diff -r 8d790d757bfb -r fcba3250fb2a src/Tools/Find_Facts/component_elm.scala
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Tools/Find_Facts/component_elm.scala	Sat Jan 11 21:31:13 2025 +0100
@@ -0,0 +1,127 @@
+/*  Author:     Fabian Huch, TU Muenchen
+
+Build Isabelle Elm component from official downloads. See also: https://elm-lang.org/
+*/
+
+package isabelle
+
+
+object Component_Elm {
+  /* platform information */
+
+  sealed case class Download_Platform(platform_name: String, file_name: String) {
+    override def toString: String = platform_name
+
+    def archive_name = file_name + ".gz"
+    def download(base_url: String, version: String): String =
+      base_url + "/" + version + "/" + archive_name
+  }
+
+  val platforms: List[Download_Platform] =
+    List(
+      Download_Platform("arm64-darwin", "binary-for-mac-64-bit-ARM"),
+      Download_Platform("x86_64-darwin", "binary-for-mac-64-bit"),
+      Download_Platform("x86_64-linux", "binary-for-linux-64-bit"),
+      Download_Platform("x86_64-windows", "binary-for-windows-64-bit"))
+
+
+  /* build elm */
+
+  val default_url = "https://github.com/elm/compiler/releases/download"
+  val default_version = "0.19.1"
+
+  def build_elm(
+    base_url: String = default_url,
+    version: String = default_version,
+    target_dir: Path = Path.current,
+    progress: Progress = new Progress
+  ): Unit = {
+    Isabelle_System.require_command("gunzip")
+
+
+    /* component */
+
+    val component = "elm-" + version
+    val component_dir =
+      Components.Directory(target_dir + Path.basic(component)).create(progress = progress)
+
+
+    /* download */
+
+    for (platform <- platforms) {
+      val platform_dir =
+        Isabelle_System.make_directory(component_dir.path + Path.basic(platform.platform_name))
+
+      val exe = Path.basic("elm")
+      val download = platform.download(base_url, version)
+
+      Isabelle_System.with_tmp_dir("download", component_dir.path.file) { download_dir =>
+        Isabelle_System.with_tmp_dir("tmp", component_dir.path.file) { tmp_dir =>
+          val archive_file = download_dir + Path.basic(platform.archive_name)
+
+          Isabelle_System.download_file(download, archive_file, progress = progress)
+          Isabelle_System.bash("gunzip " + File.bash_path(archive_file))
+          Isabelle_System.copy_file(archive_file.drop_ext, platform_dir + exe)
+          File.set_executable(platform_dir + exe)
+        }
+      }
+    }
+
+    /* license */
+
+    File.write(
+      component_dir.LICENSE,
+      Url.read("https://raw.githubusercontent.com/elm/compiler/master/LICENSE"))
+
+
+    /* settings */
+
+    component_dir.write_settings("""
+ISABELLE_ELM="$COMPONENT/${ISABELLE_WINDOWS_PLATFORM64:-${ISABELLE_APPLE_PLATFORM64:-$ISABELLE_PLATFORM64}}"
+""")
+
+
+    /* README */
+
+    File.write(component_dir.README,
+      """This Isabelle component provides elm """ + version + """.
+
+See also https://elm-lang.org and executables from """ + base_url + """
+
+        Fabian Huch
+        """ + Date.Format.date(Date.now()) + "\n")
+  }
+
+
+  /* Isabelle tool wrapper */
+
+  val isabelle_tool =
+    Isabelle_Tool("component_elm", "build elm component", Scala_Project.here,
+      { args =>
+        var target_dir = Path.current
+        var base_url = default_url
+        var version = default_version
+
+        val getopts = Getopts("""
+Usage: isabelle component_elm [OPTIONS]
+
+  Options are:
+    -D DIR       target directory (default ".")
+    -U URL       download URL (default: """" + default_url + """")
+    -V VERSION   version (default: """" + default_version + """")
+
+  Build elm component.
+""",
+          "D:" -> (arg => target_dir = Path.explode(arg)),
+          "U:" -> (arg => base_url = arg),
+          "V:" -> (arg => version = arg))
+
+        val more_args = getopts(args)
+        if (more_args.nonEmpty) getopts.usage()
+
+        val progress = new Console_Progress()
+
+        build_elm(base_url = base_url, version = version, target_dir = target_dir,
+          progress = progress)
+    })
+}
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