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Java Input-Output Monad

There is a newer version: 3.0.0-RC2

package jio.console;

import jio.IO;
import jio.Lambda;
import jio.RetryPolicies;
import jio.console.Programs.AskForInputParams;
import jsonvalues.JsObj;

import java.util.function.Function;

/**
 * Command to read the content of a specified variable with the command:
 *  *     var-get {name}
 * 
 * 
 * Users can specify the name of the variable they want to read, and the command will return the variable's content as a
 * string. If the variable doesn't exist, the command allows for multiple retries.
 * 

 * Examples:
 * 
 *     var-get age
 *     var-get $var
 * 
 *
 * @see Command
 */
class ReadVarCommand extends Command {

  private static final String COMMAND_NAME = "var-get";

  public ReadVarCommand() {
    super(COMMAND_NAME,
          """
              Read the content of the specified variable.
              var-get {name}
              Examples:
                  $command age
                  $command $var""".replace("$command",
                                           COMMAND_NAME)
         );
  }

  @Override
  public Function> apply(final JsObj conf,
                                              final State state
                                             ) {
    Lambda program = var -> IO.lazy(() -> {
      var value = state.variables.get(var);
        if (value != null) {
            return value;
        }
      var list = state.listsVariables.get(var);
        if (list != null) {
            return String.join("\n",
                               list);
        }
      return "";
    });

    return tokens -> {
      int nTokens = tokens.length;

        if (nTokens == 1) {
            return Programs.ASK_FOR_INPUT(new AskForInputParams("Type the name of the variable",
                                                                name -> state.variables.containsKey(name) ||
                                                                    state.listsVariables.containsKey(name),
                                                                "The variable doesn't exist",
                                                                RetryPolicies.limitRetries(3)
                                          )
                                         )
                           .then(program);
        }

      return program.apply(tokens[1]);


    };
  }

}