// ── Giving back what a run took ────────────────────────────────────────────
//
// EVENTS.md §C ("Cleanup is generated, never authored"), §L and its two ledger
// rules, and Phase 8 of EVENTS_PLAN.md. `events/ledger.js` is the write half;
// this is the undo half, plus the reconcile that answers "is any of it still
// there?" after something outside core restarted.
//
// **Cleanup is derived from the ledger, never authored.** An operator cannot be
// relied on to write the undo, and an aborted run never reaches the phase they
// wrote it in — so there is no cleanup phase in a spec and no `on_teardown` on an
// action. There is one function, it reads rows, and it runs on EVERY terminal
// path: completion, cancellation and abort alike.
//
// **It is not built out of `event_run_steps` rows** (org lead, 2026-09-03). The
// plan's phrase is "cleanup steps are generated from the ledger", and the
// tempting reading is a synthetic phase of real step rows so the console's
// per-step retry comes free. It is the wrong shape here for one concrete reason:
// `event_run_resources` already carries `revert_attempts` and `last_error`, so
// synthetic steps would put a second retry counter beside the first and the two
// would disagree the first time a step reverted three of its four resources.
// The manual retry the API surface promises is a route over the ledger —
// `POST /admin/events/runs/:runId/cleanup` — rather than a step control.
//
// **Where it runs from.** One place: the runner's cleanup leg, which finds
// terminal runs that still owe the world something and works their rows. Hooking
// each terminal path instead would be four call sites, three of which are inside
// a request, and none of which would survive the process dying mid-cleanup. The
// leg is ordered AFTER advance in the tick, so a run that completes in one tick
// is cleaned in the same one.
//
// **The scan's WHERE clause cost two live-walk findings, in opposite
// directions.** A run whose only resource was a LEASE never went through
// `ledger.markRunDirty` — `core.lease` reserves its own row — so its
// `cleanup_status` stayed `not_required` and the lease was never given back at
// all. And a run whose first sweep failed was moved to `incomplete` by that very
// sweep, so it was never picked up again: `MAX_REVERT_ATTEMPTS` meant ONE attempt
// rather than three. The first is why `not_required` is in the scan; the second
// is why `incomplete` is written HERE only once nothing retryable is left.
//
// **Rule 2 is what the bounds are for.** A revert that never succeeds must stay
// visible rather than cycle: `MAX_REVERT_ATTEMPTS` stops the automatic retry, the
// run reaches `completed` with `cleanup_status = 'incomplete'`, and the rows stay
// on the console with their last error. Only a human's cleanup clears the
// counter — Engagement Phase 14's rule, whose defect was a sweep that reset every
// stale row and made the ceiling unreachable for ever.

const resourcesDb = require('../model/events/eventRunResources.db')
const runsDb = require('../model/events/eventRuns.db')
const logDb = require('../model/events/eventRunLog.db')
const stepsDb = require('../model/events/eventRunSteps.db')
const registries = require('../modules/registries')
const { withDeadline } = require('./dispatch')
const log = require('../utils/logger')('events')

// How many times the automatic sweep will ask before leaving a resource for a
// human. Three, like a step's, and for the same reason: a fourth attempt against
// a shard that has answered the same way three times is not new information.
const MAX_REVERT_ATTEMPTS = Number(process.env.EVENT_REVERT_MAX_ATTEMPTS) || 3

// The bound on one revert call, when the action that made the resource is gone
// and there is no `budgetMs` to read. A restore is a round trip like any other.
const DEFAULT_REVERT_BUDGET_MS = 10_000

// How many runs one cleanup leg looks at, and how many resource groups it works
// per run. Bounds rather than targets, exactly like `RUN_BATCH`: the tick runs
// again, and an unbounded teardown is how one run's bad night stalls every other.
const CLEANUP_RUN_BATCH = Number(process.env.EVENT_CLEANUP_RUN_BATCH) || 10
const CLEANUP_GROUPS_PER_RUN = Number(process.env.EVENT_CLEANUP_GROUPS_PER_RUN) || 25

/**
 * Classify one revert answer, with `dispatch.classify`'s posture: no shape a
 * failure can take may read as success.
 *
 * The extra value here is `drifted`. It is NOT an error — the module did exactly
 * what it was asked and found somebody else's value in place — so it is a third
 * outcome rather than a failure with a flag, and the row it produces is the one
 * §L wants surfaced beside the unreverted ones.
 */
function classifyRevert(raw, what) {
  if (raw && raw.__timedOut) return { outcome: 'retry', error: raw.error }
  if (raw === null || typeof raw !== 'object' || Array.isArray(raw)) {
    return { outcome: 'retry', error: `${what} answered with no envelope` }
  }
  if (raw.ok === true) {
    // §L, and the Rust wipe: "gone, and that is fine" is a successful revert. A
    // module never has to distinguish "I deleted it" from "it was not there".
    return { outcome: 'done', failed: Array.isArray(raw.failed) ? raw.failed.map(String) : [] }
  }
  if (raw.drifted === true) {
    return {
      outcome: 'drifted',
      error: `the value is now ${JSON.stringify(raw.current)} rather than what this run applied, so it was left alone`,
    }
  }
  return {
    outcome: raw.retry === false ? 'terminal' : 'retry',
    error: raw.error ? String(raw.error) : `${what} refused`,
  }
}

/** Call a lease's `restore`, under a deadline, never throwing. */
async function restoreLease(row) {
  // Through the ref parser, because a targeted lease's ref is `<id>#<target>`
  // (Phase 12b). A bare map lookup would miss every property lease and report
  // "no module registers" for one that is registered — leaving a spawner turned
  // up for good and blaming an uninstalled module for it.
  const found = registries.eventLeaseForRef(row.ref)
  const lease = found && found.lease
  if (!lease) {
    // The module that owned it is uninstalled or failed to boot. Not a failure to
    // retry away — nothing will change until an operator reinstalls it — and not
    // an orphan either, because core has no idea whether the value is still
    // applied. It stays unresolved with the reason on it, which is exactly what
    // `cleanup_status = 'incomplete'` is for.
    return { outcome: 'terminal', error: `no module registers the lease "${row.ref}"` }
  }
  const payload = row.payload || {}
  let raw
  try {
    raw = await withDeadline(
      () =>
        lease.restore(payload.baseline, {
          expected: payload.applied,
          runId: row.run_id,
          target: found.target,
        }),
      DEFAULT_REVERT_BUDGET_MS,
      row.ref,
    )
  } catch (err) {
    return { outcome: 'retry', error: err.message }
  }
  return classifyRevert(raw, row.ref)
}

/** Call an action's `revert` over a group of its rows, under a deadline, never throwing. */
async function revertGroup(actionId, rows, idempotencyKey) {
  const action = registries.eventAction(actionId)
  if (!action || typeof action.revert !== 'function') {
    return {
      outcome: 'terminal',
      error: action
        ? `${actionId} declares no revert()`
        : `no module registers "${actionId}", so its resources cannot be given back`,
    }
  }
  const payload = rows
    .filter((r) => r.kind !== resourcesDb.STEP_KIND)
    .map((r) => ({ kind: r.kind, ref: r.ref, payload: r.payload || null, memberKey: r.member_key || null }))

  let raw
  try {
    raw = await withDeadline(
      () => action.revert({ runId: rows[0].run_id, resources: payload, idempotencyKey }),
      action.budgetMs || DEFAULT_REVERT_BUDGET_MS,
      actionId,
    )
  } catch (err) {
    // A module should not throw from `revert` any more than from `perform`, and
    // one that does has produced a transient failure rather than a crashed sweep.
    log.warn('event revert threw', { action: actionId, message: err.message })
    return { outcome: 'retry', error: err.message }
  }
  return classifyRevert(raw, actionId)
}

/**
 * Work one run's ledger once.
 *
 * Answers what it found and what it managed, and sets `cleanup_status` from the
 * rows that are left rather than from what it did — the two differ whenever
 * another writer touched the run, and the rows are the truth.
 *
 * `resetAttempts` is the human's flag. It is never set by the automatic leg.
 */
async function cleanupRun(run, { resetAttempts = false, actor = null } = {}) {
  const summary = { attempted: 0, reverted: 0, drifted: 0, failed: 0, remaining: 0 }

  if (resetAttempts) {
    const cleared = await resourcesDb.resetAttempts(run.id)
    await runsDb.setCleanupStatus(run.id, 'pending')
    if (cleared) {
      await logDb.write({
        runId: run.id,
        kind: 'cleanup.retry',
        detail: { resources: cleared, by: actor },
      })
    }
  }

  const rows = await resourcesDb.unresolvedForRun(run.id, {
    maxAttempts: resetAttempts ? null : MAX_REVERT_ATTEMPTS,
  })

  // **Grouped by the step that made them**, because that is what names the verb:
  // the resource row records the module and the opaque names, the step records
  // the action, and `revert()` takes a LIST so one round trip can give back
  // twelve creatures. A lease is its own group of one — core restores it through
  // the lease registry rather than through any action, which is the split §F
  // draws and the reason `core.lease` needs no `revert()` of its own.
  const leases = rows.filter((r) => r.kind === 'override')
  const byStep = new Map()
  for (const row of rows) {
    if (row.kind === 'override') continue
    const key = row.step_id === null ? `orphan:${row.id}` : `step:${row.step_id}`
    if (!byStep.has(key)) byStep.set(key, [])
    byStep.get(key).push(row)
  }

  const groups = [...leases.map((r) => ({ lease: r })), ...[...byStep.values()].map((rs) => ({ rows: rs }))]

  for (const group of groups.slice(0, CLEANUP_GROUPS_PER_RUN)) {
    if (group.lease) {
      const row = group.lease
      if (!(await resourcesDb.claimRevert(row.id))) continue
      summary.attempted += 1
      const verdict = await restoreLease(row)
      await applyVerdict(run, [row], verdict, summary, row.ref)
      continue
    }

    const rs = group.rows
    // The step is what names the action and carries the idempotency key. A row
    // whose step was deleted keeps the action id in its own payload, which is why
    // the placeholder writes one.
    const step = rs[0].step_id === null ? null : await stepsDb.getById(rs[0].step_id)
    const actionId = step?.action_id || rs[0].payload?.action || null
    if (!actionId) {
      await noteUnrevertable(run, rs, 'nothing records which action created this', summary)
      continue
    }
    const claimed = []
    for (const row of rs) if (await resourcesDb.claimRevert(row.id)) claimed.push(row)
    if (!claimed.length) continue
    summary.attempted += claimed.length
    const verdict = await revertGroup(actionId, claimed, step?.idempotency_key || rs[0].ref)
    await applyVerdict(run, claimed, verdict, summary, actionId)
  }

  summary.remaining = await resourcesDb.unresolvedCount(run.id)
  // **`incomplete` means "finished with, and not finished"**, so it is written
  // only once there is nothing left this sweep will try. Writing it after the
  // FIRST failure — which is what the first draft did — took the run straight out
  // of the leg's own scan, and `MAX_REVERT_ATTEMPTS` quietly meant one attempt
  // rather than three. Found by the live walk, watching `revert_attempts` sit at
  // 1 through half a minute of ticks.
  const retryable = await resourcesDb.unresolvedForRun(run.id, { maxAttempts: MAX_REVERT_ATTEMPTS })
  const status = summary.remaining === 0 ? 'complete' : retryable.length ? 'pending' : 'incomplete'
  await runsDb.setCleanupStatus(run.id, status)

  if (summary.attempted > 0) {
    await logDb.write({
      runId: run.id,
      kind: 'cleanup.swept',
      detail: { ...summary, by: actor },
    })
  }
  return summary
}

/** Write one verdict across the rows it covers, and count it. */
async function applyVerdict(run, rows, verdict, summary, what) {
  for (const row of rows) {
    if (verdict.outcome === 'done' && !(verdict.failed || []).includes(row.ref)) {
      await resourcesDb.markReverted(row.id)
      summary.reverted += 1
      continue
    }
    if (verdict.outcome === 'drifted') {
      await resourcesDb.failRevert(row.id, verdict.error, 'drifted')
      summary.drifted += 1
      continue
    }
    const error =
      verdict.outcome === 'done'
        ? `${what} could not give "${row.ref}" back`
        : verdict.error
    await resourcesDb.failRevert(row.id, error, 'confirmed')
    summary.failed += 1
  }
  await logDb.write({
    runId: run.id,
    kind: verdict.outcome === 'done' ? 'cleanup.reverted' : 'cleanup.failed',
    detail: {
      what,
      outcome: verdict.outcome,
      resources: rows.map((r) => `${r.kind}:${r.ref}`),
      ...(verdict.error ? { error: verdict.error } : {}),
    },
  })
}

/** A group core cannot even name a verb for. Counted as failed, and said once. */
async function noteUnrevertable(run, rows, reason, summary) {
  for (const row of rows) {
    if (!(await resourcesDb.claimRevert(row.id))) continue
    await resourcesDb.failRevert(row.id, reason, 'confirmed')
    summary.attempted += 1
    summary.failed += 1
  }
  await logDb.write({
    runId: run.id,
    kind: 'cleanup.failed',
    detail: { what: null, outcome: 'terminal', resources: rows.map((r) => `${r.kind}:${r.ref}`), error: reason },
  })
}

/**
 * The cleanup leg of the tick: every TERMINAL run with something left to give
 * back.
 *
 * Terminal only. A run still in flight has a ledger that is still growing, and
 * reverting a resource the next step is about to use would be core undoing an
 * event while it is happening.
 */
async function sweep() {
  // The ceiling goes INTO the query, so a run whose rows are all spent is not
  // selected, worked over and found to have nothing to do on every tick for the
  // rest of its life. It is also what excludes a run an admin cancelled without
  // cleanup, whose counters were spent deliberately.
  const candidates = await resourcesDb.runsNeedingCleanup(CLEANUP_RUN_BATCH, MAX_REVERT_ATTEMPTS)
  let swept = 0
  for (const candidate of candidates) {
    if (!runsDb.TERMINAL.includes(candidate.status)) continue
    try {
      await cleanupRun(candidate)
      swept += 1
    } catch (err) {
      log.error('event cleanup failed', { run: candidate.id, message: err.message })
    }
  }
  return swept
}

/**
 * Ask one module which of its ledgered resources the game still has (§L, and
 * §N7's "the shard stays stateless about events").
 *
 * **Core cannot know when to ask**, and that is not an omission: §F says core has
 * no concept of the game being up, because a module with six sidecars cannot
 * answer that question in the singular. So the module triggers this, through
 * `ctx.events.reconcile()`, when it sees its own reconnect — module-uo already
 * watches `bootId` for exactly that. Core also asks once at boot, for its own
 * restart.
 *
 * **A resource the module no longer has becomes `orphaned`, never `reverted`.**
 * Reverting it would be core recording that it put something back when what
 * actually happened is that the thing vanished while nobody was looking, and the
 * two are different sentences to the operator reading the console afterwards.
 *
 * A module with no `reconcile()` on the action is not broken: core keeps
 * believing its own ledger, which is precisely the behaviour before this phase.
 */
async function reconcileModule(owner) {
  const rows = await resourcesDb.liveForModule(owner)
  const summary = { asked: 0, inForce: 0, orphaned: 0, unanswered: 0 }
  if (!rows.length) return summary

  const byStep = new Map()
  for (const row of rows) {
    if (row.kind === resourcesDb.STEP_KIND) continue // nothing to ask about yet
    const key = row.step_id === null ? `orphan:${row.id}` : `step:${row.step_id}`
    if (!byStep.has(key)) byStep.set(key, [])
    byStep.get(key).push(row)
  }

  for (const group of byStep.values()) {
    const step = group[0].step_id === null ? null : await stepsDb.getById(group[0].step_id)
    const actionId = step?.action_id || group[0].payload?.action || null
    const action = actionId ? registries.eventAction(actionId) : null
    if (!action || typeof action.reconcile !== 'function') {
      summary.unanswered += group.length
      continue
    }
    summary.asked += group.length
    let raw
    try {
      raw = await withDeadline(
        () =>
          action.reconcile({
            runId: group[0].run_id,
            resources: group.map((r) => ({ kind: r.kind, ref: r.ref, payload: r.payload || null })),
          }),
        action.budgetMs || DEFAULT_REVERT_BUDGET_MS,
        actionId,
      )
    } catch (err) {
      log.warn('event reconcile threw', { action: actionId, message: err.message })
      raw = null
    }
    // Same posture as everywhere else: nothing that is not an explicit answer
    // counts as one. A module that could not answer leaves the ledger alone,
    // because "I do not know" must never be read as "it is gone".
    if (!raw || raw.__timedOut || raw.ok !== true || !Array.isArray(raw.inForce)) {
      summary.unanswered += group.length
      continue
    }
    const held = new Set(raw.inForce.map(String))
    for (const row of group) {
      if (held.has(row.ref)) {
        summary.inForce += 1
        continue
      }
      await resourcesDb.markOrphaned(row.id, 'the module reports this is no longer in force')
      summary.orphaned += 1
      await logDb.write({
        runId: row.run_id,
        kind: 'resource.orphaned',
        detail: { module: owner, resource: `${row.kind}:${row.ref}`, action: actionId },
      })
    }
  }
  return summary
}

/** Ask every module that owns a live row. Core's own boot-time sweep. */
async function reconcileAll() {
  const owners = await resourcesDb.modulesWithLiveRows()
  const out = {}
  for (const owner of owners) {
    try {
      out[owner] = await reconcileModule(owner)
    } catch (err) {
      log.error('event reconcile failed', { module: owner, message: err.message })
    }
  }
  return out
}

module.exports = {
  MAX_REVERT_ATTEMPTS,
  classifyRevert,
  cleanupRun,
  sweep,
  reconcileModule,
  reconcileAll,
}