# Ruby 3+. BOTH sides, transport-independent scaffold, not a verifier.
# Ports implement the contract in examples/README.md; no permissive default.
module BringPassDraft
  OPS = %w[REGISTER USE REVOKE RETRACT].freeze
  Envelope = Struct.new(:fields, :signature, keyword_init: true)
  Result = Struct.new(:receipt, :fresh, keyword_init: true)
  class Ports
    def challenge(op, rid, target, context) = raise(NotImplementedError)
    def verify_provider_and_approve(challenge) = raise(NotImplementedError)
    def sign_proof(challenge) = raise(NotImplementedError)
    def verify_result_and_apply(result) = raise(NotImplementedError)
    def begin_verified(proof, trusted_context) = raise(NotImplementedError)
    def recover_revoke(rid, target, trusted_context) = raise(NotImplementedError)
  end
  class Transaction
    # Created only after cryptographic verification inside a locked transaction.
    def operation = raise(NotImplementedError)
    def cached = raise(NotImplementedError)
    def register_new_key = raise(NotImplementedError)
    def require_current_entitlement = raise(NotImplementedError)
    def revoke_target = raise(NotImplementedError)
    def retract_relationship = raise(NotImplementedError)
    def sign_result = raise(NotImplementedError)
    def commit_once(result) = raise(NotImplementedError)
    def close = raise(NotImplementedError) # Roll back unless committed.
  end
  class TokenSide
    def initialize(ports) = @ports = ports
    def respond(challenge)
      @ports.verify_provider_and_approve(challenge)
      @ports.sign_proof(challenge)
    end
    def accept(result) = @ports.verify_result_and_apply(result)
  end
  class ProviderSide
    def initialize(ports) = @ports = ports
    def start(op, rid, target, context) = @ports.challenge(op, rid, target, context)
    def finish(proof, trusted_context)
      tx = @ports.begin_verified(proof, trusted_context)
      begin
        old = tx.cached
        return Result.new(receipt: old, fresh: false) if old
        case tx.operation
        when 'REGISTER' then tx.register_new_key
        when 'USE' then tx.require_current_entitlement
        when 'REVOKE' then tx.revoke_target
        when 'RETRACT' then tx.retract_relationship
        else raise ArgumentError, 'Unsupported operation'
        end
        result = tx.sign_result
        tx.commit_once(result)
        Result.new(receipt: result, fresh: true)
      ensure
        tx.close
      end
    end
    def lost(rid, target, context) = @ports.recover_revoke(rid, target, context)
  end
  def self.legacy_value(value, approved:, selected:)
    raise ArgumentError, 'Local approval/selection required' unless approved && selected && !value.empty?
    value # The only payload sent to the approved renderer/driver.
  end
end