Fix availability feature

- Bring back some missing functionality which got missing
  during the rework to new command model.
- Polish some classes.
- Restore origin sample.
- Add availability things into help templates and its
  representation model.
- Fixes #423

spring-shell-standard-commands/src/main/java/org/springframework/shell/standard/commands/CommandAvailabilityInfoModel.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.shell.standard.commands;
+
+/**
+ * Model encapsulating info about {@code command availability}.
+ *
+ * @author Janne Valkealahti
+ */
+class CommandAvailabilityInfoModel {
+
+	private boolean available;
+	private String reason;
+
+	CommandAvailabilityInfoModel(boolean available, String reason) {
+		this.available = available;
+		this.reason = reason;
+	}
+
+	/**
+	 * Builds {@link CommandAvailabilityInfoModel}.
+	 *
+	 * @param available the available flag
+	 * @param reason the reason
+	 * @return a command parameter availability model
+	 */
+	static CommandAvailabilityInfoModel of(boolean available, String reason) {
+		return new CommandAvailabilityInfoModel(available, reason);
+	}
+
+	public boolean getAvailable() {
+		return available;
+	}
+
+	public String getReason() {
+		return reason;
+	}
+}

spring-shell-standard-commands/src/main/java/org/springframework/shell/standard/commands/CommandInfoModel.java

@@ -19,6 +19,7 @@ import java.util.List;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+import org.springframework.shell.Availability;
 import org.springframework.shell.command.CommandOption;
 import org.springframework.shell.command.CommandRegistration;
 import org.springframework.util.ClassUtils;
@@ -34,11 +35,14 @@ class CommandInfoModel {
 	private String name;
 	private String description;
 	private List<CommandParameterInfoModel> parameters;
+	private CommandAvailabilityInfoModel availability;
 
-	CommandInfoModel(String name, String description, List<CommandParameterInfoModel> parameters) {
+	CommandInfoModel(String name, String description, List<CommandParameterInfoModel> parameters,
+			CommandAvailabilityInfoModel availability) {
 		this.name = name;
 		this.description = description;
 		this.parameters = parameters;
+		this.availability = availability;
 	}
 
 	/**
@@ -65,7 +69,15 @@ class CommandInfoModel {
 			.collect(Collectors.toList());
 
 		String description = registration.getDescription();
-		return new CommandInfoModel(name, description, parameters);
+		boolean available = true;
+		String availReason = "";
+		if (registration.getAvailability() != null) {
+			Availability a = registration.getAvailability();
+			available = a.isAvailable();
+			availReason = a.getReason();
+		}
+		CommandAvailabilityInfoModel availModel = CommandAvailabilityInfoModel.of(available, availReason);
+		return new CommandInfoModel(name, description, parameters, availModel);
 	}
 
 	private static String commandOptionType(CommandOption o) {
@@ -88,4 +100,8 @@ class CommandInfoModel {
 	public List<CommandParameterInfoModel> getParameters() {
 		return parameters;
 	}
+
+	public CommandAvailabilityInfoModel getAvailability() {
+		return availability;
+	}
 }

spring-shell-standard-commands/src/main/java/org/springframework/shell/standard/commands/GroupsInfoModel.java

@@ -36,11 +36,14 @@ class GroupsInfoModel {
 	private boolean showGroups = true;
 	private final List<GroupCommandInfoModel> groups;
 	private final List<CommandInfoModel> commands;
+	private boolean hasUnavailableCommands = false;
 
-	GroupsInfoModel(boolean showGroups, List<GroupCommandInfoModel> groups, List<CommandInfoModel> commands) {
+	GroupsInfoModel(boolean showGroups, List<GroupCommandInfoModel> groups, List<CommandInfoModel> commands,
+			boolean hasUnavailableCommands) {
 		this.showGroups = showGroups;
 		this.groups = groups;
 		this.commands = commands;
+		this.hasUnavailableCommands = hasUnavailableCommands;
 	}
 
 	/**
@@ -71,7 +74,17 @@ class GroupsInfoModel {
 		List<CommandInfoModel> commands = gcims.stream()
 			.flatMap(gcim -> gcim.getCommands().stream())
 			.collect(Collectors.toList());
-		return new GroupsInfoModel(showGroups, gcims, commands);
+		boolean hasUnavailableCommands = commands.stream()
+			.map(c -> {
+				if (c.getAvailability() != null) {
+					return c.getAvailability().getAvailable();
+				}
+				return true;
+			})
+			.filter(a -> !a)
+			.findFirst()
+			.isPresent();
+		return new GroupsInfoModel(showGroups, gcims, commands, hasUnavailableCommands);
 	}
 
 	public boolean getShowGroups() {
@@ -85,4 +98,8 @@ class GroupsInfoModel {
 	public List<CommandInfoModel> getCommands() {
 		return commands;
 	}
+
+	public boolean getHasUnavailableCommands() {
+		return hasUnavailableCommands;
+	}
 }

spring-shell-standard-commands/src/main/resources/template/help-command-default.stg

@@ -57,6 +57,15 @@ options(options) ::= <<
        <options:{ o | <option(o)>}>
 >>
 
+// AVAILABILITY
+availability(availability) ::= <<
+<if(!availability.available)>
+
+<("CURRENTLY UNAVAILABLE"); format="style-highlight">
+       <availability.reason>
+<endif>
+>>
+
 // main
 main(model) ::= <<
 <name(model.name, model.description)>
@@ -64,4 +73,5 @@ main(model) ::= <<
 <synopsis(model.name, model.parameters)>
 
 <options(model.parameters)>
+<availability(model.availability)>
 >>

spring-shell-standard-commands/src/main/resources/template/help-commands-default.stg

@@ -3,8 +3,21 @@ name() ::= <<
 
 >>
 
+availability(availability) ::= <%
+<if(!availability.available)>
+<("* "); format="style-highlight">
+<endif>
+%>
+
+availabilityDesc(hasUnavailableCommands) ::= <<
+<if(hasUnavailableCommands)>
+<("Commands marked with (*) are currently unavailable.")>
+<("Type `help <command>` to learn more.")>
+<endif>
+>>
+
 command(command) ::= <<
-<(command.name); format="style-highlight"><(":"); format="style-highlight"> <command.description>
+<availability(command.availability)><(command.name); format="style-highlight"><(":"); format="style-highlight"> <command.description>
 
 >>
 
@@ -29,4 +42,5 @@ main(model) ::= <<
 <else>
 <flat(model.commands)>
 <endif>
+<availabilityDesc(model.hasUnavailableCommands)>
 >>