Improve Watchlist Sentinel to Follow Industry Best Practices for Stock Alerts

[alfredorueda]

Improve Watchlist Sentinel Using Industry Alert Best Practices

Context

The current Watchlist feature allows users to:

• Create a watchlist
• Monitor a ticker
• Define a simple price threshold

This is intentionally simple for educational purposes. However, real-world portfolio systems implement stock alerts following certain best practices.

Reference:
https://pro.stockalarm.io/blog/how-to-set-stock-price-alerts

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Proposal

Without making the system overly complex, we should slightly improve the Watchlist Sentinel to better reflect industry practices while keeping the project pedagogical.

The improvement should:

• Trigger alerts only when the price crosses the threshold (not continuously while above/below)

• Allow simple support for:

  • Price above threshold
  • Price below threshold

• Store minimal alert state to avoid repeated triggering

• Keep the domain model clean and aligned with DDD principles

We do not aim to implement a fully production-ready alert engine, but rather to:

• Improve realism
• Demonstrate better domain modeling
• Avoid naive threshold checks
• Keep the implementation understandable for students

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Acceptance Criteria

• Alerts trigger only on threshold crossing
• Basic alert type (above/below) is supported
• Minimal internal state prevents alert spam
• Code remains simple and readable
• Tests cover main alert scenarios