Add support for retrieving cache files

app/src/main/java/com/bartlomiejpluta/ttsserver/core/lua/lib/ServerLibrary.kt

@@ -1,19 +1,35 @@
 package com.bartlomiejpluta.ttsserver.core.lua.lib
 
+import android.content.Context
 import com.bartlomiejpluta.ttsserver.core.util.NetworkUtil
 import org.luaj.vm2.LuaValue
+import org.luaj.vm2.lib.OneArgFunction
 import org.luaj.vm2.lib.TwoArgFunction
+import org.luaj.vm2.lib.jse.CoerceJavaToLua
+import java.io.File
 
-class ServerLibrary(private val networkUtil: NetworkUtil) : TwoArgFunction() {
+class ServerLibrary(private val context: Context, private val networkUtil: NetworkUtil) :
+   TwoArgFunction() {
    override fun call(modname: LuaValue, env: LuaValue): LuaValue {
       val server = LuaValue.tableOf().apply {
          set("port", networkUtil.port)
          set("address", networkUtil.address)
          set("url", networkUtil.url)
+         set("getCachedFile", CacheFileFunction(context))
       }
 
       env.set("server", server)
 
       return LuaValue.NIL
    }
+
+   class CacheFileFunction(context: Context) : OneArgFunction() {
+      private val cacheDir = context.cacheDir
+
+      override fun call(fileName: LuaValue) = File(cacheDir, fileName.checkjstring())
+         .takeIf { it.exists() }
+         ?.let { CoerceJavaToLua.coerce(it) }
+         ?: LuaValue.NIL
+
+   }
 }

app/src/main/java/com/bartlomiejpluta/ttsserver/di/module/LuaModule.kt

@@ -47,7 +47,8 @@ class LuaModule {
 
    @Provides
    @Singleton
-   fun serverLibrary(networkUtil: NetworkUtil) = ServerLibrary(networkUtil)
+   fun serverLibrary(context: Context, networkUtil: NetworkUtil) =
+      ServerLibrary(context, networkUtil)
 
    @Provides
    @Singleton