From 486b58525fc5ec7658b7c90f0179ea3d112d0ca4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C5=99emysl=20Eric=20Janouch?= <p@janouch.name>
Date: Thu, 6 Oct 2022 00:44:09 +0200
Subject: [PATCH] Add a basic tool for collecting web comments

---
 hswc/main.go | 101 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 hswc/main.go

diff --git a/hswc/main.go b/hswc/main.go
new file mode 100644
index 0000000..275aac6
--- /dev/null
+++ b/hswc/main.go
@@ -0,0 +1,101 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"net/url"
+	"os"
+	"regexp"
+	"strings"
+	"sync"
+	"time"
+)
+
+var (
+	long           = regexp.MustCompile(`(.{72}\S*)\s+`)
+	file, requests *os.File
+	m              sync.Mutex
+)
+
+func wrap(s string) string {
+	return strings.ReplaceAll(long.ReplaceAllString(
+		strings.ReplaceAll(s, "\r", ""), "$1\n"), "\n", "\n ")
+}
+
+func handler(w http.ResponseWriter, r *http.Request) {
+	defer r.Body.Close()
+	if err := r.ParseForm(); err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+	text := r.FormValue("text")
+	if len(text) > 64<<10 {
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+
+	m.Lock()
+	defer m.Unlock()
+
+	j, _ := json.Marshal(struct {
+		URI     string
+		Headers http.Header
+		Form    url.Values
+	}{
+		URI:     r.RequestURI,
+		Headers: r.Header,
+		Form:    r.Form,
+	})
+
+	if s, err := file.Stat(); err != nil {
+		log.Fatalln(err)
+	} else if s.Size()+int64(len(text)) > 64<<20 {
+		w.WriteHeader(http.StatusInternalServerError)
+	} else if r.Form.Has("submit") {
+		// <input type="submit"> should not be named, and thus received.
+		//
+		// If this is not enough to filter out most spammers, consider also:
+		//  - Header: "Origin" should not be missing for POST.
+		//  - Header: "Accept" should not be "*/*".
+		//  - Header: "Accept-Language" and "Accept-Encoding" should be present.
+		//  - Form: _charset_ should not be kept verbatim,
+		//    seeing as Safari/Chromium/Firefox all pass UTF-8,
+		//    in accordance with HTML5.
+		w.WriteHeader(http.StatusTeapot)
+	} else {
+		fmt.Fprintf(file, "%s %s\n %s\n",
+			time.Now().Local().Format(time.RFC1123), r.RequestURI, wrap(text))
+		if err := file.Sync(); err != nil {
+			log.Fatalln(err)
+		}
+
+		// To help filter out spammers.
+		fmt.Fprintf(requests, "%s\n", j)
+		if err := requests.Sync(); err != nil {
+			log.Fatalln(err)
+		}
+
+		fmt.Fprintln(w, "Saved.")
+	}
+}
+
+func main() {
+	if len(os.Args) != 3 {
+		log.Fatalf("Usage: %s BIND DB\n", os.Args[0])
+	}
+
+	var err error
+	if file, err = os.OpenFile(os.Args[2],
+		os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644); err != nil {
+		log.Fatalln(err)
+	}
+	if requests, err = os.OpenFile(os.Args[2]+".requests",
+		os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644); err != nil {
+		log.Fatalln(err)
+	}
+
+	http.HandleFunc("/", handler)
+	log.Fatalln(http.ListenAndServe(os.Args[1], nil))
+}