Class: KairosMcp::DslAst::AstEngine

Inherits:
Object
  • Object
show all
Defined in:
lib/kairos_mcp/dsl_ast/ast_engine.rb

Overview

AST node evaluation engine Verifies definition nodes against a binding context without using eval. Design: verification-only — does not replace behavior block execution. NOTE: The engine itself is infrastructure in Phase 2. Policy aspects (drift thresholds, etc.) may become a SkillSet in Phase 3.

Constant Summary collapse

ALLOWED_METHODS =

Allowed methods for condition evaluation via send(). Only query methods (no side effects) are permitted.

%i[
  can_evolve? has_tool? include? key? empty? nil?
  is_a? respond_to? size length count
].freeze

Class Method Summary collapse

Class Method Details

.evaluate_check(node, binding_context) ⇒ Object

Evaluate Check node



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# File 'lib/kairos_mcp/dsl_ast/ast_engine.rb', line 132

def self.evaluate_check(node, binding_context)
  opts = node.options || {}
  condition = opts[:condition]

  unless condition
    return NodeResult.new(
      node_name: node.name,
      node_type: :Check,
      satisfied: :unknown,
      detail: "No condition specified",
      evaluable: false
    )
  end

  result = match_condition(condition, binding_context)
  NodeResult.new(
    node_name: node.name,
    node_type: :Check,
    satisfied: result[:satisfied],
    detail: result[:detail],
    evaluable: result[:evaluable]
  )
end

.evaluate_constraint(node, binding_context) ⇒ Object

Evaluate Constraint node via pattern matching (no eval)



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# File 'lib/kairos_mcp/dsl_ast/ast_engine.rb', line 94

def self.evaluate_constraint(node, binding_context)
  opts = node.options || {}
  condition = opts[:condition]

  if condition.nil?
    # No condition string — check if required key exists in context
    if opts[:required] == true
      # Constraint is a declaration; structurally valid
      return NodeResult.new(
        node_name: node.name,
        node_type: :Constraint,
        satisfied: true,
        detail: "Required constraint declared (structural)",
        evaluable: true
      )
    end

    return NodeResult.new(
      node_name: node.name,
      node_type: :Constraint,
      satisfied: true,
      detail: "Constraint declared (no condition to evaluate)",
      evaluable: true
    )
  end

  # Pattern match the condition string
  result = match_condition(condition, binding_context)
  NodeResult.new(
    node_name: node.name,
    node_type: :Constraint,
    satisfied: result[:satisfied],
    detail: result[:detail],
    evaluable: result[:evaluable]
  )
end

.evaluate_node(node, binding_context: {}) ⇒ NodeResult

Evaluate a single AST node

Parameters:

  • node (KairosMcp::AstNode) —

    the node to evaluate

  • binding_context (Hash) (defaults to: {}) —

    runtime values for condition evaluation

Returns:



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# File 'lib/kairos_mcp/dsl_ast/ast_engine.rb', line 68

def self.evaluate_node(node, binding_context: {})
  case node.type
  when :Constraint
    evaluate_constraint(node, binding_context)
  when :Check
    evaluate_check(node, binding_context)
  when :Plan
    evaluate_plan(node)
  when :ToolCall
    evaluate_tool_call(node)
  when :SemanticReasoning
    evaluate_semantic_reasoning(node)
  else
    NodeResult.new(
      node_name: node.name,
      node_type: node.type,
      satisfied: :unknown,
      detail: "Unknown node type: #{node.type}",
      evaluable: false
    )
  end
end

.evaluate_plan(node) ⇒ Object

Evaluate Plan node — structural validity (steps exist and are named)



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# File 'lib/kairos_mcp/dsl_ast/ast_engine.rb', line 157

def self.evaluate_plan(node)
  opts = node.options || {}
  steps = opts[:steps]

  unless steps.is_a?(Array) && !steps.empty?
    return NodeResult.new(
      node_name: node.name,
      node_type: :Plan,
      satisfied: false,
      detail: "Plan has no steps defined",
      evaluable: true
    )
  end

  NodeResult.new(
    node_name: node.name,
    node_type: :Plan,
    satisfied: true,
    detail: "Plan has #{steps.size} steps: #{steps.map(&:to_s).join(' -> ')}",
    evaluable: true
  )
end

.evaluate_semantic_reasoning(node) ⇒ Object

SemanticReasoning — explicitly non-evaluable (requires human judgment)



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# File 'lib/kairos_mcp/dsl_ast/ast_engine.rb', line 205

def self.evaluate_semantic_reasoning(node)
  opts = node.options || {}
  prompt = opts[:prompt] || "(no prompt)"

  NodeResult.new(
    node_name: node.name,
    node_type: :SemanticReasoning,
    satisfied: :unknown,
    detail: "Requires human judgment: #{prompt}",
    evaluable: false
  )
end

.evaluate_tool_call(node) ⇒ Object

Evaluate ToolCall node — command recognition (does not execute)



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# File 'lib/kairos_mcp/dsl_ast/ast_engine.rb', line 181

def self.evaluate_tool_call(node)
  opts = node.options || {}
  command = opts[:command]

  unless command && !command.to_s.strip.empty?
    return NodeResult.new(
      node_name: node.name,
      node_type: :ToolCall,
      satisfied: false,
      detail: "No command specified",
      evaluable: true
    )
  end

  NodeResult.new(
    node_name: node.name,
    node_type: :ToolCall,
    satisfied: true,
    detail: "Command recognized: #{command}",
    evaluable: true
  )
end

.match_condition(condition, binding_context) ⇒ Object

Pattern-match a condition string against binding_context Supported patterns:

"X == true/false" — boolean comparison
"X == VALUE" — equality comparison
"X < Y" / "X > Y" / "X >= Y" / "X <= Y" — numeric comparison
"X.method?(arg)" — method call on context object
"X not in Y" — exclusion check

Unsupported patterns return evaluable: false



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# File 'lib/kairos_mcp/dsl_ast/ast_engine.rb', line 226

def self.match_condition(condition, binding_context)
  # Pattern: "X == true" or "X == false"
  if condition =~ /\A(\w+)\s*==\s*(true|false)\z/
    var_name = $1.to_sym
    expected = $2 == 'true'
    if binding_context.key?(var_name)
      actual = binding_context[var_name]
      return {
        satisfied: actual == expected,
        detail: "#{var_name}: expected #{expected}, got #{actual}",
        evaluable: true
      }
    else
      return {
        satisfied: :unknown,
        detail: "Variable '#{var_name}' not in binding context",
        evaluable: false
      }
    end
  end

  # Pattern: "X < Y" or "X > Y" or "X >= Y" or "X <= Y"
  if condition =~ /\A(\w+)\s*(<|>|<=|>=)\s*(\w+)\z/
    left_name = $1.to_sym
    op = $2
    right_name = $3.to_sym

    left_val = binding_context.key?(left_name) ? binding_context[left_name] : nil
    right_val = binding_context.key?(right_name) ? binding_context[right_name] : nil

    if left_val.nil? || right_val.nil?
      missing = []
      missing << left_name unless binding_context.key?(left_name)
      missing << right_name unless binding_context.key?(right_name)
      return {
        satisfied: :unknown,
        detail: "Missing variables: #{missing.join(', ')}",
        evaluable: false
      }
    end

    begin
      result = case op
               when '<'  then left_val < right_val
               when '>'  then left_val > right_val
               when '<=' then left_val <= right_val
               when '>=' then left_val >= right_val
               end

      return {
        satisfied: result,
        detail: "#{left_name}(#{left_val}) #{op} #{right_name}(#{right_val}) = #{result}",
        evaluable: true
      }
    rescue TypeError, ArgumentError => e
      return {
        satisfied: :unknown,
        detail: "Type error in comparison: #{e.message}",
        evaluable: false
      }
    end
  end

  # Pattern: "X.method?(arg)"
  if condition =~ /\A(\w+)\.(\w+\??)\(([^)]*)\)\z/
    obj_name = $1.to_sym
    method_name = $2.to_sym
    arg_str = $3.strip

    if binding_context.key?(obj_name)
      obj = binding_context[obj_name]
      if obj.respond_to?(method_name)
        # Security: only allow whitelisted query methods (no side effects)
        unless ALLOWED_METHODS.include?(method_name)
          return {
            satisfied: :unknown,
            detail: "Method '#{method_name}' not in allowed list",
            evaluable: false
          }
        end
        # Parse argument: try symbol, then string
        arg = arg_str.start_with?(':') ? arg_str[1..-1].to_sym : arg_str
        begin
          result = obj.send(method_name, arg)
          return {
            satisfied: !!result,
            detail: "#{obj_name}.#{method_name}(#{arg_str}) = #{result}",
            evaluable: true
          }
        rescue StandardError => e
          return {
            satisfied: :unknown,
            detail: "Error calling #{method_name}: #{e.message}",
            evaluable: false
          }
        end
      end
    end

    return {
      satisfied: :unknown,
      detail: "Cannot evaluate: #{condition}",
      evaluable: false
    }
  end

  # Pattern: "X not in Y"
  if condition =~ /\A(\w+)\s+not\s+in\s+(\w+)\z/
    item_name = $1.to_sym
    collection_name = $2.to_sym

    if binding_context.key?(item_name) && binding_context.key?(collection_name)
      item = binding_context[item_name]
      collection = binding_context[collection_name]
      if collection.respond_to?(:include?)
        result = !collection.include?(item)
        return {
          satisfied: result,
          detail: "#{item_name} not in #{collection_name}: #{result}",
          evaluable: true
        }
      end
    end

    return {
      satisfied: :unknown,
      detail: "Cannot evaluate exclusion: #{condition}",
      evaluable: false
    }
  end

  # Unrecognized pattern
  {
    satisfied: :unknown,
    detail: "Unrecognized condition pattern: #{condition}",
    evaluable: false
  }
end

.verify(skill, binding_context: {}) ⇒ VerificationReport

Verify all definition nodes for a skill

Parameters:

  • skill (KairosMcp::SkillsDsl::Skill) —

    the skill to verify

  • binding_context (Hash) (defaults to: {}) —

    runtime values for condition evaluation

Returns:



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# File 'lib/kairos_mcp/dsl_ast/ast_engine.rb', line 50

def self.verify(skill, binding_context: {})
  return nil unless skill.definition

  results = skill.definition.nodes.map do |node|
    evaluate_node(node, binding_context: binding_context)
  end

  VerificationReport.new(
    skill_id: skill.id,
    results: results,
    timestamp: Time.now.iso8601
  )
end