/*
 * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation. Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.lang;

import jdk.internal.loader.BuiltinClassLoader;
import jdk.internal.misc.VM;
import jdk.internal.module.ModuleHashes;
import jdk.internal.module.ModuleReferenceImpl;

import java.lang.module.ModuleDescriptor.Version;
import java.lang.module.ModuleReference;
import java.lang.module.ResolvedModule;
import java.util.HashSet;
import java.util.Objects;
import java.util.Optional;
import java.util.Set;

/**
 * An element in a stack trace, as returned by {@link
 * Throwable#getStackTrace()}. Each element represents a single stack frame.
 * All stack frames except for the one at the top of the stack represent
 * a method invocation. The frame at the top of the stack represents the
 * execution point at which the stack trace was generated. Typically,
 * this is the point at which the throwable corresponding to the stack trace
 * was created.
 *
 * @since 1.4
 * @author Josh Bloch
 */
public final class StackTraceElement implements java.io.Serializable {

 // For Throwables and StackWalker, the VM initially sets this field to a
 // reference to the declaring Class. The Class reference is used to
 // construct the 'format' bitmap, and then is cleared.
 //
 // For STEs constructed using the public constructors, this field is not used.
 private transient Class<?> declaringClassObject;

 // Normally initialized by VM
 private String classLoaderName;
 private String moduleName;
 private String moduleVersion;
 private String declaringClass;
 private String methodName;
 private String fileName;
 private int lineNumber;
 private byte format = 0; // Default to show all

 /**
 * Creates a stack trace element representing the specified execution
 * point. The {@link #getModuleName module name} and {@link
 * #getModuleVersion module version} of the stack trace element will
 * be {@code null}.
 *
 * @param declaringClass the fully qualified name of the class containing
 * the execution point represented by the stack trace element
 * @param methodName the name of the method containing the execution point
 * represented by the stack trace element
 * @param fileName the name of the file containing the execution point
 * represented by the stack trace element, or {@code null} if
 * this information is unavailable
 * @param lineNumber the line number of the source line containing the
 * execution point represented by this stack trace element, or
 * a negative number if this information is unavailable. A value
 * of -2 indicates that the method containing the execution point
 * is a native method
 * @throws NullPointerException if {@code declaringClass} or
 * {@code methodName} is null
 * @since 1.5
 * @revised 9
 * @spec JPMS
 */
 public StackTraceElement(String declaringClass, String methodName,
 String fileName, int lineNumber) {
 this(null, null, null, declaringClass, methodName, fileName, lineNumber);
 }

 /**
 * Creates a stack trace element representing the specified execution
 * point.
 *
 * @param classLoaderName the class loader name if the class loader of
 * the class containing the execution point represented by
 * the stack trace is named; otherwise {@code null}
 * @param moduleName the module name if the class containing the
 * execution point represented by the stack trace is in a named
 * module; otherwise {@code null}
 * @param moduleVersion the module version if the class containing the
 * execution point represented by the stack trace is in a named
 * module that has a version; otherwise {@code null}
 * @param declaringClass the fully qualified name of the class containing
 * the execution point represented by the stack trace element
 * @param methodName the name of the method containing the execution point
 * represented by the stack trace element
 * @param fileName the name of the file containing the execution point
 * represented by the stack trace element, or {@code null} if
 * this information is unavailable
 * @param lineNumber the line number of the source line containing the
 * execution point represented by this stack trace element, or
 * a negative number if this information is unavailable. A value
 * of -2 indicates that the method containing the execution point
 * is a native method
 *
 * @throws NullPointerException if {@code declaringClass} is {@code null}
 * or {@code methodName} is {@code null}
 *
 * @since 9
 * @spec JPMS
 */
 public StackTraceElement(String classLoaderName,
 String moduleName, String moduleVersion,
 String declaringClass, String methodName,
 String fileName, int lineNumber) {
 this.classLoaderName = classLoaderName;
 this.moduleName = moduleName;
 this.moduleVersion = moduleVersion;
 this.declaringClass = Objects.requireNonNull(declaringClass, "Declaring class is null");
 this.methodName = Objects.requireNonNull(methodName, "Method name is null");
 this.fileName = fileName;
 this.lineNumber = lineNumber;
 }

 /*
 * Private constructor for the factory methods to create StackTraceElement
 * for Throwable and StackFrameInfo
 */
 private StackTraceElement() {}

 /**
 * Returns the name of the source file containing the execution point
 * represented by this stack trace element. Generally, this corresponds
 * to the {@code SourceFile} attribute of the relevant {@code class}
 * file (as per <i>The Java Virtual Machine Specification</i>, Section
 * 4.7.7). In some systems, the name may refer to some source code unit
 * other than a file, such as an entry in source repository.
 *
 * @return the name of the file containing the execution point
 * represented by this stack trace element, or {@code null} if
 * this information is unavailable.
 */
 public String getFileName() {
 return fileName;
 }

 /**
 * Returns the line number of the source line containing the execution
 * point represented by this stack trace element. Generally, this is
 * derived from the {@code LineNumberTable} attribute of the relevant
 * {@code class} file (as per <i>The Java Virtual Machine
 * Specification</i>, Section 4.7.8).
 *
 * @return the line number of the source line containing the execution
 * point represented by this stack trace element, or a negative
 * number if this information is unavailable.
 */
 public int getLineNumber() {
 return lineNumber;
 }

 /**
 * Returns the module name of the module containing the execution point
 * represented by this stack trace element.
 *
 * @return the module name of the {@code Module} containing the execution
 * point represented by this stack trace element; {@code null}
 * if the module name is not available.
 * @since 9
 * @spec JPMS
 * @see Module#getName()
 */
 public String getModuleName() {
 return moduleName;
 }

 /**
 * Returns the module version of the module containing the execution point
 * represented by this stack trace element.
 *
 * @return the module version of the {@code Module} containing the execution
 * point represented by this stack trace element; {@code null}
 * if the module version is not available.
 * @since 9
 * @spec JPMS
 * @see java.lang.module.ModuleDescriptor.Version
 */
 public String getModuleVersion() {
 return moduleVersion;
 }

 /**
 * Returns the name of the class loader of the class containing the
 * execution point represented by this stack trace element.
 *
 * @return the name of the class loader of the class containing the execution
 * point represented by this stack trace element; {@code null}
 * if the class loader is not named.
 *
 * @since 9
 * @spec JPMS
 * @see java.lang.ClassLoader#getName()
 */
 public String getClassLoaderName() {
 return classLoaderName;
 }

 /**
 * Returns the fully qualified name of the class containing the
 * execution point represented by this stack trace element.
 *
 * @return the fully qualified name of the {@code Class} containing
 * the execution point represented by this stack trace element.
 */
 public String getClassName() {
 return declaringClass;
 }

 /**
 * Returns the name of the method containing the execution point
 * represented by this stack trace element. If the execution point is
 * contained in an instance or class initializer, this method will return
 * the appropriate <i>special method name</i>, {@code <init>} or
 * {@code <clinit>}, as per Section 3.9 of <i>The Java Virtual
 * Machine Specification</i>.
 *
 * @return the name of the method containing the execution point
 * represented by this stack trace element.
 */
 public String getMethodName() {
 return methodName;
 }

 /**
 * Returns true if the method containing the execution point
 * represented by this stack trace element is a native method.
 *
 * @return {@code true} if the method containing the execution point
 * represented by this stack trace element is a native method.
 */
 public boolean isNativeMethod() {
 return lineNumber == -2;
 }

 /**
 * Returns a string representation of this stack trace element.
 *
 * @apiNote The format of this string depends on the implementation, but the
 * following examples may be regarded as typical:
 * <ul>
 * <li>
 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Main.java:101)}"
 * - See the description below.
 * </li>
 * <li>
 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Main.java)}"
 * - The line number is unavailable.
 * </li>
 * <li>
 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Unknown Source)}"
 * - Neither the file name nor the line number is available.
 * </li>
 * <li>
 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Native Method)}"
 * - The method containing the execution point is a native method.
 * </li>
 * <li>
 * "{@code com.foo.loader//com.foo.bar.App.run(App.java:12)}"
 * - The class of the execution point is defined in the unnamed module of
 * the class loader named {@code com.foo.loader}.
 * </li>
 * <li>
 * "{@code acme@2.1/org.acme.Lib.test(Lib.java:80)}"
 * - The class of the execution point is defined in {@code acme} module
 * loaded by a built-in class loader such as the application class loader.
 * </li>
 * <li>
 * "{@code MyClass.mash(MyClass.java:9)}"
 * - {@code MyClass} class is on the application class path.
 * </li>
 * </ul>
 *
 * <p> The first example shows a stack trace element consisting of
 * three elements, each separated by {@code "/"} followed with
 * the source file name and the line number of the source line
 * containing the execution point.
 *
 * The first element "{@code com.foo.loader}" is
 * the name of the class loader. The second element "{@code foo@9.0}"
 * is the module name and version. The third element is the method
 * containing the execution point; "{@code com.foo.Main"}" is the
 * fully-qualified class name and "{@code run}" is the name of the method.
 * "{@code Main.java}" is the source file name and "{@code 101}" is
 * the line number.
 *
 * <p> If a class is defined in an <em>unnamed module</em>
 * then the second element is omitted as shown in
 * "{@code com.foo.loader//com.foo.bar.App.run(App.java:12)}".
 *
 * <p> If the class loader is a <a href="ClassLoader.html#builtinLoaders">
 * built-in class loader</a> or is not named then the first element
 * and its following {@code "/"} are omitted as shown in
 * "{@code acme@2.1/org.acme.Lib.test(Lib.java:80)}".
 * If the first element is omitted and the module is an unnamed module,
 * the second element and its following {@code "/"} are also omitted
 * as shown in "{@code MyClass.mash(MyClass.java:9)}".
 *
 * <p> The {@code toString} method may return two different values on two
 * {@code StackTraceElement} instances that are
 * {@linkplain #equals(Object) equal}, for example one created via the
 * constructor, and one obtained from {@link java.lang.Throwable} or
 * {@link java.lang.StackWalker.StackFrame}, where an implementation may
 * choose to omit some element in the returned string.
 *
 * @revised 9
 * @spec JPMS
 * @see Throwable#printStackTrace()
 */
 public String toString() {
 String s = "";
 if (!dropClassLoaderName() && classLoaderName != null &&
 !classLoaderName.isEmpty()) {
 s += classLoaderName + "/";
 }
 if (moduleName != null && !moduleName.isEmpty()) {
 s += moduleName;

 if (!dropModuleVersion() && moduleVersion != null &&
 !moduleVersion.isEmpty()) {
 s += "@" + moduleVersion;
 }
 }
 s = s.isEmpty() ? declaringClass : s + "/" + declaringClass;

 return s + "." + methodName + "(" +
 (isNativeMethod() ? "Native Method)" :
 (fileName != null && lineNumber >= 0 ?
 fileName + ":" + lineNumber + ")" :
 (fileName != null ? ""+fileName+")" : "Unknown Source)")));
 }

 /**
 * Returns true if the specified object is another
 * {@code StackTraceElement} instance representing the same execution
 * point as this instance. Two stack trace elements {@code a} and
 * {@code b} are equal if and only if:
 * <pre>{@code
 * equals(a.getClassLoaderName(), b.getClassLoaderName()) &&
 * equals(a.getModuleName(), b.getModuleName()) &&
 * equals(a.getModuleVersion(), b.getModuleVersion()) &&
 * equals(a.getClassName(), b.getClassName()) &&
 * equals(a.getMethodName(), b.getMethodName())
 * equals(a.getFileName(), b.getFileName()) &&
 * a.getLineNumber() == b.getLineNumber()
 *
 * }</pre>
 * where {@code equals} has the semantics of {@link
 * java.util.Objects#equals(Object, Object) Objects.equals}.
 *
 * @param obj the object to be compared with this stack trace element.
 * @return true if the specified object is another
 * {@code StackTraceElement} instance representing the same
 * execution point as this instance.
 *
 * @revised 9
 * @spec JPMS
 */
 public boolean equals(Object obj) {
 if (obj==this)
 return true;
 if (!(obj instanceof StackTraceElement))
 return false;
 StackTraceElement e = (StackTraceElement)obj;
 return Objects.equals(classLoaderName, e.classLoaderName) &&
 Objects.equals(moduleName, e.moduleName) &&
 Objects.equals(moduleVersion, e.moduleVersion) &&
 e.declaringClass.equals(declaringClass) &&
 e.lineNumber == lineNumber &&
 Objects.equals(methodName, e.methodName) &&
 Objects.equals(fileName, e.fileName);
 }

 /**
 * Returns a hash code value for this stack trace element.
 */
 public int hashCode() {
 int result = 31*declaringClass.hashCode() + methodName.hashCode();
 result = 31*result + Objects.hashCode(classLoaderName);
 result = 31*result + Objects.hashCode(moduleName);
 result = 31*result + Objects.hashCode(moduleVersion);
 result = 31*result + Objects.hashCode(fileName);
 result = 31*result + lineNumber;
 return result;
 }


 /**
 * Called from of() methods to set the 'format' bitmap using the Class
 * reference stored in declaringClassObject, and then clear the reference.
 *
 * <p>
 * If the module is a non-upgradeable JDK module, then set
 * JDK_NON_UPGRADEABLE_MODULE to omit its version string.
 * <p>
 * If the loader is one of the built-in loaders (`boot`, `platform`, or `app`)
 * then set BUILTIN_CLASS_LOADER to omit the first element (`<loader>/`).
 */
 private synchronized void computeFormat() {
 try {
 Class<?> cls = (Class<?>) declaringClassObject;
 ClassLoader loader = cls.getClassLoader0();
 Module m = cls.getModule();
 byte bits = 0;

 // First element - class loader name
 // Call package-private ClassLoader::name method

 if (loader instanceof BuiltinClassLoader) {
 bits |= BUILTIN_CLASS_LOADER;
 }

 // Second element - module name and version

 // Omit if is a JDK non-upgradeable module (recorded in the hashes
 // in java.base)
 if (isHashedInJavaBase(m)) {
 bits |= JDK_NON_UPGRADEABLE_MODULE;
 }
 format = bits;
 } finally {
 // Class reference no longer needed, clear it
 declaringClassObject = null;
 }
 }

 private static final byte BUILTIN_CLASS_LOADER = 0x1;
 private static final byte JDK_NON_UPGRADEABLE_MODULE = 0x2;

 private boolean dropClassLoaderName() {
 return (format & BUILTIN_CLASS_LOADER) == BUILTIN_CLASS_LOADER;
 }

 private boolean dropModuleVersion() {
 return (format & JDK_NON_UPGRADEABLE_MODULE) == JDK_NON_UPGRADEABLE_MODULE;
 }

 /**
 * Returns true if the module is hashed with java.base.
 * <p>
 * This method returns false when running on the exploded image
 * since JDK modules are not hashed. They have no Version attribute
 * and so "@<version>" part will be omitted anyway.
 */
 private static boolean isHashedInJavaBase(Module m) {
 // return true if module system is not initialized as the code
 // must be in java.base
 if (!VM.isModuleSystemInited())
 return true;

 return ModuleLayer.boot() == m.getLayer() && HashedModules.contains(m);
 }

 /*
 * Finds JDK non-upgradeable modules, i.e. the modules that are
 * included in the hashes in java.base.
 */
 private static class HashedModules {
 static Set<String> HASHED_MODULES = hashedModules();

 static Set<String> hashedModules() {

 Optional<ResolvedModule> resolvedModule = ModuleLayer.boot()
 .configuration()
 .findModule("java.base");
 assert resolvedModule.isPresent();
 ModuleReference mref = resolvedModule.get().reference();
 assert mref instanceof ModuleReferenceImpl;
 ModuleHashes hashes = ((ModuleReferenceImpl)mref).recordedHashes();
 if (hashes != null) {
 Set<String> names = new HashSet<>(hashes.names());
 names.add("java.base");
 return names;
 }

 return Set.of();
 }

 static boolean contains(Module m) {
 return HASHED_MODULES.contains(m.getName());
 }
 }


 /*
 * Returns an array of StackTraceElements of the given depth
 * filled from the backtrace of a given Throwable.
 */
 static StackTraceElement[] of(Throwable x, int depth) {
 StackTraceElement[] stackTrace = new StackTraceElement[depth];
 for (int i = 0; i < depth; i++) {
 stackTrace[i] = new StackTraceElement();
 }

 // VM to fill in StackTraceElement
 initStackTraceElements(stackTrace, x);

 // ensure the proper StackTraceElement initialization
 for (StackTraceElement ste : stackTrace) {
 ste.computeFormat();
 }
 return stackTrace;
 }

 /*
 * Returns a StackTraceElement from a given StackFrameInfo.
 */
 static StackTraceElement of(StackFrameInfo sfi) {
 StackTraceElement ste = new StackTraceElement();
 initStackTraceElement(ste, sfi);

 ste.computeFormat();
 return ste;
 }

 /*
 * Sets the given stack trace elements with the backtrace
 * of the given Throwable.
 */
 private static native void initStackTraceElements(StackTraceElement[] elements,
 Throwable x);
 /*
 * Sets the given stack trace element with the given StackFrameInfo
 */
 private static native void initStackTraceElement(StackTraceElement element,
 StackFrameInfo sfi);

 private static final long serialVersionUID = 6992337162326171013L;
}