gem install datadog openfeature-sdk

gem "opentelemetry-metrics-sdk", ">= 0.8"
gem "opentelemetry-exporter-otlp-metrics", ">= 0.4"

# Required: Enable the feature flags provider
DD_EXPERIMENTAL_FLAGGING_PROVIDER_ENABLED=true

# Optional: Enable flag evaluation metrics
DD_METRICS_OTEL_ENABLED=true

require 'datadog'
require 'open_feature/sdk'
require 'datadog/open_feature/provider'

INITIALIZATION_TIMEOUT = 30

# Configure Datadog with feature flagging enabled
Datadog.configure do |config|
  config.remote.enabled = true
  config.remote.boot_timeout_seconds = INITIALIZATION_TIMEOUT
  config.open_feature.enabled = true
end

# Configure OpenFeature SDK with Datadog provider and wait for initialization
OpenFeature::SDK.configure do |config|
  config.set_provider_and_wait(
    Datadog::OpenFeature::Provider.new,
    timeout: INITIALIZATION_TIMEOUT
  )
end

# Create OpenFeature client
client = OpenFeature::SDK.build_client

context = OpenFeature::SDK::EvaluationContext.new(
  targeting_key: 'user-123',  # Targeting key (typically user ID)
  email: 'user@example.com',
  country: 'US',
  tier: 'premium',
  age: 25
)

enabled = client.fetch_boolean_value(
  flag_key: 'new-checkout-flow',
  default_value: false,
  evaluation_context: context
)

if enabled
  show_new_checkout
else
  show_legacy_checkout
end

theme = client.fetch_string_value(
  flag_key: 'ui-theme',
  default_value: 'light',
  evaluation_context: context
)

case theme
when 'dark'
  set_dark_theme
when 'light'
  set_light_theme
else
  set_light_theme
end

max_items = client.fetch_integer_value(
  flag_key: 'cart-max-items',
  default_value: 20,
  evaluation_context: context
)

discount_rate = client.fetch_float_value(
  flag_key: 'discount-rate',
  default_value: 0.0,
  evaluation_context: context
)

# Generic number method (type based on default)
batch_size = client.fetch_number_value(
  flag_key: 'batch-size',
  default_value: 100,  # Returns integer
  evaluation_context: context
)

config = client.fetch_object_value(
  flag_key: 'feature-config',
  default_value: {
    'maxRetries' => 3,
    'timeout' => 30
  },
  evaluation_context: context
)

max_retries = config['maxRetries'] || 3
timeout = config['timeout'] || 30

details = client.fetch_boolean_details(
  flag_key: 'new-feature',
  default_value: false,
  evaluation_context: context
)

puts "Value: #{details.value}"
puts "Variant: #{details.variant}"
puts "Reason: #{details.reason}"
puts "Error Code: #{details.error_code}"
puts "Error Message: #{details.error_message}"

# Global feature flag - no context needed
maintenance_mode = client.fetch_boolean_value(
  flag_key: 'maintenance-mode',
  default_value: false
)

if maintenance_mode
  halt 503, { error: 'Service temporarily unavailable' }.to_json
end

# spec/support/feature_flags.rb
require 'open_feature/sdk'
require 'open_feature/sdk/provider/in_memory_provider'

RSpec.configure do |config|
  config.around(:each, :feature_flags) do |example|
    original = OpenFeature::SDK::API.instance.provider
    OpenFeature::SDK.configure do |c|
      c.set_provider(OpenFeature::SDK::Provider::InMemoryProvider.new(
        'new-checkout-flow' => true,
        'ui-theme' => 'dark',
        'discount-rate' => 0.15
      ))
    end
    example.run
  ensure
    OpenFeature::SDK.configure { |c| c.set_provider(original) } if original
  end
end

# spec/checkout_spec.rb
require 'spec_helper'

RSpec.describe Checkout, :feature_flags do
  let(:client) { OpenFeature::SDK.build_client }

  it 'returns the in-memory flag value' do
    expect(client.fetch_boolean_value(flag_key: 'new-checkout-flow', default_value: false)).to be true
  end

  it 'falls back to the default for unknown flags' do
    expect(client.fetch_boolean_value(flag_key: 'does-not-exist', default_value: false)).to be false
  end
end

# Enable startup and debug logging
Datadog.configure do |config|
  config.diagnostics.startup_logs.enabled = true
  config.diagnostics.debug = true
  config.remote.enabled = true
  config.open_feature.enabled = true
end