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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;

class ClearVarCommand extends Command {

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

  public ClearVarCommand() {
    super(COMMAND_NAME,
          """
              Remove the specified variable.
              Usage: $command {name}
              Examples:
                  $command age
                  $command $var""".replace("$command",
                                           COMMAND_NAME)
         );
  }

  @Override
  public Function> apply(final JsObj conf,
                                              final State state
                                             ) {
    Lambda program = name -> IO.lazy(() -> {
      state.variables.remove(name);
      state.listsVariables.remove(name);
      return "var removed!";
    });
    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]);


    };
  }

}