Button templates in DMs, instead of a bare URL #24

The problem

DMs are plain text. A bare URL in an Instagram DM is unappealing and converts worse than a tappable button.

What to build

Support Meta's button template on the private-reply send in src/meta.ts, so a rule can define up to three web_url buttons.

{
  "recipient": { "comment_id": "..." },
  "message": {
    "attachment": {
      "type": "template",
      "payload": {
        "template_type": "button",
        "text": "Here's the guide!",
        "buttons": [
          { "type": "web_url", "url": "https://…", "title": "Get the guide" }
        ]
      }
    }
  }
}

Meta's limits, which are not negotiable

Truncate rather than error, and warn in the rule form when the DM text exceeds 640 characters with buttons enabled.

The part that needs care

Fall back to plain text when Meta rejects the template — but only then.

Meta returns errors for template rejection and for a closed messaging window and for an already-consumed private reply. Retrying the latter two as plain text will fail again and overwrite the true error with a misleading one, which makes the Sends log actively harmful for debugging.

Match the rejection reason and fall back only for genuine template rejections. Record which path was taken.

Acceptance criteria

• Rule form accepts up to 3 buttons (label + URL), validated
• Titles truncated to 20 chars, body to 640, with a warning shown before saving
• Plain-text fallback fires only for template rejection, never for window-closed or reply-consumed
• The Sends log distinguishes a template send from a fallback send
• Tests for the limits and for the error discrimination

Where to look

• src/meta.ts — sendPrivateReply
• src/process.ts, src/routes/admin.ts, migrations/

Pairs well with tracked links.