1 files changed, 247 insertions, 0 deletions
diff --git a/matrix/history.go b/matrix/history.go
new file mode 100644
index 0000000..1b99125
--- /dev/null
+++ b/matrix/history.go
@@ -0,0 +1,247 @@
+// gomuks - A terminal Matrix client written in Go.
+// Copyright (C) 2019 Tulir Asokan
+//
+// 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 <https://www.gnu.org/licenses/>.
+
+package matrix
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/gob"
+	"sync"
+
+	bolt "go.etcd.io/bbolt"
+
+	"maunium.net/go/gomuks/matrix/rooms"
+	"maunium.net/go/mautrix"
+)
+
+type HistoryManager struct {
+	sync.Mutex
+
+	db *bolt.DB
+
+	historyEndPtr  map[*rooms.Room]uint64
+	historyLoadPtr map[*rooms.Room]uint64
+}
+
+var bucketRoomStreams = []byte("room_streams")
+var bucketRoomEventIDs = []byte("room_event_ids")
+var bucketStreamPointers = []byte("room_stream_pointers")
+
+const halfUint64 = ^uint64(0) >> 1
+
+func NewHistoryManager(dbPath string) (*HistoryManager, error) {
+	hm := &HistoryManager{
+		historyEndPtr:  make(map[*rooms.Room]uint64),
+		historyLoadPtr: make(map[*rooms.Room]uint64),
+	}
+	db, err := bolt.Open(dbPath, 0600, nil)
+	if err != nil {
+		return nil, err
+	}
+	err = db.Update(func(tx *bolt.Tx) error {
+		_, err = tx.CreateBucketIfNotExists(bucketRoomStreams)
+		if err != nil {
+			return err
+		}
+		_, err = tx.CreateBucketIfNotExists(bucketRoomEventIDs)
+		if err != nil {
+			return err
+		}
+		_, err = tx.CreateBucketIfNotExists(bucketStreamPointers)
+		if err != nil {
+			return err
+		}
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+	hm.db = db
+	return hm, nil
+}
+
+func (hm *HistoryManager) Close() error {
+	return hm.db.Close()
+}
+
+func (hm *HistoryManager) Get(room *rooms.Room, eventID string) (event *mautrix.Event, err error) {
+	err = hm.db.View(func(tx *bolt.Tx) error {
+		rid := []byte(room.ID)
+		eventIDs := tx.Bucket(bucketRoomEventIDs).Bucket(rid)
+		if eventIDs == nil {
+			return nil
+		}
+		streamIndex := eventIDs.Get([]byte(eventID))
+		if streamIndex == nil {
+			return nil
+		}
+		stream := tx.Bucket(bucketRoomStreams).Bucket(rid)
+		eventData := stream.Get(streamIndex)
+		var umErr error
+		event, umErr = unmarshalEvent(eventData)
+		return umErr
+	})
+	return
+}
+
+func (hm *HistoryManager) Append(room *rooms.Room, events []*mautrix.Event) error {
+	return hm.store(room, events, true)
+}
+
+func (hm *HistoryManager) Prepend(room *rooms.Room, events []*mautrix.Event) error {
+	return hm.store(room, events, false)
+}
+
+func (hm *HistoryManager) store(room *rooms.Room, events []*mautrix.Event, append bool) error {
+	hm.Lock()
+	defer hm.Unlock()
+	err := hm.db.Update(func(tx *bolt.Tx) error {
+		streamPointers := tx.Bucket(bucketStreamPointers)
+		rid := []byte(room.ID)
+		stream, err := tx.Bucket(bucketRoomStreams).CreateBucketIfNotExists(rid)
+		if err != nil {
+			return err
+		}
+		eventIDs, err := tx.Bucket(bucketRoomEventIDs).CreateBucketIfNotExists(rid)
+		if err != nil {
+			return err
+		}
+		if stream.Sequence() < halfUint64 {
+			// The sequence counter (i.e. the future) the part after 2^63, i.e. the second half of uint64
+			// We set it to -1 because NextSequence will increment it by one.
+			err = stream.SetSequence(halfUint64 - 1)
+			if err != nil {
+				return err
+			}
+		}
+		if append {
+			ptrStart, err := stream.NextSequence()
+			if err != nil {
+				return err
+			}
+			for i, event := range events {
+				if err := put(stream, eventIDs, event, ptrStart+uint64(i)); err != nil {
+					return err
+				}
+			}
+			err = stream.SetSequence(ptrStart + uint64(len(events)) - 1)
+			if err != nil {
+				return err
+			}
+		} else {
+			ptrStart, ok := hm.historyEndPtr[room]
+			if !ok {
+				ptrStartRaw := streamPointers.Get(rid)
+				if ptrStartRaw != nil {
+					ptrStart = btoi(ptrStartRaw)
+				} else {
+					ptrStart = halfUint64 - 1
+				}
+			}
+			eventCount := uint64(len(events))
+			for i, event := range events {
+				if err := put(stream, eventIDs, event, -ptrStart-uint64(i)); err != nil {
+					return err
+				}
+			}
+			hm.historyEndPtr[room] = ptrStart + eventCount
+			err := streamPointers.Put(rid, itob(ptrStart+eventCount))
+			if err != nil {
+				return err
+			}
+		}
+
+		return nil
+	})
+	return err
+}
+
+func (hm *HistoryManager) Load(room *rooms.Room, num int) (events []*mautrix.Event, err error) {
+	hm.Lock()
+	defer hm.Unlock()
+	err = hm.db.View(func(tx *bolt.Tx) error {
+		rid := []byte(room.ID)
+		stream := tx.Bucket(bucketRoomStreams).Bucket(rid)
+		if stream == nil {
+			return nil
+		}
+		ptrStart, ok := hm.historyLoadPtr[room]
+		if !ok {
+			ptrStart = stream.Sequence()
+		}
+		c := stream.Cursor()
+		k, v := c.Seek(itob(ptrStart - uint64(num)))
+		ptrStartFound := btoi(k)
+		if k == nil || ptrStartFound >= ptrStart {
+			return nil
+		}
+		hm.historyLoadPtr[room] = ptrStartFound - 1
+		for ; k != nil && btoi(k) < ptrStart; k, v = c.Next() {
+			event, parseError := unmarshalEvent(v)
+			if parseError != nil {
+				return parseError
+			}
+			events = append(events, event)
+		}
+		return nil
+	})
+	// Reverse array because we read/append the history in reverse order.
+	i := 0
+	j := len(events) - 1
+	for i < j {
+		events[i], events[j] = events[j], events[i]
+		i++
+		j--
+	}
+	return
+}
+
+func itob(v uint64) []byte {
+	b := make([]byte, 8)
+	binary.BigEndian.PutUint64(b, v)
+	return b
+}
+
+func btoi(b []byte) uint64 {
+	return binary.BigEndian.Uint64(b)
+}
+
+func marshalEvent(event *mautrix.Event) ([]byte, error) {
+	var buf bytes.Buffer
+	err := gob.NewEncoder(&buf).Encode(event)
+	return buf.Bytes(), err
+}
+
+func unmarshalEvent(data []byte) (*mautrix.Event, error) {
+	event := &mautrix.Event{}
+	return event, gob.NewDecoder(bytes.NewReader(data)).Decode(event)
+}
+
+func put(streams, eventIDs *bolt.Bucket, event *mautrix.Event, key uint64) error {
+	data, err := marshalEvent(event)
+	if err != nil {
+		return err
+	}
+	keyBytes := itob(key)
+	if err = streams.Put(keyBytes, data); err != nil {
+		return err
+	}
+	if err = eventIDs.Put([]byte(event.ID), keyBytes); err != nil {
+		return err
+	}
+	return nil
+}