Copyright (c) 2016, 2019 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
    
/*******************************************************************************
 * Copyright (c) 2016, 2019 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     
 *******************************************************************************/
package org.eclipse.jdt.internal.compiler.lookup;

import java.util.Arrays;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import java.util.function.Supplier;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import org.eclipse.jdt.core.compiler.CharOperation;
import org.eclipse.jdt.internal.compiler.classfmt.ClassFileConstants;
import org.eclipse.jdt.internal.compiler.env.IModuleAwareNameEnvironment;
import org.eclipse.jdt.internal.compiler.env.IUpdatableModule;
import org.eclipse.jdt.internal.compiler.util.HashtableOfPackage;
import org.eclipse.jdt.internal.compiler.util.SimpleLookupTable;
import org.eclipse.jdt.internal.compiler.util.SimpleSetOfCharArray;

This class serves a dual purpose

First, it canonically represents modules in the world of bindings.

 Secondly, it adds a graph layer on top of LookupEnvironment: ModuleBindins are linked through "read" edges as per JPMS (see java.lang.module.Configuration). Additionally, each ModuleBinding holds its own instance of LookupEnviroment, capturing all packages and types that are visible to the current module. As a subset of all visible types, the ModuleBinding knows the set of packages locally declared in this module. 
/**
 * This class serves a dual purpose
 * <p>
 * First, it canonically represents modules in the world of bindings.
 * </p>
 * <p>
 * Secondly, it adds a graph layer on top of {@link LookupEnvironment}:
 * ModuleBindins are linked through "read" edges as per JPMS (see java.lang.module.Configuration).
 * Additionally, each ModuleBinding holds its own instance of LookupEnviroment,
 * capturing all packages and types that are visible to the current module.
 * As a subset of all visible types, the ModuleBinding knows the set of
 * packages locally declared in this module.
 * </p>
 */
public class ModuleBinding extends Binding implements IUpdatableModule {

	
Name of the unnamed module. /** Name of the unnamed module. */
	public static final char[] UNNAMED = "".toCharArray(); //$NON-NLS-1$
	
Name to represent unnamed modules in --add-exports & --add-reads options. /** Name to represent unnamed modules in --add-exports & --add-reads options. */
	public static final char[] ALL_UNNAMED = "ALL-UNNAMED".toCharArray(); //$NON-NLS-1$
	
Module name for package/type lookup that doesn't care about modules. /** Module name for package/type lookup that doesn't care about modules. */
	public static final char[] ANY = "".toCharArray(); //$NON-NLS-1$
	
Module name for package/type lookup that should look into all named modules. /** Module name for package/type lookup that should look into all named modules. */
	public static final char[] ANY_NAMED = "".toCharArray(); //$NON-NLS-1$
	
Module name for an unobservable module /** Module name for an unobservable module */
	public static final char[] UNOBSERVABLE = "".toCharArray();  //$NON-NLS-1$

	public static class UnNamedModule extends ModuleBinding {

		private static final char[] UNNAMED_READABLE_NAME = "<unnamed>".toCharArray(); //$NON-NLS-1$

		@SuppressWarnings("synthetic-access")
		UnNamedModule(LookupEnvironment env) {
			super(env);
		}
		@Override
		public ModuleBinding[] getAllRequiredModules() {
			return Binding.NO_MODULES;
		}
		@Override
		public boolean canAccess(PackageBinding pkg) {
			if (pkg instanceof SplitPackageBinding) {
				for (PackageBinding p : ((SplitPackageBinding) pkg).incarnations) {
					if (canAccess(p)) {
						return true;
					}
				}
				return false;
			} else {
				ModuleBinding mod = pkg.enclosingModule;
				if (mod != null && mod != this)
					return mod.isPackageExportedTo(pkg, this);
			}
			return true;
		}
		@Override
		public boolean isPackageExportedTo(PackageBinding pkg, ModuleBinding client) {
			// per JLS 7.7.5 an unnamed module exports all its packages
			return pkg.isDeclaredIn(this) && pkg.hasCompilationUnit(false);
		}
		@Override
		PlainPackageBinding getDeclaredPackage(char[] flatName) {
			PlainPackageBinding declaredPackage = super.getDeclaredPackage(flatName);
			if (declaredPackage == null && this.environment.useModuleSystem) {
				IModuleAwareNameEnvironment moduleEnv = (IModuleAwareNameEnvironment) this.environment.nameEnvironment;
				char[][] compoundName = CharOperation.splitOn('.', flatName);
				char[][] declaringModuleNames = moduleEnv.getUniqueModulesDeclaringPackage(compoundName, nameForLookup());
				if (declaringModuleNames != null && CharOperation.containsEqual(declaringModuleNames, this.moduleName)) {
					declaredPackage = getOrCreateDeclaredPackage(compoundName);
				}
			}
			return declaredPackage;
		}
		@Override
		public boolean isUnnamed() {
			return true;
		}
		@Override
		public char[] nameForLookup() {
			return ANY;
		}
		@Override
		public char[] nameForCUCheck() {
			return UNNAMED;
		}
		@Override
		public char[] readableName() {
			return UNNAMED_READABLE_NAME;
		}
		@Override
		public String toString() {
			return "The Unnamed Module"; //$NON-NLS-1$
		}
	}
	public char[] moduleName;
	protected ModuleBinding[] requires;
	protected ModuleBinding[] requiresTransitive;
	protected PlainPackageBinding[] exportedPackages;
	private Map<PlainPackageBinding,SimpleSetOfCharArray> exportRestrictions; // RHS is unresolved names, because unresolvable names are legal in this position
	protected PlainPackageBinding[] openedPackages;
	private Map<PlainPackageBinding,SimpleSetOfCharArray> openRestrictions; // RHS is unresolved names, because unresolvable names are legal in this position
	protected TypeBinding[] uses;
	protected TypeBinding[] services;
	public Map<TypeBinding,TypeBinding[]> implementations;
	public char[] mainClassName;
	private SimpleSetOfCharArray packageNames;
	public int modifiers;
	public LookupEnvironment environment;
	public long tagBits;
	public int defaultNullness = NO_NULL_DEFAULT;
	ModuleBinding[] requiredModules = null;
	boolean isAuto = false;
	private boolean[] isComplete = new boolean[UpdateKind.values().length];
	private Set<ModuleBinding> transitiveRequires;
	SimpleLookupTable storedAnnotations = null;

	
Packages declared in this module (indexed by qualified name).
We consider a package as declared in a module,
if a compilation unit associated with the module
declares the package or a subpackage thereof.
 A package in this structures is always represented by a PlainPackageBinding, as opposed to SplitPackageBinding, which are only maintained in the trees below LookupEnvironment.knownPackages. 

This structure is populated early during compilation with all packages that
are referenced in exports and opens directives, plus their parent packages.

/**
	 * Packages declared in this module (indexed by qualified name).
	 * We consider a package as declared in a module,
	 * if a compilation unit associated with the module
	 * declares the package or a subpackage thereof.
	 * <p>
	 * A package in this structures is always represented by a {@link PlainPackageBinding},
	 * as opposed to {@link SplitPackageBinding}, which are only maintained in the trees
	 * below {@link LookupEnvironment#knownPackages}.
	 * <p>
	 * This structure is populated early during compilation with all packages that
	 * are referenced in exports and opens directives, plus their parent packages.
	 * </p>
	 */
	public HashtableOfPackage<PlainPackageBinding> declaredPackages;

	
Constructor for the unnamed module. /** Constructor for the unnamed module. */
	private ModuleBinding(LookupEnvironment env) {
		this.moduleName = ModuleBinding.UNNAMED;
		this.environment = env;
		this.requires = Binding.NO_MODULES;
		this.requiresTransitive = Binding.NO_MODULES;
		this.exportedPackages = Binding.NO_PLAIN_PACKAGES;
		this.openedPackages = Binding.NO_PLAIN_PACKAGES;
		this.declaredPackages = new HashtableOfPackage<PlainPackageBinding>();
		Arrays.fill(this.isComplete, true);
	}
	/* For error binding and sub class SourceModuleBinding. */
	ModuleBinding(char[] moduleName) {
		this.moduleName = moduleName;
		this.requires = Binding.NO_MODULES;
		this.requiresTransitive = Binding.NO_MODULES;
		this.exportedPackages = Binding.NO_PLAIN_PACKAGES;
		this.openedPackages = Binding.NO_PLAIN_PACKAGES;
		this.uses = Binding.NO_TYPES;
		this.services = Binding.NO_TYPES;
		this.declaredPackages = new HashtableOfPackage<PlainPackageBinding>(5);
	}

	/* For sub class BinaryModuleBinding */
	protected ModuleBinding(char[] moduleName, LookupEnvironment existingEnvironment) {
		this.moduleName = moduleName;
		this.requires = Binding.NO_MODULES;
		this.requiresTransitive = Binding.NO_MODULES;
		this.environment = new LookupEnvironment(existingEnvironment.root, this);
		this.declaredPackages = new HashtableOfPackage<PlainPackageBinding>(5);
	}
	
	public PlainPackageBinding[] getExports() {
		completeIfNeeded(UpdateKind.PACKAGE);
		return this.exportedPackages;
	}
	public String[] getExportRestrictions(PackageBinding pack) {
		completeIfNeeded(UpdateKind.PACKAGE);
		if (this.exportRestrictions != null) {
			SimpleSetOfCharArray set = this.exportRestrictions.get(pack);
			if (set != null) {
				char[][] names = new char[set.elementSize][]; 
				set.asArray(names);
				return CharOperation.charArrayToStringArray(names);
			}
		}
		return CharOperation.NO_STRINGS;
	}
	public PlainPackageBinding[] getOpens() {
		completeIfNeeded(UpdateKind.PACKAGE);
		return this.openedPackages;
	}
	public String[] getOpenRestrictions(PackageBinding pack) {
		completeIfNeeded(UpdateKind.PACKAGE);
		if (this.openRestrictions != null) {
			SimpleSetOfCharArray set = this.openRestrictions.get(pack);
			if (set != null) {
				char[][] names = new char[set.elementSize][]; 
				set.asArray(names);
				return CharOperation.charArrayToStringArray(names);
			}
		}
		return CharOperation.NO_STRINGS;
	}
	public TypeBinding[] getImplementations(TypeBinding binding) {
		if (this.implementations != null) {
			return this.implementations.get(binding);
		}
		return null;
	}
	public ModuleBinding[] getRequires() {
		completeIfNeeded(UpdateKind.MODULE);
		return this.requires;
	}
	public ModuleBinding[] getRequiresTransitive() {
		completeIfNeeded(UpdateKind.MODULE);
		return this.requiresTransitive;
	}
	
	public TypeBinding[] getUses() {
		return this.uses;
	}
	
	public TypeBinding[] getServices() {
		return this.services;
	}

	void completeIfNeeded(IUpdatableModule.UpdateKind kind) {
		if (!this.isComplete[kind.ordinal()]) {
			this.isComplete[kind.ordinal()] = true;
			if (this.environment.nameEnvironment instanceof IModuleAwareNameEnvironment) {
				((IModuleAwareNameEnvironment) this.environment.nameEnvironment).applyModuleUpdates(this, kind);
			}
		}
	}

	// ---  Implement IUpdatableModule: ---

	@Override
	public void addReads(char[] requiredModuleName) {
		ModuleBinding requiredModule = this.environment.getModule(requiredModuleName);
		if (requiredModule != null) {
			int len = this.requires.length;
			if (len == 0) {
				this.requires = new ModuleBinding[] { requiredModule };
			} else {
				System.arraycopy(this.requires, 0, this.requires = new ModuleBinding[len+1], 0, len);
				this.requires[len] = requiredModule;
			}
		} else {
			this.environment.problemReporter.missingModuleAddReads(requiredModuleName);
			return;
		}
	}
	@Override
	public void addExports(char[] packageName, char[][] targetModules) {
		PlainPackageBinding declaredPackage = getOrCreateDeclaredPackage(CharOperation.splitOn('.', packageName));
		if (declaredPackage != null && declaredPackage.isValidBinding())
			addResolvedExport(declaredPackage, targetModules);
	}

	@Override
	public void setMainClassName(char[] mainClassName) {
		this.mainClassName = mainClassName;
	}

	@Override
	public void setPackageNames(SimpleSetOfCharArray packageNames) {
		this.packageNames = packageNames;
	}

	// for code gen:
	
Returns:
array of names, which may contain nulls./** @return array of names, which may contain nulls. */
	public char[][] getPackageNamesForClassFile() {
		if (this.packageNames == null)
			return null;
		for (PlainPackageBinding packageBinding : this.exportedPackages)
			this.packageNames.add(packageBinding.readableName());
		for (PlainPackageBinding packageBinding : this.openedPackages)
			this.packageNames.add(packageBinding.readableName());
		if (this.implementations != null)
			for (TypeBinding[] types : this.implementations.values())
				for (TypeBinding typeBinding : types)
					this.packageNames.add(((ReferenceBinding)typeBinding).fPackage.readableName());
		return this.packageNames.values;
	}

	// ---
	PlainPackageBinding createDeclaredToplevelPackage(char[] name) {
		PlainPackageBinding packageBinding = new PlainPackageBinding(name, this.environment, this);
		this.declaredPackages.put(name, packageBinding);
		return packageBinding;
	}

	PlainPackageBinding createDeclaredPackage(char[][] compoundName, PackageBinding parent) {
		PlainPackageBinding packageBinding = new PlainPackageBinding(compoundName, parent, this.environment, this);
		this.declaredPackages.put(CharOperation.concatWith(compoundName, '.'), packageBinding);
		return packageBinding;
	}

	public PlainPackageBinding getOrCreateDeclaredPackage(char[][] compoundName) {
		char[] flatName = CharOperation.concatWith(compoundName, '.');
		PlainPackageBinding pkgBinding = this.declaredPackages.get(flatName);
		if (pkgBinding != null)
			return pkgBinding;
		if (compoundName.length > 1) {
			PlainPackageBinding parent = getOrCreateDeclaredPackage(CharOperation.subarray(compoundName, 0, compoundName.length-1));
			pkgBinding = new PlainPackageBinding(compoundName, parent, this.environment, this);
			parent.addPackage(pkgBinding, this);
		} else {
			pkgBinding = new PlainPackageBinding(compoundName[0], this.environment, this);
			PackageBinding problemPackage = this.environment.getPackage0(compoundName[0]);
			if (problemPackage == LookupEnvironment.TheNotFoundPackage)
				this.environment.knownPackages.put(compoundName[0], null); // forget TheNotFoundPackage if package was detected late (e.g. with APT in the loop)
		}
		this.declaredPackages.put(flatName, pkgBinding);
		return pkgBinding;
	}

	public void addResolvedExport(PlainPackageBinding declaredPackage, char[][] targetModules) {
		if (declaredPackage == null || !declaredPackage.isValidBinding()) {
			// TODO(SHMOD) use a problem binding (if needed by DOM clients)? See https://bugs.eclipse.org/518794#c13
			return;
		}
		if (this.exportedPackages == null || this.exportedPackages.length == 0) {
			this.exportedPackages = new PlainPackageBinding[] { declaredPackage };
		} else {
			int len = this.exportedPackages.length;
			System.arraycopy(this.exportedPackages, 0, this.exportedPackages = new PlainPackageBinding[len+1], 0, len);
			this.exportedPackages[len] = declaredPackage;
		}
		declaredPackage.isExported = Boolean.TRUE;
		recordExportRestrictions(declaredPackage, targetModules);
	}

	public void addResolvedOpens(PlainPackageBinding declaredPackage, char[][] targetModules) {
		int len = this.openedPackages.length;
		if (declaredPackage == null || !declaredPackage.isValidBinding()) {
			// TODO(SHMOD) use a problem binding (if needed by DOM clients)? See https://bugs.eclipse.org/518794#c13
			return;
		}
		if (len == 0) {
			this.openedPackages = new PlainPackageBinding[] { declaredPackage };
		} else {
			System.arraycopy(this.openedPackages, 0, this.openedPackages = new PlainPackageBinding[len+1], 0, len);
			this.openedPackages[len] = declaredPackage;
		}
		recordOpensRestrictions(declaredPackage, targetModules);
	}

	protected void recordExportRestrictions(PlainPackageBinding exportedPackage, char[][] targetModules) {
		if (targetModules != null && targetModules.length > 0) {
			SimpleSetOfCharArray targetModuleSet = null;
			if (this.exportRestrictions != null) {
				targetModuleSet = this.exportRestrictions.get(exportedPackage);
			} else {
				this.exportRestrictions = new HashMap<>();
			}
			if (targetModuleSet == null) {
				targetModuleSet = new SimpleSetOfCharArray(targetModules.length);
				this.exportRestrictions.put(exportedPackage, targetModuleSet);
			}
			for (int i = 0; i < targetModules.length; i++) {
				targetModuleSet.add(targetModules[i]);
			}
		}
	}

	protected void recordOpensRestrictions(PlainPackageBinding openedPackage, char[][] targetModules) {
		if (targetModules != null && targetModules.length > 0) {
			SimpleSetOfCharArray targetModuleSet = null;
			if (this.openRestrictions != null) {
				targetModuleSet = this.openRestrictions.get(openedPackage);
			} else {
				this.openRestrictions = new HashMap<>();
			}
			if (targetModuleSet == null) {
				targetModuleSet = new SimpleSetOfCharArray(targetModules.length);
				this.openRestrictions.put(openedPackage, targetModuleSet);
			}
			for (int i = 0; i < targetModules.length; i++) {
				targetModuleSet.add(targetModules[i]);
			}
		}
	}

	Stream<ModuleBinding> getRequiredModules(boolean transitiveOnly) {
		return Stream.of(transitiveOnly ? this.getRequiresTransitive() : this.getRequires());
	}
	private void collectAllDependencies(Set<ModuleBinding> deps) {
		getRequiredModules(false).forEach(m -> {
			if (deps.add(m)) {
				m.collectAllDependencies(deps);
			}
		});
	}
	private void collectTransitiveDependencies(Set<ModuleBinding> deps) {
		getRequiredModules(true).forEach(m -> {
			if (deps.add(m)) {
				m.collectTransitiveDependencies(deps);
			}
		});
	}

	// All modules required by this module, either directly or indirectly
	public Supplier<Collection<ModuleBinding>> dependencyGraphCollector() {
		return () -> getRequiredModules(false)
			.collect(HashSet::new,
				(set, mod) -> {
					set.add(mod);
					mod.collectAllDependencies(set);
				},
				HashSet::addAll);
	}
	// All direct and transitive dependencies of this module
	public Supplier<Collection<ModuleBinding>> dependencyCollector() {
		return () -> getRequiredModules(false)
			.collect(HashSet::new,
				(set, mod) -> {
					set.add(mod);
					mod.collectTransitiveDependencies(set);
				},
				HashSet::addAll);
	}

	
Get all the modules required by this module
All required modules include modules explicitly specified as required in the module declaration
as well as implicit dependencies - those specified as ' requires transitive ' by one of the
dependencies
Returns:

  An array of all required modules/**
	 * Get all the modules required by this module
	 * All required modules include modules explicitly specified as required in the module declaration
	 * as well as implicit dependencies - those specified as ' requires transitive ' by one of the
	 * dependencies
	 * 
	 * @return
	 *   An array of all required modules
	 */
	public ModuleBinding[] getAllRequiredModules() {
		if (this.requiredModules != null)
			return this.requiredModules;

		Collection<ModuleBinding> allRequires = dependencyCollector().get();
		if (allRequires.contains(this)) {
			return NO_MODULES; // avoid entering unbounded recursion due to cyclic requires
		}
		ModuleBinding javaBase = this.environment.javaBaseModule();
																			// add java.base?
		if (!CharOperation.equals(this.moduleName, TypeConstants.JAVA_BASE)	// ... not if this *is* java.base 
				&& javaBase != null 										// ... nor when java.base is absent
				&& javaBase != this.environment.UnNamedModule)				// ..... or faked by the unnamed module 
		{
			allRequires.add(javaBase);
		}
		return this.requiredModules = allRequires.size() > 0 ? allRequires.toArray(new ModuleBinding[allRequires.size()]) : Binding.NO_MODULES;
	}

	
Answer the name of this module. The unnamed module is identified by UNNAMED. /** Answer the name of this module. The unnamed module is identified by {@link #UNNAMED}. */
	@Override
	public char[] name() {
		return this.moduleName;
	}

	
Answer the name of this module as it should be used for package or type lookup. Unnamed and automatic modules answer ANY or ANY_NAMED resp., to signal that lookup should search in all accessible (named) modules. /**
	 * Answer the name of this module as it should be used for package or type lookup.
	 * Unnamed and automatic modules answer {@link #ANY} or {@link #ANY_NAMED} resp.,
	 * to signal that lookup should search in all accessible (named) modules.
	 */
	public char[] nameForLookup() {
		return this.moduleName;
	}

	
Answer the name of this module as it should be used for hasCompilationUnit() checks.
/**
	 * Answer the name of this module as it should be used for hasCompilationUnit() checks.
	 */
	public char[] nameForCUCheck() {
		return nameForLookup();
	}

	
Check if the specified package is owned by the current module and exported to the client module.
True if the package appears in the list of exported packages and when the export is targeted,
the module appears in the targets of the exports statement.
Params:
pkg – - the package whose visibility is to be checked
client – - the module that wishes to use the package
Returns:
true if the package is visible to the client module, false otherwise/**
	 * Check if the specified package is owned by the current module and exported to the client module.
	 * True if the package appears in the list of exported packages and when the export is targeted,
	 * the module appears in the targets of the exports statement.
	 * @param pkg - the package whose visibility is to be checked
	 * @param client - the module that wishes to use the package
	 * @return true if the package is visible to the client module, false otherwise
	 */
	public boolean isPackageExportedTo(PackageBinding pkg, ModuleBinding client) {
		// TODO(SHMOD): cache the result?
		PackageBinding resolved = pkg.getIncarnation(this);
		if (resolved != null) {
			if (this.isAuto) { // all packages are exported by an automatic module
				return pkg.enclosingModule == this; // no transitive export
			}
			PackageBinding[] initializedExports = getExports();
			for (int i = 0; i < initializedExports.length; i++) {
				PackageBinding export = initializedExports[i];
				if (export.subsumes(resolved)) {
					if (this.exportRestrictions != null) {
						SimpleSetOfCharArray restrictions = this.exportRestrictions.get(export);
						if (restrictions != null) {
							if (client.isUnnamed())
								return restrictions.includes(ALL_UNNAMED);
							else
								return restrictions.includes(client.name());
						}
					}
					return true;
				}
			}
		}
		return false;
	}

	
Return a package binding if there exists a package named name in this module's context and it can be seen by this module.
A package can be seen by this module if it is declared in this module or any other module read by this module 
(JLS 7.4.3 for packages based on JLS 7.3 for compilation units).
Package exports are not considered for visibility check (only when checking "uniquely visible" (JLS 7.4.3)).
 The returned package may be a SplitPackageBinding, if more than one package of the given name is visible. 

When asked via the unnamed module or an automatic module all other named modules are considered visible. 

/**
	 * Return a package binding if there exists a package named name in this module's context and it can be seen by this module.
	 * A package can be seen by this module if it is declared in this module or any other module read by this module 
	 * (JLS 7.4.3 for packages based on JLS 7.3 for compilation units).
	 * Package exports are not considered for visibility check (only when checking "uniquely visible" (JLS 7.4.3)).
	 * <p>
	 * The returned package may be a {@link SplitPackageBinding}, if more than one package of the given name is visible.
	 * </p>
	 * <p>
	 * When asked via the unnamed module or an automatic module all other named modules are considered visible. 
	 * </p>
	 */
	public PackageBinding getTopLevelPackage(char[] name) {
		return getVisiblePackage(null, name);
	}

	PlainPackageBinding getDeclaredPackage(char[] flatName) {
		return this.declaredPackages.get(flatName);
	}

	// Given parent is visible in this module, see if there is sub package named name visible in this module
	PackageBinding getVisiblePackage(PackageBinding parent, char[] name) {
		// check caches in PackageBinding/LookupEnvironment, which contain the full SplitPackageBinding if appropriate:
		PackageBinding pkg;
		if (parent != null)
			pkg = parent.getPackage0(name);
		else
			pkg = this.environment.getPackage0(name);
		if (pkg != null) {
			if (pkg == LookupEnvironment.TheNotFoundPackage)
				return null;
			else
				return pkg;
		}

		// check cached plain PackageBinding in declaredPackages (which may need combining with siblings):
		char[][] parentName = parent == null ? CharOperation.NO_CHAR_CHAR : parent.compoundName;
		char[][] subPkgCompoundName = CharOperation.arrayConcat(parentName, name);
		char[] fullFlatName = CharOperation.concatWith(subPkgCompoundName, '.');
		PackageBinding binding = this.declaredPackages.get(fullFlatName);

		char[][] declaringModuleNames = null;
		if (this.environment.useModuleSystem) {
			IModuleAwareNameEnvironment moduleEnv = (IModuleAwareNameEnvironment) this.environment.nameEnvironment;
			declaringModuleNames = moduleEnv.getUniqueModulesDeclaringPackage(subPkgCompoundName, nameForLookup());
			if (binding == null) {
				if (declaringModuleNames != null) {
					if (CharOperation.containsEqual(declaringModuleNames, this.moduleName)) {
						if (parent != null) {
							PackageBinding singleParent = parent.getIncarnation(this);
							if (singleParent != null && singleParent != parent) {
								// parent.getPackage0() may have been too shy, so drill into the split:
								binding = singleParent.getPackage0(name);
							}
						}
						if (binding == null) {
							// declared here, not yet known, so create it now:
							binding = this.createDeclaredPackage(subPkgCompoundName, parent);
						}
					} else {
						// visible but foreign (when current is unnamed or auto):
						for (char[] declaringModuleName : declaringModuleNames) {
							ModuleBinding declaringModule = this.environment.root.getModule(declaringModuleName);
							if (declaringModule != null) {
								PlainPackageBinding declaredPackage = declaringModule.getDeclaredPackage(fullFlatName);
								binding = SplitPackageBinding.combine(declaredPackage, binding, this);
							}
						}
					}
				}
			}
		} else {
			if (this.environment.nameEnvironment.isPackage(parentName, name))
				binding = this.createDeclaredPackage(subPkgCompoundName, parent);
		}
		
		binding = combineWithPackagesFromOtherRelevantModules(binding, subPkgCompoundName, declaringModuleNames);

		assert binding == null || binding instanceof PlainPackageBinding || binding.enclosingModule == this;
		
		if (binding == null || !binding.isValidBinding()) {
			if (parent != null) {
				if (binding == null) {
					parent.addNotFoundPackage(name);
				} else {
					parent.knownPackages.put(name, binding);
				}
			} else {
				this.environment.knownPackages.put(name, LookupEnvironment.TheNotFoundPackage);
			}
			return null;
		}
		// remember
		if (parentName.length == 0) {
			this.environment.knownPackages.put(name, binding);
		} else if (parent != null) {
			binding = parent.addPackage(binding, this);
		}
		return binding;
	}

	
Answer the package of the given qualified name and visible in this module, or null if no such package exists. Accessibility (based on package exports) is not checked.
 May answer a SplitPackageBinding. 
/**
	 * Answer the package of the given qualified name and visible in this module,
	 * or {@code null} if no such package exists.
	 * Accessibility (based on package exports) is <strong>not</strong> checked.
	 * <p>
	 * May answer a {@link SplitPackageBinding}.
	 * </p>
	 */
	public PackageBinding getVisiblePackage(char[][] qualifiedPackageName) {
		if (qualifiedPackageName == null || qualifiedPackageName.length == 0) {
			return this.environment.defaultPackage;
		}

		PackageBinding parent = getTopLevelPackage(qualifiedPackageName[0]);
		if (parent == null)
			return null;

		// check each sub package
		for (int i = 1; i < qualifiedPackageName.length; i++) {
			PackageBinding binding = getVisiblePackage(parent, qualifiedPackageName[i]); 
			if (binding == null) {
				return null;
			}
			parent = binding;
		}
		return parent;
	}

	PackageBinding combineWithPackagesFromOtherRelevantModules(PackageBinding currentBinding, char[][] compoundName, char[][] declaringModuleNames) {
		for (ModuleBinding moduleBinding : otherRelevantModules(declaringModuleNames)) {
			PlainPackageBinding nextBinding = moduleBinding.getDeclaredPackage(CharOperation.concatWith(compoundName, '.'));
			currentBinding = SplitPackageBinding.combine(nextBinding, currentBinding, this);
		}
		return currentBinding;
	}

	List<ModuleBinding> otherRelevantModules(char[][] declaringModuleNames) {
		if (isUnnamed() && declaringModuleNames != null) {
			// unnamed module reads all named modules,
			// so all modules declaring the given package are relevant:
			return Arrays.stream(declaringModuleNames)
				.filter(modName -> modName != UNNAMED)
				.map(modName -> this.environment.getModule(modName))
				.filter(Objects::nonNull)
				.collect(Collectors.toList());
		} else {
			return Arrays.asList(getAllRequiredModules());
		}
	}

	
Check if the given package is accessible by this module. True when the package is declared in this module or exported by some required module to this module. See isPackageExportedTo(PackageBinding, ModuleBinding) 
Params:
pkg – 
Returns:
True, if the package is accessible by this module, false otherwise/**
	 * Check if the given package is accessible by this module. True when the package is declared in
	 * this module or exported by some required module to this module.
	 * See {@link #isPackageExportedTo(PackageBinding, ModuleBinding)}
	 * 
	 * @param pkg
	 * 
	 * @return True, if the package is accessible by this module, false otherwise
	 */
	public boolean canAccess(PackageBinding pkg) {
		if (pkg.isDeclaredIn(this))
			return true;
		for (ModuleBinding requiredModule : getAllRequiredModules()) {
			// If pkg is a SplitPackageBinding, we actually ask the intersection of all required modules
			// and modules declaring the package, if any of them exports the package to this module.
			// The intersection is computed when inside isPackageExportedTo we ask for pkg's incarnation in requiredModule.
			if (requiredModule.isPackageExportedTo(pkg, ModuleBinding.this))
				return true;
			// TODO(SHMOD): store export status in the PackageBinding?
		}
		return false;
	}
	@Override
	public char[] computeUniqueKey(boolean isLeaf) {
		return CharOperation.prepend('"', this.moduleName);
	}

	@Override
	public int kind() {
		//
		return Binding.MODULE;
	}

	@Override
	public char[] readableName() {
		return this.moduleName;
	}

	@Override
	public String toString() {
		StringBuffer buffer = new StringBuffer(30);
		if (isOpen())
			buffer.append("open "); //$NON-NLS-1$
		buffer.append("module " + new String(readableName())); //$NON-NLS-1$
		if (this.requires.length > 0) {
			buffer.append("\n/*    requires    */\n"); //$NON-NLS-1$
			for (int i = 0; i < this.requires.length; i++) {
				buffer.append("\n\t"); //$NON-NLS-1$
				if (this.requiresTransitive != null) {
					for (ModuleBinding reqTrans : this.requiresTransitive) {
						if (reqTrans == this.requires[i]) {
							buffer.append("transitive "); //$NON-NLS-1$
							break;
						}
					}
				}
				buffer.append(this.requires[i].moduleName);
			}
		} else {
			buffer.append("\nNo Requires"); //$NON-NLS-1$
		}
		if (this.exportedPackages != null && this.exportedPackages.length > 0) {
			buffer.append("\n/*    exports    */\n"); //$NON-NLS-1$
			for (int i = 0; i < this.exportedPackages.length; i++) {
				PackageBinding export = this.exportedPackages[i];
				buffer.append("\n\t"); //$NON-NLS-1$
				if (export == null) {
					buffer.append("<unresolved>"); //$NON-NLS-1$
					continue;
				}
				buffer.append(export.readableName());
				SimpleSetOfCharArray restrictions = this.exportRestrictions != null ? this.exportRestrictions.get(export) : null;
				if (restrictions != null) {
					buffer.append(" to "); //$NON-NLS-1$
					String sep = ""; //$NON-NLS-1$
					char[][] allNames = new char[restrictions.elementSize][];
					restrictions.asArray(allNames);
					for (char[] targetModule : allNames) {
						buffer.append(sep);
						buffer.append(targetModule);
						sep = ", "; //$NON-NLS-1$
					}
				}
			}
		} else {
			buffer.append("\nNo Exports"); //$NON-NLS-1$
		}
		if (this.openedPackages != null && this.openedPackages.length > 0) {
			buffer.append("\n/*    exports    */\n"); //$NON-NLS-1$
			for (int i = 0; i < this.openedPackages.length; i++) {
				PackageBinding opens = this.openedPackages[i];
				buffer.append("\n\t"); //$NON-NLS-1$
				if (opens == null) {
					buffer.append("<unresolved>"); //$NON-NLS-1$
					continue;
				}
				buffer.append(opens.readableName());
				SimpleSetOfCharArray restrictions = this.openRestrictions != null ? this.openRestrictions.get(opens) : null;
				if (restrictions != null) {
					buffer.append(" to "); //$NON-NLS-1$
					String sep = ""; //$NON-NLS-1$
					char[][] allNames = new char[restrictions.elementSize][];
					restrictions.asArray(allNames);
					for (char[] targetModule : allNames) {
						buffer.append(sep);
						buffer.append(targetModule);
						sep = ", "; //$NON-NLS-1$
					}
				}
			}
		} else {
			buffer.append("\nNo Opens"); //$NON-NLS-1$
		}
		if (this.uses != null && this.uses.length > 0) {
			buffer.append("\n/*    uses    /*\n"); //$NON-NLS-1$
			for (int i = 0; i < this.uses.length; i++) {
				buffer.append("\n\t"); //$NON-NLS-1$
				buffer.append(this.uses[i].debugName());
			}
		} else {
			buffer.append("\nNo Uses"); //$NON-NLS-1$
		}
		if (this.services != null && this.services.length > 0) {
			buffer.append("\n/*    Services    */\n"); //$NON-NLS-1$
			for (int i = 0; i < this.services.length; i++) {
				buffer.append("\n\t"); //$NON-NLS-1$
				buffer.append("provides "); //$NON-NLS-1$
				buffer.append(this.services[i].debugName());
				buffer.append(" with "); //$NON-NLS-1$
				if (this.implementations != null && this.implementations.containsKey(this.services[i])) {
					String sep = ""; //$NON-NLS-1$
					for (TypeBinding impl : this.implementations.get(this.services[i])) {
						buffer.append(sep).append(impl.debugName());
						sep = ", "; //$NON-NLS-1$
					}
				} else {
					buffer.append("<missing implementations>"); //$NON-NLS-1$
				}
			}
		} else {
			buffer.append("\nNo Services"); //$NON-NLS-1$
		}
		return buffer.toString();
	}
	public boolean isUnnamed() {
		return false;
	}
	public boolean isOpen() {
		return (this.modifiers & ClassFileConstants.ACC_OPEN) != 0;
	}
	public boolean isDeprecated() {
		return (this.tagBits & TagBits.AnnotationDeprecated) != 0;
	}
	public boolean hasUnstableAutoName() {
		return false;
	}
	public boolean isTransitivelyRequired(ModuleBinding otherModule) {
		if (this.transitiveRequires == null) {
			Set<ModuleBinding> transitiveDeps = new HashSet<>();
			collectTransitiveDependencies(transitiveDeps);
			this.transitiveRequires = transitiveDeps;
		}
		return this.transitiveRequires.contains(otherModule);
	}

	public int getDefaultNullness() {
		getAnnotationTagBits(); // ensure annotations are initialized
		return this.defaultNullness;
	}
	SimpleLookupTable storedAnnotations(boolean forceInitialize, boolean forceStore) {
		
		if (forceInitialize && this.storedAnnotations == null) {
			if (!this.environment.globalOptions.storeAnnotations && !forceStore)
				return null; // not supported during this compile
			this.storedAnnotations = new SimpleLookupTable(3);
		}
		return this.storedAnnotations;
	}
	public AnnotationHolder retrieveAnnotationHolder(Binding binding, boolean forceInitialization) {
		SimpleLookupTable store = storedAnnotations(forceInitialization, false);
		return store == null ? null : (AnnotationHolder) store.get(binding);
	}

	AnnotationBinding[] retrieveAnnotations(Binding binding) {
		AnnotationHolder holder = retrieveAnnotationHolder(binding, true);
		return holder == null ? Binding.NO_ANNOTATIONS : holder.getAnnotations();
	}

	@Override
	public void setAnnotations(AnnotationBinding[] annotations, boolean forceStore) {
		storeAnnotations(this, annotations, forceStore);
	}
	void storeAnnotationHolder(Binding binding, AnnotationHolder holder) {
		if (holder == null) {
			SimpleLookupTable store = storedAnnotations(false, false);
			if (store != null)
				store.removeKey(binding);
		} else {
			SimpleLookupTable store = storedAnnotations(true, false);
			if (store != null)
				store.put(binding, holder);
		}
	}

	void storeAnnotations(Binding binding, AnnotationBinding[] annotations, boolean forceStore) {
		AnnotationHolder holder = null;
		if (annotations == null || annotations.length == 0) {
			SimpleLookupTable store = storedAnnotations(false, forceStore);
			if (store != null)
				holder = (AnnotationHolder) store.get(binding);
			if (holder == null) return; // nothing to delete
		} else {
			SimpleLookupTable store = storedAnnotations(true, forceStore);
			if (store == null) return; // not supported
			holder = (AnnotationHolder) store.get(binding);
			if (holder == null)
				holder = new AnnotationHolder();
		}
		storeAnnotationHolder(binding, holder.setAnnotations(annotations));
	}
}