%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    autonumber
    participant Admin as Admin (NewsletterAdminPage)
    participant FE as Frontend Services (admin/newsletter.ts)
    participant BE as Backend /api/v1/admin/newsletter
    participant Email as EmailService (SMTP)

    Note over Admin,BE: Manual send/test/preview/status
    Admin->>FE: Click Send/Preview/Test
    FE->>BE: POST /newsletter/send | /preview | /test
    BE->>BE: Build content (newsletter_content)
    BE->>Email: Send via SMTP (per-recipient)
    Email-->>BE: Accepted/Failed
    BE-->>FE: Result + stats

    Note over FE,BE: Status & stats
    FE->>BE: GET /newsletter/status
    BE-->>FE: Enabled/automation state
    FE->>BE: GET /newsletter/stats/recent
    BE-->>FE: List recent sends, events

    rect rgba(225,255,225,0.2)
    Note over BE,Email: Automation (weekly, match alerts, blog notifications, results)
    BE->>BE: NewsletterScheduler tick
    BE->>BE: NewsletterAutomation decides digests/reminders
    BE->>Email: Send batches
    Email-->>BE: Delivery responses
    end