unit uLua;

interface
uses lua, lualib, lauxlib,
    Dialogs;

type
 TLUAExternMethod = record
   Name:string;
   Address:lua_CFunction;
 end;

 TLUAParser = class
 protected
   FLUAState:Pointer;
   FExternMethods:array of TLUAExternMethod;
   Procedure   LuaInit;
   Procedure   LuaClose;
   Procedure   LuaUpdateMethods;
   Procedure   LuaAddMethod(const MethodName:string; Method:lua_CFunction);
 public
   Constructor Create();
   Destructor  Destroy(); override;
   Procedure   Clear();
   Procedure   LoadFromMemory(const Text:string);
   Function    Call(const ProcName:string; Params:array of const):boolean;
   Function    CallResultInt(const ProcName:string; Params:array of const):integer;
   Function    CallResultDoudble(const ProcName:string; Params:array of const):double;
   Function    CallResultString(const ProcName:string; Params:array of const):string;
   Procedure   AddMethod(const MethodName:string; Method:lua_CFunction);
 end;

implementation

{ TLUAParser }

procedure TLUAParser.AddMethod(const MethodName: string; Method: lua_CFunction);
begin
 SetLength(FExternMethods,Length(FExternMethods)+1);
 FExternMethods[Length(FExternMethods)-1].Name:=MethodName;
 FExternMethods[Length(FExternMethods)-1].Address:=Method;
 LuaAddMethod(MethodName,Method);
end;

Function TLUAParser.Call(const ProcName: string; Params: array of const):boolean;
var
 i:integer;
begin
 Result:=true;
 lua_getglobal(FLUAState, PChar(ProcName));
 for i := 0 to Length(Params) - 1 do begin
   case Params[i].VType of
     vtExtended:lua_pushnumber(FLUAState, Params[i].vExtended^);
     vtInteger:lua_pushnumber(FLUAState, Params[i].VInteger);
     vtString:lua_pushstring(FLUAState, PChar(Params[i].VString));
     vtPointer:lua_pushnumber(FLUAState, Params[i].VInteger);
   end;
 end;
 if (lua_pcall(FLUAState, Length(Params), 0, 0) <> 0) then begin
   ShowMessage('error running function '+ProcName+': '+lua_tostring(FLUAState, -1));
   lua_pop(FLUAState, 1);
   Result:=false;
 end;
end;

function TLUAParser.CallResultDoudble(const ProcName: string;
 Params: array of const): double;
begin
 if Call(ProcName,Params) then begin
   Result:=lua_tonumber(FLUAState,-1);
   lua_pop(FLUAState, 1);
 end;
end;

function TLUAParser.CallResultInt(const ProcName: string;
 Params: array of const): integer;
begin
 if Call(ProcName,Params) then begin
   Result:=Round(lua_tonumber(FLUAState,-1));
   lua_pop(FLUAState, 1);
 end;
end;

function TLUAParser.CallResultString(const ProcName: string;
 Params: array of const): string;
begin
 if Call(ProcName,Params) then begin
   Result:=lua_tostring(FLUAState,-1);
   lua_pop(FLUAState, 1);
 end;
end;

procedure TLUAParser.Clear;
begin
 LuaClose();
 LuaInit();
 LuaUpdateMethods;
end;

constructor TLUAParser.Create;
begin
 LuaInit();
end;

destructor TLUAParser.Destroy;
begin
 LuaClose();
 inherited;
end;

procedure TLUAParser.LoadFromMemory(const Text: string);
var
 error:integer;
begin
 error:=luaL_loadbuffer(FLUAState, PChar(Text), length(Text), 'Chunk');
 if error=0 then
   error:=lua_pcall(FLUAState, 0, 0, 0);
 if (error<>0) then begin
   ShowMessage(lua_tostring(FLUAState, -1));
   lua_pop(FLUAState, 1);
 end
end;

procedure TLUAParser.LuaAddMethod(const MethodName: string;
 Method: lua_CFunction);
begin
 lua_pushcfunction(FLUAState, Method);
 lua_setglobal(FLUAState, PChar(MethodName));
end;

procedure TLUAParser.LuaClose;
begin
 lua_close(FLUAState);
end;

procedure TLUAParser.LuaInit;
begin
 FLUAState:=lua_open();
 luaopen_base(FLUAState);
 luaopen_table(FLUAState);
 luaopen_string(FLUAState);
 luaopen_math(FLUAState);
end;

procedure TLUAParser.LuaUpdateMethods;
var
 i:integer;
begin
 for I := 0 to Length(FExternMethods) - 1 do
   LuaAddMethod(FExternMethods[i].Name,FExternMethods[i].Address);
end;

end.