From 935da56d0b759519085755c9fa5c447e77f74825 Mon Sep 17 00:00:00 2001
From: Erisa A <erisa@tailscale.com>
Date: Wed, 25 Dec 2024 04:43:22 +0000
Subject: [PATCH] cmd/bsky-webhook: add support for facets

Reference: https://docs.bsky.app/docs/advanced-guides/post-richtext
Fixes #9

Signed-off-by: Erisa A <erisa@tailscale.com>
---
 cmd/bsky-webhook/facets.go | 90 ++++++++++++++++++++++++++++++++++++++
 cmd/bsky-webhook/main.go   | 14 +++++-
 cmd/bsky-webhook/types.go  | 29 ++++++++++--
 3 files changed, 129 insertions(+), 4 deletions(-)
 create mode 100644 cmd/bsky-webhook/facets.go

diff --git a/cmd/bsky-webhook/facets.go b/cmd/bsky-webhook/facets.go
new file mode 100644
index 0000000..7087fdf
--- /dev/null
+++ b/cmd/bsky-webhook/facets.go
@@ -0,0 +1,90 @@
+package main
+
+import (
+	"fmt"
+	"slices"
+	"strings"
+)
+
+func bskyMessageToSlackMarkup(bskyMessage BskyMessage) (string, error) {
+	var slackStringBuilder strings.Builder
+
+	fragments, err := facetsToFragments(bskyMessage)
+	if err != nil {
+		return "", err
+	}
+
+	for _, fragment := range fragments {
+		if fragment.Features == nil {
+			slackStringBuilder.WriteString(fragment.Text)
+		} else {
+			uri := ""
+			for _, feature := range fragment.Features {
+				if feature.Type == "app.bsky.richtext.facet#link" {
+					uri = feature.Uri
+					break
+				} else if feature.Type == "app.bsky.richtext.facet#mention" {
+					uri = fmt.Sprintf("https://bsky.app/profile/%s", feature.Did)
+					break
+				} else if feature.Type == "app.bsky.richtext.facet#tag" {
+					uri = fmt.Sprintf("https://bsky.app/hashtag/%s", feature.Tag)
+				}
+			}
+			if uri != "" {
+				slackStringBuilder.WriteString(fmt.Sprintf("<%s|%s>", uri, fragment.Text))
+			} else {
+				slackStringBuilder.WriteString(fragment.Text)
+			}
+		}
+	}
+
+	return slackStringBuilder.String(), nil
+}
+
+func facetsToFragments(bskyMessage BskyMessage) ([]BskyTextFragment, error) {
+	facets := bskyMessage.Commit.Record.Facets
+	runes := []rune(bskyMessage.Commit.Record.Text)
+
+	fragments := []BskyTextFragment{}
+
+	slices.SortStableFunc(facets, func(a, b BskyFacet) int {
+		return a.Index.ByteStart - b.Index.ByteStart
+	})
+
+	textCursor := 0
+	facetCursor := 0
+
+	for facetCursor < len(facets) {
+		currentFacet := facets[facetCursor]
+
+		if textCursor < currentFacet.Index.ByteStart {
+			fragments = append(fragments, BskyTextFragment{Text: string(runes[textCursor:currentFacet.Index.ByteStart])})
+		} else if textCursor > currentFacet.Index.ByteStart {
+			facetCursor++
+			continue
+		}
+
+		if currentFacet.Index.ByteStart < currentFacet.Index.ByteEnd {
+			fragmentText := string(runes[currentFacet.Index.ByteStart:currentFacet.Index.ByteEnd])
+
+			// dont add the features if the text is blank
+			if strings.TrimSpace(fragmentText) == "" {
+				fragments = append(fragments, BskyTextFragment{
+					Text: string(runes[currentFacet.Index.ByteStart:currentFacet.Index.ByteEnd]),
+				})
+			} else {
+				fragments = append(fragments, BskyTextFragment{
+					Text:     string(runes[currentFacet.Index.ByteStart:currentFacet.Index.ByteEnd]),
+					Features: currentFacet.Features,
+				})
+			}
+		}
+		textCursor = currentFacet.Index.ByteEnd
+		facetCursor++
+	}
+	if textCursor < len(runes) {
+		fragments = append(fragments, BskyTextFragment{Text: string(runes[textCursor:])})
+	}
+
+	return fragments, nil
+}
diff --git a/cmd/bsky-webhook/main.go b/cmd/bsky-webhook/main.go
index 1755b79..bd1f333 100644
--- a/cmd/bsky-webhook/main.go
+++ b/cmd/bsky-webhook/main.go
@@ -288,12 +288,24 @@ func getBskyProfile(ctx context.Context, bskyMessage BskyMessage, bsky *bluesky.
 }
 
 func sendToSlack(ctx context.Context, jetstreamMessageStr string, bskyMessage BskyMessage, imageURL string, profile bluesky.Profile, postTime time.Time) error {
+	var messageText string
+	var err error
+
+	if len(bskyMessage.Commit.Record.Facets) != 0 {
+		messageText, err = bskyMessageToSlackMarkup(bskyMessage)
+		if err != nil {
+			return err
+		}
+	} else {
+		messageText = bskyMessage.Commit.Record.Text
+	}
+
 	attachments := []SlackAttachment{
 		{
 			AuthorName: fmt.Sprintf("%s (@%s)", profile.Name, profile.Handle),
 			AuthorIcon: profile.AvatarURL,
 			AuthorLink: fmt.Sprintf("https://bsky.app/profile/%s", profile.Handle),
-			Text:       fmt.Sprintf("%s\n<%s|View post on Bluesky ↗>", bskyMessage.Commit.Record.Text, bskyMessage.toURL(&profile.Handle)),
+			Text:       fmt.Sprintf("%s\n<%s|View post on Bluesky ↗>", messageText, bskyMessage.toURL(&profile.Handle)),
 			ImageUrl:   imageURL,
 			Footer:     "Posted",
 			Ts:         strconv.FormatInt(postTime.Unix(), 10),
diff --git a/cmd/bsky-webhook/types.go b/cmd/bsky-webhook/types.go
index e480c04..8cc3a99 100644
--- a/cmd/bsky-webhook/types.go
+++ b/cmd/bsky-webhook/types.go
@@ -29,9 +29,10 @@ type BskyCommit struct {
 }
 
 type BskyRecord struct {
-	Text            string    `json:"text"`
-	Embed           BskyEmbed `json:"embed"`
-	CreatedAtString string    `json:"createdAt"`
+	Text            string      `json:"text"`
+	Embed           BskyEmbed   `json:"embed"`
+	CreatedAtString string      `json:"createdAt"`
+	Facets          []BskyFacet `json:"facets"`
 }
 
 type BskyEmbed struct {
@@ -50,6 +51,28 @@ type BskyImageRef struct {
 	Link string `json:"$link"`
 }
 
+type BskyFacet struct {
+	Features []BskyFacetFeatures `json:"features"`
+	Index    BskyFacetIndex      `json:"index"`
+}
+
+type BskyFacetFeatures struct {
+	Type string `json:"$type"`
+	Uri  string `json:"uri"`
+	Did  string `json:"did"`
+	Tag  string `json:"tag"`
+}
+
+type BskyFacetIndex struct {
+	ByteEnd   int `json:"byteEnd"`
+	ByteStart int `json:"byteStart"`
+}
+
+type BskyTextFragment struct {
+	Text     string
+	Features []BskyFacetFeatures
+}
+
 type SlackAttachment struct {
 	AuthorName string `json:"author_name"`
 	AuthorIcon string `json:"author_icon"`