/**
 * Revocation + GOAWAY teardown — PLAN_RELAY_AGENT T14 (INV12). Distinguishes a `revoked` GOAWAY
 * (immediate teardown, NO reconnect) from the graceful `operatorDrain`/`shutdown` reasons
 * (finish in-flight, reconnect elsewhere) using ONLY the FROZEN §4.1 3-value `GoAwayReason` +
 * `decodeGoAwayReason` — never a locally-invented numeric mapping (cross-plan drift = silent
 * INV12 defeat). An unknown numeric code FAILS CLOSED to `revoked`.
 *
 * The RevocationState seam is imported from transport/seams.ts (W0), not redeclared. Its
 * `isRevoked()` is what T10's reconnectLoop consumes (one-way edge, no task cycle).
 */
import { decodeGoAwayReason } from 'relay-contracts'
import type { GoAwayReason } from 'relay-contracts'
import type { RevocationState, RevokeReason } from '../transport/seams.js'

export type GoAwayAction = 'drain' | 'revoked'

/**
 * Pure exhaustive map over the FROZEN 3-value union. `operatorDrain`/`shutdown` → drain (reconnect
 * elsewhere); `revoked` → revoked (stop). No integer literals — the reason is already a label.
 */
export function classifyGoAway(reason: GoAwayReason): GoAwayAction {
  switch (reason) {
    case 'operatorDrain':
    case 'shutdown':
      return 'drain'
    case 'revoked':
      return 'revoked'
  }
}

export function createRevocationState(onTeardown: () => void): RevocationState {
  let revoked = false
  return {
    isRevoked(): boolean {
      return revoked
    },
    markRevoked(_reason: RevokeReason): void {
      if (revoked) return
      revoked = true
      onTeardown() // close all streams + tunnel immediately
    },
  }
}

/**
 * Apply a decoded GOAWAY reason to the revocation state. On `revoked`, marks the state revoked
 * (⇒ teardown + reconnect suppression). Returns the action taken.
 */
export function applyGoAway(reason: GoAwayReason, state: RevocationState): GoAwayAction {
  const action = classifyGoAway(reason)
  if (action === 'revoked') state.markRevoked('goaway-revoked')
  return action
}

/**
 * Apply a raw GOAWAY wire code. Decodes via the FROZEN decoder; an UNKNOWN code (decoder throws)
 * FAILS CLOSED to `revoked` (a default that guessed "drain" would defeat INV12).
 */
export function applyGoAwayCode(code: number, state: RevocationState): GoAwayAction {
  let reason: GoAwayReason
  try {
    reason = decodeGoAwayReason(code)
  } catch {
    state.markRevoked('goaway-revoked') // fail closed
    return 'revoked'
  }
  return applyGoAway(reason, state)
}
