Log session to ~/.ijp_imagej_launcher.log #6

notes/v.0.2.0.md

@@ -0,0 +1,5 @@
+### New Features
+
+* Use launcher location to infer `ij-dir`. #5
+* Session log is saved to `~/.ijp_imagej_launcher.log` to facilitate troubleshooting when not running from command
+  prompt. The log is reset for each session. #6

src/main/scala/ij_plugins/imagej_launcher/Logger.scala

@@ -5,20 +5,60 @@
 
 package ij_plugins.imagej_launcher
 
-import ij_plugins.imagej_launcher.Logger.Level
+import ij_plugins.imagej_launcher.Logger.{Level, logToFile}
+import os.Path
+
+import java.nio.file.{Files, StandardOpenOption}
+import scala.util.control.NonFatal
 
 class Logger(val level: Level = Level.Info):
+
   def debug(msg: String): Unit = pprint(Level.Debug, msg)
   def info(msg: String): Unit  = pprint(Level.Info, msg)
   def error(msg: String): Unit = pprint(Level.Error, msg)
 
   private def pprint(l: Level, message: String): Unit =
+    val m = f"${l.name}%-5s: $message"
     if l.level <= level.level then println(f"${l.name}%-5s: $message")
+    logToFile(m)
 
 object Logger:
+
+  private val LogFile: Path         = os.home / ".ijp_imagej_launcher.log"
+  private var logFileReset: Boolean = true
+
   enum Level(val level: Int, val name: String):
     case Off   extends Level(0, "OFF")
     case Error extends Level(200, "ERROR")
     case Info  extends Level(400, "INFO")
     case Debug extends Level(500, "DEBUG")
     case All   extends Level(Int.MaxValue, "DEBUG")
+
+  private def logToFile(message: String): Unit =
+    try
+      if logFileReset && os.exists(LogFile) then
+        val _ = os.remove(LogFile)
+        logFileReset = false
+
+      val data  = readableTimeStamp() + ": " + message + "\n"
+      val lines = data.getBytes()
+      val _ = Files.write(
+        LogFile.toNIO,
+        lines,
+        StandardOpenOption.CREATE,
+        StandardOpenOption.APPEND,
+        StandardOpenOption.WRITE
+      )
+    catch
+      case NonFatal(_) =>
+      // Ignore exceptions
+
+  private def readableTimeStamp(): String =
+    // Simple implementation returns GMT time (no date)
+    // Use custom code as DateTimeFormatter is not available in Scala Native 0.4.14
+    val t   = System.currentTimeMillis()
+    val sss = t                               % 1000
+    val ss  = (t / 1000L).toInt               % 60
+    val mm  = (t / (1000L * 60L)).toInt       % 60
+    val hh  = (t / (1000L * 60L * 60L)).toInt % 24
+    f"$hh%02d-$mm%02d-$ss%02d_$sss%03dZ"