Add JShell-based basic installation support

.bach/install.jshell

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+/*
+ * Copyright (c) 2024 Christian Stein
+ * Licensed under the Universal Permissive License v 1.0 -> https://opensource.org/license/upl
+ */
+
+System.out.printf(
+    """
+       ___      ___      ___      ___
+      /\\  \\    /\\  \\    /\\  \\    /\\__\\
+     /::\\  \\  /::\\  \\  /::\\  \\  /:/__/_
+    /::\\:\\__\\/::\\:\\__\\/:/\\:\\__\\/::\\/\\__\\
+    \\:\\::/  /\\/\\::/  /\\:\\ \\/__/\\/\\::/  / Java %s
+     \\::/  /   /:/  /  \\:\\__\\    /:/  / %s
+      \\/__/    \\/__/    \\/__/    \\/__/ %s
+    """,
+    Runtime.version(),
+    System.getProperty("os.name"),
+    Path.of("").toUri()
+)
+
+System.out.println("| Source Bach's installer from " + Path.of("src/bach.run/BachInstaller.java").toUri())
+
+/open src/bach.run/BachInstaller.java
+
+int code = 0
+try {
+  // BachInstaller.installDefaultVersionIntoDefaultDirectory();
+  new BachInstaller("main", Path.of(".bach/var/tmp/installed")).install();
+}
+catch(Throwable throwable) {
+  System.err.println(throwable);
+  code = 1;
+}
+
+System.out.println("| Installation of Bach finished with exit code " + code)
+
+/exit code

src/README.md

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+# Bach's Modular Sources
+
+For the time being, this folder only contains a subdirectory named `bach.run`.
+The `bach.run` subdirectory contains helper files used by https://bach.run path forwarding rules.

src/bach.run/BachInstaller.java

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+/*
+ * Copyright (c) 2024 Christian Stein
+ * Licensed under the Universal Permissive License v 1.0 -> https://opensource.org/license/upl
+ */
+
+import java.net.*;
+import java.nio.file.*;
+import java.util.*;
+
+record BachInstaller(String version, Path home) {
+  static String DEFAULT_VERSION = System.getProperty("-Default.version".substring(2), "main");
+  static Path DEFAULT_HOME = Path.of(System.getProperty("-Default.home".substring(2), ".bach"));
+
+  @SuppressWarnings("unused")
+  static void installDefaultVersionIntoDefaultDirectory() throws Exception {
+    var installer = new BachInstaller(DEFAULT_VERSION);
+    installer.install();
+  }
+
+  @SuppressWarnings("unused")
+  static void listInstallableVersions() {
+    System.out.println("- Default version: " + DEFAULT_VERSION);
+    System.out.println("- Released versions: https://github.com/sormuras/run.bach/releases");
+    System.out.println("- Head revisions: https://github.com/sormuras/run.bach/branches");
+  }
+
+  BachInstaller(String version) {
+    this(version, DEFAULT_HOME);
+  }
+
+  void install() throws Exception {
+    var uris =
+        List.of(
+            "https://github.com/sormuras/run.bach/archive/refs/tags/" + version + ".zip",
+            "https://github.com/sormuras/run.bach/archive/refs/heads/" + version + ".zip");
+    for (var uri : uris) {
+      if (Internal.head(uri)) {
+        install(uri);
+        return;
+      }
+    }
+  }
+
+  void install(String uri) throws Exception {
+    System.out.println("Install Bach " + version + " to " + home.toUri() + "...");
+    var tmp = Files.createTempDirectory("run.bach-" + version + "-");
+    var dir = Files.createDirectories(home.resolve("src/run.bach/run/bach"));
+    var zip = tmp.resolve("run.bach-" + version + ".zip");
+    // download and unzip
+    Internal.copy(uri, zip, StandardCopyOption.REPLACE_EXISTING);
+    Internal.unzip(zip, dir, 1);
+
+    // clean up
+    Internal.delete(tmp);
+  }
+
+  private interface Internal {
+    boolean DEBUG = Boolean.getBoolean("-Debug".substring(2));
+
+    static void debug(String message) {
+      if (DEBUG) System.out.println(message);
+    }
+
+    static boolean head(String source) throws Exception {
+      var url = URI.create(source).toURL();
+      var con = (HttpURLConnection) url.openConnection();
+      try {
+        con.setRequestMethod("HEAD");
+        var status = con.getResponseCode();
+        debug("%d <- HEAD %s".formatted(status, source));
+        if (status < 299) return true;
+      } finally {
+        con.disconnect();
+      }
+      return false;
+    }
+
+    static void copy(String source, Path target, CopyOption... options) throws Exception {
+      debug("<< %s".formatted(source));
+      Files.createDirectories(target.getParent());
+      try (var stream =
+          source.startsWith("http")
+              ? URI.create(source).toURL().openStream()
+              : Files.newInputStream(Path.of(source))) {
+        var size = Files.copy(stream, target, options);
+        debug(">> %,7d %s".formatted(size, target.getFileName()));
+      }
+    }
+
+    static void delete(Path path) throws Exception {
+      var start = path.normalize().toAbsolutePath();
+      if (Files.notExists(start)) return;
+      for (var root : start.getFileSystem().getRootDirectories()) {
+        if (start.equals(root)) {
+          debug("deletion of root directory?! " + path);
+          return;
+        }
+      }
+      debug("delete directory tree " + start);
+      try (var stream = Files.walk(start)) {
+        var files = stream.sorted((p, q) -> -p.compareTo(q));
+        for (var file : files.toArray(Path[]::new)) Files.deleteIfExists(file);
+      }
+    }
+
+    static void unzip(Path zip, Path dir, int sub) throws Exception {
+      debug("<< %s".formatted(zip.toUri()));
+      debug(">> %s".formatted(dir.toUri()));
+      var files = new ArrayList<Path>();
+      try (var fs = FileSystems.newFileSystem(zip)) {
+        for (var root : fs.getRootDirectories()) {
+          try (var stream = Files.walk(root)) {
+            var list = stream.filter(Files::isRegularFile).toList();
+            for (var file : list) {
+              var relative = root.relativize(file);
+              var source = sub == 0 ? relative : relative.subpath(sub, relative.getNameCount());
+              var target = dir.resolve(source.toString());
+              debug(">> - " + target.toUri());
+              Files.createDirectories(target.getParent());
+              Files.copy(file, target, StandardCopyOption.REPLACE_EXISTING);
+              files.add(target);
+            }
+          }
+        }
+      }
+      debug(">> %d files unzipped".formatted(files.size()));
+    }
+  }
+
+  public static void main(String... args) throws Exception {
+    installDefaultVersionIntoDefaultDirectory();
+  }
+}

src/bach.run/README.md

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+# Bach's `src/bach.run` folder
+
+This folder contains Java source files (`.java`) and Java Shell scripts (`.jshell`) helping to install Bach.
+
+## Install default version of Bach
+
+```shell
+mkdir example && cd example
+jshell
+/open https://install.bach.run
+```
+
+- https://install.bach.run forwards to the _"install default version of Bach into `.bach` directory of the current working directory"_ [Java Shell](install.jshell) script.
+
+Above's script is a shortcut for the following Java Shell commands and snippets.
+
+```shell
+/open https://src.bach.run/BachInstaller.java
+BachInstaller.installDefaultVersionIntoDefaultDirectory()
+/exit
+```
+
+## Path forwarding
+
+- https://src.bach.run forwards to https://raw.githubusercontent.com/sormuras/bach/main/src/bach.run - resulting in `404: Not Found`
+- https://src.bach.run/install.jshell forwards to https://raw.githubusercontent.com/sormuras/bach/main/src/bach.run/install.jshell
+- https://src.bach.run/BachInstaller.java forwards to https://raw.githubusercontent.com/sormuras/bach/main/src/bach.run/BachInstaller.java
+- https://src.bach.run/Hello.java forwards to https://raw.githubusercontent.com/sormuras/bach/main/src/bach.run/Hello.java

src/bach.run/install.jshell

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+/*
+ * Copyright (c) 2024 Christian Stein
+ * Licensed under the Universal Permissive License v 1.0 -> https://opensource.org/license/upl
+ */
+
+System.out.printf(
+    """
+       ___      ___      ___      ___
+      /\\  \\    /\\  \\    /\\  \\    /\\__\\
+     /::\\  \\  /::\\  \\  /::\\  \\  /:/__/_
+    /::\\:\\__\\/::\\:\\__\\/:/\\:\\__\\/::\\/\\__\\
+    \\:\\::/  /\\/\\::/  /\\:\\ \\/__/\\/\\::/  / Java %s
+     \\::/  /   /:/  /  \\:\\__\\    /:/  / %s
+      \\/__/    \\/__/    \\/__/    \\/__/ %s
+    """,
+    Runtime.version(),
+    System.getProperty("os.name"),
+    Path.of("").toUri()
+)
+
+System.out.println("| Source Bach's installer from https://src.bach.run/BachInstaller.java ...")
+
+/open https://src.bach.run/BachInstaller.java
+
+int code = 0
+try {
+  BachInstaller.installDefaultVersionIntoDefaultDirectory();
+}
+catch(Throwable throwable) {
+  System.err.println(throwable);
+  code = 1;
+}
+
+System.out.println("| Installation of Bach finished with exit code " + code)
+
+/exit code