/*
   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 message

import (
	"net/http"

	"github.com/sirupsen/logrus"
	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
	"github.com/superseriousbusiness/gotosocial/internal/config"
	"github.com/superseriousbusiness/gotosocial/internal/db"
	"github.com/superseriousbusiness/gotosocial/internal/federation"
	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
	"github.com/superseriousbusiness/gotosocial/internal/media"
	"github.com/superseriousbusiness/gotosocial/internal/oauth"
	"github.com/superseriousbusiness/gotosocial/internal/storage"
	"github.com/superseriousbusiness/gotosocial/internal/typeutils"
)

// Processor should be passed to api modules (see internal/apimodule/...). It is used for
// passing messages back and forth from the client API and the federating interface, via channels.
// It also contains logic for filtering which messages should end up where.
// It is designed to be used asynchronously: the client API and the federating API should just be able to
// fire messages into the processor and not wait for a reply before proceeding with other work. This allows
// for clean distribution of messages without slowing down the client API and harming the user experience.
type Processor interface {
	// ToClientAPI returns a channel for putting in messages that need to go to the gts client API.
	ToClientAPI() chan ToClientAPI
	// FromClientAPI returns a channel for putting messages in that come from the client api going to the processor
	FromClientAPI() chan FromClientAPI
	// ToFederator returns a channel for putting in messages that need to go to the federator (activitypub).
	ToFederator() chan ToFederator
	// FromFederator returns a channel for putting messages in that come from the federator (activitypub) going into the processor
	FromFederator() chan FromFederator
	// Start starts the Processor, reading from its channels and passing messages back and forth.
	Start() error
	// Stop stops the processor cleanly, finishing handling any remaining messages before closing down.
	Stop() error

	/*
		CLIENT API-FACING PROCESSING FUNCTIONS
		These functions are intended to be called when the API client needs an immediate (ie., synchronous) reply
		to an HTTP request. As such, they will only do the bare-minimum of work necessary to give a properly
		formed reply. For more intensive (and time-consuming) calls, where you don't require an immediate
		response, pass work to the processor using a channel instead.
	*/

	// AccountCreate processes the given form for creating a new account, returning an oauth token for that account if successful.
	AccountCreate(authed *oauth.Auth, form *apimodel.AccountCreateRequest) (*apimodel.Token, error)
	// AccountGet processes the given request for account information.
	AccountGet(authed *oauth.Auth, targetAccountID string) (*apimodel.Account, error)
	// AccountUpdate processes the update of an account with the given form
	AccountUpdate(authed *oauth.Auth, form *apimodel.UpdateCredentialsRequest) (*apimodel.Account, error)

	// AppCreate processes the creation of a new API application
	AppCreate(authed *oauth.Auth, form *apimodel.ApplicationCreateRequest) (*apimodel.Application, error)

	// StatusCreate processes the given form to create a new status, returning the api model representation of that status if it's OK.
	StatusCreate(authed *oauth.Auth, form *apimodel.AdvancedStatusCreateForm) (*apimodel.Status, error)
	// StatusDelete processes the delete of a given status, returning the deleted status if the delete goes through.
	StatusDelete(authed *oauth.Auth, targetStatusID string) (*apimodel.Status, error)
	// StatusFave processes the faving of a given status, returning the updated status if the fave goes through.
	StatusFave(authed *oauth.Auth, targetStatusID string) (*apimodel.Status, error)
	// StatusFavedBy returns a slice of accounts that have liked the given status, filtered according to privacy settings.
	StatusFavedBy(authed *oauth.Auth, targetStatusID string) ([]*apimodel.Account, error)
	// StatusGet gets the given status, taking account of privacy settings and blocks etc.
	StatusGet(authed *oauth.Auth, targetStatusID string) (*apimodel.Status, error)
	// StatusUnfave processes the unfaving of a given status, returning the updated status if the fave goes through.
	StatusUnfave(authed *oauth.Auth, targetStatusID string) (*apimodel.Status, error)

	// MediaCreate handles the creation of a media attachment, using the given form.
	MediaCreate(authed *oauth.Auth, form *apimodel.AttachmentRequest) (*apimodel.Attachment, error)
	// MediaGet handles the fetching of a media attachment, using the given request form.
	MediaGet(authed *oauth.Auth, form *apimodel.GetContentRequestForm) (*apimodel.Content, error)
	// AdminEmojiCreate handles the creation of a new instance emoji by an admin, using the given form.
	AdminEmojiCreate(authed *oauth.Auth, form *apimodel.EmojiCreateRequest) (*apimodel.Emoji, error)

	/*
		FEDERATION API-FACING PROCESSING FUNCTIONS
		These functions are intended to be called when the federating client needs an immediate (ie., synchronous) reply
		to an HTTP request. As such, they will only do the bare-minimum of work necessary to give a properly
		formed reply. For more intensive (and time-consuming) calls, where you don't require an immediate
		response, pass work to the processor using a channel instead.
	*/

	// GetFediUser handles the getting of a fedi/activitypub representation of a user/account, performing appropriate authentication
	// before returning a JSON serializable interface to the caller.
	GetFediUser(requestedUsername string, request *http.Request) (interface{}, ErrorWithCode)
}

// processor just implements the Processor interface
type processor struct {
	// federator     pub.FederatingActor
	toClientAPI   chan ToClientAPI
	fromClientAPI chan FromClientAPI
	toFederator   chan ToFederator
	fromFederator chan FromFederator
	federator     federation.Federator
	stop          chan interface{}
	log           *logrus.Logger
	config        *config.Config
	tc            typeutils.TypeConverter
	oauthServer   oauth.Server
	mediaHandler  media.Handler
	storage       storage.Storage
	db            db.DB
}

// NewProcessor returns a new Processor that uses the given federator and logger
func NewProcessor(config *config.Config, tc typeutils.TypeConverter, federator federation.Federator, oauthServer oauth.Server, mediaHandler media.Handler, storage storage.Storage, db db.DB, log *logrus.Logger) Processor {
	return &processor{
		toClientAPI:   make(chan ToClientAPI, 100),
		fromClientAPI: make(chan FromClientAPI, 100),
		toFederator:   make(chan ToFederator, 100),
		fromFederator: make(chan FromFederator, 100),
		federator:     federator,
		stop:          make(chan interface{}),
		log:           log,
		config:        config,
		tc:            tc,
		oauthServer:   oauthServer,
		mediaHandler:  mediaHandler,
		storage:       storage,
		db:            db,
	}
}

func (p *processor) ToClientAPI() chan ToClientAPI {
	return p.toClientAPI
}

func (p *processor) FromClientAPI() chan FromClientAPI {
	return p.fromClientAPI
}

func (p *processor) ToFederator() chan ToFederator {
	return p.toFederator
}

func (p *processor) FromFederator() chan FromFederator {
	return p.fromFederator
}

// Start starts the Processor, reading from its channels and passing messages back and forth.
func (p *processor) Start() error {
	go func() {
	DistLoop:
		for {
			select {
			case clientMsg := <-p.toClientAPI:
				p.log.Infof("received message TO client API: %+v", clientMsg)
			case clientMsg := <-p.fromClientAPI:
				p.log.Infof("received message FROM client API: %+v", clientMsg)
			case federatorMsg := <-p.toFederator:
				p.log.Infof("received message TO federator: %+v", federatorMsg)
			case federatorMsg := <-p.fromFederator:
				p.log.Infof("received message FROM federator: %+v", federatorMsg)
			case <-p.stop:
				break DistLoop
			}
		}
	}()
	return nil
}

// Stop stops the processor cleanly, finishing handling any remaining messages before closing down.
// TODO: empty message buffer properly before stopping otherwise we'll lose federating messages.
func (p *processor) Stop() error {
	close(p.stop)
	return nil
}

// ToClientAPI wraps a message that travels from the processor into the client API
type ToClientAPI struct {
	APObjectType   gtsmodel.ActivityStreamsObject
	APActivityType gtsmodel.ActivityStreamsActivity
	Activity       interface{}
}

// FromClientAPI wraps a message that travels from client API into the processor
type FromClientAPI struct {
	APObjectType   gtsmodel.ActivityStreamsObject
	APActivityType gtsmodel.ActivityStreamsActivity
	Activity       interface{}
}

// ToFederator wraps a message that travels from the processor into the federator
type ToFederator struct {
	APObjectType   gtsmodel.ActivityStreamsObject
	APActivityType gtsmodel.ActivityStreamsActivity
	Activity       interface{}
}

// FromFederator wraps a message that travels from the federator into the processor
type FromFederator struct {
	APObjectType   gtsmodel.ActivityStreamsObject
	APActivityType gtsmodel.ActivityStreamsActivity
	Activity       interface{}
}