fix: chat accepts quotes now

internal/service/chat_service.go

@@ -7,6 +7,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"net/url"
 	"path"
 	"strings"
 	"time"
@@ -41,6 +42,7 @@ var (
 	ErrAvatarUnset          = errors.New("this group has no photo")
 	ErrChatNotAccepting     = errors.New("this person isn't accepting messages from you")
 	ErrChatBadWhoCanMessage = errors.New("unknown messaging restriction")
+	ErrChatBadQuote         = errors.New("that quote is not a valid passage reference")
 	ErrChatBadAccountAge    = errors.New("account age must be between 1 and 120 months")
 	ErrChatGenderUnset      = errors.New("add your gender in profile settings to use this option")
 )
@@ -377,6 +379,9 @@ type SendRequest struct {
 	// fetches the title, description and image itself, because a client that
 	// could supply them could make any link claim to be anything.
 	PreviewURL *string
+	// Quote is a passage shared from the library, rendered as a quote the
+	// reader can tap to return to the exact phrase.
+	Quote *QuoteAttachment
 	// Attachments are files already uploaded to the private bucket via
 	// PresignAttachment; their keys are checked against the caller's prefix.
 	Attachments []MediaAttachment
@@ -407,10 +412,14 @@ func (s *ChatService) Send(ctx context.Context, userID, conversationID string, r
 		return nil, err
 	}
 
+	if req.Quote != nil && !req.Quote.valid() {
+		return nil, ErrChatBadQuote
+	}
+
 	body := strings.TrimSpace(req.Body)
-	// A photo with no caption is an ordinary message; only a message with
-	// neither text nor attachments is empty.
-	if body == "" && len(req.Attachments) == 0 {
+	// A photo or a shared passage with no caption is an ordinary message; only
+	// a message with nothing at all in it is empty.
+	if body == "" && len(req.Attachments) == 0 && req.Quote == nil {
 		return nil, ErrChatEmptyBody
 	}
 	if len([]rune(body)) > maxBodyRunes {
@@ -445,6 +454,7 @@ func (s *ChatService) Send(ctx context.Context, userID, conversationID string, r
 		return s.withAttachments(ctx, msg)
 	}
 
+	s.attachQuote(ctx, conversationID, msg, req.Quote)
 	s.attachMedia(ctx, conversationID, userID, msg, req.Attachments)
 	s.attachLinkPreview(ctx, conversationID, msg, entities, req.PreviewURL)
 
@@ -499,6 +509,83 @@ func (s *ChatService) attachMedia(ctx context.Context, conversationID, userID st
 	}
 }
 
+// QuoteAttachment is a passage shared out of the library.
+type QuoteAttachment struct {
+	// Path is an APP-RELATIVE deep link, e.g. "/books/bg/2/13?hl=…".
+	//
+	// Deliberately not a full URL. A quote renders as trusted in-app content,
+	// so allowing an absolute URL would let a sender dress an off-site link up
+	// as a scripture citation. A path cannot leave the app, which removes the
+	// question of which origins to trust.
+	Path string
+	// Title is the source reference shown above the passage.
+	Title string
+	// Text is the quoted passage itself.
+	Text string
+}
+
+const (
+	maxQuoteTitleRunes = 200
+	maxQuoteTextRunes  = 2000
+	maxQuotePathBytes  = 2048
+)
+
+func (q *QuoteAttachment) valid() bool {
+	if strings.TrimSpace(q.Text) == "" {
+		return false
+	}
+	if len([]rune(q.Title)) > maxQuoteTitleRunes || len([]rune(q.Text)) > maxQuoteTextRunes {
+		return false
+	}
+	return safeAppPath(q.Path)
+}
+
+// safeAppPath accepts only a path within this app.
+//
+// "//evil.com" and "/\evil.com" are protocol-relative and would navigate
+// off-site, so a leading slash alone is not enough to check.
+func safeAppPath(p string) bool {
+	if p == "" || len(p) > maxQuotePathBytes {
+		return false
+	}
+	if p[0] != '/' {
+		return false
+	}
+	if strings.HasPrefix(p, "//") || strings.HasPrefix(p, "/\\") {
+		return false
+	}
+	if strings.ContainsAny(p, "\\") {
+		return false
+	}
+	for _, r := range p {
+		if r < 0x20 || r == 0x7f {
+			return false
+		}
+	}
+	// A parsed path must not carry a scheme or host of its own.
+	u, err := url.Parse(p)
+	if err != nil || u.Scheme != "" || u.Host != "" {
+		return false
+	}
+	return true
+}
+
+// attachQuote stores a shared passage. Unlike a link card, the contents come
+// from the client — but they are only ever rendered as a quotation, and the
+// path has already been constrained to this app.
+func (s *ChatService) attachQuote(ctx context.Context, conversationID string, msg *model.Message, q *QuoteAttachment) {
+	if q == nil {
+		return
+	}
+	path, title, text := q.Path, strings.TrimSpace(q.Title), strings.TrimSpace(q.Text)
+	if _, err := s.chat.AddAttachment(ctx, repository.AddAttachmentParams{
+		MessageID: msg.ID, ConversationID: conversationID, Ord: 0,
+		Kind: model.AttachmentQuote, URL: &path, Title: &title, Description: &text,
+	}); err != nil {
+		s.logger.Warn("chat: attach quote failed", zap.Error(err))
+	}
+}
+
 // attachLinkPreview unfurls the chosen link and stores the card.
 //
 // Two rules make this safe. The URL must be one the parser actually found in