sendra-core 0.1.0

//! [`Auth`]/[`BasicAuth`]/[`ApiKeyAuth`]: [`crate::Request::auth`]'s shape,
//! resolved to a header or query parameter by [`crate::Request::resolve_auth`].
//!
//! Also reused verbatim as [`crate::environment::Environment::auth`] — an
//! environment-level default applied to a request that sets no `auth:` of
//! its own — so the validation this module owns (mutual exclusivity,
//! header/query collision) is written here once and called from both
//! [`crate::Request::validate`] and [`crate::environment`], never
//! duplicated.

use serde::{Deserialize, Serialize};

/// [`crate::Request::auth`]: exactly one of `bearer`, `basic`, `api_key` or
/// `oauth`, enforced by [`Auth::validate_exclusivity`].
///
/// This is also the shape a default `auth:` at the environment level reuses
/// unchanged (see [`crate::environment::Environment::auth`]) — `api_key`
/// and `oauth` join `bearer`/`basic` as mutually-exclusive cases in that same
/// shape, so kept as its own type rather than inlined onto `Request`, the
/// same way `MultipartPart` is its own type rather than an inline tuple.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[cfg_attr(feature = "schema", derive(schemars::JsonSchema))]
#[serde(deny_unknown_fields)]
pub struct Auth {
    /// Sets `Authorization: Bearer <bearer>`.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub bearer: Option<String>,
    /// Sets `Authorization: Basic <base64(user:pass)>`.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub basic: Option<BasicAuth>,
    /// Sets a named header or query parameter to a static value — see
    /// [`ApiKeyAuth`].
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub api_key: Option<ApiKeyAuth>,
    /// Acquires a bearer token from an OAuth token endpoint before the
    /// request is sent — see [`OAuthAuth`].
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub oauth: Option<OAuthAuth>,
}

impl Auth {
    /// Exactly one of `bearer`/`basic`/`api_key`/`oauth` must be set. Called
    /// wherever an `Auth` value is parsed — a request's own `auth:` block
    /// ([`crate::Request::validate`]) and an environment's default
    /// ([`crate::environment::Environment::from_yaml_str`]/`from_path`) —
    /// so the rule is written once and cannot drift between the two.
    pub(crate) fn validate_exclusivity(&self) -> Result<(), String> {
        let mut set = Vec::new();
        if self.bearer.is_some() {
            set.push("bearer");
        }
        if self.basic.is_some() {
            set.push("basic");
        }
        if self.api_key.is_some() {
            set.push("api_key");
        }
        if self.oauth.is_some() {
            set.push("oauth");
        }
        if set.len() != 1 {
            return Err(format!(
                "exactly one of `auth.bearer`, `auth.basic`, `auth.api_key` or `auth.oauth` must \
                 be set, but found: {}",
                if set.is_empty() {
                    "neither".to_string()
                } else {
                    set.join(", ")
                }
            ));
        }
        Ok(())
    }

    /// Whether sending this `auth` would collide with an explicit header or
    /// query entry already on the request — the same "two things claiming
    /// ownership of one header" rule for every case `auth` can set:
    /// `bearer`/`basic` vs. an explicit `Authorization` header, and
    /// `api_key` vs. an explicit `headers:`/`query:` entry of the same name.
    ///
    /// Reused for a request's own `auth:` (checked once, at parse time,
    /// against the request's own `headers`/`query`) and for an
    /// environment-level default (checked once substitution has produced
    /// the final header/query names, since an environment's `auth:` cannot
    /// know at parse time what a request that later picks it up will look
    /// like) — see [`crate::Request::validate`] and
    /// [`crate::environment::Environment::apply`].
    pub(crate) fn collision_reason(
        &self,
        headers: &[(String, String)],
        query: &[(String, String)],
    ) -> Option<String> {
        if (self.bearer.is_some() || self.basic.is_some() || self.oauth.is_some())
            && headers
                .iter()
                .any(|(name, _)| name.eq_ignore_ascii_case("Authorization"))
        {
            return Some(
                "`auth` and an explicit `Authorization` header cannot both be set on the same \
                 request; remove one"
                    .to_string(),
            );
        }

        if let Some(api_key) = &self.api_key {
            match api_key.r#in {
                ApiKeyLocation::Header => {
                    if headers
                        .iter()
                        .any(|(name, _)| name.eq_ignore_ascii_case(&api_key.name))
                    {
                        return Some(format!(
                            "`auth.api_key` and an explicit `headers.{}` cannot both be set on \
                             the same request; remove one",
                            api_key.name
                        ));
                    }
                }
                ApiKeyLocation::Query => {
                    if query.iter().any(|(name, _)| name == &api_key.name) {
                        return Some(format!(
                            "`auth.api_key` and an explicit `query.{}` cannot both be set on the \
                             same request; remove one",
                            api_key.name
                        ));
                    }
                }
            }
        }

        None
    }
}

/// [`Auth::basic`]'s credentials, base64-encoded as `user:pass` by
/// [`crate::Request::resolve_auth`].
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[cfg_attr(feature = "schema", derive(schemars::JsonSchema))]
#[serde(deny_unknown_fields)]
pub struct BasicAuth {
    pub user: String,
    pub pass: String,
}

/// [`Auth::api_key`]: a static value sent as either a header or a query
/// parameter.
///
/// ```text
/// auth:
///   api_key:
///     in: header          # or: query
///     name: X-API-Key     # or a query param name
///     value: {{api_key}}
/// ```
///
/// `in: header` sets the header named `name` to `value`, the same as an
/// entry under `headers:` would. `in: query` adds `name`/`value` as an
/// additional query parameter through the same mechanism
/// [`crate::Request::resolve_query`] already uses for `query:` — not a
/// separate ad-hoc code path — so it inherits that mechanism's percent-
/// encoding and its "the more structured source wins on a name collision
/// with the URL's own query string" rule. See
/// [`crate::Request::resolve_auth`] for exactly how.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[cfg_attr(feature = "schema", derive(schemars::JsonSchema))]
#[serde(deny_unknown_fields)]
pub struct ApiKeyAuth {
    pub r#in: ApiKeyLocation,
    pub name: String,
    pub value: String,
}

/// Where [`ApiKeyAuth`] places its `name`/`value` pair.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[cfg_attr(feature = "schema", derive(schemars::JsonSchema))]
#[serde(rename_all = "lowercase")]
pub enum ApiKeyLocation {
    Header,
    Query,
}

/// [`Auth::oauth`]: acquire a bearer token from an OAuth token endpoint
/// before the request is sent, under one of three grants.
///
/// ```text
/// auth:
///   oauth:
///     grant_type: client_credentials   # or: password, authorization_code
///     token_url: https://auth.example.com/token
///     client_id: {{client_id}}
///     client_secret: {{client_secret}}
///     scope: read write                 # optional
///     # required only for grant_type: password
///     username: {{username}}
///     password: {{password}}
///     # required only for grant_type: authorization_code
///     authorization_url: https://auth.example.com/authorize
///     redirect_uri: http://127.0.0.1:8899/callback
/// ```
///
/// `client_credentials` and `password` are acquired automatically —
/// [`crate::Request::resolve_oauth`] fetches (or reuses a cached) token
/// before every send with no human involved. `authorization_code` cannot
/// work that way: it needs a human to approve access in a browser, so
/// `resolve_oauth` refuses to attempt it automatically and instead reports a
/// clear error directing the caller to log in interactively first. The TUI
/// is the one caller that can do that — see [`crate::oauth`]'s module docs
/// for the interactive flow and why `client_secret` is optional only for
/// this grant (a desktop client cannot keep a secret confidential, so PKCE
/// stands in for it; see [RFC 8252 §8.1/§8.5]).
///
/// [`crate::Request::resolve_oauth`] acquires the token — through
/// [`crate::oauth::OAuthTokenCache`], reusing one already acquired for the
/// same `token_url`/`client_id`/`grant_type`/`scope` within this run rather
/// than re-authenticating per request — and hands it to the exact same
/// `Authorization: Bearer` code path [`Auth::bearer`] already resolves to;
/// see [`crate::Request::resolve_auth`].
///
/// [RFC 8252 §8.1/§8.5]: https://www.rfc-editor.org/rfc/rfc8252#section-8.1
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[cfg_attr(feature = "schema", derive(schemars::JsonSchema))]
#[serde(deny_unknown_fields)]
pub struct OAuthAuth {
    pub grant_type: OAuthGrantType,
    pub token_url: String,
    pub client_id: String,
    /// Required for [`OAuthGrantType::ClientCredentials`] and
    /// [`OAuthGrantType::Password`]; optional for
    /// [`OAuthGrantType::AuthorizationCode`], whose native/desktop clients
    /// typically have none — see [`validate_grant_fields`](Self::validate_grant_fields).
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub client_secret: Option<String>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub scope: Option<String>,
    /// Required when [`grant_type`](Self::grant_type) is
    /// [`OAuthGrantType::Password`] — see [`validate_grant_fields`](Self::validate_grant_fields).
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub username: Option<String>,
    /// Required when [`grant_type`](Self::grant_type) is
    /// [`OAuthGrantType::Password`] — see [`validate_grant_fields`](Self::validate_grant_fields).
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub password: Option<String>,
    /// The provider's authorization endpoint — where the browser is sent to
    /// let the user approve access. Required when
    /// [`grant_type`](Self::grant_type) is
    /// [`OAuthGrantType::AuthorizationCode`]; unused by the other two grants,
    /// which never open a browser. See [`validate_grant_fields`](Self::validate_grant_fields).
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub authorization_url: Option<String>,
    /// Where the provider redirects back with the authorization code — must
    /// match what is registered with the provider. Required when
    /// [`grant_type`](Self::grant_type) is
    /// [`OAuthGrantType::AuthorizationCode`]; the TUI's local callback
    /// listener binds to this exact address. See
    /// [`validate_grant_fields`](Self::validate_grant_fields).
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub redirect_uri: Option<String>,
}

impl OAuthAuth {
    /// `grant_type: password` requires both `username` and `password`;
    /// `grant_type: client_credentials` requires `client_secret`;
    /// `grant_type: authorization_code` requires `authorization_url` and
    /// `redirect_uri` (`client_secret` stays optional — see the type's own
    /// doc comment). Checked wherever [`Auth::validate_exclusivity`] already
    /// is — a request's own `auth:` block and an environment's default —
    /// for the same typed-error rigor every other schema rule in this
    /// project gets, rather than discovering the gap only once a token
    /// request is attempted.
    pub(crate) fn validate_grant_fields(&self) -> Result<(), String> {
        match self.grant_type {
            OAuthGrantType::Password if self.username.is_none() || self.password.is_none() => Err(
                "`auth.oauth` with `grant_type: password` requires both `username` and \
                     `password` to be set"
                    .to_string(),
            ),
            OAuthGrantType::ClientCredentials if self.client_secret.is_none() => Err(
                "`auth.oauth` with `grant_type: client_credentials` requires `client_secret` to \
                 be set"
                    .to_string(),
            ),
            OAuthGrantType::AuthorizationCode
                if self.authorization_url.is_none() || self.redirect_uri.is_none() =>
            {
                Err(
                    "`auth.oauth` with `grant_type: authorization_code` requires both \
                     `authorization_url` and `redirect_uri` to be set"
                        .to_string(),
                )
            }
            _ => Ok(()),
        }
    }
}

/// [`OAuthAuth::grant_type`]: which of the three supported OAuth grants to
/// use. See [`crate::oauth`]'s module docs for how `authorization_code`
/// differs from the other two.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
#[cfg_attr(feature = "schema", derive(schemars::JsonSchema))]
#[serde(rename_all = "snake_case")]
pub enum OAuthGrantType {
    ClientCredentials,
    Password,
    AuthorizationCode,
}

impl OAuthGrantType {
    /// The exact `grant_type` value OAuth's token request wire format
    /// expects — see [RFC 6749 §4.3.2/§4.4.2/§4.1.3].
    pub(crate) fn as_str(self) -> &'static str {
        match self {
            OAuthGrantType::ClientCredentials => "client_credentials",
            OAuthGrantType::Password => "password",
            OAuthGrantType::AuthorizationCode => "authorization_code",
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn base(grant_type: OAuthGrantType) -> OAuthAuth {
        OAuthAuth {
            grant_type,
            token_url: "https://auth.example.com/token".to_string(),
            client_id: "client".to_string(),
            client_secret: None,
            scope: None,
            username: None,
            password: None,
            authorization_url: None,
            redirect_uri: None,
        }
    }

    #[test]
    fn client_credentials_requires_a_client_secret() {
        let err = base(OAuthGrantType::ClientCredentials)
            .validate_grant_fields()
            .expect_err("no client_secret must be rejected");
        assert!(err.contains("client_secret"), "got {err}");

        let ok = OAuthAuth {
            client_secret: Some("s".to_string()),
            ..base(OAuthGrantType::ClientCredentials)
        };
        assert!(ok.validate_grant_fields().is_ok());
    }

    #[test]
    fn password_requires_username_and_password() {
        let err = base(OAuthGrantType::Password)
            .validate_grant_fields()
            .expect_err("no username/password must be rejected");
        assert!(
            err.contains("username") && err.contains("password"),
            "got {err}"
        );

        let ok = OAuthAuth {
            username: Some("ada".to_string()),
            password: Some("hunter2".to_string()),
            ..base(OAuthGrantType::Password)
        };
        assert!(ok.validate_grant_fields().is_ok());
    }

    #[test]
    fn authorization_code_requires_authorization_url_and_redirect_uri_but_not_client_secret() {
        let err = base(OAuthGrantType::AuthorizationCode)
            .validate_grant_fields()
            .expect_err("no authorization_url/redirect_uri must be rejected");
        assert!(
            err.contains("authorization_url") && err.contains("redirect_uri"),
            "got {err}"
        );

        let ok = OAuthAuth {
            authorization_url: Some("https://auth.example.com/authorize".to_string()),
            redirect_uri: Some("http://127.0.0.1:8899/callback".to_string()),
            // client_secret deliberately left None — a public client is a
            // valid authorization_code config, unlike the other two grants.
            ..base(OAuthGrantType::AuthorizationCode)
        };
        assert!(
            ok.validate_grant_fields().is_ok(),
            "authorization_code must not require client_secret"
        );
    }

    #[test]
    fn authorization_code_missing_only_redirect_uri_is_still_rejected() {
        let err = OAuthAuth {
            authorization_url: Some("https://auth.example.com/authorize".to_string()),
            ..base(OAuthGrantType::AuthorizationCode)
        }
        .validate_grant_fields()
        .expect_err("redirect_uri alone missing must still be rejected");
        assert!(err.contains("redirect_uri"), "got {err}");
    }
}