Add default conversation title

internal/conversation/title.go

@@ -0,0 +1,67 @@
+package conversation
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+	"strings"
+	"unicode/utf8"
+
+	"code.chimeric.al/chimerical/odidere/internal/db"
+	"code.chimeric.al/chimerical/odidere/internal/llm"
+)
+
+// MaxTitleLength is the maximum length of a conversation title in
+// Unicode code points.
+const MaxTitleLength = 256
+
+// deriveTitle returns a title from the first line of text that
+// contains non-whitespace characters. It replaces runs of
+// whitespace on that line with single spaces and truncates to
+// MaxTitleLength runes. It returns "" if text has no
+// non-whitespace characters.
+func deriveTitle(text string) string {
+	for line := range strings.SplitSeq(text, "\n") {
+		title := strings.Join(strings.Fields(line), " ")
+		if title == "" {
+			continue
+		}
+		if utf8.RuneCountInString(title) <= MaxTitleLength {
+			return title
+		}
+		runes := []rune(title)
+		return string(runes[:MaxTitleLength])
+	}
+	return ""
+}
+
+// setTitle derives a title from msg and sets the conversation
+// title if the conversation has no title yet. It does nothing if
+// msg has no non-whitespace text or if the conversation already
+// has a title.
+func (c *Conversation) setTitle(
+	ctx context.Context,
+	msg llm.Message,
+) error {
+	title := deriveTitle(msg.Text())
+	if title == "" {
+		return nil
+	}
+	_, err := c.dbw.UpdateConversationTitleIfUnset(
+		ctx,
+		db.UpdateConversationTitleIfUnsetParams{
+			Id:    c.id,
+			Title: title,
+		},
+	)
+	// sql.ErrNoRows means the conversation already has a title (or
+	// does not exist).
+	if errors.Is(err, sql.ErrNoRows) {
+		return nil
+	}
+	if err != nil {
+		return fmt.Errorf("update conversation title: %w", err)
+	}
+	return nil
+}