Autocomplete for commands (#173)

## What is the goal of this PR?

Introduce context-aware autocomplete for interactive TypeDB Console sessions. 

## What are the changes implemented in this PR?

Fix #172

* Make all commands' `token`s public so they can be reused when instantiating completer classes
* Instantiate a completer using `TreeCompleter` class from JLine. It's aware of context: where database name is expected, it completes database names; same is true for user names in `user delete <username>` command.

Author: Max Vorobev

TypeDBConsole.java

@@ -28,6 +28,7 @@
 import com.vaticle.typedb.client.api.answer.Numeric;
 import com.vaticle.typedb.client.api.answer.NumericGroup;
 import com.vaticle.typedb.client.api.connection.database.Database;
+import com.vaticle.typedb.client.api.connection.user.User;
 import com.vaticle.typedb.client.common.exception.TypeDBClientException;
 import com.vaticle.typedb.common.collection.Either;
 import com.vaticle.typedb.common.util.Java;
@@ -45,8 +46,12 @@
 import com.vaticle.typeql.lang.query.TypeQLQuery;
 import com.vaticle.typeql.lang.query.TypeQLUndefine;
 import com.vaticle.typeql.lang.query.TypeQLUpdate;
+import org.jline.builtins.Completers;
+import org.jline.reader.Candidate;
+import org.jline.reader.Completer;
 import org.jline.reader.LineReader;
 import org.jline.reader.LineReaderBuilder;
+import org.jline.reader.impl.completer.StringsCompleter;
 import org.jline.terminal.Terminal;
 import org.jline.terminal.TerminalBuilder;
 import org.jline.utils.InfoCmp;
@@ -62,6 +67,7 @@
 import java.nio.file.Paths;
 import java.time.Duration;
 import java.time.Instant;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Iterator;
 import java.util.List;
@@ -74,6 +80,7 @@
 import java.util.function.Consumer;
 import java.util.stream.Stream;
 
+import static org.jline.builtins.Completers.TreeCompleter.node;
 import static com.vaticle.typedb.common.collection.Collections.set;
 import static com.vaticle.typedb.console.common.exception.ErrorMessage.Console.INCOMPATIBLE_JAVA_RUNTIME;
 import static java.util.stream.Collectors.toList;
@@ -162,6 +169,7 @@ private void runREPLMode(CLIOptions options) {
             LineReader reader = LineReaderBuilder.builder()
                     .terminal(terminal)
                     .variable(LineReader.HISTORY_FILE, COMMAND_HISTORY_FILE)
+                    .completer(getCompleter(client))
                     .build();
             while (true) {
                 REPLCommand command;
@@ -213,6 +221,52 @@ private void runREPLMode(CLIOptions options) {
         }
     }
 
+    private Completers.TreeCompleter getCompleter(TypeDBClient client) {
+        Completer databaseNameCompleter = (reader, line, candidates) -> client.databases().all().stream()
+                .map(Database::name)
+                .filter(name -> name.startsWith(line.word()))
+                .forEach(name -> candidates.add(new Candidate(name)));
+        Completer userNameCompleter = (reader, line, candidates) -> {
+            client.asCluster().users().all().stream()
+                    .map(User::name)
+                    // "admin" user is excluded as it can't be deleted
+                    .filter(name -> name.startsWith(line.word()) && !"admin".equals(name))
+                    .forEach(name -> candidates.add(new Candidate(name)));
+        };
+        final List<Completers.TreeCompleter.Node> nodes = new ArrayList<>();
+        nodes.add(
+                node(REPLCommand.Database.token,
+                        node(REPLCommand.Database.List.token),
+                        node(REPLCommand.Database.Create.token),
+                        node(REPLCommand.Database.Delete.token,
+                                node(databaseNameCompleter)),
+                        node(REPLCommand.Database.Schema.token,
+                                node(databaseNameCompleter)
+                        )
+                ));
+        if (client.isCluster()) {
+            nodes.add(node(REPLCommand.User.token,
+                    node(REPLCommand.User.List.token),
+                    node(REPLCommand.User.Create.token),
+                    node(REPLCommand.User.Delete.token,
+                            node(userNameCompleter))
+            ));
+        }
+        nodes.add(node(REPLCommand.Transaction.token,
+                node(databaseNameCompleter,
+                        node(new StringsCompleter("schema", "data"),
+                                node(new StringsCompleter("read", "write")
+                                        // TODO(vmax): complete [transaction-options] here
+                                )
+                        )
+                )
+        ));
+        nodes.add(node(REPLCommand.Help.token));
+        nodes.add(node(REPLCommand.Clear.token));
+        nodes.add(node(REPLCommand.Exit.token));
+        return new Completers.TreeCompleter(nodes);
+    }
+
     private boolean transactionREPL(TypeDBClient client, String database, TypeDBSession.Type sessionType, TypeDBTransaction.Type transactionType, TypeDBOptions options) {
         LineReader reader = LineReaderBuilder.builder()
                 .terminal(terminal)

command/REPLCommand.java

@@ -138,7 +138,7 @@ default Transaction asTransaction() {
 
     class Exit implements REPLCommand {
 
-        private static String token = "exit";
+        public static String token = "exit";
         private static String helpCommand = token;
         private static String description = "Exit console";
 
@@ -155,7 +155,7 @@ public Exit asExit() {
 
     class Help implements REPLCommand {
 
-        private static String token = "help";
+        public static String token = "help";
         private static String helpCommand = token;
         private static String description = "Print this help menu";
 
@@ -172,7 +172,7 @@ public Help asHelp() {
 
     class Clear implements REPLCommand {
 
-        private static String token = "clear";
+        public static String token = "clear";
         private static String helpCommand = token;
         private static String description = "Clear console screen";
 
@@ -189,11 +189,11 @@ public Clear asClear() {
 
     abstract class Database implements REPLCommand {
 
-        private static String token = "database";
+        public static String token = "database";
 
         public static class List extends REPLCommand.Database {
 
-            private static String token = "list";
+            public static String token = "list";
             private static String helpCommand = Database.token + " " + token;
             private static String description = "List the databases on the server";
 
@@ -210,7 +210,7 @@ public Database.List asDatabaseList() {
 
         public static class Create extends REPLCommand.Database {
 
-            private static String token = "create";
+            public static String token = "create";
             private static String helpCommand = Database.token + " " + token + " " + "<db>";
             private static String description = "Create a database with name <db> on the server";
 
@@ -237,7 +237,7 @@ public Database.Create asDatabaseCreate() {
 
         public static class Delete extends REPLCommand.Database {
 
-            private static String token = "delete";
+            public static String token = "delete";
             private static String helpCommand = Database.token + " " + token + " " + "<db>";
             private static String description = "Delete a database with name <db> on the server";
 
@@ -264,7 +264,7 @@ public Database.Delete asDatabaseDelete() {
 
         public static class Schema extends REPLCommand.Database {
 
-            private static String token = "schema";
+            public static String token = "schema";
             private static String helpCommand = Database.token + " " + token + " " + "<db>";
             private static String description = "Print the schema of the database with name <db>";
 
@@ -291,7 +291,7 @@ public Database.Schema asDatabaseSchema() {
 
         public static class Replicas extends REPLCommand.Database {
 
-            private static String token = "replicas";
+            public static String token = "replicas";
             private static String helpCommand = Database.token + " " + token + " " + "<db>";
             private static String description = "List replicas of a database with name <db>";
 
@@ -319,11 +319,11 @@ public Database.Replicas asDatabaseReplicas() {
 
     abstract class User implements REPLCommand {
 
-        private static String token = "user";
+        public static String token = "user";
 
         public static class List extends REPLCommand.User {
 
-            private static String token = "list";
+            public static String token = "list";
             private static String helpCommand = User.token + " " + token;
             private static String description = "List the users on the server";
 
@@ -340,7 +340,7 @@ public User.List asUserList() {
 
         public static class Create extends REPLCommand.User {
 
-            private static String token = "create";
+            public static String token = "create";
             private static String helpCommand = User.token + " " + token + " " + "<username> <password>";
             private static String description = "Create a user with name <username> and password <password> on the server";
 
@@ -373,7 +373,7 @@ public User.Create asUserCreate() {
 
         public static class Delete extends REPLCommand.User {
 
-            private static String token = "delete";
+            public static String token = "delete";
             private static String helpCommand = User.token + " " + token + " " + "<username>";
             private static String description = "Delete a user with name <username> on the server";
 
@@ -401,7 +401,7 @@ public User.Delete asUserDelete() {
 
     class Transaction implements REPLCommand {
 
-        private static final String token = "transaction";
+        public static final String token = "transaction";
         private static final String helpCommand = token + " <db> schema|data read|write [" + Options.token + "]";
         private static final String description = "Start a transaction to database <db> with schema or data session, with read or write transaction";