// GoToSocial
// Copyright (C) GoToSocial Authors admin@gotosocial.org
// SPDX-License-Identifier: AGPL-3.0-or-later
//
// 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 federatingdb

import (
	"context"
	"errors"
	"fmt"
	"strings"

	"codeberg.org/gruf/go-logger/v2/level"
	"github.com/superseriousbusiness/activity/streams/vocab"
	"github.com/superseriousbusiness/gotosocial/internal/ap"
	"github.com/superseriousbusiness/gotosocial/internal/config"
	"github.com/superseriousbusiness/gotosocial/internal/db"
	"github.com/superseriousbusiness/gotosocial/internal/gtscontext"
	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
	"github.com/superseriousbusiness/gotosocial/internal/id"
	"github.com/superseriousbusiness/gotosocial/internal/log"
	"github.com/superseriousbusiness/gotosocial/internal/messages"
	"github.com/superseriousbusiness/gotosocial/internal/util"
)

// Create adds a new entry to the database which must be able to be
// keyed by its id.
//
// Note that Activity values received from federated peers may also be
// created in the database this way if the Federating Protocol is
// enabled. The client may freely decide to store only the id instead of
// the entire value.
//
// The library makes this call only after acquiring a lock first.
//
// Under certain conditions and network activities, Create may be called
// multiple times for the same ActivityStreams object.
func (f *federatingDB) Create(ctx context.Context, asType vocab.Type) error {
	if log.Level() >= level.TRACE {
		i, err := marshalItem(asType)
		if err != nil {
			return err
		}

		log.
			WithContext(ctx).
			WithField("create", i).
			Trace("entering Create")
	}

	receivingAccount, requestingAccount, internal := extractFromCtx(ctx)
	if internal {
		return nil // Already processed.
	}

	switch asType.GetTypeName() {
	case ap.ActivityBlock:
		// BLOCK SOMETHING
		return f.activityBlock(ctx, asType, receivingAccount, requestingAccount)
	case ap.ActivityCreate:
		// CREATE SOMETHING
		return f.activityCreate(ctx, asType, receivingAccount, requestingAccount)
	case ap.ActivityFollow:
		// FOLLOW SOMETHING
		return f.activityFollow(ctx, asType, receivingAccount, requestingAccount)
	case ap.ActivityLike:
		// LIKE SOMETHING
		return f.activityLike(ctx, asType, receivingAccount, requestingAccount)
	case ap.ActivityFlag:
		// FLAG / REPORT SOMETHING
		return f.activityFlag(ctx, asType, receivingAccount, requestingAccount)
	}

	return nil
}

/*
	BLOCK HANDLERS
*/

func (f *federatingDB) activityBlock(ctx context.Context, asType vocab.Type, receiving *gtsmodel.Account, requestingAccount *gtsmodel.Account) error {
	blockable, ok := asType.(vocab.ActivityStreamsBlock)
	if !ok {
		return errors.New("activityBlock: could not convert type to block")
	}

	block, err := f.converter.ASBlockToBlock(ctx, blockable)
	if err != nil {
		return fmt.Errorf("activityBlock: could not convert Block to gts model block")
	}

	block.ID = id.NewULID()

	if err := f.state.DB.PutBlock(ctx, block); err != nil {
		return fmt.Errorf("activityBlock: database error inserting block: %s", err)
	}

	f.state.Workers.EnqueueFediAPI(ctx, messages.FromFediAPI{
		APObjectType:     ap.ActivityBlock,
		APActivityType:   ap.ActivityCreate,
		GTSModel:         block,
		ReceivingAccount: receiving,
	})

	return nil
}

/*
	CREATE HANDLERS
*/

// activityCreate handles asType Create by checking
// the Object entries of the Create and calling other
// handlers as appropriate.
func (f *federatingDB) activityCreate(
	ctx context.Context,
	asType vocab.Type,
	receivingAccount *gtsmodel.Account,
	requestingAccount *gtsmodel.Account,
) error {
	create, ok := asType.(vocab.ActivityStreamsCreate)
	if !ok {
		return gtserror.Newf("could not convert asType %T to ActivityStreamsCreate", asType)
	}

	var errs gtserror.MultiError

	// Extract objects from create activity.
	objects := ap.ExtractObjects(create)

	// Extract PollOptionables (votes!) from objects slice.
	optionables, objects := ap.ExtractPollOptionables(objects)

	if len(optionables) > 0 {
		// Handle provided poll vote(s) creation, this can
		// be for single or multiple votes in the same poll.
		err := f.createPollOptionables(ctx,
			receivingAccount,
			requestingAccount,
			optionables,
		)
		if err != nil {
			errs.Appendf("error creating poll vote(s): %w", err)
		}
	}

	// Extract Statusables from objects slice (this must be
	// done AFTER extracting options due to how AS typing works).
	statusables, objects := ap.ExtractStatusables(objects)

	for _, statusable := range statusables {
		// Check if this is a forwarded object, i.e. did
		// the account making the request also create this?
		forwarded := !isSender(statusable, requestingAccount)

		// Handle create event for this statusable.
		if err := f.createStatusable(ctx,
			receivingAccount,
			requestingAccount,
			statusable,
			forwarded,
		); err != nil {
			errs.Appendf("error creating statusable: %w", err)
		}
	}

	if len(objects) > 0 {
		// Log any unhandled objects after filtering for debug purposes.
		log.Debugf(ctx, "unhandled CREATE types: %v", typeNames(objects))
	}

	return errs.Combine()
}

// createPollOptionable handles a Create activity for a PollOptionable.
// This function doesn't handle database insertion, only validation checks
// before passing off to a worker for asynchronous processing.
func (f *federatingDB) createPollOptionables(
	ctx context.Context,
	receiver *gtsmodel.Account,
	requester *gtsmodel.Account,
	options []ap.PollOptionable,
) error {
	var (
		// the origin Status w/ Poll the vote
		// options are in. This gets set on first
		// iteration, relevant checks performed
		// then re-used in each further iteration.
		inReplyTo *gtsmodel.Status

		// the resulting slices of Poll.Option
		// choice indices passed into the new
		// created PollVote object.
		choices []int
	)

	for _, option := range options {
		// Extract the "inReplyTo" property.
		inReplyToURIs := ap.GetInReplyTo(option)
		if len(inReplyToURIs) != 1 {
			return gtserror.Newf("invalid inReplyTo property length: %d", len(inReplyToURIs))
		}

		// Stringify the inReplyTo URI.
		statusURI := inReplyToURIs[0].String()

		if inReplyTo == nil {
			var err error

			// This is the first object in the activity slice,
			// check database for the poll source status by URI.
			inReplyTo, err = f.state.DB.GetStatusByURI(ctx, statusURI)
			if err != nil {
				return gtserror.Newf("error getting poll source from database %s: %w", statusURI, err)
			}

			switch {
			// The origin status isn't a poll?
			case inReplyTo.PollID == "":
				return gtserror.Newf("poll vote in status %s without poll", statusURI)

			// We don't own the poll ...
			case !*inReplyTo.Local:
				return gtserror.Newf("poll vote in remote status %s", statusURI)
			}

			// Check whether user has already vote in this poll.
			// (we only check this for the first object, as multiple
			// may be sent in response to a multiple-choice poll).
			vote, err := f.state.DB.GetPollVoteBy(
				gtscontext.SetBarebones(ctx),
				inReplyTo.PollID,
				requester.ID,
			)
			if err != nil && !errors.Is(err, db.ErrNoEntries) {
				return gtserror.Newf("error getting status %s poll votes from database: %w", statusURI, err)
			}

			if vote != nil {
				log.Warnf(ctx, "%s has already voted in poll %s", requester.URI, statusURI)
				return nil // this is a useful warning for admins to report to us from logs
			}
		}

		if statusURI != inReplyTo.URI {
			// All activity votes should be to the same poll per activity.
			return gtserror.New("votes to multiple polls in single activity")
		}

		// Extract the poll option name.
		name := ap.ExtractName(option)

		// Check that this is a valid option name.
		choice := inReplyTo.Poll.GetChoice(name)
		if choice == -1 {
			return gtserror.Newf("poll vote in status %s invalid: %s", statusURI, name)
		}

		// Append the option index to choices.
		choices = append(choices, choice)
	}

	// Enqueue message to the fedi API worker with poll vote(s).
	f.state.Workers.EnqueueFediAPI(ctx, messages.FromFediAPI{
		APActivityType: ap.ActivityCreate,
		APObjectType:   ap.ActivityQuestion,
		GTSModel: &gtsmodel.PollVote{
			ID:        id.NewULID(),
			Choices:   choices,
			AccountID: requester.ID,
			Account:   requester,
			PollID:    inReplyTo.PollID,
			Poll:      inReplyTo.Poll,
		},
		ReceivingAccount: receiver,
	})

	return nil
}

// createStatusable handles a Create activity for a Statusable.
// This function won't insert anything in the database yet,
// but will pass the Statusable (if appropriate) through to
// the processor for further asynchronous processing.
func (f *federatingDB) createStatusable(
	ctx context.Context,
	receiver *gtsmodel.Account,
	requester *gtsmodel.Account,
	statusable ap.Statusable,
	forwarded bool,
) error {

	// Check whether we should accept this new status,
	// we do this BEFORE even handling forwards to us.
	accept, err := f.shouldAcceptStatusable(ctx,
		receiver,
		requester,
		statusable,
	)
	if err != nil {
		return gtserror.Newf("error checking status acceptibility: %w", err)
	}

	if !accept {
		// This is a status sent with no relation to receiver, i.e.
		// - receiving account does not follow requesting account
		// - received status does not mention receiving account
		//
		// We just pretend that all is fine (dog with cuppa, flames everywhere)
		log.Trace(ctx, "status failed acceptability check")
		return nil
	}

	// If we do have a forward, we should ignore the content
	// and instead deref based on the URI of the statusable.
	//
	// In other words, don't automatically trust whoever sent
	// this status to us, but fetch the authentic article from
	// the server it originated from.
	if forwarded {

		// Pass the statusable URI (APIri) into the processor
		// worker and do the rest of the processing asynchronously.
		f.state.Workers.EnqueueFediAPI(ctx, messages.FromFediAPI{
			APObjectType:     ap.ObjectNote,
			APActivityType:   ap.ActivityCreate,
			APIri:            ap.GetJSONLDId(statusable),
			APObjectModel:    nil,
			GTSModel:         nil,
			ReceivingAccount: receiver,
		})
		return nil
	}

	// Do the rest of the processing asynchronously. The processor
	// will handle inserting/updating + further dereferencing the status.
	f.state.Workers.EnqueueFediAPI(ctx, messages.FromFediAPI{
		APObjectType:     ap.ObjectNote,
		APActivityType:   ap.ActivityCreate,
		APIri:            nil,
		GTSModel:         nil,
		APObjectModel:    statusable,
		ReceivingAccount: receiver,
	})

	return nil
}

func (f *federatingDB) shouldAcceptStatusable(ctx context.Context, receiver *gtsmodel.Account, requester *gtsmodel.Account, statusable ap.Statusable) (bool, error) {
	host := config.GetHost()
	accountDomain := config.GetAccountDomain()

	// Check whether status mentions the receiver,
	// this is the quickest check so perform it first.
	mentions, _ := ap.ExtractMentions(statusable)
	for _, mention := range mentions {

		// Extract placeholder mention vars.
		accURI := mention.TargetAccountURI
		name := mention.NameString

		switch {
		case accURI != "" &&
			accURI == receiver.URI || accURI == receiver.URL:
			// Mention target is receiver,
			// they are mentioned in status.
			return true, nil

		case accURI == "" && name != "":
			// Only a name was provided, extract the user@domain parts.
			user, domain, err := util.ExtractNamestringParts(name)
			if err != nil {
				return false, gtserror.Newf("error extracting mention name parts: %w", err)
			}

			// Check if the name points to our receiving local user.
			isLocal := (domain == host || domain == accountDomain)
			if isLocal && strings.EqualFold(user, receiver.Username) {
				return true, nil
			}
		}
	}

	// Check whether receiving account follows the requesting account.
	follows, err := f.state.DB.IsFollowing(ctx, receiver.ID, requester.ID)
	if err != nil {
		return false, gtserror.Newf("error checking follow status: %w", err)
	}

	// Status will only be acceptable
	// if receiver follows requester.
	return follows, nil
}

/*
	FOLLOW HANDLERS
*/

func (f *federatingDB) activityFollow(ctx context.Context, asType vocab.Type, receivingAccount *gtsmodel.Account, requestingAccount *gtsmodel.Account) error {
	follow, ok := asType.(vocab.ActivityStreamsFollow)
	if !ok {
		return errors.New("activityFollow: could not convert type to follow")
	}

	followRequest, err := f.converter.ASFollowToFollowRequest(ctx, follow)
	if err != nil {
		return fmt.Errorf("activityFollow: could not convert Follow to follow request: %s", err)
	}

	followRequest.ID = id.NewULID()

	if err := f.state.DB.PutFollowRequest(ctx, followRequest); err != nil {
		return fmt.Errorf("activityFollow: database error inserting follow request: %s", err)
	}

	f.state.Workers.EnqueueFediAPI(ctx, messages.FromFediAPI{
		APObjectType:     ap.ActivityFollow,
		APActivityType:   ap.ActivityCreate,
		GTSModel:         followRequest,
		ReceivingAccount: receivingAccount,
	})

	return nil
}

/*
	LIKE HANDLERS
*/

func (f *federatingDB) activityLike(ctx context.Context, asType vocab.Type, receivingAccount *gtsmodel.Account, requestingAccount *gtsmodel.Account) error {
	like, ok := asType.(vocab.ActivityStreamsLike)
	if !ok {
		return errors.New("activityLike: could not convert type to like")
	}

	fave, err := f.converter.ASLikeToFave(ctx, like)
	if err != nil {
		return fmt.Errorf("activityLike: could not convert Like to fave: %w", err)
	}

	fave.ID = id.NewULID()

	if err := f.state.DB.PutStatusFave(ctx, fave); err != nil {
		if errors.Is(err, db.ErrAlreadyExists) {
			// The Like already exists in the database, which
			// means we've already handled side effects. We can
			// just return nil here and be done with it.
			return nil
		}
		return fmt.Errorf("activityLike: database error inserting fave: %w", err)
	}

	f.state.Workers.EnqueueFediAPI(ctx, messages.FromFediAPI{
		APObjectType:     ap.ActivityLike,
		APActivityType:   ap.ActivityCreate,
		GTSModel:         fave,
		ReceivingAccount: receivingAccount,
	})

	return nil
}

/*
	FLAG HANDLERS
*/

func (f *federatingDB) activityFlag(ctx context.Context, asType vocab.Type, receivingAccount *gtsmodel.Account, requestingAccount *gtsmodel.Account) error {
	flag, ok := asType.(vocab.ActivityStreamsFlag)
	if !ok {
		return errors.New("activityFlag: could not convert type to flag")
	}

	report, err := f.converter.ASFlagToReport(ctx, flag)
	if err != nil {
		return fmt.Errorf("activityFlag: could not convert Flag to report: %w", err)
	}

	report.ID = id.NewULID()

	if err := f.state.DB.PutReport(ctx, report); err != nil {
		return fmt.Errorf("activityFlag: database error inserting report: %w", err)
	}

	f.state.Workers.EnqueueFediAPI(ctx, messages.FromFediAPI{
		APObjectType:     ap.ActivityFlag,
		APActivityType:   ap.ActivityCreate,
		GTSModel:         report,
		ReceivingAccount: receivingAccount,
	})

	return nil
}