                    .to_str()
                    .expect("secrets file path should be a string"),
            );

            runtime.block_on(async {
                let configuration = ClientConfiguration::load_profile(profile_name.to_string())
                    .expect("should load the profile");

                assert_eq!(configuration.profile(), profile_name);
                assert_eq!(configuration.credentials_name(), credentials_name);

                // The stored access token is expired, so this refreshes and persists.
                let access_token = configuration
                    .get_bearer_access_token()
                    .await
                    .expect("should refresh the expired access token");

                oidc_mock.assert_async().await;
                issuer_mock.assert_async().await;

                assert_eq!(
                    access_token,
                    SecretAccessToken::from(new_access_token.clone())
                );

                let mut credentials = Secrets::load_from_path(&secrets_file_path)
                    .expect("should load secrets")
                    .credentials;

                let token_payload = expect_token_payload(
                    credentials
                        .remove(credentials_name)
                        .expect("should get the credential the profile points at"),
                );

                assert_eq!(
                    token_payload.access_token,
                    Some(SecretAccessToken::from(new_access_token.clone())),
                    "the refreshed access token should be persisted under `credentials_name`, \
                     which is where the next load reads it from"
                );
                assert_eq!(
                    token_payload.refresh_token,
                    Some(SecretRefreshToken::from(rotated_refresh_token.clone())),
                    "the rotated refresh token should be persisted under `credentials_name`"
                );

                let decoy_payload = expect_token_payload(
                    credentials
                        .remove(profile_name)
                        .expect("decoy credential should still exist"),
                );

                assert_eq!(
                    decoy_payload.access_token,
                    Some(SecretAccessToken::from("decoy_access_token".to_string())),
                    "the credential named after the profile is not the one in use and \
                     should be left untouched"
                );
            });

            Ok(())
        });
    }

    /// The `secrets.toml` for a profile whose credential is externally managed. `access_token`
    /// is printed by the program, so it must be a token the client can actually validate.
    fn externally_managed_config_files(access_token: &str) -> (&'static str, String) {
        let settings = r#"
default_profile_name = "default"

[profiles]
[profiles.default]
api_url = ""
auth_server_name = "default"
credentials_name = "default"

[auth_servers]
[auth_servers.default]
client_id = ""
issuer = ""
"#;

        let (program, flag) = super::external_command::shell();
        let args = format!(r#"["{flag}", "echo {access_token}"]"#);

        let secrets = format!(
            r"
[credentials]
[credentials.default]
[credentials.default.externally_managed]
command = {program:?}
args = {args}
"
        );

        (settings, secrets)
    }

    /// Write `settings.toml` and `secrets.toml` into the jail and point the environment at them.
    fn jail_config_files(
        jail: &mut figment::Jail,
        settings: &str,
        secrets: &str,
    ) -> std::path::PathBuf {
        let directory = jail.directory().to_path_buf();
        jail.create_file("settings.toml", settings)
            .expect("should create test settings.toml");
        jail.create_file("secrets.toml", secrets)
            .expect("should create test secrets.toml");

        jail.set_env(
            SETTINGS_PATH_VAR,
            directory
                .join("settings.toml")
                .to_str()
                .expect("settings path should be a string"),
        );
        let secrets_path = directory.join("secrets.toml");
        jail.set_env(
            SECRETS_PATH_VAR,
            secrets_path
                .to_str()
                .expect("secrets path should be a string"),
        );

        secrets_path
    }

    /// An externally managed credential should get its access token by running the configured
    /// program, without any authorization server being involved.
    #[test]
    fn test_externally_managed_credential_runs_the_configured_program() {
        let access_token = Claims::new_valid().to_encoded();
        let (settings, secrets) = externally_managed_config_files(&access_token);

        figment::Jail::expect_with(|jail| {
            jail_config_files(jail, settings, &secrets);

            let runtime = tokio::runtime::Runtime::new().expect("should create runtime");
            runtime.block_on(async {
                let config = ClientConfiguration::load_default().expect("should load config");

                assert_eq!(
                    config
                        .get_bearer_access_token()
                        .await
                        .expect("should get an access token from the external program"),
                    SecretAccessToken::from(access_token.clone())
                );
            });

            Ok(())
        });
    }

    /// Tokens from an external program belong to whatever produced them, and must not be copied
    /// into `secrets.toml`.
    #[test]
    fn test_externally_managed_credential_is_never_persisted() {
        let access_token = Claims::new_valid().to_encoded();
        let (settings, secrets) = externally_managed_config_files(&access_token);

        figment::Jail::expect_with(|jail| {
            jail.set_env(SECRETS_READ_ONLY_VAR, "false");
            let secrets_path = jail_config_files(jail, settings, &secrets);
            let before =
                std::fs::read_to_string(&secrets_path).expect("should read the secrets file");

            let runtime = tokio::runtime::Runtime::new().expect("should create runtime");
            runtime.block_on(async {
                let config = ClientConfiguration::load_default().expect("should load config");
                config
                    .refresh()
                    .await
                    .expect("should refresh via the external program");
            });

            let after =
                std::fs::read_to_string(&secrets_path).expect("should read the secrets file");
            assert_eq!(
                before, after,
                "an externally managed credential's tokens should never be written to disk"
            );

            Ok(())
        });
    }

    /// `load_with_login` must not start an interactive login for a credential that can always
    /// produce a token on demand. The auth server here points nowhere, so a PKCE flow would
    /// fail rather than hang.
    #[test]
    fn test_externally_managed_credential_skips_the_login_flow() {
        let access_token = Claims::new_valid().to_encoded();
        let (settings, secrets) = externally_managed_config_files(&access_token);

        figment::Jail::expect_with(|jail| {
            jail_config_files(jail, settings, &secrets);

            let runtime = tokio::runtime::Runtime::new().expect("should create runtime");
            runtime.block_on(async {
                let config = ClientConfiguration::load_with_login(CancellationToken::new(), None)
                    .await
                    .expect("should load without an interactive login");

                assert_eq!(
                    config
                        .get_bearer_access_token()
                        .await
                        .expect("should get an access token from the external program"),
                    SecretAccessToken::from(access_token.clone())
                );
            });

            Ok(())
        });
    }

    /// A valid token is reused rather than re-fetched, so the program runs once instead of once
    /// per request. Without this, every API call would spawn a process.
    #[cfg(unix)]
    #[test]
    fn test_externally_managed_credential_reuses_a_valid_token() {
        let access_token = Claims::new_valid().to_encoded();
        let (settings, _) = externally_managed_config_files(&access_token);

        figment::Jail::expect_with(|jail| {
            let counter = jail.directory().join("invocations");
            // Appends a line per run, so the file's length is the number of invocations.
            let secrets = format!(
                r#"
[credentials]
[credentials.default]
[credentials.default.externally_managed]
command = "/bin/sh"
args = ["-c", "echo run >> {counter} && printf '%s' '{access_token}'"]
"#,
                counter = counter.display(),
            );
            jail_config_files(jail, settings, &secrets);

            let runtime = tokio::runtime::Runtime::new().expect("should create runtime");
            runtime.block_on(async {
                let config = ClientConfiguration::load_default().expect("should load config");
                for _ in 0..5_u8 {
                    config
                        .get_bearer_access_token()
                        .await
                        .expect("should get an access token");
                }
            });

            let invocations = std::fs::read_to_string(&counter)
                .expect("the program should have run at least once")
                .lines()
                .count();
            assert_eq!(
                invocations, 1,
                "a valid token should be reused across requests, not re-fetched"
            );

            Ok(())
        });
    }

    /// A program that never produces a token the client can validate must not be re-run in a
    /// loop. Each token request runs it exactly once and hands back whatever it printed, leaving
    /// it to the API to reject; the alternative is an unbounded stream of subprocesses whenever a
    /// credential helper is misconfigured or returns an opaque (non-JWT) token, which the client
    /// has no way to validate locally.
    #[cfg(unix)]
    #[test]
    fn test_externally_managed_credential_does_not_loop_on_invalid_tokens() {
        let (settings, _) = externally_managed_config_files("unused");
        let expired = Claims::new_expired().to_encoded();

        // Both shapes of token that fail local validation: one expired, one not a JWT at all.
        for (label, token) in [("expired", expired.as_str()), ("opaque", "not-a-jwt")] {
            figment::Jail::expect_with(|jail| {
                let counter = jail.directory().join("invocations");
                // Appends a line per run, so the file's length is the number of invocations.
                let secrets = format!(
                    r#"
[credentials]
[credentials.default]
[credentials.default.externally_managed]
command = "/bin/sh"
args = ["-c", "echo run >> {counter} && printf '%s' '{token}'"]
"#,
                    counter = counter.display(),
                );
                jail_config_files(jail, settings, &secrets);

                let requests = 3_usize;
                let runtime = tokio::runtime::Runtime::new().expect("should create runtime");
                runtime.block_on(async {
                    let config = ClientConfiguration::load_default().expect("should load config");

                    // A timeout so an actual loop fails the test instead of hanging it.
                    tokio::time::timeout(std::time::Duration::from_secs(30), async {
                        for _ in 0..requests {
                            assert_eq!(
                                config
                                    .get_bearer_access_token()
                                    .await
                                    .expect(
                                        "an unvalidatable token is still returned to the caller"
                                    )
                                    .secret(),
                                token,
                                "the {label} token from the program should be returned as-is"
                            );
                        }
                    })
                    .await
                    .expect("requesting a token should not loop on the external program");
                });

                let invocations = std::fs::read_to_string(&counter)
                    .expect("the program should have run at least once")
                    .lines()
                    .count();
                assert_eq!(
                    invocations, requests,
                    "a program returning {label} tokens should run once per request, not \
                     repeatedly until it produces a valid one"
                );

                Ok(())
            });
        }
    }

    /// A credential carrying both kinds of configuration should use the external program, since
    /// stored tokens can only be a stale copy of what it produces.
    #[test]
    fn test_externally_managed_credential_takes_precedence_over_stored_tokens() {
        let access_token = Claims::new_valid().to_encoded();
        let (settings, secrets) = externally_managed_config_files(&access_token);
        let secrets = format!(
            "{secrets}\n[credentials.default.token_payload]\naccess_token = \"{}\"\n",
            Claims::new_valid().to_encoded()
        );

        figment::Jail::expect_with(|jail| {
            jail_config_files(jail, settings, &secrets);

            let runtime = tokio::runtime::Runtime::new().expect("should create runtime");
            runtime.block_on(async {
                let config = ClientConfiguration::load_default().expect("should load config");

                assert_eq!(
                    config
                        .get_bearer_access_token()
                        .await
                        .expect("should get an access token from the external program"),
                    SecretAccessToken::from(access_token.clone()),
                    "the external program should win over the stored access token"
                );
            });

            Ok(())
        });
    }

    /// The client secret used by the client-credentials tests.
    const TEST_CLIENT_ID: &str = "a-client-id";
    const TEST_CLIENT_SECRET: &str = "a-client-secret";

    fn expected_basic_auth(client_id: &str, client_secret: &str) -> String {
        use base64::Engine as _;

        let encoded = base64::engine::general_purpose::STANDARD
            .encode(format!("{client_id}:{client_secret}"));
        format!("Basic {encoded}")
    }

    /// The `settings.toml`/`secrets.toml` pair for a profile where the credential is a client secret.
    fn client_credentials_fixture_files(issuer: &str) -> (String, String) {
        let settings = format!(
            r#"
default_profile_name = "default"

[profiles]
[profiles.default]
api_url = ""
auth_server_name = "default"
credentials_name = "default"

[auth_servers]
[auth_servers.default]
client_id = "ignored"
issuer = "{issuer}"
"#
        );

        let secrets = format!(
            r#"
[credentials]
[credentials.default.client_credentials]
client_id = "{TEST_CLIENT_ID}"
client_secret = "{TEST_CLIENT_SECRET}"
"#
        );

        (settings, secrets)
    }

    fn mock_client_credentials_issuer<'server>(
        runtime: &tokio::runtime::Runtime,
        mock_server: &'server MockServer,
        access_token: &str,
    ) -> (httpmock::Mock<'server>, httpmock::Mock<'server>) {
        let oidc_mock = runtime.block_on(mock_server.mock_async(|when, then| {
            when.method(GET).path("/.well-known/openid-configuration");
            then.status(200)
                .json_body_obj(&oidc::Discovery::new_for_test(
                    mock_server.base_url().parse().unwrap(),
                ));
        }));

        let authorization = expected_basic_auth(TEST_CLIENT_ID, TEST_CLIENT_SECRET);
        let access_token = access_token.to_string();
        let token_mock = runtime.block_on(mock_server.mock_async(|when, then| {
            when.method(POST)
                .path("/v1/token")
                .header("authorization", authorization)
                .body_includes("grant_type=client_credentials");
            then.status(200).json_body_obj(&ClientCredentialsResponse {
                access_token: SecretAccessToken::from(access_token),
            });
        }));

        (oidc_mock, token_mock)
    }

    /// Make sure the `auth_server`'s client_id is not used
    #[test]
    fn test_client_credentials_credential_authenticates_as_its_own_client_id() {
        let access_token = Claims::new_valid().to_encoded();

        let runtime = tokio::runtime::Runtime::new().expect("should create runtime");
        let mock_server = runtime.block_on(MockServer::start_async());
        let (oidc_mock, token_mock) =
            mock_client_credentials_issuer(&runtime, &mock_server, &access_token);

        let (settings, secrets) = client_credentials_fixture_files(&mock_server.base_url());

        figment::Jail::expect_with(|jail| {
            jail_config_files(jail, &settings, &secrets);

            runtime.block_on(async {
                let config = ClientConfiguration::load_default().expect("should load config");

                assert_eq!(
                    config
                        .get_bearer_access_token()
                        .await
                        .expect("should exchange the client secret for an access token"),
                    SecretAccessToken::from(access_token.clone()),
                );
            });

            oidc_mock.assert();
            token_mock.assert();

            Ok(())
        });
    }

    #[test]
    fn test_client_credentials_credential_is_never_persisted() {
        let access_token = Claims::new_valid().to_encoded();

        let runtime = tokio::runtime::Runtime::new().expect("should create runtime");
        let mock_server = runtime.block_on(MockServer::start_async());
        let (_oidc_mock, _token_mock) =
            mock_client_credentials_issuer(&runtime, &mock_server, &access_token);

        let (settings, secrets) = client_credentials_fixture_files(&mock_server.base_url());

        figment::Jail::expect_with(|jail| {
            jail.set_env(SECRETS_READ_ONLY_VAR, "false");
            let secrets_path = jail_config_files(jail, &settings, &secrets);
            let before =
                std::fs::read_to_string(&secrets_path).expect("should read the secrets file");

            runtime.block_on(async {
                let config = ClientConfiguration::load_default().expect("should load config");
                config
                    .refresh()
                    .await
                    .expect("should exchange the client secret for an access token");
            });

            let after =
                std::fs::read_to_string(&secrets_path).expect("should read the secrets file");
            assert_eq!(
                before, after,
                "a client credentials grant has nothing to persist: no refresh token, and an \
                 access token the secret can mint again at any time"
            );

            Ok(())
        });
    }

    #[test]
    fn test_client_credentials_credential_skips_the_login_flow() {
        let access_token = Claims::new_valid().to_encoded();

        let runtime = tokio::runtime::Runtime::new().expect("should create runtime");
        let mock_server = runtime.block_on(MockServer::start_async());
        let (_oidc_mock, token_mock) =
            mock_client_credentials_issuer(&runtime, &mock_server, &access_token);

        let (settings, secrets) = client_credentials_fixture_files(&mock_server.base_url());

        figment::Jail::expect_with(|jail| {
            jail_config_files(jail, &settings, &secrets);

            runtime.block_on(async {
                let config = ClientConfiguration::load_with_login(CancellationToken::new(), None)
                    .await
                    .expect("should load without an interactive login");

                assert_eq!(
                    config
                        .get_bearer_access_token()
                        .await
                        .expect("should exchange the client secret for an access token"),
                    SecretAccessToken::from(access_token.clone()),
                );
            });

            token_mock.assert();

            Ok(())
        });
    }
}