// Package connector defines interfaces for federated identity strategies.
package connector

import (
	"context"
	"net/http"
)

// Connector is a mechanism for federating login to a remote identity service.
//
// Implementations are expected to implement either the PasswordConnector or
// CallbackConnector interface.
type Connector interface{}

// Scopes represents additional data requested by the clients about the end user.
type Scopes struct {
	// The client has requested a refresh token from the server.
	OfflineAccess bool

	// The client has requested group information about the end user.
	Groups bool
}

// Identity represents the ID Token claims supported by the server.
type Identity struct {
	UserID            string
	Username          string
	PreferredUsername string
	Email             string
	EmailVerified     bool

	Groups []string

	// ConnectorData holds data used by the connector for subsequent requests after initial
	// authentication, such as access tokens for upstream provides.
	//
	// This data is never shared with end users, OAuth clients, or through the API.
	ConnectorData []byte
}

// PasswordConnector is an interface implemented by connectors which take a
// username and password.
// Prompt() is used to inform the handler what to display in the password
// template. If this returns an empty string, it'll default to "Username".
type PasswordConnector interface {
	Prompt() string
	Login(ctx context.Context, s Scopes, username, password string) (identity Identity, validPassword bool, err error)
}

// CallbackConnector is an interface implemented by connectors which use an OAuth
// style redirect flow to determine user information.
type CallbackConnector interface {
	// The initial URL to redirect the user to.
	//
	// OAuth2 implementations should request different scopes from the upstream
	// identity provider based on the scopes requested by the downstream client.
	// For example, if the downstream client requests a refresh token from the
	// server, the connector should also request a token from the provider.
	//
	// Many identity providers have arbitrary restrictions on refresh tokens. For
	// example Google only allows a single refresh token per client/user/scopes
	// combination, and wont return a refresh token even if offline access is
	// requested if one has already been issues. There's no good general answer
	// for these kind of restrictions, and may require this package to become more
	// aware of the global set of user/connector interactions.
	LoginURL(s Scopes, callbackURL, state string) (string, error)

	// Handle the callback to the server and return an identity.
	HandleCallback(s Scopes, r *http.Request) (identity Identity, err error)
}

// SAMLConnector represents SAML connectors which implement the HTTP POST binding.
//  RelayState is handled by the server.
//
// See: https://docs.oasis-open.org/security/saml/v2.0/saml-bindings-2.0-os.pdf
// "3.5 HTTP POST Binding"
type SAMLConnector interface {
	// POSTData returns an encoded SAML request and SSO URL for the server to
	// render a POST form with.
	//
	// POSTData should encode the provided request ID in the returned serialized
	// SAML request.
	POSTData(s Scopes, requestID string) (ssoURL, samlRequest string, err error)

	// HandlePOST decodes, verifies, and maps attributes from the SAML response.
	// It passes the expected value of the "InResponseTo" response field, which
	// the connector must ensure matches the response value.
	//
	// See: https://www.oasis-open.org/committees/download.php/35711/sstc-saml-core-errata-2.0-wd-06-diff.pdf
	// "3.2.2 Complex Type StatusResponseType"
	HandlePOST(s Scopes, samlResponse, inResponseTo string) (identity Identity, err error)
}

// RefreshConnector is a connector that can update the client claims.
type RefreshConnector interface {
	// Refresh is called when a client attempts to claim a refresh token. The
	// connector should attempt to update the identity object to reflect any
	// changes since the token was last refreshed.
	Refresh(ctx context.Context, s Scopes, identity Identity) (Identity, error)
}
