initial commit, read-only NNTP server

go.mod

@@ -0,0 +1,5 @@
+module iris-news
+
+go 1.19
+
+require github.com/dustin/go-nntp v0.0.0-20210723005859-f00d51cf8cc1

go.sum

@@ -0,0 +1,4 @@
+github.com/dustin/go-couch v0.0.0-20160816170231-8251128dab73/go.mod h1:WG/TWzFd/MRvOZ4jjna3FQ+K8AKhb2jOw4S2JMw9VKI=
+github.com/dustin/go-nntp v0.0.0-20210723005859-f00d51cf8cc1 h1:R90ND7acg9HKYj3oJBKKefk73DULdC7IlcnS7MV0X1s=
+github.com/dustin/go-nntp v0.0.0-20210723005859-f00d51cf8cc1/go.mod h1:elGbp3dKCIIdwu6jm3y6L93EVn+I6MSzYrcZXhpNS3Y=
+github.com/dustin/httputil v0.0.0-20170305193905-c47743f54f89/go.mod h1:ZoDWdnxro8Kesk3zrCNOHNFWtajFPSnDMjVEjGjQu/0=

main.go

@@ -0,0 +1,212 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net"
+	"net/textproto"
+	"os"
+	"os/exec"
+	"path"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/dustin/go-nntp"
+	nntpserver "github.com/dustin/go-nntp/server"
+)
+
+func main() {
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	if err := writeLocation(l.Addr().String()); err != nil {
+		log.Fatal(err)
+	}
+
+	s := nntpserver.NewServer(&backend{})
+
+	for {
+		c, err := l.Accept()
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		go s.Process(c)
+	}
+}
+
+func writeLocation(location string) error {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return err
+	}
+
+	filepath := path.Join(home, ".iris-news-server")
+	f, err := os.Create(filepath)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = f.Close() }()
+
+	_, err = fmt.Fprintln(f, location)
+	return err
+}
+
+var group = &nntp.Group{
+	Name:        "ctrl-c.iris",
+	Description: "The iris message board.",
+	Posting:     nntp.PostingNotPermitted,
+	Low:         1,
+}
+
+type backend struct {
+	messages []*nntp.Article
+}
+
+func (b backend) ListGroups(max int) ([]*nntp.Group, error) {
+	return []*nntp.Group{group}, nil
+}
+
+func (b *backend) GetGroup(name string) (*nntp.Group, error) {
+	if name != group.Name {
+		return nil, nntpserver.ErrNoSuchGroup
+	}
+	if err := b.refresh(); err != nil {
+		return nil, err
+	}
+
+	return group, nil
+}
+
+func (b *backend) refresh() error {
+	binpath, err := exec.LookPath("iris")
+	if err != nil {
+		return err
+	}
+	cmd := exec.Command(binpath, "-d")
+	buf := &bytes.Buffer{}
+	cmd.Stdout = buf
+
+	if err := cmd.Run(); err != nil {
+		return err
+	}
+
+	msgs := irisDump{}
+	if err := json.NewDecoder(buf).Decode(&msgs); err != nil {
+		return err
+	}
+
+	b.messages = msgs.Articles()
+	group.High = int64(len(b.messages))
+	group.Count = int64(len(b.messages))
+	return nil
+}
+
+func (b *backend) GetArticles(_ *nntp.Group, from, to int64) ([]nntpserver.NumberedArticle, error) {
+	if err := b.refresh(); err != nil {
+		return nil, err
+	}
+
+	numbered := make([]nntpserver.NumberedArticle, 0, len(b.messages))
+	for i, msg := range b.messages {
+		num := int64(i + 1)
+		if num >= from && num <= to {
+			numbered = append(numbered, nntpserver.NumberedArticle{
+				Num:     num,
+				Article: msg,
+			})
+		}
+	}
+
+	return numbered, nil
+}
+
+func (b *backend) GetArticle(_ *nntp.Group, messageID string) (*nntp.Article, error) {
+	if len(b.messages) == 0 {
+		if err := b.refresh(); err != nil {
+			return nil, err
+		}
+	}
+
+	for _, msg := range b.messages {
+		if msg.Header.Get("Message-Id") == messageID {
+			return msg, nil
+		}
+	}
+
+	num, err := strconv.Atoi(messageID)
+	if err == nil && num <= len(b.messages) {
+		return b.messages[num-1], nil
+	}
+
+	return nil, nntpserver.ErrInvalidMessageID
+}
+
+func (b backend) Authorized() bool {
+	return true
+}
+
+func (b backend) Authenticate(user, pass string) (nntpserver.Backend, error) {
+	return nil, nil
+}
+
+func (b backend) AllowPost() bool {
+	return false
+}
+
+func (b backend) Post(article *nntp.Article) error {
+	return nntpserver.ErrPostingNotPermitted
+}
+
+type irisDump []struct {
+	Hash      string `json:"hash"`
+	EditHash  string `json:"edit_hash"`
+	IsDeleted *bool  `json:"is_deleted"`
+	Data      struct {
+		Author    string    `json:"author"`
+		Parent    *string   `json:"parent"`
+		Timestamp time.Time `json:"timestamp"`
+		Message   string    `json:"message"`
+	} `json:"data"`
+}
+
+func (id irisDump) Articles() []*nntp.Article {
+	out := make([]*nntp.Article, len(id))
+	subjects := make(map[string]string)
+
+	for i, d := range id {
+		msgID := toMsgID(d.Hash)
+		out[i] = &nntp.Article{
+			Header: textproto.MIMEHeader{
+				"Message-Id": []string{msgID},
+				"From":       []string{d.Data.Author},
+				"Newsgroups": []string{group.Name},
+				"Date":       []string{d.Data.Timestamp.Format(time.RFC1123Z)},
+			},
+			Body:  bytes.NewBufferString(d.Data.Message),
+			Bytes: len(d.Data.Message),
+			Lines: strings.Count(d.Data.Message, "\n"),
+		}
+
+		if d.Data.Parent != nil {
+			parentID := toMsgID(*d.Data.Parent)
+			out[i].Header.Add("References", parentID)
+			out[i].Header.Add("Subject", "Re: "+subjects[parentID])
+		} else {
+			subject := strings.SplitN(d.Data.Message, "\n", 2)[0]
+			out[i].Header.Add("Subject", subject)
+			subjects[msgID] = subject
+		}
+	}
+
+	return out
+}
+
+func toMsgID(irisID string) string {
+	return "<" + strings.TrimSuffix(irisID, "\n") + ">"
+}