// ── The public event surface ───────────────────────────────────────────────
//
// EVENTS.md § API surface, and Phase 14a of EVENTS_PLAN.md: the calendar an
// anonymous visitor reads, one event's page, and an arc.
//
// **This file is a projection, and the projection is the security boundary.**
// Every other reader of these tables is staff, and every field they are shown is
// one somebody with a role was allowed to see. What comes out of here is read by
// nobody at all, so the rule is the opposite of the admin shapes': nothing is
// spread, and a field reaches a public entry because a line below put it there.
// The day somebody adds a column to `event_runs` — a claim token, an operator's
// note, a last error — a `{ ...run }` anywhere here would publish it, silently,
// in the release after the one anybody reviewed.
//
// Three things are absent from every shape below, and each is a decision:
//
//   • **The spec.** Phases, steps, actions and their params are the plan for
//     changing a live world. A visitor is told what is happening and when, and
//     the LABEL of the phase while it is happening; the steps are the operator's.
//   • **Health, cleanup, claims and errors.** A degraded run is a fact about the
//     deployment's plumbing. "The event is running" is the fact about the event.
//   • **`member_key`.** It is the game's own identifier for a character, it is
//     module-opaque, and core cannot say what it discloses — so it stays unsent
//     even on a results table where every other column is published.
//
// **What makes something public is `listed` AND `ready` AND not a rehearsal**,
// and all three live in SQL (`eventDefinitions.db.getPublicBySlug`, and
// `publicOnly` on `eventRuns.db.listInWindow`). Filtering in JavaScript after
// the read would work exactly as well, right up until the first caller that
// forgot to.

const definitionsDb = require('./eventDefinitions.db')
const runsDb = require('./eventRuns.db')
const seriesDb = require('./eventSeries.db')
const versionsDb = require('./eventVersions.db')
const participantsDb = require('./eventRunParticipants.db')
const calendarModel = require('./eventCalendar.model')
const recurrence = require('../../events/recurrence')

// The public calendar's window when a caller names neither end: a few days BACK
// through a month out. A visitor arriving at /site/events wants "what is on", and
// a client that had to compute a window before it could ask anything would make
// every deep link carry two ISO instants.
//
// **The backward tail is not padding — it is the "recent" in §I's "upcoming, live
// and recent".** The default used to start at `now`, so an event that finished an
// hour ago was already gone and a visitor had nowhere to find the results of the
// thing they had just attended. The LIVE half is answered by `listInWindow`'s
// overlap test rather than by this number, so the tail only has to be long enough
// to be a "recently" a reader would recognise.
const DEFAULT_WINDOW_DAYS = 31
const DEFAULT_RECENT_DAYS = 7

// How many past occurrences an event page carries. It shows what is next and
// what happened recently; the whole history of a three-year-old weekly event is
// a different screen and nobody has asked for one.
const PAST_RUNS = 10
const RESULTS_LIMIT = 100

// The status words a visitor is told. `paused` maps to `live` deliberately: an
// operator holding a run for two minutes while they deal with something is not a
// state a public page should render, and a page that said "paused" would invite
// a question whose answer is internal.
const PUBLIC_STATUS = {
  scheduled: 'scheduled',
  starting: 'live',
  running: 'live',
  paused: 'live',
  ending: 'live',
  completed: 'completed',
  cancelled: 'cancelled',
  failed: 'cancelled',
  missed: 'cancelled',
}

/**
 * The public status word for a run.
 *
 * **`failed` and `missed` are published as `cancelled`**, which is the mapping
 * worth defending. To a visitor the three are one event: it was on the calendar
 * and it did not happen. The difference between them is entirely about the
 * deployment — `failed` names broken machinery, `missed` names a process that
 * was down when the schedule came round — so publishing either word would tell a
 * stranger something true about the server and nothing about the event.
 */
const publicStatus = (status) => PUBLIC_STATUS[status] || 'scheduled'

/** Is this a run a visitor should be shown as happening now? */
const isLive = (status) => publicStatus(status) === 'live'

/**
 * The label of the phase a run is in, resolved from the PINNED version's spec.
 *
 * A phase id is a slug an author typed and the label is what they meant it to
 * read as, so a page rendering the id would show `phase-2` to the public. A
 * phase the spec does not name answers null and the page shows nothing, which is
 * the right answer for a version edited since: the run pinned the old spec and
 * the old spec is what it is executing.
 */
function phaseLabel(spec, phaseId) {
  if (!phaseId || !spec || !Array.isArray(spec.phases)) return null
  const phase = spec.phases.find((p) => p && p.id === phaseId)
  return (phase && (phase.label || phase.id)) || null
}

/** One calendar entry, from a materialised run. */
const publicRunEntry = (run) => ({
  kind: 'run',
  title: run.definition_title,
  slug: run.definition_slug,
  seriesName: run.series_name || null,
  seriesSlug: run.series_slug || null,
  scheduledFor: run.scheduled_for,
  timezone: run.timezone,
  status: publicStatus(run.status),
  live: isLive(run.status),
})

/**
 * One calendar entry, from a projection.
 *
 * A projection is arithmetic past the materialisation horizon (§I), and the
 * public entry keeps the distinction for the visitor's version of the operator's
 * reason: a forecast three weeks out is a plan rather than a booking, and a page
 * drawing the two identically would promise something nothing has committed to.
 * `adjusted` rides along because a DST-shifted occurrence is worth explaining
 * before it happens rather than after.
 */
const publicProjectedEntry = (definition, occurrence) => ({
  kind: 'projected',
  title: definition.title,
  slug: definition.slug,
  seriesName: definition.series_name || null,
  seriesSlug: definition.series_slug || null,
  scheduledFor: occurrence.at,
  timezone: definition.timezone,
  status: 'scheduled',
  live: false,
  adjusted: occurrence.adjusted,
  shiftMinutes: occurrence.shiftMinutes,
})

/**
 * The public calendar for a window.
 *
 * **The run half is read here rather than borrowed from `eventCalendar.model`**,
 * and the reason is the file header's: that model answers with `status`,
 * `health`, `version` and `waitingSteps` on every entry, so reusing it would
 * mean building the public answer by DELETING fields from an operator's, which
 * is the direction that fails silently. The arithmetic IS shared —
 * `occurrencesBetween` is the same function the runner calls, so a forecast
 * still cannot disagree with what later appears — and so are the window bound
 * and the entry cap, which are a defence against an expensive query on the one
 * surface that has no login in front of it.
 */
async function calendar({ from, to, seriesId = null, now = new Date() } = {}) {
  // The default `to` is measured from NOW, not from `start` — otherwise the
  // backward tail would silently push the horizon a week further out and a caller
  // naming only `from` would get a different span than one naming neither.
  const start = from
    ? new Date(from)
    : new Date(new Date(now).getTime() - DEFAULT_RECENT_DAYS * recurrence.DAY_MS)
  const end = to
    ? new Date(to)
    : new Date(new Date(now).getTime() + DEFAULT_WINDOW_DAYS * recurrence.DAY_MS)

  if (Number.isNaN(start.getTime()) || Number.isNaN(end.getTime())) {
    return { ok: false, status: 400, errors: ['from and to must be dates'] }
  }
  if (end <= start) {
    return { ok: false, status: 400, errors: ['to must be after from'] }
  }
  if (end - start > calendarModel.MAX_WINDOW_DAYS * recurrence.DAY_MS) {
    return {
      ok: false,
      status: 400,
      errors: [`the window may span at most ${calendarModel.MAX_WINDOW_DAYS} days`],
    }
  }

  const runs = await runsDb.listInWindow({ from: start, to: end, seriesId, publicOnly: true })
  const entries = runs.map(publicRunEntry)

  // Every instant a run already occupies, so the fortnight inside the horizon is
  // not drawn twice — and so a CANCELLED occurrence is not re-forecast as though
  // it were still coming. The same key the admin calendar uses, for the same
  // reason: projections are per definition at the empty scope.
  const taken = new Set(
    runs
      .filter((r) => !r.scope)
      .map((r) => `${r.definition_id}@${new Date(r.scheduled_for).getTime()}`),
  )

  const definitions = await definitionsDb.findSchedulable({ listedOnly: true })
  for (const definition of definitions) {
    if (seriesId && Number(definition.series_id) !== Number(seriesId)) continue
    const schedule = definition.version_spec?.schedule
    if (!schedule || schedule.kind === 'manual') continue
    let occurrences = []
    try {
      // **Forecast from `now`, never from `start`.** The default window now
      // reaches a week backwards so that "recent" has somewhere to live, and a
      // projection into that tail would advertise an occurrence that did not
      // happen — a run that WAS created is a real row and arrives above, and one
      // that was not is a slot the runner has already passed. A forecast is about
      // the future; the tail is about the past. Only the materialised half fills
      // it.
      const forecastFrom = start > now ? start : new Date(now)
      if (forecastFrom < end) {
        occurrences = recurrence.occurrencesBetween(
          schedule,
          definition.timezone || 'UTC',
          forecastFrom,
          end,
        )
      }
    } catch {
      // A version whose schedule the recurrence engine will not read is one the
      // runner will not expand either. The calendar then shows that definition's
      // materialised runs and no forecast, rather than failing the whole page.
      continue
    }
    for (const occurrence of occurrences) {
      if (taken.has(`${definition.id}@${occurrence.at.getTime()}`)) continue
      entries.push(publicProjectedEntry(definition, occurrence))
    }
  }

  entries.sort((a, b) => new Date(a.scheduledFor) - new Date(b.scheduledFor))

  return {
    ok: true,
    status: 200,
    window: { from: start, to: end },
    entries: entries.slice(0, calendarModel.MAX_ENTRIES),
    truncated: entries.length > calendarModel.MAX_ENTRIES,
  }
}

/** One participant, as a results table publishes them. */
const publicParticipant = (p) => ({
  // NOT `memberKey` — see the file header. A display name is whatever the module
  // chose to put in `meta`, because core has no name for a character and must
  // not invent one from the key.
  name: (p.meta && (p.meta.name || p.meta.displayName)) || null,
  score: p.score,
  rank: p.rank_at,
  meta: p.meta || null,
})

/** One occurrence, as an event page lists it. */
const publicOccurrence = (run, spec) => ({
  runId: run.id,
  scheduledFor: run.scheduled_for,
  timezone: run.timezone,
  startedAt: run.started_at,
  endedAt: run.ended_at,
  status: publicStatus(run.status),
  live: isLive(run.status),
  scope: run.scope || null,
  phase: isLive(run.status) ? phaseLabel(spec, run.current_phase) : null,
  resultsPublishedAt: run.results_published_at || null,
})

/**
 * One event's public page: the storyline, its arc, its occurrences, and a
 * results table when there is one to show.
 *
 * **`runId` selects WHICH occurrence the results are about, and it is optional
 * for a reason that exists only because of the announcements.** The page lives
 * at the definition's slug, so a weekly event has one address and a visitor
 * arriving at it should be shown what is next. But an `event.run.completed` mail
 * is about ONE occurrence, and a link in it that opened next Friday's would
 * answer a different question from the one the reader clicked. So the trigger's
 * `eventUrl` carries `?run=`, and this is what resolves it.
 *
 * **A `runId` that does not belong to this definition is ignored rather than
 * refused.** It names some other event's run, or none; the honest answer to
 * "show me this event" is still this event, and a 404 for the whole page would
 * turn a stale link in a months-old mail into a dead end rather than a page
 * about the thing the mail was about.
 */
async function event(slug, { runId = null } = {}) {
  const definition = await definitionsDb.getPublicBySlug(String(slug || ''))
  if (!definition) return { ok: false, status: 404, errors: ['Not found'] }

  const series = definition.series_id ? await seriesDb.getById(definition.series_id) : null
  const runs = await runsDb.listPublicForDefinition(definition.id, PAST_RUNS + 20)

  const now = Date.now()
  const live = runs.filter((r) => isLive(r.status))

  // **Split on the instant, not on the status**, and the difference is visible
  // in both directions. A `missed` run is in the past whatever its status says,
  // and so is a `scheduled` one whose moment went by while the runner had not
  // reached it — but a run an operator CANCELLED next Friday is still next
  // Friday, and filing it under "previously" tells a visitor it already
  // happened, which is the one thing that is certainly untrue about it. That a
  // cancelled occurrence still appears under what is coming is the point:
  // "next Friday is off" is exactly what somebody checking the calendar came to
  // find out.
  const upcoming = runs
    .filter((r) => !live.includes(r) && new Date(r.scheduled_for).getTime() >= now)
    .sort((a, b) => new Date(a.scheduled_for) - new Date(b.scheduled_for))
  const past = runs.filter((r) => !live.includes(r) && !upcoming.includes(r)).slice(0, PAST_RUNS)

  // `next` is narrower than `upcoming[0]`, deliberately: the headline answers
  // "when is the next one", and a cancelled occurrence is not one. An event
  // whose only future occurrence has been called off has no `next` and says so,
  // while the cancellation itself is still listed below.
  const next = upcoming.find((r) => r.status === 'scheduled') || null

  // Which occurrence the results table is about. An explicit `run` wins; then a
  // live one, because that is what the visitor is looking at; then the most
  // recent that actually published results, because a page with a table on it is
  // more use than one with an empty heading.
  const named = runId ? runs.find((r) => String(r.id) === String(runId)) : null
  const resultsRun = named || live[0] || past.find((r) => r.results_published_at) || null

  let participants = []
  if (resultsRun && resultsRun.results_published_at) {
    participants = (await participantsDb.listForRun(resultsRun.id, RESULTS_LIMIT)).map(
      publicParticipant,
    )
  }

  // Phase labels come from the version the run is EXECUTING rather than from the
  // definition's working draft, which an author may be halfway through editing.
  // One extra read, and only when there is a run to label at all.
  const specRun = named || live[0] || null
  const spec = specRun ? (await versionsDb.getById(specRun.version_id))?.spec || null : null

  return {
    ok: true,
    status: 200,
    event: {
      title: definition.title,
      slug: definition.slug,
      summary: definition.summary,
      body: definition.body,
      imageUrl: definition.image_url,
      timezone: definition.timezone,
      series: series ? { name: series.name, slug: series.slug } : null,
      live: live.length > 0,
      current: live[0] ? publicOccurrence(live[0], spec) : null,
      next: next ? publicOccurrence(next, spec) : null,
      upcoming: upcoming.map((r) => publicOccurrence(r, spec)),
      past: past.map((r) => publicOccurrence(r, spec)),
      results:
        resultsRun && resultsRun.results_published_at
          ? {
              runId: resultsRun.id,
              scheduledFor: resultsRun.scheduled_for,
              publishedAt: resultsRun.results_published_at,
              participants,
            }
          : null,
    },
  }
}

/**
 * One arc: the series, and the listed events in it in the order an editor
 * dragged them into.
 *
 * **A series with no listed events is a 404 rather than an empty page.** The arc
 * is a label on its definitions and nothing else, so a page for an empty one
 * would publish the single fact that an operator has named something they have
 * not announced.
 */
async function series(slug) {
  const row = await seriesDb.getBySlug(String(slug || ''))
  if (!row) return { ok: false, status: 404, errors: ['Not found'] }

  const definitions = await definitionsDb.listPublicBySeries(row.id)
  if (!definitions.length) return { ok: false, status: 404, errors: ['Not found'] }

  return {
    ok: true,
    status: 200,
    series: {
      name: row.name,
      slug: row.slug,
      description: row.description,
      events: definitions.map((d) => ({
        title: d.title,
        slug: d.slug,
        summary: d.summary,
        imageUrl: d.image_url,
      })),
    },
  }
}

/**
 * One account's participation history.
 *
 * Self-scoped by the caller's own id and nothing else. There is no route on
 * which one account reads another's, and deliberately no id parameter that could
 * later grow into one.
 */
async function history(userId, { limit = 50, before = null } = {}) {
  const rows = await participantsDb.listForUser(userId, { limit, before })
  return {
    ok: true,
    status: 200,
    entries: rows.map((r) => ({
      id: r.id,
      runId: r.run_id,
      title: r.definition_title,
      slug: r.definition_slug,
      seriesName: r.series_name || null,
      seriesSlug: r.series_slug || null,
      scheduledFor: r.scheduled_for,
      startedAt: r.started_at,
      endedAt: r.ended_at,
      timezone: r.timezone,
      status: publicStatus(r.status),
      joinedAt: r.joined_at,
      score: r.score,
      // Null until `core.results.publish` ran. The screen says so rather than
      // inventing a position nobody computed.
      rank: r.rank_at,
      resultsPublishedAt: r.results_published_at || null,
      meta: r.meta || null,
    })),
  }
}

module.exports = {
  calendar,
  event,
  series,
  history,
  publicStatus,
  phaseLabel,
  DEFAULT_WINDOW_DAYS,
  DEFAULT_RECENT_DAYS,
  PAST_RUNS,
}