added OS and Application classes

gradle.properties

@@ -1,4 +1,4 @@
-gradle.version = 7.4.1
+gradle.version = 7.4.2
 jwo.version=1.0-SNAPSHOT
 junitJupiter.version=5.8.2
 lombok.version=1.18.22

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.4.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.4.2-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

src/main/java/net/woggioni/jwo/Application.java

@@ -0,0 +1,117 @@
+package net.woggioni.jwo;
+
+import lombok.AccessLevel;
+import lombok.NoArgsConstructor;
+import lombok.SneakyThrows;
+import lombok.extern.slf4j.Slf4j;
+
+import java.io.FileNotFoundException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Optional;
+import java.util.stream.Stream;
+
+@Slf4j
+@NoArgsConstructor(access = AccessLevel.PRIVATE)
+class Application {
+
+    private static boolean validateConfigurationDirectory(Path candidate) {
+        try {
+            if (!Files.exists(candidate)) {
+                Files.createDirectories(candidate);
+                return true;
+            } else if (!Files.isDirectory(candidate)) {
+                log.debug("Configuration directory '{}' discarded because it is not a directory", candidate);
+                return false;
+            } else if (!Files.isWritable(candidate)) {
+                log.debug("Configuration directory '{}' discarded because it is not writable", candidate);
+                return false;
+            } else {
+                log.debug("Using configuration directory '{}'", candidate);
+                return true;
+            }
+        } catch (Exception ioe) {
+            log.debug(
+                    String.format("configuration directory '%s' discarded: %s", candidate.toString(), ioe.getMessage()),
+                    ioe
+            );
+            return false;
+        }
+    }
+
+    @SneakyThrows
+    private static Path selectCandidate(Stream<Path> candidates, String successMessage, String errorMessage) {
+        return candidates
+                .filter(Application::validateConfigurationDirectory)
+                .peek(p -> log.debug(successMessage, p))
+                .findFirst()
+                .orElseThrow((Sup<Throwable>)() -> new FileNotFoundException(errorMessage));
+    }
+
+    @SneakyThrows
+    private static Path computeCacheDirectory(String appName, String jvmPropertyKey) {
+        Stream<Path> candidates;
+        if(OS.isUnix) {
+            candidates = JWO.optional2Stream(
+                Optional.ofNullable(System.getProperty(jvmPropertyKey)).map(Paths::get),
+                Optional.ofNullable(System.getenv("XDG_CACHE_HOME")).map(prefix -> Paths.get(prefix, appName)),
+                Optional.ofNullable(System.getProperty("user.home")).map(prefix -> Paths.get(prefix, ".cache", appName)),
+                Optional.ofNullable(System.getProperty("user.home")).map(prefix -> Paths.get(prefix, "." + appName, "cache"))
+            );
+        } else if(OS.isMac) {
+            candidates = JWO.optional2Stream(
+                Optional.ofNullable(System.getProperty("user.home"))
+                    .map(prefix -> Paths.get(prefix, "Library", "Application support", appName, "cache")),
+                Optional.ofNullable(System.getProperty("user.home"))
+                    .map(prefix -> Paths.get(prefix, "." + appName, "cache"))
+            );
+        } else if(OS.isWindows) {
+            candidates = JWO.optional2Stream(
+                Optional.ofNullable(System.getenv("LOCALAPPDATA"))
+                    .map(prefix -> Paths.get(prefix, appName, "cache")),
+                Optional.ofNullable(System.getProperty("user.home"))
+                    .map(prefix -> Paths.get(prefix, "Application Data", "Local Settings", "Application Data", appName, "cache")));
+        } else {
+            candidates = JWO.optional2Stream(
+                Optional.ofNullable(System.getProperty("user.home"))
+                    .map(prefix -> Paths.get(prefix, "." + appName, "cache")));
+        }
+        return selectCandidate(candidates,
+                "Using cache directory '{}'",
+                "Unable to find a usable cache directory");
+    }
+
+
+    @SneakyThrows
+    private static Path computeConfigurationDirectory(String appName, String jvmPropertyKey) {
+        Stream<Path> candidates;
+        if(OS.isUnix) {
+            candidates = JWO.optional2Stream(
+                    Optional.ofNullable(System.getProperty(jvmPropertyKey)).map(Paths::get),
+                    Optional.ofNullable(System.getenv("XDG_CONFIG_HOME")).map(prefix -> Paths.get(prefix, appName)),
+                    Optional.ofNullable(System.getProperty("user.home")).map(prefix -> Paths.get(prefix, ".config", appName)),
+                    Optional.ofNullable(System.getProperty("user.home")).map(prefix -> Paths.get(prefix, "." + appName, "config"))
+            );
+        } else if(OS.isMac) {
+            candidates = JWO.optional2Stream(
+                    Optional.ofNullable(System.getProperty("user.home"))
+                        .map(prefix -> Paths.get(prefix, "Library", "Application support", appName, "config")),
+                    Optional.ofNullable(System.getProperty("user.home")).map(prefix -> Paths.get(prefix, "." + appName, "config"))
+            );
+        } else if(OS.isWindows) {
+            candidates = JWO.optional2Stream(
+                    Optional.ofNullable(System.getenv("LOCALAPPDATA"))
+                        .map(prefix -> Paths.get(prefix, appName, "config")),
+                    Optional.ofNullable(System.getProperty("user.home"))
+                        .map(prefix -> Paths.get(prefix, "Application Data", "Local Settings", "Application Data", appName, "config")));
+        } else {
+            candidates = JWO.optional2Stream(Optional.ofNullable(System.getProperty("user.home"))
+                .map(prefix -> Paths.get(prefix, "." + appName, "config")));
+        }
+        return selectCandidate(candidates,
+                "Using configuration directory '{}'",
+                "Unable to find a usable configuration directory");
+    }
+
+}

src/main/java/net/woggioni/jwo/JWO.java

@@ -554,6 +554,15 @@ public class JWO {
         };
     }
 
+    @SafeVarargs
+    public static <T> Stream<T> optional2Stream(Optional<T>...opts) {
+        return Arrays.stream(opts).filter(Optional::isPresent).map(Optional::get);
+    }
+
+    public static <T> Stream<T> optional2Stream(Iterable<Optional<T>> opts) {
+        return iterable2Stream(opts).filter(Optional::isPresent).map(Optional::get);
+    }
+
     public static String decapitalize(String s, Locale locale) {
         if (!s.isEmpty() && !Character.isLowerCase(s.charAt(0)))
             return s.substring(0, 1).toLowerCase(locale) + s.substring(1);

src/main/java/net/woggioni/jwo/OS.java

@@ -0,0 +1,43 @@
+package net.woggioni.jwo;
+
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public enum OS {
+    WINDOWS("windows"),
+    MACOS("mac os x"),
+    LINUX("linux"),
+    SOLARIS("solaris"),
+    BSD("bsd"),
+    AIX("aix"),
+    HP_UX("hp-ux"),
+    UNIX("unix"),
+    POSIX("posix"),
+    VMS("vms");
+
+    private final String value;
+
+    OS(String value) {
+        this.value = value;
+    }
+
+    public static final OS current;
+    public static final boolean isUnix;
+    public static final boolean isWindows;
+    public static final boolean isMac;
+
+    static {
+        OS currentOs = null;
+        String osName = System.getProperty("os.name").toLowerCase();
+        for(OS os : values()) {
+            if(osName.startsWith(os.value)) {
+                currentOs = os;
+            }
+        }
+        if(currentOs == null) throw new IllegalArgumentException(String.format("Unrecognized OS '%s'", osName));
+        current = currentOs;
+        isUnix = Stream.of(LINUX, SOLARIS, BSD, AIX, HP_UX).collect(Collectors.toSet()).contains(current);
+        isWindows = current == WINDOWS;
+        isMac = current == MACOS;
+    }
+}