Add java binary finder

3 files changed, 155 insertions, 1 deletions

diff --git a/src/main/java/moe/nea/modernjava/launch/relaunch/FCPRelauncher.java b/src/main/java/moe/nea/modernjava/launch/relaunch/FCPRelauncher.java
index fe74c42..3e13806 100644
--- a/src/main/java/moe/nea/modernjava/launch/relaunch/FCPRelauncher.java
+++ b/src/main/java/moe/nea/modernjava/launch/relaunch/FCPRelauncher.java
@@ -46,7 +46,19 @@ public class FCPRelauncher {
     }
 
     public static File findJavaLauncher() {
-        return new File("/home/nea/.sdkman/candidates/java/16.0.2-tem/bin/java");
+        JavaScanner javaScanner = new JavaScanner();
+        javaScanner.scanDefaultPaths();
+        javaScanner.prettyPrint();
+        JavaScanner.LocalJavaVersion candidate = javaScanner.findCandidate();
+        if (candidate == null) {
+            System.err.println("Looks like we couldn't find a java candidate. Either install one, or if you have one" +
+                    " and we just cannot find it, specify -D" + PropertyNames.JAVA_SCAN_PATH + "=<java home here>." +
+                    " We need a Java 16 JDK. Exiting now.");
+            IAMFML.shutdown(1);
+            throw new RuntimeException();
+        }
+        System.out.println("Choosing Java Candidate:\n" + candidate.prettyPrint());
+        return candidate.getJavaBinary();
     }
 
     public static File findAgentJar() {
diff --git a/src/main/java/moe/nea/modernjava/launch/relaunch/JavaScanner.java b/src/main/java/moe/nea/modernjava/launch/relaunch/JavaScanner.java
new file mode 100644
index 0000000..0003097
--- /dev/null
+++ b/src/main/java/moe/nea/modernjava/launch/relaunch/JavaScanner.java
@@ -0,0 +1,137 @@
+package moe.nea.modernjava.launch.relaunch;
+
+import moe.nea.modernjava.launch.util.PropertyNames;
+import moe.nea.modernjava.launch.util.TextIoUtils;
+import org.apache.commons.io.IOUtils;
+import org.apache.commons.lang3.SystemUtils;
+
+import java.io.File;
+import java.util.ArrayList;
+import java.util.List;
+
+public class JavaScanner {
+
+    public static final String JAVA_BINARY_PATH = "bin/java" + (SystemUtils.IS_OS_WINDOWS ? ".exe" : "");
+    public static final String JAVA_COMPILER_PATH = "bin/javac" + (SystemUtils.IS_OS_WINDOWS ? ".exe" : "");
+
+    public boolean isJavaHome(File potential) {
+        if (new File(potential, JAVA_BINARY_PATH).exists()) {
+            return true;
+        }
+        return false;
+    }
+
+    private List<LocalJavaVersion> versionList = new ArrayList<>();
+
+    public void scanDirectory(File file) {
+        scanDirectory(file, 1);
+    }
+
+    public void scanDirectory(File file, int depthLimit) {
+        if (depthLimit < 0) return;
+        if (isJavaHome(file)) {
+            versionList.add(new LocalJavaVersion(file));
+        } else {
+            for (File listFile : file.listFiles()) {
+                if (listFile.isDirectory()) {
+                    scanDirectory(listFile, depthLimit - 1);
+                }
+            }
+        }
+    }
+
+    public void prettyPrint() {
+        String s = "Fun fact these are the found Java Runtime Environments:\n";
+        for (LocalJavaVersion localJavaVersion : versionList) {
+            s += localJavaVersion.prettyPrint();
+        }
+        System.out.println(s);
+    }
+
+    public void scanDefaultPaths() {
+        File home = new File(System.getProperty("user.home"));
+        scanDirectory(new File(home, ".sdkman/candidates/java"));
+        scanDirectory(new File(home, ".jdks"));
+        scanDirectory(new File("/usr"), 0);
+        String[] paths = System.getProperty(PropertyNames.JAVA_SCAN_PATH, "").split(File.pathSeparator);
+        for (String path : paths) {
+            if (!path.isEmpty()) {
+                scanDirectory(new File(path).getParentFile(), 3);
+            }
+        }
+    }
+
+    public LocalJavaVersion findCandidate() {
+        LocalJavaVersion bestFit = null;
+        for (LocalJavaVersion localJavaVersion : versionList) {
+            if (localJavaVersion.isJdk() && localJavaVersion.getMajorVersion() == 16) {
+                bestFit = localJavaVersion;
+            }
+        }
+        return bestFit;
+    }
+
+    public static class LocalJavaVersion {
+        private final File javaHome;
+        private String versionString;
+
+        public LocalJavaVersion(File javaHome) {
+            this.javaHome = javaHome;
+        }
+
+        public File getJavaHome() {
+            return javaHome;
+        }
+
+        public File getJavaBinary() {
+            return new File(javaHome, JAVA_BINARY_PATH);
+        }
+
+        public boolean isJdk() {
+            return new File(javaHome, JAVA_COMPILER_PATH).exists();
+        }
+
+        public String getVersionString() {
+            if (versionString == null) {
+                ProcessBuilder processBuilder = new ProcessBuilder();
+                processBuilder.command(getJavaBinary().getAbsolutePath(), "-version");
+                processBuilder.redirectInput(ProcessBuilder.Redirect.PIPE);
+                processBuilder.redirectOutput(ProcessBuilder.Redirect.PIPE);
+                processBuilder.redirectError(ProcessBuilder.Redirect.PIPE);
+                try {
+                    Process process = processBuilder.start();
+                    process.waitFor();
+                    versionString = IOUtils.toString(process.getInputStream()) + IOUtils.toString(process.getErrorStream());
+                } catch (Exception e) {
+                    e.printStackTrace();
+                    versionString = "<invalid>";
+                }
+            }
+            return versionString;
+        }
+
+        public String prettyPrint() {
+            return javaHome.getAbsolutePath() + ":\n"
+                    + "\tJava Binary: " + getJavaBinary().getAbsolutePath() + "\n"
+                    + "\tMajor Version: " + getMajorVersion() + "\n"
+                    + "\tFull Version: " + getVersion() + "\n"
+                    + "\tIs Jdk: " + isJdk() + "\n"
+                    ;
+        }
+
+        public String getVersion() {
+            String v = getVersionString();
+            String[] s = v.split("\"");
+            if (s.length < 2) return null;
+            return s[1];
+        }
+
+        public int getMajorVersion() {
+            try {
+                return Integer.parseInt(getVersion().split("\\.")[0]);
+            } catch (Exception e) {
+                return -1;
+            }
+        }
+    }
+}
diff --git a/src/main/java/moe/nea/modernjava/launch/util/PropertyNames.java b/src/main/java/moe/nea/modernjava/launch/util/PropertyNames.java
index 8540dde..22d3b20 100644
--- a/src/main/java/moe/nea/modernjava/launch/util/PropertyNames.java
+++ b/src/main/java/moe/nea/modernjava/launch/util/PropertyNames.java
@@ -13,4 +13,9 @@ public class PropertyNames {
      * Starts a debugger on the given port if present.
      */
     public static final String DEBUG_PORT = "modernjava.debugport";
+
+    /**
+     * Scans the given directories for java binaries.
+     */
+    public static final String JAVA_SCAN_PATH = "modernjava.scanpath";
 }