Module: Feat::Eval

Defined in:
lib/feat/eval.rb

Class Method Summary collapse

Class Method Details

.call(flag_key:, default_value:, ctx:, datafile:) ⇒ Object

Run the precedence pipeline:

1. archived flag        -> off variation        DISABLED
2. !isEnabled           -> off variation        DISABLED
3. individual target    -> target variation     TARGETING_MATCH
4. first matching rule  -> rule variation/rollout TARGETING_MATCH / SPLIT
5. default              -> default variation/rollout FALLTHROUGH / SPLIT
6. nothing matched      -> off variation        DEFAULT



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# File 'lib/feat/eval.rb', line 31

def call(flag_key:, default_value:, ctx:, datafile:)
  flag = datafile.flags[flag_key]
  if flag.nil?
    return EvaluationResult.new(
      value: default_value, reason: Reason::ERROR,
      error_message: "flag could not be evaluated"
    )
  end

  if flag.archived || !flag.isEnabled
    return resolve_variation(flag, flag.offVariationId, Reason::DISABLED, default_value)
  end

  flag.targets.each do |target|
    ctx_key = ContextResolver.read_context_key(ctx, target.contextKindKey)
    if !ctx_key.nil? && ctx_key == target.contextKey
      return resolve_variation(flag, target.variationId, Reason::TARGETING_MATCH, default_value)
    end
  end

  flag.rules.each do |rule|
    next unless match_rule?(rule, ctx, datafile)

    if !rule.variationId.nil?
      return resolve_variation(flag, rule.variationId, Reason::TARGETING_MATCH, default_value)
    end
    if !rule.rollout.nil?
      picked = pick_rollout(flag, rule.rollout, ctx)
      return resolve_variation(flag, picked, Reason::SPLIT, default_value) unless picked.nil?
    end
  end

  if !flag.defaultVariationId.nil?
    return resolve_variation(flag, flag.defaultVariationId, Reason::FALLTHROUGH, default_value)
  end
  if !flag.defaultRollout.nil?
    picked = pick_rollout(flag, flag.defaultRollout, ctx)
    return resolve_variation(flag, picked, Reason::SPLIT, default_value) unless picked.nil?
  end

  resolve_variation(flag, flag.offVariationId, Reason::DEFAULT, default_value)
end

.match_rule?(rule, ctx, datafile) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/feat/eval.rb', line 74

def match_rule?(rule, ctx, datafile)
  return false if rule.groups.empty?

  rule.groups.any? do |group|
    next false if group.conditions.empty?

    group.conditions.all? { |cond| Segments.match_condition(cond, ctx, datafile) }
  end
end

.pick_rollout(flag, rollout, ctx) ⇒ Object 



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# File 'lib/feat/eval.rb', line 84

def pick_rollout(flag, rollout, ctx)
  ctx_key = ContextResolver.read_context_key(ctx, rollout.bucketingContextKindKey)
  return nil if ctx_key.nil?

  b = Bucketing.bucket(salt: flag.salt, flag_key: flag.key, context_key: ctx_key)
  Bucketing.pick_by_weight(b, rollout.variations)
end

.resolve_variation(flag, variation_id, reason, default_value) ⇒ Object 



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# File 'lib/feat/eval.rb', line 92

def resolve_variation(flag, variation_id, reason, default_value)
  v = flag.variations.find { |x| x.id == variation_id }
  if v.nil?
    return EvaluationResult.new(
      value: default_value, reason: Reason::ERROR,
      error_message: "flag could not be evaluated"
    )
  end
  EvaluationResult.new(value: v.value, variation_id: variation_id, reason: reason)
end