// ── The dry run ────────────────────────────────────────────────────────────
//
// EVENTS.md §I ("four affordances worth building in from the start") and §K's
// last bound, in Phase 6. Materialise nothing, dispatch every step with
// `verify: true`, and report what would happen and what it would cost.
//
// > **Dry run before anything unattended.** A scheduled definition that has never
// > been verified is the case worth refusing to start; verification is cheap and
// > it is the last point a human sees the plan.
//
// **What it verifies depends on the definition's state, and that is not a
// compromise.** A `ready` definition is verified against its PUBLISHED VERSION,
// because a published version is the only thing that ever actually runs and §K's
// gate is about letting one run unattended. A draft is verified against its
// working spec, because §API's note is explicit that an author prices their work
// *before* asking an admin to publish it. The two readings do not conflict — they
// are the same act at two moments — and the answer says which one it did.
//
// **Only a pass against a version is recorded.** A version is immutable, so a dry
// run that passed against one stays true; a draft changes under the author's
// hands, so a pass on it would be a claim about a spec that no longer exists.
//
// ## The finding that only exists here
//
// Every per-step check — is the action registered, is it enabled, does this one
// invocation fit the cap — is a check something else also makes, at save or at
// dispatch. **The TOTAL is not.** Three steps each spawning 15 creatures under a
// cap of 30 pass every individual check and breach the cap on the third, at two
// in the morning, with the world half-changed. Adding the costs up across the
// whole version is the one thing that can only be done by looking at the plan as
// a whole, and it is the reason a dry run is worth more than the sum of its
// step checks.

const { dispatchStep } = require('./dispatch')
const authorize = require('./authorize')
const settingsDb = require('../model/events/eventActionSettings.db')
const registries = require('../modules/registries')

/** The most advice lines one step's dry run carries, and the longest one. */
const ADVICE_MAX = 10
const ADVICE_CHARS = 500

/**
 * A dry run's `detail.warnings`, as the lines a dry run shows: strings only,
 * trimmed, the empty dropped, at most ten, each cut at 500 characters. Anything
 * else a module put there is ignored rather than refused — advice that cannot be
 * read is not a reason to fail a plan that would run.
 */
function adviceOf(detail) {
  if (!detail || typeof detail !== 'object' || !Array.isArray(detail.warnings)) return []
  return detail.warnings
    .filter((w) => typeof w === 'string')
    .map((w) => w.trim())
    .filter(Boolean)
    .slice(0, ADVICE_MAX)
    .map((w) => (w.length > ADVICE_CHARS ? `${w.slice(0, ADVICE_CHARS - 1)}…` : w))
}

/**
 * Dry-run a spec.
 *
 * `user` is the caller, so the role layer answers for *them* — an editor gets
 * told that a step needs an administrator, at the moment they can still do
 * something about it, rather than at the moment it does not run.
 *
 * Never throws: a `perform()` that explodes under `verify: true` is a finding
 * about that action, not a 500 on the author's screen. `dispatchStep` already
 * guarantees that, and this file adds no path around it.
 */
async function verifySpec(spec, { user = null, scope = '' } = {}) {
  const phases = spec?.phases || []
  const flat = []
  for (const phase of phases) {
    for (const [seq, step] of (phase.steps || []).entries()) {
      flat.push({ phase: phase.key, seq, step })
    }
  }

  const settings = await settingsDb.byIds(flat.map(({ step }) => step.actionId))
  const findings = []
  const totals = {}

  for (const { phase, seq, step } of flat) {
    const where = { phase, seq, actionId: step.actionId, label: step.label || null }
    const action = registries.eventAction(step.actionId)
    if (!action) {
      // The same fact `publishable()` refuses on, said in the dry run's voice.
      // Reported rather than thrown so that an author sees EVERY problem in one
      // pass — a verification that stops at the first finding makes fixing a
      // twelve-step definition twelve round trips.
      findings.push({ ...where, level: 'error', code: 'dormant', message: `no module registers "${step.actionId}"` })
      continue
    }

    const verdict = await authorize.mayInvoke({
      user,
      action,
      params: step.params || {},
      settings: settings.get(action.id) || null,
    })
    if (!verdict.ok) {
      findings.push({ ...where, level: 'error', code: verdict.code, message: verdict.reason })
      continue
    }

    for (const [dimension, amount] of Object.entries(verdict.cost || {})) {
      totals[dimension] = (totals[dimension] || 0) + amount
    }

    // The module's own answer. This is the half core cannot compute: whether the
    // landmark exists, whether the creature is on the allowlist, whether the
    // shard is reachable at all. `verify: true` rides through the real
    // dispatcher rather than down a second path, because a dry run down a second
    // path is a dry run OF the second path.
    const result = await dispatchStep(
      {
        id: null,
        run_id: null,
        phase,
        seq,
        action_id: step.actionId,
        params: step.params || {},
        action_version: step.actionVersion || null,
        idempotency_key: null,
        attempts: 0,
      },
      { run: { id: null, scope }, actor: user ? user.id : null, verify: true },
    )
    if (result.outcome === 'retry' || result.outcome === 'terminal') {
      findings.push({ ...where, level: 'error', code: 'refused', message: result.error })
    } else {
      if (result.actionVersionDrift) {
        findings.push({
          ...where,
          level: 'warning',
          code: 'version-drift',
          message: `authored against version ${result.actionVersionDrift.authored}; ${step.actionId} is now version ${result.actionVersionDrift.registered}`,
        })
      }
      // MODULE_API 1.16.0: a module's ADVICE on a step that would run — the
      // world as it stands now, which may change before the run does (Rust
      // PLAN_REDESIGNS §11.4, D391). A warning, so it never fails the dry run.
      for (const message of adviceOf(result.detail)) {
        findings.push({ ...where, level: 'warning', code: 'advice', message })
      }
    }
  }

  // ── The whole-plan check ──
  const caps = authorize.effectiveCaps(
    flat.map(({ step }) => ({ actionId: step.actionId, params: step.params || {} })),
    settings,
  )
  const cost = Object.entries(totals)
    .sort(([a], [b]) => a.localeCompare(b))
    .map(([dimension, total]) => {
      const cap = (caps[dimension] || {}).cap ?? null
      const over = cap !== null && total > cap
      if (over) {
        findings.push({
          phase: null,
          seq: null,
          actionId: null,
          label: null,
          level: 'error',
          code: 'cap-total',
          message: `this event asks for ${total} of "${dimension}" across all its steps, and this deployment allows ${cap} per run`,
        })
      }
      return { dimension, total, cap, from: (caps[dimension] || {}).from || null, over }
    })

  return {
    ok: !findings.some((f) => f.level === 'error'),
    steps: flat.length,
    findings,
    cost,
  }
}

module.exports = { verifySpec, adviceOf }