com.novetta.ibg.common.sys.Whicher Maven / Gradle / Ivy
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/*
* (c) 2014 IBG, A Novetta Solutions Company.
*/
package com.novetta.ibg.common.sys;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.CharMatcher;
import com.google.common.base.Function;
import com.google.common.base.Optional;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.base.Splitter;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.common.io.Files;
import java.io.File;
import java.util.ArrayList;
import java.util.List;
import javax.annotation.Nullable;
/**
* Class that provides a method of determining the pathname of
* an executable. This class's functionality approximates that of the GNU
* {@code which} program.
* @author mchaberski
* @since 3.1.0
*/
public class Whicher {
private final ImmutableSet parents;
private final Predicate validPredicate;
private final Function> transform;
public Whicher(Iterable parents, Predicate validPredicate) {
this(parents, validPredicate, IdentityTransform.instance);
}
public Whicher(Iterable parents, Predicate validPredicate, Function> transform) {
super();
this.validPredicate = checkNotNull(validPredicate);
this.parents = ImmutableSet.copyOf(checkNotNull(parents));
this.transform = checkNotNull(transform);
}
@VisibleForTesting
static Predicate newIsExecutablePredicate() {
return new Predicate() {
@Override
public boolean apply(File input) {
return input.canExecute();
}
};
}
@VisibleForTesting
static Predicate newIsFilePredicate() {
return new Predicate() {
@Override
public boolean apply(File input) {
return input.isFile();
}
};
}
/**
* Returns the which'd value for a single filename.
* @param filename the filename to search for
* @return the {@code File} object, or null if not found
* @see #which(java.lang.Iterable)
*/
public Optional which(String filename) {
return which(ImmutableList.of(filename));
}
/**
* Returns the {@code File} object representing the pathname that is
* the result of joining a parent pathname with the argument filename and
* is valid for a given predicate. The predicate is checked with
* {@link #isValidResult(java.io.File) }.
* @param filenames the filenames to search for
* @return the {@code File} object, or null if not found
*/
public Optional which(Iterable filenames) {
for (File parent : ImmutableList.copyOf(parents)) {
for (String filename : filenames) {
Iterable filenameVariations = transform.apply(filename);
for (String filenameVariation : filenameVariations) {
File file = new File(parent, filenameVariation);
if (isValidResult(file)) {
return Optional.of(file);
}
}
}
}
return Optional.absent();
}
static final class IdentityTransform implements Function> {
@Override
public Iterable apply(String input) {
return ImmutableList.of(input);
}
private static final IdentityTransform instance = new IdentityTransform();
}
static final class WindowsTransform extends MultipleSuffixTransform {
private static final ImmutableList windowsExecutableSuffixes = ImmutableList.of(".exe", ".bat", ".com");
public WindowsTransform() {
super(windowsExecutableSuffixes);
}
private static final WindowsTransform instance = new WindowsTransform();
}
static class MultipleSuffixTransform implements Function> {
private final ImmutableList suffixes;
public MultipleSuffixTransform(Iterable suffixes) {
this.suffixes = ImmutableList.copyOf(suffixes);
}
@Override
public Iterable apply(String filename) {
String ext = Files.getFileExtension(filename);
if (ext.isEmpty()) {
ImmutableList.Builder b = ImmutableList.builder();
b.add(filename);
for (String suffix : suffixes) {
b.add(filename + suffix);
}
return b.build();
} else {
return ImmutableList.of(filename);
}
}
}
/**
* Checks whether this instance's predicate is true for a pathname.
* @param file the file
* @return true if and only if this instance's predicate returns true
*/
protected boolean isValidResult(File file) {
return validPredicate.apply(file);
}
@VisibleForTesting
static class Pathnames {
private static final CharMatcher pathSeparatorMatcher = CharMatcher.is(File.pathSeparatorChar);
private static final Splitter pathListSplitter = Splitter.on(pathSeparatorMatcher).omitEmptyStrings();
/**
* Splits a string on the system path separator. Use
* {@link Iterables#transform(java.lang.Iterable, com.google.common.base.Function)
* Iterables.transform} and the {@link #STRING_TO_FILE} function to
* get an iterable over {@code File} objects.
* @param pathsList
* @return the constituent paths
* @see File#pathSeparator
*
*/
public static Iterable splitPaths(String pathsList) {
return pathListSplitter.split(pathsList);
}
/**
* Gets an iterable over the directories enumerated in the {@code PATH}
* environment variable.
* @return the iterable of file objects
*/
static Iterable getSystemPathDirs() {
return Iterables.transform(splitPaths(System.getenv("PATH")), newFileFunction());
}
/**
* Gets an immutable list containing the directories enumerated in the
* {@code PATH} environment variable.
* @return the list
*/
static List getSystemPathDirList() {
return ImmutableList.copyOf(getSystemPathDirs());
}
/**
* Function that constructs files from strings, using the single argument
* {@code File} constructor.
*/
static Function newFileFunction() {
return new Function () {
@Override
public File apply(String input) {
return new File(input);
}
};
}
static boolean hasAnyExtension(@Nullable String pathname) {
return pathname == null ? false : !Files.getFileExtension(pathname).equals("");
}
}
/**
* Constructs and returns a GNU-style instance that searches the system
* path for executable files, checking Windows extensions if the platform
* is Windows.
* @return a constructed instance
*/
public static Whicher gnu() {
return builder()
.inAny(Pathnames.getSystemPathDirList())
.executable()
.detectPlatform()
.build();
}
/**
* Creates a new builder with no parent directories to be searched.
* Warning: you'll never find anything if you don't add any parents.
* @return the builder
*/
public static Builder builder() {
return new Builder();
}
/**
* Creates a new builder.
* @param parent the first parent directory to be searched
* @return the builder
*/
public static Builder builder(File parent) {
return new Builder().in(parent);
}
/**
* Builder for whicher instances. Provides a fluent way to build
* valid whichers.
*/
public static class Builder {
private final List parents;
private Predicate validPredicate;
private Function> transform = IdentityTransform.instance;
private Builder() {
parents = new ArrayList<>();
validPredicate = newIsFilePredicate();
}
/**
* Add a directory to be searched.
* @param parent a directory
* @return this builder instance
*/
public Builder in(File parent) {
parents.add(checkNotNull(parent));
return this;
}
/**
* Add multiple directories to be searched
* @param parents the directories to search
* @return this instance
*/
public Builder inAny(Iterable parents) {
Iterables.addAll(this.parents, parents);
return this;
}
/**
* Require that the found file satisfies the given predicate, along
* with all predicates previously added.
* @param validPredicate the predicate
* @return this instance
*/
public Builder check(Predicate validPredicate) {
this.validPredicate = Predicates.and(this.validPredicate, validPredicate);
return this;
}
/**
* Builds and returns the whicher instance.
* @return the whicher
*/
public Whicher build() {
return new Whicher(parents, validPredicate, transform);
}
/**
* Require that the found file be executable.
* @return this instance
*/
public Builder executable() {
return check(newIsExecutablePredicate());
}
/**
* Set the transform that maps a single filename to multiple filenames,
* all of which are to be considered matches. The primary use for
* a transform is to allow 'foo' to match against 'foo.exe'.
* @param transform the transform
* @return this instance
*/
public Builder transform(Function> transform) {
this.transform = checkNotNull(transform);
return this;
}
/**
* Set transform that maps to filenames with windows executable
* suffixes. The suffixes are .exe, .bat, and .com.
* @return this instance
*/
public Builder windowsSuffixes() {
return transform(WindowsTransform.instance);
}
/**
* Set tranform for Windows suffixes if on Windows, otherwise
* do nothing.
* @return this instance
* @see #windowsSuffixes()
*/
public Builder detectPlatform() {
Platform platform = Platforms.getPlatform();
if (platform.isWindows()) {
return windowsSuffixes();
} else {
return this;
}
}
}
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