application_lua_kernel.cpp

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/*
    Copyright (C) 2014 - 2025
    by Chris Beck <render787@gmail.com>
    Part of the Battle for Wesnoth Project https://www.wesnoth.org/
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY.
 
    See the COPYING file for more details.
*/
 
/**
 * @file
 * Provides a Lua interpreter, to drive the game_controller.
 *
 * @note Naming conventions:
 *   - intf_ functions are exported in the wesnoth domain,
 *   - impl_ functions are hidden inside metatables,
 *   - cfun_ functions are closures,
 *   - luaW_ functions are helpers in Lua style.
 */
 
#include "scripting/application_lua_kernel.hpp"
 
#include "config.hpp"
#include "game_config.hpp"
#include "game_errors.hpp"
#include "log.hpp"
#include "scripting/lua_attributes.hpp"
#include "scripting/lua_common.hpp"
#include "scripting/lua_cpp_function.hpp"
#include "scripting/lua_fileops.hpp"
#include "scripting/lua_kernel_base.hpp"
#include "scripting/lua_preferences.hpp"
#include "scripting/plugins/context.hpp"
#include "scripting/plugins/manager.hpp"
#include "scripting/push_check.hpp"
#include "utils/ranges.hpp"
 
#ifdef DEBUG_LUA
#include "scripting/debug_lua.hpp"
#endif
 
#include <map>
#include <sstream>
#include <string>
#include <thread>
#include <utility>
 
#include <functional>
 
#include "lua/wrapper_lauxlib.h"
 
static lg::log_domain log_scripting_lua("scripting/lua");
#define DBG_LUA LOG_STREAM(debug, log_scripting_lua)
#define LOG_LUA LOG_STREAM(info, log_scripting_lua)
#define WRN_LUA LOG_STREAM(warn, log_scripting_lua)
#define ERR_LUA LOG_STREAM(err, log_scripting_lua)
 
static int intf_describe_plugins(lua_State * L)
{
    PLAIN_LOG << "describe plugins (" << plugins_manager::get()->size() << "):";
    lua_getglobal(L, "print");
    for (std::size_t i = 0; i < plugins_manager::get()->size(); ++i) {
        lua_pushvalue(L,-1); //duplicate the print
 
        std::stringstream line;
        line << i
             << ":\t"
             << plugin_manager_status::get_string(plugins_manager::get()->get_status(i))
             << "\t\t"
             << plugins_manager::get()->get_name(i)
             << "\n";
 
        DBG_LUA << line.str();
 
        lua_pushstring(L, line.str().c_str());
        lua_call(L, 1, 0);
    }
    if (!plugins_manager::get()->size()) {
        lua_pushstring(L, "No plugins available.\n");
        lua_call(L, 1, 0);
    }
    return 0;
}
 
static int intf_delay(lua_State* L)
{
    std::this_thread::sleep_for(std::chrono::milliseconds{luaL_checkinteger(L, 1)});
    return 0;
}
 
static int intf_execute(lua_State* L);
 
application_lua_kernel::application_lua_kernel()
 : lua_kernel_base()
{
    lua_getglobal(mState, "wesnoth");
    lua_pushcfunction(mState, intf_delay);
    lua_setfield(mState, -2, "delay");
 
    lua_settop(mState, 0);
 
    lua_pushcfunction(mState, &intf_describe_plugins);
    lua_setglobal(mState, "describe_plugins");
    lua_settop(mState, 0);
 
    // Create the preferences table.
    cmd_log_ << lua_preferences::register_table(mState);
 
    // Create the wesnoth.plugin table
    luaW_getglobal(mState, "wesnoth");
    lua_newtable(mState);
    lua_pushcfunction(mState, intf_execute);
    lua_setfield(mState, -2, "execute");
    lua_setfield(mState, -2, "plugin");
    lua_pop(mState, 1);
}
 
application_lua_kernel::thread::thread(application_lua_kernel& owner, lua_State * T) : owner_(owner), T_(T), started_(false) {}
 
std::string application_lua_kernel::thread::status()
{
    if (!started_) {
        if (lua_status(T_) == LUA_OK) {
            return "not started";
        } else {
            return "load error";
        }
    }
    switch (lua_status(T_)) {
        case LUA_OK:
            return "dead";
        case LUA_YIELD:
            return "started";
        default:
            return "error";
    }
}
 
bool application_lua_kernel::thread::is_running() {
    return started_ ? (lua_status(T_) == LUA_YIELD) : (lua_status(T_) == LUA_OK);
}
 
static char * v_threadtableKey = nullptr;
static void * const threadtableKey = static_cast<void *> (& v_threadtableKey);
 
static lua_State * get_new_thread(lua_State * L)
{
    lua_pushlightuserdata(L , threadtableKey);
    lua_pushvalue(L,1);             // duplicate script key, since we need to store later
                            // stack is now [script key] [script key]
 
    lua_rawget(L, LUA_REGISTRYINDEX);       // get the script table from the registry, on the top of the stack
    if (!lua_istable(L,-1)) {           // if it doesn't exist create it
        lua_pop(L,1);
        lua_newtable(L);
    }                       // stack is now [script key] [table]
 
    lua_pushinteger(L, lua_rawlen(L, -1) + 1);  // push #table + 1 onto the stack
 
    lua_State * T = lua_newthread(L);       // create new thread T
                            // stack is now [script key] [table] [#table + 1] [thread]
    lua_rawset(L, -3);              // store the new thread at #table +1 index of the table.
                            // stack is now [script key] [table]
    lua_rawset(L, LUA_REGISTRYINDEX);
                            // stack L is now empty
    return T;                   // now we can set up T's stack appropriately
}
 
application_lua_kernel::thread * application_lua_kernel::load_script_from_string(const std::string & prog)
{
    lua_State * T = get_new_thread(mState);
    // now we are operating on T's stack, leaving a compiled C function on it.
 
    DBG_LUA << "created thread: status = " << lua_status(T) << (lua_status(T) == LUA_OK ? " == OK" : " == ?");
    DBG_LUA << "loading script from string:\n<<\n" << prog << "\n>>";
 
    // note: this is unsafe for umc as it allows loading lua baytecode, but umc cannot add application lua kernel scipts.
    int errcode = luaL_loadstring(T, prog.c_str());
    if (errcode != LUA_OK) {
        const char * err_str = lua_tostring(T, -1);
        std::string msg = err_str ? err_str : "null string";
 
        std::string context = "When parsing a string to a lua thread, ";
 
        if (errcode == LUA_ERRSYNTAX) {
            context += " a syntax error";
        } else if(errcode == LUA_ERRMEM){
            context += " a memory error";
        } else {
            context += " an unknown error";
        }
 
        throw game::lua_error(msg, context);
    }
    if (!lua_kernel_base::protected_call(T, 0, 1, std::bind(&lua_kernel_base::log_error, this, std::placeholders::_1, std::placeholders::_2))) {
        throw game::lua_error("Error when executing a script to make a lua thread.");
    }
    if (!lua_isfunction(T, -1)) {
        throw game::lua_error(std::string("Error when executing a script to make a lua thread -- function was not produced, found a ") + lua_typename(T, lua_type(T, -1)) );
    }
 
    return new application_lua_kernel::thread(*this, T);
}
 
application_lua_kernel::thread * application_lua_kernel::load_script_from_file(const std::string & file)
{
    lua_State * T = get_new_thread(mState);
    // now we are operating on T's stack, leaving a compiled C function on it.
 
    lua_pushstring(T, file.c_str());
    lua_fileops::load_file(T);
    if (!lua_kernel_base::protected_call(T, 0, 1, std::bind(&lua_kernel_base::log_error, this, std::placeholders::_1, std::placeholders::_2))) {
        throw game::lua_error("Error when executing a file to make a lua thread.");
    }
    if (!lua_isfunction(T, -1)) {
        throw game::lua_error(std::string("Error when executing a file to make a lua thread -- function was not produced, found a ") + lua_typename(T, lua_type(T, -1)) );
    }
 
    return new application_lua_kernel::thread(*this, T);
}
 
struct lua_context_backend {
    std::vector<plugins_manager::event> requests;
    lua_kernel_base* execute;
    bool valid;
 
    lua_context_backend()
        : requests()
        , valid(true)
    {}
};
 
static int impl_context_backend(lua_State * L, const std::shared_ptr<lua_context_backend>& backend, std::string req_name)
{
    if (!backend->valid) {
        luaL_error(L , "Error, you tried to use an invalid context object in a lua thread");
    }
 
    plugins_manager::event evt;
    evt.name = std::move(req_name);
    evt.data = luaW_checkconfig(L, -1);
 
    backend->requests.push_back(evt);
    return 0;
}
 
static int impl_context_accessor(lua_State * L, const std::shared_ptr<lua_context_backend>& backend, const plugins_context::accessor_function& func)
{
    if (!backend->valid) {
        luaL_error(L , "Error, you tried to use an invalid context object in a lua thread");
    }
 
    if(lua_gettop(L)) {
        config temp;
        if(!luaW_toconfig(L, 1, temp)) {
            luaL_argerror(L, 1, "Error, tried to parse a config but some fields were invalid");
        }
        luaW_pushconfig(L, func(temp));
        return 1;
    } else {
        luaW_pushconfig(L, func(config()));
        return 1;
    }
}
 
extern luaW_Registry& gameConfigReg();
static auto& dummy = gameConfigReg(); // just to ensure it's constructed.
 
GAME_CONFIG_SETTER("debug", bool, application_lua_kernel) {
    (void)k;
    game_config::set_debug(value);
}
 
static int intf_execute(lua_State* L)
{
    static const int CTX = 1, FUNC = 2, EVT = 3, EXEC = 4;
    if(lua_gettop(L) == 2) lua_pushnil(L);
    if(!luaW_table_get_def(L, CTX, "valid", false)) {
        lua_pushboolean(L, false);
        lua_pushstring(L, "context not valid");
        return 2;
    }
    if(!luaW_tableget(L, CTX, "execute")) {
        lua_pushboolean(L, false);
        lua_pushstring(L, "context cannot execute");
        return 2;
    }
    if(!lua_islightuserdata(L, EXEC)) {
        lua_pushboolean(L, false);
        lua_pushstring(L, "execute is not a thread");
        return 2;
    }
    try {
        config data = luaW_serialize_function(L, FUNC);
        if(data["params"] != 0) {
            lua_pushboolean(L, false);
            lua_pushstring(L, "cannot execute function with parameters");
            return 2;
        }
        if(!lua_isnil(L, EVT)) data["name"] = luaL_checkstring(L, EVT);
        lua_pushvalue(L, FUNC);
        data["ref"] = luaL_ref(L, LUA_REGISTRYINDEX);
        std::shared_ptr<lua_context_backend>* context = static_cast<std::shared_ptr<lua_context_backend>*>(lua_touserdata(L, EXEC));
        luaW_pushconfig(L, data);
        impl_context_backend(L, *context, "execute");
    } catch(luafunc_serialize_error& e) {
        lua_pushboolean(L, false);
        lua_pushstring(L, e.what());
        return 2;
    }
    lua_pushboolean(L, true);
    return 1;
}
bool luaW_copy_upvalues(lua_State* L, const config& cfg);
application_lua_kernel::request_list application_lua_kernel::thread::run_script(const plugins_context & ctxt, const std::vector<plugins_manager::event> & queue)
{
    // There are two possibilities: (1) this is the first execution, and the C function is the only thing on the stack
    // (2) this is a subsequent execution, and there is nothing on the stack.
    // Either way we push the arguments to the function and call resume.
 
    // First we have to create the event table, by concatenating the event queue into a table.
    config events;
    for(const auto& event : queue) {
        events.add_child(event.name, event.data);
    }
    luaW_pushconfig(T_, events); //this will be the event table
 
    // Now we have to create the context object. It is arranged as a table of boost functions.
    auto this_context_backend = std::make_shared<lua_context_backend>();
    lua_newtable(T_); // this will be the context table
    lua_pushstring(T_, "valid");
    lua_pushboolean(T_, true);
    lua_settable(T_, -3);
    for (const std::string & key : ctxt.callbacks_ | utils::views::keys ) {
        lua_pushstring(T_, key.c_str());
        lua_cpp::push_function(T_, std::bind(&impl_context_backend, std::placeholders::_1, this_context_backend, key));
        lua_settable(T_, -3);
    }
    if(ctxt.execute_kernel_) {
        lua_pushstring(T_, "execute");
        lua_pushlightuserdata(T_, &this_context_backend);
        lua_settable(T_, -3);
    }
 
    // Now we have to create the info object (context accessors). It is arranged as a table of boost functions.
    lua_newtable(T_); // this will be the info table
    lua_pushstring(T_, "name");
    lua_pushstring(T_, ctxt.name_.c_str());
    lua_settable(T_, -3);
    lua_pushstring(T_, "valid");
    lua_pushboolean(T_, true);
    lua_settable(T_, -3);
    for (const plugins_context::accessor_list::value_type & v : ctxt.accessors_) {
        const std::string & key = v.first;
        const plugins_context::accessor_function & func = v.second;
        lua_pushstring(T_, key.c_str());
        lua_cpp::push_function(T_, std::bind(&impl_context_accessor, std::placeholders::_1, this_context_backend, func));
        lua_settable(T_, -3);
    }
 
    // Push copies of the context and info tables so that we can mark them invalid for the next slice
    lua_pushvalue(T_, -2);
    lua_pushvalue(T_, -2);
    // However, Lua can't handle having extra values on the stack when resuming a coroutine,
    // so move the extra copy to the main thread instead.
    lua_xmove(T_, owner_.get_state(), 2);
    // Now we resume the function, calling the coroutine with the three arguments (events, context, info).
    // We ignore any values returned via arguments to yield()
    int numres = 0;
    lua_resume(T_, nullptr, 3, &numres);
 
    started_ = true;
 
    this_context_backend->valid = false; //invalidate the context object for lua
 
    if (lua_status(T_) != LUA_YIELD) {
        LOG_LUA << "Thread status = '" << lua_status(T_) << "'";
        if (lua_status(T_) != LUA_OK) {
            std::stringstream ss;
            ss << "encountered a";
            switch(lua_status(T_)) {
                case LUA_ERRSYNTAX:
                    ss << " syntax ";
                    break;
                case LUA_ERRRUN:
                    ss << " runtime ";
                    break;
                case LUA_ERRERR:
                    ss << " error-handler ";
                    break;
                default:
                    ss << " ";
                    break;
            }
            ss << "error:\n" << lua_tostring(T_, -1) << "\n";
            ERR_LUA << ss.str();
        }
    }
 
    // Pop any values that the resume left on the stack
    lua_pop(T_, numres);
    // Set "valid" to false on the now-expired context and info tables
    lua_pushstring(owner_.get_state(), "valid");
    lua_pushboolean(owner_.get_state(), false);
    lua_settable(owner_.get_state(), -3);
    lua_pushstring(owner_.get_state(), "valid");
    lua_pushboolean(owner_.get_state(), false);
    lua_settable(owner_.get_state(), -4);
    lua_pop(owner_.get_state(), 2);
 
    application_lua_kernel::request_list results;
 
    for (const plugins_manager::event & req : this_context_backend->requests) {
        if(ctxt.execute_kernel_ && req.name == "execute") {
            results.push_back([this, lk = ctxt.execute_kernel_, data = req.data]() {
                auto result = lk->run_binary_lua_tag(data);
                int ref = result["ref"].to_int();
                if(auto func = result.optional_child("executed")) {
                    lua_rawgeti(T_, LUA_REGISTRYINDEX, ref);
                    luaW_copy_upvalues(T_, *func);
                    luaL_unref(T_, LUA_REGISTRYINDEX, ref);
                    lua_pop(T_, 1);
                }
                result.remove_children("executed");
                result.remove_attribute("ref");
                plugins_manager::get()->notify_event(result["name"], result);
                return true;
            });
            continue;
        }
        results.push_back(std::bind(ctxt.callbacks_.find(req.name)->second, req.data));
        //results.emplace_back(ctxt.callbacks_.find(req.name)->second, req.data);
    }
    return results;
}
 
bool luaW_copy_upvalues(lua_State* L, const config& cfg)
{
    if(auto upvalues = cfg.optional_child("upvalues")) {
        lua_pushvalue(L, -1); // duplicate function because lua_getinfo will pop it
        lua_Debug info;
        lua_getinfo(L, ">u", &info);
        int funcindex = lua_absindex(L, -1);
        for(int i = 1; i <= info.nups; i++, lua_pop(L, 1)) {
            std::string_view name = lua_getupvalue(L, funcindex, i);
            if(name == "_ENV") {
                lua_pushglobaltable(L);
            } else if(upvalues->has_attribute(name)) {
                luaW_pushscalar(L, (*upvalues)[name]);
            } else if(upvalues->has_child(name)) {
                const auto& child = upvalues->mandatory_child(name);
                if(child["upvalue_type"] == "array") {
                    auto children = upvalues->child_range(name);
                    lua_createtable(L, children.size(), 0);
                    for(const auto& cfg : children) {
                        luaW_pushscalar(L, cfg["value"]);
                        lua_rawseti(L, -2, lua_rawlen(L, -2) + 1);
                    }
                } else if(child["upvalue_type"] == "named tuple") {
                    auto children = upvalues->child_range(name);
                    std::vector<std::string> names;
                    for(const auto& cfg : children) {
                        names.push_back(cfg["name"]);
                    }
                    luaW_push_namedtuple(L, names);
                    for(const auto& cfg : children) {
                        luaW_pushscalar(L, cfg["value"]);
                        lua_rawseti(L, -2, lua_rawlen(L, -2) + 1);
                    }
                } else if(child["upvalue_type"] == "config") {
                    luaW_pushconfig(L, child);
                } else if(child["upvalue_type"] == "function") {
                    luaW_copy_upvalues(L, child);
                    lua_pushvalue(L, -1);
                }
            } else continue;
            lua_setupvalue(L, funcindex, i);
        }
    }
    return true;
}