A plugins/link-handler.go

@@ -0,0 +1,141 @@
+// Plugin that looks for links and provides additional info whenever
+// someone posts an URL.
+// Author: nojusr
+package plugins
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"golang.org/x/net/html"
+	"gopkg.in/irc.v3"
+)
+
+// This plugin is an example of how to make something that will
+// respond (or just have read access to) every message that comes in.
+// The plugins.go file has a special case for handling an 'empty' Triggers string.
+// on such a case, it will simply run Execute on every message that it sees.
+
+func init() {
+	Register(LinkHandler{})
+}
+
+type LinkHandler struct{}
+
+func (LinkHandler) Triggers() []string {
+	return []string{""} // More than a single empty string here will probs get you undefined behaviour
+}
+
+func (LinkHandler) Execute(m *irc.Message) (string, error) {
+
+	var output string
+
+	// in PRIVMSG's case, the second (first, if counting from 0) parameter
+	// is the string that contains the complete message.
+	for _, value := range strings.Split(m.Params[1], " ") {
+		u, err := url.Parse(value)
+
+		if err != nil {
+			continue
+		}
+
+		// just a test check for the time being.
+		// this if statement block will be used for content that is
+		// non-generic. I.e it belongs to a specific website, like
+		// stackoverflow or youtube.
+		if u.Hostname() == "youtube.com" || u.Hostname() == "youtu.be" {
+			// TODO finish this
+			output += "[Youtube] yeah you definitely posted a youtube link\n"
+		} else if len(u.Hostname()) > 0 {
+			desc, err := getDescriptionFromURL(value)
+			if err != nil {
+				log.Printf("Failed to get title from http URL")
+				fmt.Println(err)
+				continue
+			}
+			output += fmt.Sprintf("[URL] %s (%s)\n", desc, u.Hostname())
+		}
+	}
+
+	return output, nil
+}
+
+// the three funcs below are taken from:
+// https://siongui.github.io/2016/05/10/go-get-html-title-via-net-html/
+func isTitleElement(n *html.Node) bool {
+	return n.Type == html.ElementNode && n.Data == "title"
+}
+
+func traverse(n *html.Node) (string, bool) {
+	if isTitleElement(n) {
+		return n.FirstChild.Data, true
+	}
+
+	for c := n.FirstChild; c != nil; c = c.NextSibling {
+		result, ok := traverse(c)
+		if ok {
+			return result, ok
+		}
+	}
+
+	return "", false
+}
+
+func getHtmlTitle(r io.Reader) (string, bool) {
+	doc, err := html.Parse(r)
+	if err != nil {
+		return "", false
+	}
+
+	return traverse(doc)
+}
+
+// yoinkies from
+// https://yourbasic.org/golang/formatting-byte-size-to-human-readable-format/
+func byteCountSI(b int64) string {
+	const unit = 1000
+	if b < unit {
+		return fmt.Sprintf("%d B", b)
+	}
+	div, exp := int64(unit), 0
+	for n := b / unit; n >= unit; n /= unit {
+		div *= unit
+		exp++
+	}
+	return fmt.Sprintf("%.1f %cB",
+		float64(b)/float64(div), "kMGTPE"[exp])
+}
+
+// provides a basic, short description of whatever is inside
+// a posted URL.
+func getDescriptionFromURL(url string) (string, error) {
+	resp, err := http.Get(url)
+
+	if err != nil {
+		return "", err
+	}
+
+	defer resp.Body.Close()
+
+	mime := resp.Header.Get("content-type")
+
+	switch mime {
+	case "image/jpeg":
+		return fmt.Sprintf("JPEG image, size: %s", byteCountSI(resp.ContentLength)), nil
+	case "image/png":
+		return fmt.Sprintf("PNG image, size: %s", byteCountSI(resp.ContentLength)), nil
+	default:
+		output, ok := getHtmlTitle(resp.Body)
+
+		if !ok {
+			return "", errors.New("Failed to find <title> in html")
+		}
+
+		return output, nil
+	}
+}