rsslair/lua.go

package main

import (
	"encoding/xml"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"sort"
	"strings"

	lua "github.com/yuin/gopher-lua"
)

func InitLua() *lua.LState {
	logger.Info("Initializing lua")
	L := lua.NewState()
	// load_log_library(L)
	bind_lua_functions(L)
	LoadScripts(L)
	return L
}

func LoadLogFunctions(L *lua.LState) {
	table := L.NewTable()
	L.SetFuncs(table, map[string]lua.LGFunction{
		"info":  luaLogInfo,
		"debug": luaLogDebug,
		"error": luaLogError,
		"fatal": luaLogFatal,
	})
	L.SetGlobal("log", table)
}

func loadScript(L *lua.LState, script string) error {
	if err := L.DoFile(script); err != nil {
		logger.Fatal(err)
		return err
	}
	logger.Debug("Loaded script: ", script)
	return nil
}

func LoadScripts(L *lua.LState) error {
	// iterate over the scripts directory and load each script
	files, err := os.ReadDir("scripts")
	if err != nil {
		logger.Fatal(err)
		return err
	}

	loadAllScripts := appConfig.Scripts[0] == "all" || appConfig.Scripts[0] == ""
	if loadAllScripts {
		for _, file := range files {
			var extension = filepath.Ext(file.Name())
			if file.IsDir() || extension != ".lua" {
				continue
			}
			if err := loadScript(L, "scripts/"+file.Name()); err != nil {
				logger.Fatal(err)
				return err
			}
		}
	} else {
		for _, script := range appConfig.Scripts {
			if err := loadScript(L, "scripts/"+script+".lua"); err != nil {
				logger.Fatal(err)
				return err
			}
		}
	}
	return nil
}

func execute_route(L *lua.LState, route string, script string) (string, error) {
	logger.Debug("Executing route: ", route)

	// Get table by script name
	table := L.GetGlobal(script)
	// Get the function from the table
	fn := L.GetField(table, "route")
	// TODO: The message should say something else
	if fn.Type() != lua.LTFunction {
		logger.Error("route function was not found in script: ", script)
		return "", nil
	}

	if err := L.CallByParam(lua.P{
		Fn:      fn,
		NRet:    1,
		Protect: true,
	}); err != nil {
		logger.Error(err)
		return "", err
	}
	ret := L.Get(-1)
	responses[route] = strings.Clone(ret.String())

	return ret.String(), nil
}

func add_html_parser(L *lua.LState) int {
	// Create a table for the html_parser add_functions
	html_table := L.NewTable()
	L.SetFuncs(html_table, map[string]lua.LGFunction{
		"parse":  newHtmlParser,
		"select": select_html_node,
	})
	L.Push(html_table)
	return 1
}

func bind_lua_functions(L *lua.LState) error {
	// Add global functions to lua
	LoadLogFunctions(L)

	L.SetGlobal("add_route", L.NewFunction(lua_add_route))
	L.SetGlobal("get", L.NewFunction(get_request))
	L.SetGlobal("parse_xml_feed", L.NewFunction(parse_xml_feed))
	L.SetGlobal("create_rss_feed", L.NewFunction(create_rss_feed))

	// Register Golang structs with lua
	registerDatabaseType(L)
	registerRSSItemType(L)
	registerHtmlParserType(L)
	registerRssImageType(L)

	return nil
}

func lua_add_route(L *lua.LState) int {
	// TODO: Check that the parameters are correct
	// Handle errors
	script := L.ToString(1)
	route := L.ToString(2)
	table := L.NewTable()

	L.SetGlobal(script, table)

	routes[route] = script
	responses[route] = ""
	logger.Debug("Adding route: ", route, " -> ", script)
	return 0
}

func get_request(L *lua.LState) int {
	url := L.ToString(1)
	logger.Debug("GET: ", url)
	resp, err := http.Get(url)
	if err != nil {
		logger.Error(err)
		return 0
	}
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		logger.Fatal(err)
		return 0
	}
	L.Push(lua.LString(string(body)))
	return 1
}

func parse_xml_feed(L *lua.LState) int {
	xml_str := L.ToString(1)

	var rss RssRoot
	err := xml.Unmarshal([]byte(xml_str), &rss)
	if err != nil {
		logger.Fatal(err)
		return 0
	}
	feed_items := L.NewTable()
	items := rss.Channel.Items

	for i := range items {
		ud := L.NewUserData()
		ud.Value = &items[i]
		L.SetMetatable(ud, L.GetTypeMetatable(luaRSSItemTypeName))
		feed_items.Append(ud)
	}
	L.Push(feed_items)
	return 1
}

// TODO: Move this into the rss table
func create_rss_feed(L *lua.LState) int {
	//TODO: Check that the parameters are correct
	feed := RssRoot{}

	//TODO: Bind RssImage to lua and pass it in
	// Also needs to be added to the database and then re-served through the server
	title := L.CheckString(1)
	link := L.CheckString(2)
	image := L.CheckUserData(3)
	// TODO: Channel needs to also be passed in
	feed.Channel = RssChannel{
		Title: title,
		Image: *image.Value.(*RssImage),
		Link:  link,
	}

	// Append the items to the feed
	// Notably the <channel> tag as <item>s
	entries := L.CheckTable(4)
	if entries.Len() == 0 {
		logger.Error("No entries to create rss feed found in table")
		return 0
	}

	for i := 1; i <= entries.Len(); i++ {
		entry := entries.RawGetInt(i)
		ud := entry.(*lua.LUserData)
		item := ud.Value.(*RssItem)
		feed.Channel.Items = append(feed.Channel.Items, *item)
	}

	// sort by date
	sort.Sort(ByPubDate(feed.Channel.Items))

	output, err := xml.MarshalIndent(feed, "", "  ")
	if err != nil {
		logger.Fatal(err)
		return 0
	}

	L.Push(lua.LString(string(output)))
	return 1
}

func luaLogInfo(L *lua.LState) int {
	loc := L.Where(1)
	msg := L.ToString(1)
	logger.Info(loc, msg)
	return 0
}

func luaLogDebug(L *lua.LState) int {
	// Get the where and message
	loc := L.Where(1)
	msg := L.ToString(1)
	logger.Debug(loc, msg)
	return 0
}

func luaLogError(L *lua.LState) int {
	loc := L.Where(1)
	msg := L.ToString(1)
	logger.Error(loc, msg)
	return 0
}

func luaLogFatal(L *lua.LState) int {
	loc := L.Where(1)
	msg := L.ToString(1)
	logger.Fatal(loc, msg)
	return 0
}