import {
  bayesianScore,
  compareMints,
  NEUTRAL_PRIOR_MEAN,
  parseNuts,
  type Health,
  type MintDetail,
  type MintInfo,
  type MintListItem,
  type MintStatus,
  type MintType,
  type ProbeSample,
  type RatingDistribution,
  type LnurlFields,
  type Stats,
} from '@cashumints/shared';
import { config, startedAt } from './config.ts';
import { getDb, getStateNumber, getState } from './db.ts';
import { lastDiscoveryReport } from './discovery.ts';
import { mintByHost, parseEcosystem, type MintRow } from './mints.ts';

/**
 * One review per author per mint, newest wins.
 *
 * Kind 38000 is in the addressable range, so a later event from the same author
 * replaces the earlier one. The old site applied the same rule in memory
 * (aggregateReviews, keyed by pubkey); doing it in SQL keeps counts honest and stops
 * one npub from moving a mint's average by re-posting.
 *
 * The `AS ranked` alias is not decoration: Postgres rejects an unaliased subquery in
 * FROM, and SQLite does not care either way.
 */
export const LATEST_REVIEWS = `
  SELECT mint_url, pubkey, rating, created_at FROM (
    SELECT mint_url, pubkey, rating, created_at,
           ROW_NUMBER() OVER (
             PARTITION BY mint_url, pubkey ORDER BY created_at DESC, event_id
           ) AS rn
    FROM reviews
  ) AS ranked WHERE rn = 1
`;

interface AggRow {
  mint_url: string;
  review_count: number;
  rating_avg: number | null;
  last_review_at: number | null;
}

/**
 * Review counts and averages, for one mint or for all of them.
 *
 * A detail page passes its own URL. Computing the whole table to read one row off it
 * is free on a local SQLite file and is not on a Postgres server across a socket.
 */
async function aggregates(mintUrl?: string): Promise<Map<string, AggRow>> {
  const db = await getDb();
  const where = mintUrl === undefined ? '' : 'WHERE mint_url = ?';
  const params = mintUrl === undefined ? [] : [mintUrl];

  const rows = await db.all<AggRow>(
    `WITH latest AS (${LATEST_REVIEWS})
     SELECT mint_url,
            COUNT(*)          AS review_count,
            AVG(rating)       AS rating_avg,
            MAX(created_at)   AS last_review_at
     FROM latest ${where} GROUP BY mint_url`,
    ...params,
  );

  return new Map(rows.map((r) => [r.mint_url, r]));
}

/**
 * C in the Bayesian formula.
 *
 * Defaults to a neutral 3, not the observed global mean: see the long comment in
 * shared/src/score.ts for why the observed mean (about 4.7 here) makes the formula
 * fail its own stated purpose. `SCORE_PRIOR_MEAN=global` restores literal BACKEND.md
 * behaviour, or set any number to pin it.
 */
async function priorMean(): Promise<number> {
  const override = process.env['SCORE_PRIOR_MEAN'];

  if (override && override !== 'global') {
    const n = Number.parseFloat(override);
    if (Number.isFinite(n) && n >= 1 && n <= 5) return n;
  }

  if (override === 'global') {
    const db = await getDb();
    const row = await db.get<{ avg: number | null }>(
      `WITH latest AS (${LATEST_REVIEWS}) SELECT AVG(rating) AS avg FROM latest`,
    );
    return row?.avg ?? NEUTRAL_PRIOR_MEAN;
  }

  return NEUTRAL_PRIOR_MEAN;
}

function iconPath(row: MintRow): string | null {
  return row.icon_file ? `/icons/${row.icon_file}` : null;
}

function round1(n: number | null): number | null {
  return n === null ? null : Math.round(n * 10) / 10;
}

function toListItem(row: MintRow, agg: AggRow | undefined, mean: number, now: number): MintListItem {
  const base = {
    review_count: agg?.review_count ?? 0,
    rating_avg: agg?.rating_avg ?? null,
    status: row.status,
    last_review_at: agg?.last_review_at ?? null,
  };

  return {
    url: row.url,
    host: row.host,
    name: row.name,
    icon: iconPath(row),
    type: row.type as MintType,
    status: row.status as MintStatus,
    last_online: row.last_online,
    review_count: base.review_count,
    rating_avg: round1(base.rating_avg),
    score: bayesianScore(base, mean, now),
    last_review_at: base.last_review_at,
    version: row.version,
  };
}

/**
 * The list, optionally narrowed to one ecosystem.
 *
 * `type` is filtered in SQL rather than after scoring, because the two list pages ask
 * for one ecosystem each and there is no reason to score fifty federations to render
 * /mints. Unfiltered still returns everything, so `/api/mints` on its own is the whole
 * index with a `type` on every item.
 */
export async function listMints(limit?: number, type?: string): Promise<MintListItem[]> {
  const now = Math.floor(Date.now() / 1000);
  const db = await getDb();
  const [agg, mean, rows] = await Promise.all([
    aggregates(),
    priorMean(),
    type
      ? db.all<MintRow>('SELECT * FROM mints WHERE type = ?', type)
      : db.all<MintRow>('SELECT * FROM mints'),
  ]);

  const items = rows.map((row) => toListItem(row, agg.get(row.url), mean, now)).sort(compareMints);

  return limit && limit > 0 ? items.slice(0, limit) : items;
}

async function distribution(mintUrl: string): Promise<RatingDistribution> {
  const db = await getDb();
  const rows = await db.all<{ rating: number; n: number }>(
    `WITH latest AS (${LATEST_REVIEWS})
     SELECT rating, COUNT(*) AS n FROM latest
     WHERE mint_url = ? AND rating IS NOT NULL GROUP BY rating`,
    mintUrl,
  );

  const dist: RatingDistribution = { '1': 0, '2': 0, '3': 0, '4': 0, '5': 0 };
  for (const r of rows) {
    const key = String(r.rating) as keyof RatingDistribution;
    if (key in dist) dist[key] = r.n;
  }
  return dist;
}

async function reviews90d(mintUrl: string): Promise<number> {
  const cutoff = Math.floor(Date.now() / 1000) - 90 * 24 * 60 * 60;
  const db = await getDb();
  const row = await db.get<{ n: number }>(
    `WITH latest AS (${LATEST_REVIEWS})
     SELECT COUNT(*) AS n FROM latest WHERE mint_url = ? AND created_at >= ?`,
    mintUrl,
    cutoff,
  );
  return row?.n ?? 0;
}

async function uptime30d(mintUrl: string): Promise<number | null> {
  const cutoff = Math.floor(Date.now() / 1000) - 30 * 24 * 60 * 60;
  const db = await getDb();
  const row = await db.get<{ up: number | null; n: number }>(
    'SELECT AVG(ok) AS up, COUNT(*) AS n FROM probes WHERE mint_url = ? AND ts >= ?',
    mintUrl,
    cutoff,
  );

  if (!row?.n || row.up === null) return null;
  return Math.round(row.up * 1000) / 1000;
}

async function recentProbes(mintUrl: string): Promise<ProbeSample[]> {
  const cutoff = Math.floor(Date.now() / 1000) - 48 * 60 * 60;
  const db = await getDb();
  return db.all<ProbeSample>(
    'SELECT ts, ok, latency_ms FROM probes WHERE mint_url = ? AND ts >= ? ORDER BY ts ASC',
    mintUrl,
    cutoff,
  );
}

function parseInfo(json: string | null): MintInfo | null {
  if (!json) return null;
  try {
    return JSON.parse(json) as MintInfo;
  } catch {
    return null;
  }
}

export async function getMintDetail(host: string): Promise<MintDetail | null> {
  const row = await mintByHost(host);
  if (!row) return null;

  const now = Math.floor(Date.now() / 1000);
  // One round trip's worth of latency instead of six, which is the difference between
  // a local file and a Postgres server on another host.
  const [agg, mean, ratingDistribution, reviews, uptime, probes] = await Promise.all([
    aggregates(row.url),
    priorMean(),
    distribution(row.url),
    reviews90d(row.url),
    uptime30d(row.url),
    recentProbes(row.url),
  ]);

  const item = toListItem(row, agg.get(row.url), mean, now);
  const info = parseInfo(row.info_json);

  let nuts: string[] = [];
  if (row.nuts_json) {
    try {
      nuts = JSON.parse(row.nuts_json) as string[];
    } catch {
      nuts = [];
    }
  }
  if (nuts.length === 0 && info) nuts = parseNuts(info.nuts);

  /*
   * Type-specific columns are spread across the payload rather than nested under a key.
   *
   * That is what keeps a Cashu detail byte for byte what it was: `ecosystem_json` is
   * null for a mint, so nothing is added and no consumer sees a new empty object to
   * handle. A federation gets `federation_id`, `invite_codes`, `modules`, `network` and
   * the rest at the top level, where the page reads them beside `status` and `name`
   * without unwrapping anything.
   */
  const ecosystem = parseEcosystem(row);

  return {
    ...item,
    ...(ecosystem ?? {}),
    description: row.description,
    pubkey: row.pubkey,
    info,
    nuts,
    first_seen: row.first_seen,
    last_probe: row.last_probe,
    updated_at: row.updated_at,
    rating_distribution: ratingDistribution,
    reviews_90d: reviews,
    uptime_30d: uptime,
    probes_recent: probes,
  };
}

let statsCache: { at: number; value: Stats } | null = null;
const STATS_TTL_S = 60;

export async function getStats(): Promise<Stats> {
  const now = Math.floor(Date.now() / 1000);
  if (statsCache && now - statsCache.at < STATS_TTL_S) return statsCache.value;

  const db = await getDb();
  /*
   * The four `mints_*` fields are scoped to `type = 'cashu'`, which is what they always
   * counted and what every consumer of them still means: the pulse ticker's "mints
   * indexed", the /mints page description, the home page. Letting federations quietly
   * inflate a number three pages print in a sentence would be a worse kind of breakage
   * than a missing field, because nothing would fail — the sentences would just stop
   * being true.
   *
   * COUNT(*) FILTER, not SUM(status = 'online'): Postgres has no implicit cast from
   * boolean to integer, so the SQLite spelling is a type error there.
   */
  const [counts, federations, lnurl, lnurlFunding, reviews, fedimintReviews, lnurlReviews] =
    await Promise.all([
    db.get<{ total: number; online: number; offline: number; degraded: number }>(
      `SELECT
         COUNT(*)                                      AS total,
         COUNT(*) FILTER (WHERE status = 'online')     AS online,
         COUNT(*) FILTER (WHERE status = 'offline')    AS offline,
         COUNT(*) FILTER (WHERE status = 'degraded')   AS degraded
       FROM mints WHERE type = 'cashu'`,
    ),
    db.get<{ total: number; online: number; offline: number; announced: number }>(
      `SELECT
         COUNT(*)                                      AS total,
         COUNT(*) FILTER (WHERE status = 'online')     AS online,
         COUNT(*) FILTER (WHERE status = 'offline')    AS offline,
         COUNT(*) FILTER (WHERE status = 'announced')  AS announced
       FROM mints WHERE type = 'fedimint'`,
    ),
    db.get<{ total: number; online: number; offline: number }>(
      `SELECT
         COUNT(*)                                      AS total,
         COUNT(*) FILTER (WHERE status = 'online')     AS online,
         COUNT(*) FILTER (WHERE status = 'offline')    AS offline
       FROM mints WHERE type = 'lnurl'`,
    ),
    /*
     * The degraded-funding count is read in JavaScript rather than in SQL, because the
     * flag lives inside `ecosystem_json` and neither a `LIKE '%"funding_available":false%'`
     * (which depends on how the two drivers happen to serialise) nor a JSON operator
     * (which SQLite and Postgres spell differently) is portable. There are a handful of
     * these rows, the whole result is memoised for a minute, and a correct answer on
     * both backends is worth one small scan.
     */
    db.all<{ ecosystem_json: string | null }>(
      `SELECT ecosystem_json FROM mints WHERE type = 'lnurl' AND status = 'online'`,
    ),
    db.get<{ n: number; last: number | null }>(
      `WITH latest AS (${LATEST_REVIEWS}) SELECT COUNT(*) AS n, MAX(created_at) AS last FROM latest`,
    ),
    db.get<{ n: number }>(
      `WITH latest AS (${LATEST_REVIEWS})
       SELECT COUNT(*) AS n FROM latest
       WHERE mint_url IN (SELECT url FROM mints WHERE type = 'fedimint')`,
    ),
    db.get<{ n: number }>(
      `WITH latest AS (${LATEST_REVIEWS})
       SELECT COUNT(*) AS n FROM latest
       WHERE mint_url IN (SELECT url FROM mints WHERE type = 'lnurl')`,
    ),
    ]);

  let lnurlDegradedFunding = 0;
  for (const row of lnurlFunding) {
    const fields = parseEcosystem<LnurlFields>(row);
    if (fields?.funding_available === false) lnurlDegradedFunding++;
  }

  const cashuTotal = counts?.total ?? 0;

  const value: Stats = {
    mints_total: cashuTotal,
    mints_online: counts?.online ?? 0,
    mints_offline: counts?.offline ?? 0,
    mints_degraded: counts?.degraded ?? 0,
    reviews_total: reviews?.n ?? 0,
    last_review_at: reviews?.last ?? null,
    updated_at: now,
    cashu_total: cashuTotal,
    fedimint_total: federations?.total ?? 0,
    fedimint_online: federations?.online ?? 0,
    fedimint_offline: federations?.offline ?? 0,
    fedimint_announced: federations?.announced ?? 0,
    fedimint_reviews: fedimintReviews?.n ?? 0,
    lnurl_total: lnurl?.total ?? 0,
    lnurl_online: lnurl?.online ?? 0,
    lnurl_offline: lnurl?.offline ?? 0,
    lnurl_degraded_funding: lnurlDegradedFunding,
    lnurl_reviews: lnurlReviews?.n ?? 0,
  };

  statsCache = { at: now, value };
  return value;
}

/** Drop the in-process stats cache. For tests that mutate the database underneath it. */
export function resetStatsCache(): void {
  statsCache = null;
}

/**
 * Health bypasses the stats cache: it is the endpoint you page on.
 *
 * Three things can degrade it, and they are three different failures:
 *
 *   probeStale         nothing has checked a mint in three intervals
 *   !discoveryOk       the last discovery cycle threw
 *   report.starved     the last backfill read less than BACKFILL_MIN_EVENTS
 *
 * The third is the one added after the postmortem, and it is the only one that would
 * have caught a year of the index sitting at eight mints: the cycles were completing,
 * `ok` was true, the probes were fresh, and the relay list simply did not contain the
 * relay holding the archive. "Ran without throwing" is not the same claim as "read
 * anything", and only the second one is worth a green light.
 *
 * A deployment with an empty database reports degraded until its first backfill lands,
 * because until then nothing has confirmed the relay set reads anything at all. That is
 * intended: it holds `cashumints-web.service` at its health gate rather than letting it
 * publish a site built from nothing.
 */
export async function getHealth(): Promise<Health> {
  const now = Math.floor(Date.now() / 1000);
  const db = await getDb();

  const [lastProbe, lastDiscovery, discoveryOkRaw, tracked, report] = await Promise.all([
    getStateNumber('last_probe_at'),
    getStateNumber('last_discovery_at'),
    getState('last_discovery_ok'),
    db.get<{ n: number }>('SELECT COUNT(*) AS n FROM mints'),
    lastDiscoveryReport(),
  ]);

  const discoveryOk = discoveryOkRaw !== '0';
  const staleAfter = config.probeIntervalMin * 60 * 3;
  const probeStale = lastProbe === null || now - lastProbe > staleAfter;
  // No report at all is starvation by default: see the note above.
  const starved = report?.starved ?? true;

  return {
    status: probeStale || !discoveryOk || starved ? 'degraded' : 'ok',
    uptime_s: now - startedAt,
    last_probe_at: lastProbe,
    last_discovery_at: lastDiscovery,
    mints_tracked: tracked?.n ?? 0,
    updated_at: now,
    discovery_relays: report?.relays ?? [],
    last_discovery_events: report?.events ?? null,
    last_discovery_mode: report?.mode ?? null,
    discovery_starved: starved,
    backfill_min_events: config.backfillMinEvents,
  };
}