// Kotlin/JVM. Paired transport-free scaffold; production ports are intentionally abstract.
// beginVerified performs ALL verification inside a transaction. close rolls back
// unless committed. See examples/README.md for crypto, freshness and authority rules.
package bringpass.draft
import java.io.Closeable

enum class Op { REGISTER, USE, REVOKE, RETRACT }
data class Envelope(val fields: List<String>, val signature: String)
data class Result(val receipt: Envelope, val fresh: Boolean)
interface Tx : Closeable {
  val operation: Op
  fun cached(): Envelope?
  fun registerNewKey()
  fun requireCurrentEntitlement()
  fun revokeTarget()
  fun retractRelationship()
  fun signResult(): Envelope
  fun commitOnce(result: Envelope)
}
interface Ports {
  fun challenge(op: Op, rid: String, target: String, trustedContext: String): Envelope
  fun verifyProviderAndApprove(challenge: Envelope)
  fun signProof(challenge: Envelope): Envelope
  fun verifyResultAndApply(result: Envelope)
  fun beginVerified(proof: Envelope, trustedContext: String): Tx
  fun recoverRevoke(rid: String, target: String, trustedContext: String): Envelope
}
class TokenSide(private val ports: Ports) {
  fun respond(challenge: Envelope): Envelope {
    ports.verifyProviderAndApprove(challenge)
    return ports.signProof(challenge)
  }
  fun accept(result: Envelope) = ports.verifyResultAndApply(result)
}
class ProviderSide(private val ports: Ports) {
  fun start(op: Op, rid: String, target: String, context: String) =
    ports.challenge(op, rid, target, context)
  fun finish(proof: Envelope, trustedContext: String): Result =
    ports.beginVerified(proof, trustedContext).use { tx ->
      val cached = tx.cached()
      if (cached != null) Result(cached, false)
      else {
        when (tx.operation) {
          Op.REGISTER -> tx.registerNewKey()
          Op.USE -> tx.requireCurrentEntitlement()
          Op.REVOKE -> tx.revokeTarget()
          Op.RETRACT -> tx.retractRelationship()
        }
        val result = tx.signResult()
        tx.commitOnce(result)
        Result(result, true)
      }
    }
  fun lost(rid: String, target: String, context: String) =
    ports.recoverRevoke(rid, target, context)
}
fun legacyValue(value: String, approved: Boolean, selected: Boolean): String {
  require(approved && selected && value.isNotEmpty())
  return value // No new message reaches the legacy reader.
}