[chore] Deinterface processor and subprocessors (#1501)

* [chore] Deinterface processor and subprocessors

* expose subprocessors via function calls

* missing license header

internal/processing/stream/open.go

@@ -0,0 +1,121 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2023 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 stream
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"codeberg.org/gruf/go-kv"
+	"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/stream"
+)
+
+// Open returns a new Stream for the given account, which will contain a channel for passing messages back to the caller.
+func (p *Processor) Open(ctx context.Context, account *gtsmodel.Account, streamTimeline string) (*stream.Stream, gtserror.WithCode) {
+	l := log.WithContext(ctx).WithFields(kv.Fields{
+		{"account", account.ID},
+		{"streamType", streamTimeline},
+	}...)
+	l.Debug("received open stream request")
+
+	// each stream needs a unique ID so we know to close it
+	streamID, err := id.NewRandomULID()
+	if err != nil {
+		return nil, gtserror.NewErrorInternalError(fmt.Errorf("error generating stream id: %s", err))
+	}
+
+	thisStream := &stream.Stream{
+		ID:        streamID,
+		Timeline:  streamTimeline,
+		Messages:  make(chan *stream.Message, 100),
+		Hangup:    make(chan interface{}, 1),
+		Connected: true,
+	}
+	go p.waitToCloseStream(account, thisStream)
+
+	v, ok := p.streamMap.Load(account.ID)
+	if !ok || v == nil {
+		// there is no entry in the streamMap for this account yet, so make one and store it
+		streamsForAccount := &stream.StreamsForAccount{
+			Streams: []*stream.Stream{
+				thisStream,
+			},
+		}
+		p.streamMap.Store(account.ID, streamsForAccount)
+	} else {
+		// there is an entry in the streamMap for this account
+		// parse the interface as a streamsForAccount
+		streamsForAccount, ok := v.(*stream.StreamsForAccount)
+		if !ok {
+			return nil, gtserror.NewErrorInternalError(errors.New("stream map error"))
+		}
+
+		// append this stream to it
+		streamsForAccount.Lock()
+		streamsForAccount.Streams = append(streamsForAccount.Streams, thisStream)
+		streamsForAccount.Unlock()
+	}
+
+	return thisStream, nil
+}
+
+// waitToCloseStream waits until the hangup channel is closed for the given stream.
+// It then iterates through the map of streams stored by the processor, removes the stream from it,
+// and then closes the messages channel of the stream to indicate that the channel should no longer be read from.
+func (p *Processor) waitToCloseStream(account *gtsmodel.Account, thisStream *stream.Stream) {
+	<-thisStream.Hangup // wait for a hangup message
+
+	// lock the stream to prevent more messages being put in it while we work
+	thisStream.Lock()
+	defer thisStream.Unlock()
+
+	// indicate the stream is no longer connected
+	thisStream.Connected = false
+
+	// load and parse the entry for this account from the stream map
+	v, ok := p.streamMap.Load(account.ID)
+	if !ok || v == nil {
+		return
+	}
+	streamsForAccount, ok := v.(*stream.StreamsForAccount)
+	if !ok {
+		return
+	}
+
+	// lock the streams for account while we remove this stream from its slice
+	streamsForAccount.Lock()
+	defer streamsForAccount.Unlock()
+
+	// put everything into modified streams *except* the stream we're removing
+	modifiedStreams := []*stream.Stream{}
+	for _, s := range streamsForAccount.Streams {
+		if s.ID != thisStream.ID {
+			modifiedStreams = append(modifiedStreams, s)
+		}
+	}
+	streamsForAccount.Streams = modifiedStreams
+
+	// finally close the messages channel so no more messages can be read from it
+	close(thisStream.Messages)
+}