Provide the typical dir for storing data

mailbox-cli/src/main/java/org/briarproject/mailbox/cli/JavaCliModule.kt

@@ -9,7 +9,16 @@ import org.briarproject.mailbox.core.db.DatabaseConfig
 import org.briarproject.mailbox.core.event.DefaultEventExecutorModule
 import org.briarproject.mailbox.core.system.DefaultTaskSchedulerModule
 import org.briarproject.mailbox.core.tor.JavaTorModule
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory.getLogger
 import java.io.File
+import java.io.File.separator
+import java.io.IOException
+import java.nio.file.Files.setPosixFilePermissions
+import java.nio.file.attribute.PosixFilePermission
+import java.nio.file.attribute.PosixFilePermission.OWNER_EXECUTE
+import java.nio.file.attribute.PosixFilePermission.OWNER_READ
+import java.nio.file.attribute.PosixFilePermission.OWNER_WRITE
 import javax.inject.Singleton
 
 @Module(
@@ -22,12 +31,42 @@ import javax.inject.Singleton
 )
 @InstallIn(SingletonComponent::class)
 internal class JavaCliModule {
+
+    companion object {
+        private val LOG: Logger = getLogger(JavaCliModule::class.java)
+
+        private val DEFAULT_DATAHOME = System.getProperty("user.home") +
+            separator + ".local" + separator + "share"
+        private val DATAHOME_SUBDIR = "briar-mailbox"
+    }
+
     @Singleton
     @Provides
     fun provideDatabaseConfig() = object : DatabaseConfig {
         override fun getDatabaseDirectory(): File {
-            // TODO: use a correct location
-            return File("/tmp")
+            val dataHome = when (val custom = System.getenv("XDG_DATA_HOME").orEmpty()) {
+                "" -> File(DEFAULT_DATAHOME)
+                else -> File(custom)
+            }
+            if (!dataHome.exists() || !dataHome.isDirectory()) {
+                throw IOException("datahome missing or not a directory: ${dataHome.absolutePath}")
+            }
+
+            val dataDir = File(dataHome.absolutePath + separator + DATAHOME_SUBDIR)
+            if (!dataDir.exists() && !dataDir.mkdirs()) {
+                throw IOException("datadir could not be created: ${dataDir.absolutePath}")
+            } else if (!dataDir.isDirectory()) {
+                throw IOException("datadir is not a directory: ${dataDir.absolutePath}")
+            }
+
+            val perms = HashSet<PosixFilePermission>()
+            perms.add(OWNER_READ)
+            perms.add(OWNER_WRITE)
+            perms.add(OWNER_EXECUTE)
+            setPosixFilePermissions(dataDir.toPath(), perms)
+
+            LOG.info("Datadir set to: " + dataDir.absolutePath)
+            return dataDir
         }
     }
 }