package tb;

import drjava.util.Tree;
import net.luaos.tb.common.Solution;
import org.luaj.vm2.Globals;
import org.luaj.vm2.LuaTable;
import org.luaj.vm2.LuaValue;
import org.luaj.vm2.compiler.LuaC;
import org.luaj.vm2.lib.jse.JsePlatform;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;

public class sol_lua extends Solution {
  String code;

  public sol_lua() {}

  public sol_lua(String code) {
    this.code = code;
  }

  public void fromTree(Tree tree) {
    code = tree.getString(0);
  }

  public Tree toTree() {
    return new Tree(this).add(code);
  }

  public String compute(String input) {
    return callLuaSolution(createLuaEnvironment(), code, input);
  }

  public static String callLuaSolution(LuaTable _G, String code, String input) {
    if (input != null)
      _G.set("input", input);

    // compile into a chunk, or load as a class
    InputStream is =  new ByteArrayInputStream(code.getBytes());
    LuaValue chunk = null;
    try {
      chunk = LuaC.instance.load(is, "script", _G);
    } catch (IOException e) {  // not gonna happen anyway
      throw new RuntimeException(e);
    }

    // Check correct type (probably optional)
    chunk.checkclosure();

    // The chunk can be called with arguments as desired.
    LuaValue result = chunk.call();

    return luaResultToString(result);
  }

  public static String luaResultToString(LuaValue result) {
    return result.isnil() ? null : result.toString();
  }

  /** If this is changed, make sure the environment is extendable (not a singleton!)
   *  Or change the caller site to make a clone first. */
  public static LuaTable createLuaEnvironment() {
    // create an environment to run in
    LuaTable _G = new LuaTable(); //JsePlatform.standardGlobals();

    Globals standardGlobals = JsePlatform.standardGlobals();
    _G.set("_G", _G);
    _G.set("print", standardGlobals.get("print"));
    _G.set("pairs", standardGlobals.get("pairs"));
    return _G;
  }
}