/** Transfers variables from one interpreter's bindings to another. */
private void copyBindings(final ScriptInterpreter src, final ScriptInterpreter dest) {
if (src == null) return; // nothing to copy
final Bindings srcBindings = src.getBindings();
final Bindings destBindings = dest.getBindings();
for (final String key : src.getBindings().keySet()) {
final Object value = src.getLanguage().decode(srcBindings.get(key));
destBindings.put(key, value);
}
}
/**
* Evaluates the line, including handling of special colon-prefixed REPL commands.
*
* @param line The line to evaluate.
* @return False iff the REPL should exit.
*/
public boolean evaluate(final String line) {
try {
final String tLine = line.trim();
if (tLine.equals(":help")) help();
else if (tLine.equals(":vars")) vars();
else if (tLine.equals(":langs")) langs();
else if (tLine.equals(":debug")) debug();
else if (tLine.startsWith(":lang ")) lang(line.substring(6).trim());
else if (tLine.equals(":quit")) return false;
else {
// ensure that a script language is active
if (interpreter == null) return true;
// pass the input to the current interpreter for evaluation
final Object result = interpreter.interpret(line);
if (result != ScriptInterpreter.MORE_INPUT_PENDING) {
out.println(s(result));
}
}
} catch (final ScriptException exc) {
// NB: Something went wrong interpreting the line of code.
// Let's just display the error message, unless we are in debug mode.
if (debug) exc.printStackTrace(out);
else {
final String msg = exc.getMessage();
out.println(msg == null ? exc.getClass().getName() : msg);
}
} catch (final Throwable exc) {
// NB: Something unusual went wrong. Dump the whole exception always.
exc.printStackTrace(out);
}
return true;
}
/**
* Creates a new {@link ScriptInterpreter} to interpret statements, preserving existing variables
* from the previous interpreter.
*
* @param langName The script language of the new interpreter.
* @throws IllegalArgumentException if the requested language is not available.
*/
public void lang(final String langName) {
// create the new interpreter
final ScriptLanguage language = scriptService.getLanguageByName(langName);
if (language == null) {
out.println("No such language: " + langName);
return;
}
final ScriptInterpreter newInterpreter = new DefaultScriptInterpreter(language);
// preserve state of the previous interpreter
try {
copyBindings(interpreter, newInterpreter);
} catch (final Throwable t) {
t.printStackTrace(out);
}
out.println("language -> " + newInterpreter.getLanguage().getLanguageName());
interpreter = newInterpreter;
}
/** Lists variables in the script context. */
public void vars() {
if (interpreter == null) return; // no active script language
final List<String> keys = new ArrayList<>();
final List<Object> types = new ArrayList<>();
final Bindings bindings = interpreter.getBindings();
for (final String key : bindings.keySet()) {
final Object value = bindings.get(key);
keys.add(key);
types.add(type(value));
}
printColumns(keys, types);
}
/** Outputs a greeting, and sets up the initial language of the REPL. */
public void initialize() {
out.println("Welcome to the SciJava REPL!");
out.println();
help();
final List<ScriptLanguage> langs = getInterpretedLanguages();
if (langs.isEmpty()) {
out.println("--------------------------------------------------------------");
out.println("Uh oh! There are no SciJava script languages available!");
out.println("Are any on your classpath? E.g.: org.scijava:scripting-groovy?");
out.println("--------------------------------------------------------------");
out.println();
return;
}
out.println("Have fun!");
out.println();
lang(langs.get(0).getLanguageName());
populateBindings(interpreter.getBindings());
}
private String type(final Object value) {
if (value == null) return NULL;
final Object decoded = interpreter.getLanguage().decode(value);
if (decoded == null) return NULL;
return "[" + decoded.getClass().getName() + "]";
}
/** Outputs the prompt. */
public void prompt() {
out.print(interpreter == null || interpreter.isReady() ? "> " : "\\ ");
}
