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package javax.tools;

import java.io.File;
import java.io.Writer;
import java.nio.charset.Charset;
import java.util.Locale;
import java.util.concurrent.Callable;
import javax.annotation.processing.Processor;

/**
 * Interface to invoke Java™ programming language compilers from
 * programs.
 *
 * <p>The compiler might generate diagnostics during compilation (for
 * example, error messages). If a diagnostic listener is provided,
 * the diagnostics will be supplied to the listener. If no listener
 * is provided, the diagnostics will be formatted in an unspecified
 * format and written to the default output, which is {@code
 * System.err} unless otherwise specified. Even if a diagnostic
 * listener is supplied, some diagnostics might not fit in a {@code
 * Diagnostic} and will be written to the default output.
 *
 * <p>A compiler tool has an associated standard file manager, which
 * is the file manager that is native to the tool (or built-in). The
 * standard file manager can be obtained by calling {@linkplain
 * #getStandardFileManager getStandardFileManager}.
 *
 * <p>A compiler tool must function with any file manager as long as
 * any additional requirements as detailed in the methods below are
 * met. If no file manager is provided, the compiler tool will use a
 * standard file manager such as the one returned by {@linkplain
 * #getStandardFileManager getStandardFileManager}.
 *
 * <p>An instance implementing this interface must conform to
 * <cite>The Java&trade; Language Specification</cite>
 * and generate class files conforming to
 * <cite>The Java&trade; Virtual Machine Specification</cite>.
 * The versions of these
 * specifications are defined in the {@linkplain Tool} interface.
 *
 * Additionally, an instance of this interface supporting {@link
 * javax.lang.model.SourceVersion#RELEASE_6 SourceVersion.RELEASE_6}
 * or higher must also support {@linkplain javax.annotation.processing
 * annotation processing}.
 *
 * <p>The compiler relies on two services: {@linkplain
 * DiagnosticListener diagnostic listener} and {@linkplain
 * JavaFileManager file manager}. Although most classes and
 * interfaces in this package defines an API for compilers (and
 * tools in general) the interfaces {@linkplain DiagnosticListener},
 * {@linkplain JavaFileManager}, {@linkplain FileObject}, and
 * {@linkplain JavaFileObject} are not intended to be used in
 * applications. Instead these interfaces are intended to be
 * implemented and used to provide customized services for a
 * compiler and thus defines an SPI for compilers.
 *
 * <p>There are a number of classes and interfaces in this package
 * which are designed to ease the implementation of the SPI to
 * customize the behavior of a compiler:
 *
 * <dl>
 * <dt>{@link StandardJavaFileManager}</dt>
 * <dd>
 *
 * Every compiler which implements this interface provides a
 * standard file manager for operating on regular {@linkplain
 * java.io.File files}. The StandardJavaFileManager interface
 * defines additional methods for creating file objects from
 * regular files.
 *
 * <p>The standard file manager serves two purposes:
 *
 * <ul>
 * <li>basic building block for customizing how a compiler reads
 * and writes files</li>
 * <li>sharing between multiple compilation tasks</li>
 * </ul>
 *
 * <p>Reusing a file manager can potentially reduce overhead of
 * scanning the file system and reading jar files. Although there
 * might be no reduction in overhead, a standard file manager must
 * work with multiple sequential compilations making the following
 * example a recommended coding pattern:
 *
 * <pre>
 * File[] files1 = ... ; // input for first compilation task
 * File[] files2 = ... ; // input for second compilation task
 *
 * JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
 * StandardJavaFileManager fileManager = compiler.getStandardFileManager(null, null, null);
 *
 * {@code Iterable<? extends JavaFileObject>} compilationUnits1 =
 * fileManager.getJavaFileObjectsFromFiles({@linkplain java.util.Arrays#asList Arrays.asList}(files1));
 * compiler.getTask(null, fileManager, null, null, null, compilationUnits1).call();
 *
 * {@code Iterable<? extends JavaFileObject>} compilationUnits2 =
 * fileManager.getJavaFileObjects(files2); // use alternative method
 * // reuse the same file manager to allow caching of jar files
 * compiler.getTask(null, fileManager, null, null, null, compilationUnits2).call();
 *
 * fileManager.close();</pre>
 *
 * </dd>
 *
 * <dt>{@link DiagnosticCollector}</dt>
 * <dd>
 * Used to collect diagnostics in a list, for example:
 * <pre>
 * {@code Iterable<? extends JavaFileObject>} compilationUnits = ...;
 * JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
 * {@code DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();}
 * StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, null, null);
 * compiler.getTask(null, fileManager, diagnostics, null, null, compilationUnits).call();
 *
 * for ({@code Diagnostic<? extends JavaFileObject>} diagnostic : diagnostics.getDiagnostics())
 * System.out.format("Error on line %d in %s%n",
 * diagnostic.getLineNumber(),
 * diagnostic.getSource().toUri());
 *
 * fileManager.close();</pre>
 * </dd>
 *
 * <dt>
 * {@link ForwardingJavaFileManager}, {@link ForwardingFileObject}, and
 * {@link ForwardingJavaFileObject}
 * </dt>
 * <dd>
 *
 * Subclassing is not available for overriding the behavior of a
 * standard file manager as it is created by calling a method on a
 * compiler, not by invoking a constructor. Instead forwarding
 * (or delegation) should be used. These classes makes it easy to
 * forward most calls to a given file manager or file object while
 * allowing customizing behavior. For example, consider how to
 * log all calls to {@linkplain JavaFileManager#flush}:
 *
 * <pre>
 * final {@linkplain java.util.logging.Logger Logger} logger = ...;
 * {@code Iterable<? extends JavaFileObject>} compilationUnits = ...;
 * JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
 * StandardJavaFileManager stdFileManager = compiler.getStandardFileManager(null, null, null);
 * JavaFileManager fileManager = new ForwardingJavaFileManager(stdFileManager) {
 * public void flush() throws IOException {
 * logger.entering(StandardJavaFileManager.class.getName(), "flush");
 * super.flush();
 * logger.exiting(StandardJavaFileManager.class.getName(), "flush");
 * }
 * };
 * compiler.getTask(null, fileManager, null, null, null, compilationUnits).call();</pre>
 * </dd>
 *
 * <dt>{@link SimpleJavaFileObject}</dt>
 * <dd>
 *
 * This class provides a basic file object implementation which
 * can be used as building block for creating file objects. For
 * example, here is how to define a file object which represent
 * source code stored in a string:
 *
 * <pre>
 * /**
 * * A file object used to represent source coming from a string.
 * {@code *}/
 * public class JavaSourceFromString extends SimpleJavaFileObject {
 * /**
 * * The source code of this "file".
 * {@code *}/
 * final String code;
 *
 * /**
 * * Constructs a new JavaSourceFromString.
 * * {@code @}param name the name of the compilation unit represented by this file object
 * * {@code @}param code the source code for the compilation unit represented by this file object
 * {@code *}/
 * JavaSourceFromString(String name, String code) {
 * super({@linkplain java.net.URI#create URI.create}("string:///" + name.replace('.','/') + Kind.SOURCE.extension),
 * Kind.SOURCE);
 * this.code = code;
 * }
 *
 * {@code @}Override
 * public CharSequence getCharContent(boolean ignoreEncodingErrors) {
 * return code;
 * }
 * }</pre>
 * </dd>
 * </dl>
 *
 * @author Peter von der Ah&eacute;
 * @author Jonathan Gibbons
 * @see DiagnosticListener
 * @see Diagnostic
 * @see JavaFileManager
 * @since 1.6
 */
public interface JavaCompiler extends Tool, OptionChecker {

 /**
 * Creates a future for a compilation task with the given
 * components and arguments. The compilation might not have
 * completed as described in the CompilationTask interface.
 *
 * <p>If a file manager is provided, it must be able to handle all
 * locations defined in {@link StandardLocation}.
 *
 * <p>Note that annotation processing can process both the
 * compilation units of source code to be compiled, passed with
 * the {@code compilationUnits} parameter, as well as class
 * files, whose names are passed with the {@code classes}
 * parameter.
 *
 * @param out a Writer for additional output from the compiler;
 * use {@code System.err} if {@code null}
 * @param fileManager a file manager; if {@code null} use the
 * compiler's standard filemanager
 * @param diagnosticListener a diagnostic listener; if {@code
 * null} use the compiler's default method for reporting
 * diagnostics
 * @param options compiler options, {@code null} means no options
 * @param classes names of classes to be processed by annotation
 * processing, {@code null} means no class names
 * @param compilationUnits the compilation units to compile, {@code
 * null} means no compilation units
 * @return an object representing the compilation
 * @throws RuntimeException if an unrecoverable error
 * occurred in a user supplied component. The
 * {@linkplain Throwable#getCause() cause} will be the error in
 * user code.
 * @throws IllegalArgumentException if any of the options are invalid,
 * or if any of the given compilation units are of other kind than
 * {@linkplain JavaFileObject.Kind#SOURCE source}
 */
 CompilationTask getTask(Writer out,
 JavaFileManager fileManager,
 DiagnosticListener<? super JavaFileObject> diagnosticListener,
 Iterable<String> options,
 Iterable<String> classes,
 Iterable<? extends JavaFileObject> compilationUnits);

 /**
 * Gets a new instance of the standard file manager implementation
 * for this tool. The file manager will use the given diagnostic
 * listener for producing any non-fatal diagnostics. Fatal errors
 * will be signaled with the appropriate exceptions.
 *
 * <p>The standard file manager will be automatically reopened if
 * it is accessed after calls to {@code flush} or {@code close}.
 * The standard file manager must be usable with other tools.
 *
 * @param diagnosticListener a diagnostic listener for non-fatal
 * diagnostics; if {@code null} use the compiler's default method
 * for reporting diagnostics
 * @param locale the locale to apply when formatting diagnostics;
 * {@code null} means the {@linkplain Locale#getDefault() default locale}.
 * @param charset the character set used for decoding bytes; if
 * {@code null} use the platform default
 * @return the standard file manager
 */
 StandardJavaFileManager getStandardFileManager(
 DiagnosticListener<? super JavaFileObject> diagnosticListener,
 Locale locale,
 Charset charset);

 /**
 * Interface representing a future for a compilation task. The
 * compilation task has not yet started. To start the task, call
 * the {@linkplain #call call} method.
 *
 * <p>Before calling the call method, additional aspects of the
 * task can be configured, for example, by calling the
 * {@linkplain #setProcessors setProcessors} method.
 */
 interface CompilationTask extends Callable<Boolean> {

 /**
 * Sets processors (for annotation processing). This will
 * bypass the normal discovery mechanism.
 *
 * @param processors processors (for annotation processing)
 * @throws IllegalStateException if the task has started
 */
 void setProcessors(Iterable<? extends Processor> processors);

 /**
 * Set the locale to be applied when formatting diagnostics and
 * other localized data.
 *
 * @param locale the locale to apply; {@code null} means apply no
 * locale
 * @throws IllegalStateException if the task has started
 */
 void setLocale(Locale locale);

 /**
 * Performs this compilation task. The compilation may only
 * be performed once. Subsequent calls to this method throw
 * IllegalStateException.
 *
 * @return true if and only all the files compiled without errors;
 * false otherwise
 *
 * @throws RuntimeException if an unrecoverable error occurred
 * in a user-supplied component. The
 * {@linkplain Throwable#getCause() cause} will be the error
 * in user code.
 * @throws IllegalStateException if called more than once
 */
 Boolean call();
 }
}