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class Email < T::Struct
  const :subject, String
  const :from, String
  const :to, String
  const :body, String
end

class EmailCategory < T::Enum
  enums do
    Technical = new('technical')
    Billing = new('billing')
    General = new('general')
  end
end

class Priority < T::Enum
  enums do
    Low = new('low')
    Medium = new('medium')
    High = new('high')
  end
end

class ClassifyEmail < DSPy::Signature
  description "Classify customer support emails by analyzing content and urgency"
  
  input do
    const :email, Email, 
          description: "The email to classify with all headers and content"
  end
  
  output do
    const :category, EmailCategory,
          description: "Main topic: technical (API, bugs), billing (payment, pricing), or general"
    const :priority, Priority,
          description: "Urgency level based on keywords like 'production', 'ASAP', 'urgent'"
    const :summary, String,
          description: "One-line summary of the issue for support dashboard"
  end
end

classifier = DSPy::ChainOfThought.new(ClassifyEmail)

# Create a properly typed email object
email = Email.new(
  subject: "URGENT: API Key Not Working!!!",
  from: "john.doe@acmecorp.com",
  to: "support@yourcompany.com",
  body: "My API key stopped working after the update. I need this fixed ASAP for our production deployment!"
)

classification = classifier.call(email: email)  # Type-checked at runtime!

irb> classification.reasoning
=> "Let me analyze this email step by step:
1. The customer mentions an API key issue - this is technical
2. They mention it stopped working after an update - suggests a system change
3. They emphasize 'ASAP' and 'production deployment' - this is urgent
4. Production issues always warrant high priority"

irb> classification.category
=> #<EmailCategory::Technical:0x00007f8b2c0a1b80>

irb> classification.category.class
=> EmailCategory::Technical

irb> classification.category == EmailCategory::Technical  # Type-safe comparison
=> true

irb> classification.priority
=> #<Priority::High:0x00007f8b2c0a1c20>

irb> classification.priority.serialize  # Get the string value when needed
=> "high"

irb> classification.summary
=> "API key authentication failure post-update affecting production"

# Your IDE knows these are the ONLY valid values:
irb> EmailCategory.values
=> [#<EmailCategory::Technical>, #<EmailCategory::Billing>, #<EmailCategory::General>]

# Type errors caught at runtime (or by Sorbet static analysis):
irb> classification.category = "invalid"  # This would raise an error!