3 files changed, 259 insertions, 0 deletions
diff --git a/tools/blog_cli/README.md b/tools/blog_cli/README.md
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+++ b/tools/blog_cli/README.md
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+tazblog CLI
+===========
+
+My blog stores its content in DNS, spread out over three types of `TXT` entries:
+
+* `TXT _posts.blog.tazj.in.`: A sorted list of posts, serialised as a JSON list of
+  strings (e.g. `["1486830338", "1476807384"]`)
+
+* `TXT _chunks.$postID.blog.tazj.in`: JSON chunks containing the blog post text
+
+* `TXT _meta.$postID.blog.tazj.in`: JSON blob with blog post metadata
+
+All JSON blobs are base64-encoded.
+
+This CLI tool helps to update those records.
+
+Each blog post data is a series of JSON-encoded structures which follow one of
+these formats:
+
+```
+struct metadata {
+    chunks: int
+    title: string
+    date: date
+}
+```
+
+Where `chunks` describes the number of chunks following this format:
+
+```
+struct chunk {
+    c: int
+    t: string
+}
+```
+
+Writing a blog post to DNS means taking its text and metadata, chunking it up
+and writing the chunks.
+
+Reading a blog post means retrieving all data, reading the metadata and then
+assembling the chunks in order.
diff --git a/tools/blog_cli/default.nix b/tools/blog_cli/default.nix
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+++ b/tools/blog_cli/default.nix
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+{ pkgs, ... }:
+
+pkgs.buildGo.program {
+  name = "blog_cli";
+  srcs = [ ./main.go ];
+  deps = with pkgs.third_party; [
+    gopkgs."google.golang.org".api.dns.v1.gopkg
+  ];
+} // { meta.enableCI = true; }
diff --git a/tools/blog_cli/main.go b/tools/blog_cli/main.go
new file mode 100644
index 000000000000..db64f8378e40
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+++ b/tools/blog_cli/main.go
@@ -0,0 +1,209 @@
+// The tazblog CLI implements updating my blog records in DNS, see the
+// README in this folder for details.
+//
+// The post input format is a file with the title on one line,
+// followed by the date on a line, followed by an empty line, followed
+// by the post text.
+package main
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"time"
+
+	"google.golang.org/api/dns/v1"
+)
+
+var (
+	project = flag.String("project", "tazjins-infrastructure", "Target GCP project")
+	zone    = flag.String("zone", "blog-tazj-in", "Target Cloud DNS zone")
+	title   = flag.String("title", "", "Title of the blog post")
+	date    = flag.String("date", "", "Date the post was written on")
+	infile  = flag.String("text", "", "Text file containing the blog post")
+	id      = flag.String("id", "", "Post ID - will be generated if unset")
+)
+
+// Number of runes to include in a single chunk. If any chunks exceed
+// the limit of what can be encoded, the chunk size is reduced and we
+// try again.
+var chunkSize = 200
+
+type day time.Time
+
+func (d day) MarshalJSON() ([]byte, error) {
+	j := (time.Time(d)).Format(`"2006-01-02"`)
+	return []byte(j), nil
+}
+
+type metadata struct {
+	Chunks int    `json:"c"`
+	Title  string `json:"t"`
+	Date   day    `json:"d"`
+}
+
+type chunk struct {
+	Chunk int
+	Text  string
+}
+
+type post struct {
+	ID     string
+	Meta   metadata
+	Chunks []string
+}
+
+func (p *post) writeToDNS() error {
+	var additions []*dns.ResourceRecordSet
+	additions = append(additions, &dns.ResourceRecordSet{
+		Name: fmt.Sprintf("_meta.%s.blog.tazj.in.", p.ID),
+		Type: "TXT",
+		Ttl:  1200,
+		Rrdatas: []string{
+			encodeJSON(p.Meta),
+		},
+	})
+
+	for i, c := range p.Chunks {
+		additions = append(additions, &dns.ResourceRecordSet{
+			Name:    fmt.Sprintf("_%v.%s.blog.tazj.in.", i, p.ID),
+			Type:    "TXT",
+			Ttl:     1200,
+			Rrdatas: []string{c},
+		})
+	}
+
+	ctx := context.Background()
+	dnsSvc, err := dns.NewService(ctx)
+	if err != nil {
+		return err
+	}
+
+	change := dns.Change{
+		Additions: additions,
+	}
+
+	_, err = dnsSvc.Changes.Create(*project, *zone, &change).Do()
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Encode given value as JSON and base64-encode it.
+func encodeJSON(v interface{}) string {
+	outer, err := json.Marshal(v)
+	if err != nil {
+		log.Fatalln("Failed to encode JSON", err)
+	}
+
+	return base64.RawStdEncoding.EncodeToString(outer)
+}
+
+// Encode a chunk and check whether it is too large
+func encodeChunk(c chunk) (string, bool) {
+	tooLarge := false
+	s := base64.RawStdEncoding.EncodeToString([]byte(c.Text))
+
+	if len(s) >= 255 {
+		tooLarge = true
+	}
+
+	return s, tooLarge
+}
+
+func createPost(id, title, text string, date day) post {
+	runes := []rune(text)
+	n := 0
+	tooLarge := false
+
+	var chunks []string
+
+	for chunkSize < len(runes) {
+		c, l := encodeChunk(chunk{
+			Chunk: n,
+			Text:  string(runes[0:chunkSize:chunkSize]),
+		})
+
+		tooLarge = tooLarge || l
+		chunks = append(chunks, c)
+		runes = runes[chunkSize:]
+		n++
+	}
+
+	if len(runes) > 0 {
+		c, l := encodeChunk(chunk{
+			Chunk: n,
+			Text:  string(runes),
+		})
+
+		tooLarge = tooLarge || l
+		chunks = append(chunks, c)
+		n++
+	}
+
+	if tooLarge {
+		log.Println("Too large at chunk size", chunkSize)
+		chunkSize -= 5
+		return createPost(id, title, text, date)
+	}
+
+	return post{
+		ID: id,
+		Meta: metadata{
+			Chunks: n,
+			Title:  title,
+			Date:   date,
+		},
+		Chunks: chunks,
+	}
+}
+
+func main() {
+	flag.Parse()
+
+	if *title == "" {
+		log.Fatalln("Post title must be set (-title)")
+	}
+
+	if *infile == "" {
+		log.Fatalln("Post text file must be set (-text)")
+	}
+
+	if *id == "" {
+		log.Fatalln("Post ID must be set (-id)")
+	}
+
+	var postDate day
+	if *date != "" {
+		t, err := time.Parse("2006-01-02", *date)
+		if err != nil {
+			log.Fatalln("Invalid post date", err)
+		}
+
+		postDate = day(t)
+	} else {
+		postDate = day(time.Now())
+	}
+
+	t, err := ioutil.ReadFile(*infile)
+	if err != nil {
+		log.Fatalln("Failed to read post:", err)
+	}
+
+	post := createPost(*id, *title, string(t), postDate)
+
+	log.Println("Writing post to DNS ...")
+	err = post.writeToDNS()
+
+	if err != nil {
+		log.Fatalln("Failed to write post:", err)
+	}
+
+	log.Println("Successfully wrote entries")
+}