Add trim functionality

db.go

@@ -166,3 +166,28 @@ func SetDatabase() {
 	// If not, create them
 	InitDatabase(DB)
 }
+
+func TrimDatabase() {
+	// Ask how many messages to keep
+	fmt.Println("How many messages to keep?")
+	var num int
+	fmt.Scan(&num)
+	// Get the database
+	db := GetDatabase()
+	// Get the list of messages
+	msgs := GetMessagesFromDatabase(db)
+	// Trim the list of messages
+	msgs.Trim(num)
+	// Delete all messages from the database
+	_, err := db.Exec("DELETE FROM messages")
+	if err != nil {
+		fmt.Println(err)
+	}
+	// Add the trimmed list of messages to the database
+	msgs.Each(func(m *message.Message) {
+		_, err := db.Exec("INSERT INTO messages(hash, message, nonce, timestamp) VALUES(?, ?, ?, ?)", m.Stamp(), m.Message, m.Nonce, m.Timestamp)
+		if err != nil {
+			fmt.Println(err)
+		}
+	})
+}

localmessages.go

@@ -89,3 +89,12 @@ func WriteMessage() {
 		}
 	}
 }
+
+func TrimMessages() {
+	// Get the number of messages to keep from the user
+	fmt.Println("How many messages do you want to keep?")
+	var keep int
+	fmt.Scanln(&keep)
+	// Trim the messages
+	LocalMessages.Trim(keep)
+}

main.go

@@ -83,6 +83,8 @@ func main() {
 			{"Read Messages", ReadMessages},
 			{"Write Message", WriteMessage},
 			{"Sync Messages", SyncMenu},
+			{"Trim Messages", TrimMessages},
+			{"Trim Database", TrimDatabase},
 			{"Settings", SettingsMenu},
 			{"Quit", func() { os.Exit(0) }},
 		})

message/message.go

@@ -158,6 +158,25 @@ func MessagesFromIPFS(cid string) (*Messages, error) {
 	return &messages, nil
 }
 
+// Trim the Messages map to the given number of messages based on the importance of the messages
+func (m *Messages) Trim(n int) {
+	// Create a slice of Messages sorted by importance
+	// Cannot lock the Messages map yet, Messages.MessageList() will lock it
+	msgs := m.MessageList()
+	// Now lock the Messages map and trim the map to the given number of messages
+	m.lock.Lock()
+	defer m.lock.Unlock()
+	// If the number of messages is less than or equal to the number of messages to keep, do nothing
+	if len(msgs) <= n {
+		return
+	}
+	fmt.Println("Trimming messages")
+	// Otherwise, remove the messages after the nth message from the map
+	for i := n; i < len(msgs); i++ {
+		delete(m.msgs, msgs[i].Stamp())
+	}
+}
+
 // Add a message to the Messages map
 func (m *Messages) Add(msg *Message) {
 	m.lock.Lock()