// ── Starting a run from a trigger: the emit path's third subscriber ────────
//
// Rust PLAN_REDESIGNS §14.3.12 (D370), and EVENTS.md §E "Starting a run from a
// trigger". *"When anyone destroys Bradley on Main, start Launch Site
// Lockdown"*; *"when a champion's boss appears, start Champion's Call"*. Before
// this a trigger could only advance a phase of a run already going (`gates.js`)
// or send a notice (`engine.dispatch`); now a definition's published version may
// carry `starts`, and a firing that matches one creates a run of it, now.
//
// **Same seam and posture as the other two subscribers**: called from
// `engagementEmit.emit`, never awaited, never allowed to reject. Whether some
// event wanted to start is core's business, and a failure of core's must not
// become the module's control flow.
//
// **Four rules decide whether a matching firing starts anything:**
//
//   1. The version must have passed its dry run. A trigger start is unattended,
//      as a scheduled one is, and §K's gate falls on the path where nobody is.
//   2. One run at a time per definition. A firing while a run of it is going
//      starts nothing and is counted.
//   3. A cooldown after the last trigger-started run (default 30 minutes, 0 to
//      7 days). A firing inside it starts nothing and is counted. Rules 2 and 3
//      are what stop twelve road Bradleys dying in a minute starting twelve runs.
//   4. Core's own `event.*` triggers never start a run (refused at save, and
//      skipped here as well), so a run starting can never start another.
//
// Rules 2 and 3 are ONE conditional UPDATE (`eventTriggerStarts.db.claim`); the
// occurrence key `UNIQUE (definition_id, scope, scheduled_for)` with
// `scheduled_for` = the firing's time is what makes one firing reported twice
// (two instances ingesting one feed) create one run.

const definitionsDb = require('../model/events/eventDefinitions.db')
const startsDb = require('../model/events/eventTriggerStarts.db')
const runsModel = require('../model/events/eventRuns.model')
const conditions = require('../engagement/conditions')
const registries = require('../modules/registries')
const spec = require('./spec')
const gates = require('./gates')
const log = require('../utils/logger')('event-starts')

// What of a firing's data is kept on the run. The run row is admin-only, and it
// is the answer to "why did this run happen", so the trigger's DECLARED
// variables are kept and nothing else a module happened to send. Bounded, so
// one oversized payload cannot make the insert the thing that fails.
const MAX_ORIGIN_BYTES = 4096

/** The firing's time, in whole seconds (the column's precision), never in the future. */
function firingTime(occurredAt, now) {
  const parsed = occurredAt ? new Date(occurredAt) : now
  const at = Number.isNaN(parsed.getTime()) || parsed > now ? now : parsed
  return new Date(Math.floor(at.getTime() / 1000) * 1000)
}

const sameSecond = (a, b) =>
  a && b && Math.floor(new Date(a).getTime() / 1000) === Math.floor(new Date(b).getTime() / 1000)

/** The firing as the run will remember it. */
function originOf(event, declaration, start, at) {
  const declared = (declaration?.variables || []).map((v) => v.name)
  const data = event.data || {}
  let variables = Object.fromEntries(declared.filter((n) => n in data).map((n) => [n, data[n]]))
  if (Buffer.byteLength(JSON.stringify(variables), 'utf8') > MAX_ORIGIN_BYTES) {
    // Too big to keep whole: keep the ones the start's condition named, which
    // are the reason it matched, and say the rest were dropped.
    const named = gates.variablesIn(start.where)
    variables = Object.fromEntries(named.filter((n) => n in data).map((n) => [n, data[n]]))
    variables._truncated = true
  }
  return {
    kind: 'trigger',
    triggerId: event.triggerId,
    label: declaration?.label || event.triggerId,
    occurredAt: at.toISOString(),
    subject: event.subject ?? null,
    // The start's condition in the builder's own words, so the console can say
    // what it matched on without re-reading the version.
    matched: gates.phrase(start.where),
    variables,
  }
}

/**
 * Why a firing that matched did not get the claim. A duplicate of the firing
 * that started the last run is not counted: it is the same thing happening once,
 * reported twice.
 */
async function whyNot(definitionId, at, now) {
  const state = await startsDb.forDefinition(definitionId)
  if (state && sameSecond(state.last_started_at, at)) return 'duplicate'
  if (await startsDb.isGoing(definitionId, now)) return 'running'
  // A live claim is another firing starting it this instant: the run is going in
  // every sense but the row.
  if (state?.claimed_at && now - new Date(state.claimed_at) < startsDb.CLAIM_STALE_MS) return 'running'
  return 'cooldown'
}

/** One definition, one firing. Answers what happened, for the summary and the tests. */
async function consider(definition, event, at, now) {
  const starts = (definition.version_spec?.starts || []).filter((s) => s.on === event.triggerId && !s.dormant)
  const start = starts.find((s) => conditions.evaluate(s.where, event.data || {}))
  if (!start) return 'unmatched'

  if (now - at > Number(definition.grace_seconds || 0) * 1000) {
    // A firing older than the grace window would make a run the missed sweep
    // takes on its next tick. Said, and not started.
    log.warn('a firing too old to start a run', { definition: definition.id, trigger: event.triggerId, at })
    return 'stale'
  }

  if (!definition.version_verified_at) {
    await startsDb.ignore(definition.id, 'unverified', now)
    log.warn('trigger start held: the published version has never been verified', {
      definition: definition.id,
      title: definition.title,
      trigger: event.triggerId,
    })
    return 'unverified'
  }

  const cooldownSeconds = spec.parseCooldown(start.cooldown ?? spec.DEFAULT_COOLDOWN) ?? 0
  if (!(await startsDb.claim(definition.id, { at, cooldownSeconds, now }))) {
    const reason = await whyNot(definition.id, at, now)
    if (reason !== 'duplicate') await startsDb.ignore(definition.id, reason, now)
    return reason
  }

  const declaration = registries.eventTrigger(event.triggerId)
  let result
  try {
    result = await runsModel.create(
      definition.id,
      // Scope is empty, as a scheduled occurrence's is (org lead, 2026-09-02): a
      // scope registry does not exist, and the condition is what narrows a start
      // to one server.
      { scope: '', scheduledFor: at, source: 'trigger', origin: originOf(event, declaration, start, at) },
      null,
    )
  } catch (err) {
    await startsDb.release(definition.id)
    throw err
  }

  if (!result.ok) {
    await startsDb.release(definition.id)
    if (result.code === 'unverified') await startsDb.ignore(definition.id, 'unverified', now)
    log.warn('trigger start refused', { definition: definition.id, errors: result.errors })
    return 'refused'
  }

  if (!result.created) {
    // The occurrence already existed: this firing was reported twice, and the
    // claimant that made the run has recorded it. Nothing to count.
    await startsDb.release(definition.id)
    return 'duplicate'
  }
  await startsDb.started(definition.id, { at, runId: result.run.id })
  log.info('run started by a trigger', { definition: definition.id, run: result.run.id, trigger: event.triggerId })
  return 'started'
}

/**
 * The trigger stream's third subscriber.
 *
 * The common answer is one indexed-by-nothing query over the ready definitions
 * returning no rows: a deployment has tens of definitions, not thousands, and a
 * JSON column cannot carry an index. If that ever changes, a side table of
 * (trigger, definition) written at publish is the fix.
 */
async function observe(event, { now = new Date() } = {}) {
  const summary = { definitions: 0, started: 0, ignored: 0 }
  try {
    if (!event?.triggerId || event.triggerId.startsWith(spec.CORE_EVENT_PREFIX)) return summary
    const candidates = await definitionsDb.findStartingOn(event.triggerId)
    summary.definitions = candidates.length
    if (!candidates.length) return summary

    const at = firingTime(event.occurredAt, now)
    for (const definition of candidates) {
      try {
        const outcome = await consider(definition, event, at, now)
        if (outcome === 'started') summary.started += 1
        if (['running', 'cooldown', 'unverified'].includes(outcome)) summary.ignored += 1
      } catch (err) {
        log.error('trigger start failed', { definition: definition.id, trigger: event.triggerId, message: err.message })
      }
    }
  } catch (err) {
    log.error('trigger start observation failed', { trigger: event?.triggerId, message: err.message })
  }
  return summary
}

/**
 * The editor's line about a definition's trigger starts, from the state row.
 * Null when no trigger has ever tried to start it.
 */
function describeState(row) {
  if (!row) return null
  return {
    lastStartedAt: row.last_started_at || null,
    lastRunId: row.last_run_id || null,
    ignoredRunning: Number(row.ignored_running || 0),
    ignoredCooldown: Number(row.ignored_cooldown || 0),
    ignoredUnverified: Number(row.ignored_unverified || 0),
    lastIgnoredAt: row.last_ignored_at || null,
    lastIgnoredReason: row.last_ignored_reason || null,
  }
}

module.exports = { observe, consider, describeState, firingTime, originOf, MAX_ORIGIN_BYTES }