/*
   GoToSocial
   Copyright (C) 2021 GoToSocial Authors admin@gotosocial.org

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU Affero General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Affero General Public License for more details.

   You should have received a copy of the GNU Affero General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

// Package federation provides ActivityPub/federation functionality for GoToSocial
package federation

import (
	"context"
	"net/http"
	"net/url"
	"time"

	"github.com/go-fed/activity/pub"
	"github.com/go-fed/activity/streams/vocab"
	"github.com/sirupsen/logrus"
	"github.com/superseriousbusiness/gotosocial/internal/db"
)

// New returns a go-fed compatible federating actor
func New(db db.DB, log *logrus.Logger) pub.FederatingActor {
	f := &Federator{
		db: db,
	}
	return pub.NewFederatingActor(f, f, db.Federation(), f)
}

// Federator implements several go-fed interfaces in one convenient location
type Federator struct {
	db db.DB
}

/*
	GO FED FEDERATING PROTOCOL INTERFACE
	FederatingProtocol contains behaviors an application needs to satisfy for the
	full ActivityPub S2S implementation to be supported by this library.
	It is only required if the client application wants to support the server-to-
	server, or federating, protocol.
	It is passed to the library as a dependency injection from the client
	application.
*/

// PostInboxRequestBodyHook callback after parsing the request body for a federated request
// to the Actor's inbox.
//
// Can be used to set contextual information based on the Activity
// received.
//
// Only called if the Federated Protocol is enabled.
//
// Warning: Neither authentication nor authorization has taken place at
// this time. Doing anything beyond setting contextual information is
// strongly discouraged.
//
// If an error is returned, it is passed back to the caller of
// PostInbox. In this case, the DelegateActor implementation must not
// write a response to the ResponseWriter as is expected that the caller
// to PostInbox will do so when handling the error.
func (f *Federator) PostInboxRequestBodyHook(ctx context.Context, r *http.Request, activity pub.Activity) (context.Context, error) {
	// TODO
	return nil, nil
}

// AuthenticatePostInbox delegates the authentication of a POST to an
// inbox.
//
// If an error is returned, it is passed back to the caller of
// PostInbox. In this case, the implementation must not write a
// response to the ResponseWriter as is expected that the client will
// do so when handling the error. The 'authenticated' is ignored.
//
// If no error is returned, but authentication or authorization fails,
// then authenticated must be false and error nil. It is expected that
// the implementation handles writing to the ResponseWriter in this
// case.
//
// Finally, if the authentication and authorization succeeds, then
// authenticated must be true and error nil. The request will continue
// to be processed.
func (f *Federator) AuthenticatePostInbox(ctx context.Context, w http.ResponseWriter, r *http.Request) (context.Context, bool, error) {
	// TODO
	return nil, false, nil
}

// Blocked should determine whether to permit a set of actors given by
// their ids are able to interact with this particular end user due to
// being blocked or other application-specific logic.
//
// If an error is returned, it is passed back to the caller of
// PostInbox.
//
// If no error is returned, but authentication or authorization fails,
// then blocked must be true and error nil. An http.StatusForbidden
// will be written in the wresponse.
//
// Finally, if the authentication and authorization succeeds, then
// blocked must be false and error nil. The request will continue
// to be processed.
func (f *Federator) Blocked(ctx context.Context, actorIRIs []*url.URL) (bool, error) {
	// TODO
	return false, nil
}

// FederatingCallbacks returns the application logic that handles
// ActivityStreams received from federating peers.
//
// Note that certain types of callbacks will be 'wrapped' with default
// behaviors supported natively by the library. Other callbacks
// compatible with streams.TypeResolver can be specified by 'other'.
//
// For example, setting the 'Create' field in the
// FederatingWrappedCallbacks lets an application dependency inject
// additional behaviors they want to take place, including the default
// behavior supplied by this library. This is guaranteed to be compliant
// with the ActivityPub Social protocol.
//
// To override the default behavior, instead supply the function in
// 'other', which does not guarantee the application will be compliant
// with the ActivityPub Social Protocol.
//
// Applications are not expected to handle every single ActivityStreams
// type and extension. The unhandled ones are passed to DefaultCallback.
func (f *Federator) FederatingCallbacks(ctx context.Context) (pub.FederatingWrappedCallbacks, []interface{}, error) {
	// TODO
	return pub.FederatingWrappedCallbacks{}, nil, nil
}

// DefaultCallback is called for types that go-fed can deserialize but
// are not handled by the application's callbacks returned in the
// Callbacks method.
//
// Applications are not expected to handle every single ActivityStreams
// type and extension, so the unhandled ones are passed to
// DefaultCallback.
func (f *Federator) DefaultCallback(ctx context.Context, activity pub.Activity) error {
	// TODO
	return nil
}

// MaxInboxForwardingRecursionDepth determines how deep to search within
// an activity to determine if inbox forwarding needs to occur.
//
// Zero or negative numbers indicate infinite recursion.
func (f *Federator) MaxInboxForwardingRecursionDepth(ctx context.Context) int {
	// TODO
	return 0
}

// MaxDeliveryRecursionDepth determines how deep to search within
// collections owned by peers when they are targeted to receive a
// delivery.
//
// Zero or negative numbers indicate infinite recursion.
func (f *Federator) MaxDeliveryRecursionDepth(ctx context.Context) int {
	// TODO
	return 0
}

// FilterForwarding allows the implementation to apply business logic
// such as blocks, spam filtering, and so on to a list of potential
// Collections and OrderedCollections of recipients when inbox
// forwarding has been triggered.
//
// The activity is provided as a reference for more intelligent
// logic to be used, but the implementation must not modify it.
func (f *Federator) FilterForwarding(ctx context.Context, potentialRecipients []*url.URL, a pub.Activity) ([]*url.URL, error) {
	// TODO
	return nil, nil
}

// GetInbox returns the OrderedCollection inbox of the actor for this
// context. It is up to the implementation to provide the correct
// collection for the kind of authorization given in the request.
//
// AuthenticateGetInbox will be called prior to this.
//
// Always called, regardless whether the Federated Protocol or Social
// API is enabled.
func (f *Federator) GetInbox(ctx context.Context, r *http.Request) (vocab.ActivityStreamsOrderedCollectionPage, error) {
	// TODO
	return nil, nil
}

/*
	GOFED COMMON BEHAVIOR INTERFACE
	Contains functions required for both the Social API and Federating Protocol.
	It is passed to the library as a dependency injection from the client
	application.
*/

// AuthenticateGetInbox delegates the authentication of a GET to an
// inbox.
//
// Always called, regardless whether the Federated Protocol or Social
// API is enabled.
//
// If an error is returned, it is passed back to the caller of
// GetInbox. In this case, the implementation must not write a
// response to the ResponseWriter as is expected that the client will
// do so when handling the error. The 'authenticated' is ignored.
//
// If no error is returned, but authentication or authorization fails,
// then authenticated must be false and error nil. It is expected that
// the implementation handles writing to the ResponseWriter in this
// case.
//
// Finally, if the authentication and authorization succeeds, then
// authenticated must be true and error nil. The request will continue
// to be processed.
func (f *Federator) AuthenticateGetInbox(ctx context.Context, w http.ResponseWriter, r *http.Request) (context.Context, bool, error) {
	// TODO
	// use context.WithValue() and context.Value() to set and get values through here
	return nil, false, nil
}

// AuthenticateGetOutbox delegates the authentication of a GET to an
// outbox.
//
// Always called, regardless whether the Federated Protocol or Social
// API is enabled.
//
// If an error is returned, it is passed back to the caller of
// GetOutbox. In this case, the implementation must not write a
// response to the ResponseWriter as is expected that the client will
// do so when handling the error. The 'authenticated' is ignored.
//
// If no error is returned, but authentication or authorization fails,
// then authenticated must be false and error nil. It is expected that
// the implementation handles writing to the ResponseWriter in this
// case.
//
// Finally, if the authentication and authorization succeeds, then
// authenticated must be true and error nil. The request will continue
// to be processed.
func (f *Federator) AuthenticateGetOutbox(ctx context.Context, w http.ResponseWriter, r *http.Request) (context.Context, bool, error) {
	// TODO
	return nil, false, nil
}

// GetOutbox returns the OrderedCollection inbox of the actor for this
// context. It is up to the implementation to provide the correct
// collection for the kind of authorization given in the request.
//
// AuthenticateGetOutbox will be called prior to this.
//
// Always called, regardless whether the Federated Protocol or Social
// API is enabled.
func (f *Federator) GetOutbox(ctx context.Context, r *http.Request) (vocab.ActivityStreamsOrderedCollectionPage, error) {
	// TODO
	return nil, nil
}

// NewTransport returns a new Transport on behalf of a specific actor.
//
// The actorBoxIRI will be either the inbox or outbox of an actor who is
// attempting to do the dereferencing or delivery. Any authentication
// scheme applied on the request must be based on this actor. The
// request must contain some sort of credential of the user, such as a
// HTTP Signature.
//
// The gofedAgent passed in should be used by the Transport
// implementation in the User-Agent, as well as the application-specific
// user agent string. The gofedAgent will indicate this library's use as
// well as the library's version number.
//
// Any server-wide rate-limiting that needs to occur should happen in a
// Transport implementation. This factory function allows this to be
// created, so peer servers are not DOS'd.
//
// Any retry logic should also be handled by the Transport
// implementation.
//
// Note that the library will not maintain a long-lived pointer to the
// returned Transport so that any private credentials are able to be
// garbage collected.
func (f *Federator) NewTransport(ctx context.Context, actorBoxIRI *url.URL, gofedAgent string) (pub.Transport, error) {
	// TODO
	return nil, nil
}

/*
	GOFED CLOCK INTERFACE
	Determines the time.
*/

// Now returns the current time.
func (f *Federator) Now() time.Time {
	return time.Now()
}