arns-lt-gemini/mention.go

package main

// Trying to implement gemini mentions from https://codeberg.org/bacardi55/gemini-mentions-rfc
// Thanks to @bacardi55 and his example https://git.sr.ht/~bacardi55/ggm (this is forked from there)

import (
	"context"
	"fmt"
	"io"
	"log"
	"net/url"
	"regexp"
	"strings"
	"time"

	"g.arns.lt/zordsdavini/zordfsdb"
	"git.sr.ht/~adnano/go-gemini"
)

const (
	STATUS_MENTION_NOT_REVIEWED = "0"
	STATUS_MENTION_REVIEWED     = "1"
)

// Nota: Gemini servers might have max execution time for cgi scripts.
// Eg: Gemserv has a 5s maximum policy before killing the request.
const maxRequestTime = 4

func ProcessMention(remoteUrl string, pageId string) (bool, error) {
	u, err := validateUrl(remoteUrl)
	if err != nil {
		return false, fmt.Errorf("[gemini-mentions] Url is not valid.")
	}

	response, err := fetchGeminiPage(u)
	if err != nil || response.Status.Class() != gemini.StatusSuccess {
		return false, fmt.Errorf("[gemini-mentions] Error retrieving content from %s: %s", u, err)
	}

	if respCert := response.TLS().PeerCertificates; len(respCert) > 0 &&
		time.Now().After(respCert[0].NotAfter) {
		return false, fmt.Errorf(
			"[gemini-mentions] Ignored url (invalid certificate for capsule): %s",
			u,
		)
	}

	// If all good, let's find gemini mentions link inside.
	var content []byte
	content, err = io.ReadAll(response.Body)
	defer response.Body.Close()

	if err != nil {
		return false, fmt.Errorf("[gemini-mentions] Couldn't retrieve the provided URL content")
	}
	links := findMentionLinks(string(content), hostname)
	if len(links) < 1 {
		return false, fmt.Errorf("[gemini-mentions] Recieved a link with no mention: %s", u)
	}

	// log to db
	db, err := zordfsdb.InitDB("./db")
	if err != nil {
		return false, fmt.Errorf("[gemini-mentions] no db: %s", err)
	}
	_, found := db.GetNode("mentions")
	if !found {
		db.CreateNode("mentions")
	}
	_, found = db.GetNode("mentions." + pageId)
	if !found {
		db.CreateNode("mentions." + pageId)
		db.CreateNode("mentions." + pageId + ".mentions")
	}

	message := "# Naus gemini patiemėjėms " + hostname + "\n=> gemini://" + hostname + "/r/" + pageId + " Spausk nūruoda i puslapi parveizetė\n\nPamėnavuojėma:\n"

	for _, link := range links {
		id, err := db.AddObject("mentions." + pageId + ".mentions")
		if err != nil {
			return false, fmt.Errorf("[gemini-mentions] couldn't add object: %s", err)
		}
		db.Save("mentions."+pageId+".mentions."+id+".url", extractUrl(link))
		db.Save("mentions."+pageId+".mentions."+id+".reviewed", STATUS_MENTION_NOT_REVIEWED)

		message += fmt.Sprintf("=> %s\n", extractUrl(link))
	}

	message += "\nau/\n"

	err = SendMisfinMessage(message, ZORDSDAVINI_MISFIN)
	if err != nil {
		return false, err
	}

	return true, nil
}

func validateUrl(remoteUrl string) (string, error) {
	remote, e := url.QueryUnescape(remoteUrl)
	if e != nil {
		return "", fmt.Errorf("Provided URL is not a good URL: %s", e)
	}
	remote = strings.Replace(remote, "..", "", -1)

	u, err := url.Parse(remote)

	if err != nil {
		return "", fmt.Errorf("Provided URL is not a good URL: %s", err)
	} else if u.Scheme != "gemini" && u.Scheme != "" {
		return "", fmt.Errorf("Only gemini url are supported for now.")
	} else {
		return "gemini://" + u.Host + u.Path, nil
	}
}

func fetchGeminiPage(remoteUrl string) (*gemini.Response, error) {
	gemclient := &gemini.Client{}
	ctx, _ := context.WithTimeout(context.Background(), time.Duration(maxRequestTime)*time.Second)
	response, err := gemclient.Get(ctx, remoteUrl)
	if err != nil {
		return response, err
	}

	if respCert := response.TLS().PeerCertificates; len(respCert) > 0 &&
		time.Now().After(respCert[0].NotAfter) {
		return response, fmt.Errorf("Certificate is unvalid")
	}

	return response, nil
}

func findMentionLinks(content string, capsuleRootAddress string) []string {
	exp := "(?im)^(=>)[ ]?gemini://" + capsuleRootAddress + "[^ ]+([ ](.*))?$"
	re := regexp.MustCompile(exp)
	return re.FindAllString(content, -1)
}

func extractUrl(url string) string {
	exp := "(?im)gemini://[^ ]+"
	re := regexp.MustCompile(exp)
	return re.FindString(url)
}

func GetMentionsForPage(pageId string, reviewStatus string) map[string]string {
	mentions := make(map[string]string)
	db, err := zordfsdb.InitDB("./db")
	if err != nil {
		log.Fatal(err)
		return mentions
	}

	_, found := db.Get("mentions." + pageId + ".mentions")
	if !found {
		return mentions
	}

	for _, id := range db.Keys("mentions." + pageId + ".mentions") {
		reviewed, _ := db.Get("mentions." + pageId + ".mentions." + id + ".reviewed")
		if reviewed == reviewStatus {
			url, _ := db.Get("mentions." + pageId + ".mentions." + id + ".url")
			mentions[id] = url
		}
	}

	return mentions
}

func MarkReviewed(pageId string, id string) {
	db, err := zordfsdb.InitDB("./db")
	if err != nil {
		log.Fatal(err)
	}

	db.Save("mentions."+pageId+".mentions."+id+".reviewed", STATUS_MENTION_REVIEWED)
}

func RemoveMention(pageId string, id string) {
	db, err := zordfsdb.InitDB("./db")
	if err != nil {
		log.Fatal(err)
	}

	db.Del("mentions." + pageId + ".mentions." + id)
}