import {
  and,
  asc,
  desc,
  eq,
  gte,
  lte,
  ledgerEvents,
  sessions,
  subscriptions,
  tariffVersions,
  tariffs,
  type Db,
} from "@parking/db";
import { siteTz } from "./subscription-window.js";

// Admin reporting — LEDGER-FIRST aggregation (decision 2026-06-22). The numbers an
// admin sees on the Reports page are summed from the SIGNED, hash-chained
// ledger_events (vehicle_entry/exit + payment), the same source the shift Z-report
// reconciles against — so a chart total always ties out to the drawer. Only the
// duration/occupancy view leans on the derived `sessions` cache, where the ledger is
// awkward (you'd have to pair every entry with its exit by hand); that's flagged as a
// cache, not the financial truth. See wiki/concepts/reports.md, event-streams-split.md.
//
// All bucketing is in the SITE TIMEZONE (siteConfig.timezone) — a "day" is a local
// calendar day, not a UTC one, so a 01:00-local payment lands on the right date and the
// peak-hour chart reads in wall-clock. Pure date math on the stored ISO strings; no
// floats (money is integer minor units throughout).

export type Bucket = "hour" | "day" | "month";

export interface ReportQuery {
  /** Inclusive lower bound (ISO instant). */
  readonly from: string;
  /** Exclusive upper bound (ISO instant). */
  readonly to: string;
  /** Time grain for the series. Default "day". */
  readonly bucket: Bucket;
}

/** One point in a time series, keyed by its local-time bucket label (e.g. "2026-06-22"
 *  for a day, "2026-06-22 14" for an hour). */
export interface SeriesPoint {
  readonly bucket: string;
  readonly entries: number;
  readonly exits: number;
  /** Net transient revenue collected in the bucket (minor units), all tenders. */
  readonly revenueMinor: number;
  /** Payment COUNT in the bucket (transactions, not amount). */
  readonly payments: number;
}

export interface ReportTotals {
  readonly entries: number;
  readonly exits: number;
  readonly payments: number;
  readonly revenueMinor: number;
  readonly cashMinor: number;
  readonly cardMinor: number;
  /** Revenue split by what was sold. ticket = transient parking; subscriptionSales =
   *  new/renewed subscriptions; subscriptionWindow = out-of-window tariff-bridge charges. */
  readonly ticketMinor: number;
  readonly subscriptionSalesMinor: number;
  readonly subscriptionWindowMinor: number;
  /** Closed transient sessions in range + their parked-minutes stats (from the cache). */
  readonly closedSessions: number;
  readonly totalParkedMinutes: number;
  readonly avgParkedMinutes: number;
  readonly medianParkedMinutes: number;
}

export interface SubscriptionStats {
  readonly active: number;
  readonly suspended: number;
  readonly revoked: number;
  /** Active subscriptions whose window covers `to` (the report's "now"). */
  readonly currentlyValid: number;
  /** Cars covered by currently-valid subscriptions (Σ quantity). */
  readonly coveredCars: number;
}

export interface ReportSummary {
  readonly from: string;
  readonly to: string;
  readonly bucket: Bucket;
  readonly tz: string;
  readonly currency: string | null;
  readonly totals: ReportTotals;
  readonly series: SeriesPoint[];
  /** Entries by local hour-of-day (0–23), summed across the range — the peak-hour view. */
  readonly entriesByHour: number[];
  readonly subscriptions: SubscriptionStats;
}

/** Local wall-clock parts of an ISO instant in a given IANA tz. Reuses Intl (no dep). */
function localParts(iso: string, tz: string): { y: number; mo: number; d: number; h: number } {
  const fmt = new Intl.DateTimeFormat("en-CA", {
    timeZone: tz,
    year: "numeric",
    month: "2-digit",
    day: "2-digit",
    hour: "2-digit",
    hourCycle: "h23",
  });
  const parts = Object.fromEntries(fmt.formatToParts(new Date(iso)).map((p) => [p.type, p.value]));
  return {
    y: Number(parts.year),
    mo: Number(parts.month),
    d: Number(parts.day),
    h: Number(parts.hour),
  };
}

/** Bucket label for an instant at the chosen grain, in local time. Sorts lexically. */
function bucketLabel(iso: string, tz: string, bucket: Bucket): string {
  const p = localParts(iso, tz);
  const mo = String(p.mo).padStart(2, "0");
  const d = String(p.d).padStart(2, "0");
  const h = String(p.h).padStart(2, "0");
  if (bucket === "month") return `${p.y}-${mo}`;
  if (bucket === "hour") return `${p.y}-${mo}-${d} ${h}`;
  return `${p.y}-${mo}-${d}`;
}

interface PaymentPayload {
  amountMinor?: number;
  currency?: string;
  tender?: "cash" | "card";
  subscriptionSale?: boolean;
  subscriptionWindowCharge?: boolean;
}

function median(sorted: number[]): number {
  if (sorted.length === 0) return 0;
  const mid = Math.floor(sorted.length / 2);
  const hi = sorted[mid] ?? 0;
  if (sorted.length % 2) return hi;
  const lo = sorted[mid - 1] ?? 0;
  return Math.round((lo + hi) / 2);
}

/**
 * Build the admin report summary for [from, to) at the chosen grain. Entry/exit counts
 * and money are summed from the signed ledger; duration stats from the closed sessions
 * in range; subscription counts from the subscriptions table as of `to`.
 */
export function reportSummary(db: Db, q: ReportQuery): ReportSummary {
  const tz = siteTz(db);

  // --- Ledger: entry/exit/payment in range, oldest-first so the series builds in order.
  const rows = db
    .select()
    .from(ledgerEvents)
    .where(and(gte(ledgerEvents.occurredAt, q.from), lte(ledgerEvents.occurredAt, q.to)))
    .orderBy(asc(ledgerEvents.index))
    .all();

  // Currency for display: money everywhere is { minorUnits, currency }; payments carry
  // the currency they were taken in, so take it from a payment in range (then fall back
  // to the active tariff version). Reports never mix currencies (single-currency site).
  let currency: string | null = null;

  const seriesMap = new Map<string, SeriesPoint>();
  const entriesByHour = new Array<number>(24).fill(0);
  const totals = {
    entries: 0,
    exits: 0,
    payments: 0,
    revenueMinor: 0,
    cashMinor: 0,
    cardMinor: 0,
    ticketMinor: 0,
    subscriptionSalesMinor: 0,
    subscriptionWindowMinor: 0,
  };

  function point(label: string): SeriesPoint {
    let p = seriesMap.get(label);
    if (!p) {
      p = { bucket: label, entries: 0, exits: 0, revenueMinor: 0, payments: 0 };
      seriesMap.set(label, p);
    }
    return p;
  }

  // Pre-pass: identities cancelled by a `void` in range. A voided entry was a wrongly-
  // printed ticket (no car entered), so it must NOT inflate the "entries" stat. (The void's
  // entry is normally in the same window; this skips it when both are in range.)
  const voided = new Set<string>();
  for (const row of rows) if (row.type === "void" && row.identity) voided.add(row.identity);

  for (const row of rows) {
    const label = bucketLabel(row.occurredAt, tz, q.bucket);
    const p = point(label) as { -readonly [K in keyof SeriesPoint]: SeriesPoint[K] };
    if (row.type === "vehicle_entry") {
      if (row.identity && voided.has(row.identity)) continue; // cancelled — not a real entry
      totals.entries++;
      p.entries++;
      const h = localParts(row.occurredAt, tz).h;
      entriesByHour[h] = (entriesByHour[h] ?? 0) + 1;
    } else if (row.type === "vehicle_exit") {
      totals.exits++;
      p.exits++;
    } else if (row.type === "payment") {
      const pl = (row.payload ?? {}) as PaymentPayload;
      const amt = typeof pl.amountMinor === "number" ? pl.amountMinor : 0;
      if (!currency && typeof pl.currency === "string") currency = pl.currency;
      totals.payments++;
      totals.revenueMinor += amt;
      p.payments++;
      p.revenueMinor += amt;
      if (pl.tender === "card") totals.cardMinor += amt;
      else totals.cashMinor += amt;
      // Revenue split mirrors the shift Z-report: subscription sale / window charge /
      // (the rest is) transient ticket revenue.
      if (pl.subscriptionSale === true) totals.subscriptionSalesMinor += amt;
      else if (pl.subscriptionWindowCharge === true) totals.subscriptionWindowMinor += amt;
      else totals.ticketMinor += amt;
    }
  }

  const series = [...seriesMap.values()].sort((a, b) => a.bucket.localeCompare(b.bucket));

  // No payment in range? Fall back to the site tariff's latest version currency, so a
  // zero-revenue range still labels its money column.
  if (!currency) {
    const tariff = db.select().from(tariffs).where(eq(tariffs.scope, "site")).get();
    if (tariff) {
      const tv = db
        .select()
        .from(tariffVersions)
        .where(eq(tariffVersions.tariffId, tariff.id))
        .orderBy(desc(tariffVersions.effectiveFrom))
        .get();
      currency = tv?.currency ?? null;
    }
  }

  // --- Duration: closed transient sessions whose EXIT fell in range (the cache; flagged).
  const closed = db
    .select()
    .from(sessions)
    .where(and(gte(sessions.exitedAt, q.from), lte(sessions.exitedAt, q.to)))
    .all();
  const durations: number[] = [];
  for (const s of closed) {
    if (!s.enteredAt || !s.exitedAt) continue;
    const mins = Math.max(0, Math.round((Date.parse(s.exitedAt) - Date.parse(s.enteredAt)) / 60000));
    durations.push(mins);
  }
  durations.sort((a, b) => a - b);
  const totalParkedMinutes = durations.reduce((a, b) => a + b, 0);

  // --- Subscriptions: status counts + currently-valid (window covers `to`).
  const subs = db.select().from(subscriptions).all();
  const subStats = { active: 0, suspended: 0, revoked: 0, currentlyValid: 0, coveredCars: 0 };
  for (const s of subs) {
    if (s.status === "active") subStats.active++;
    else if (s.status === "suspended") subStats.suspended++;
    else if (s.status === "revoked") subStats.revoked++;
    const validNow =
      s.status === "active" &&
      (!s.validFrom || s.validFrom <= q.to) &&
      (!s.validTo || s.validTo >= q.to);
    if (validNow) {
      subStats.currentlyValid++;
      subStats.coveredCars += s.quantity ?? 1;
    }
  }

  return {
    from: q.from,
    to: q.to,
    bucket: q.bucket,
    tz,
    currency,
    totals: {
      ...totals,
      closedSessions: durations.length,
      totalParkedMinutes,
      avgParkedMinutes: durations.length ? Math.round(totalParkedMinutes / durations.length) : 0,
      medianParkedMinutes: median(durations),
    },
    series,
    entriesByHour,
    subscriptions: subStats,
  };
}