/**
 * TEMPORARY sample data for the dashboard charts.
 *
 * ── Why this exists ──────────────────────────────────────────────────────
 * A new merchant's reports come back empty or near-empty, and an empty axis
 * teaches nothing about what the panel is for. Until the platform has history
 * for a shop, each chart falls back to this sample and wears a "Sample data"
 * token so it can never be mistaken for the merchant's own numbers.
 *
 * ── Rules ────────────────────────────────────────────────────────────────
 * - Real data always wins — see `shared/mocks/withSample.ts`.
 * - The KPI row never uses this — a headline number must be real or absent.
 * - Values are deterministic (no Math.random) so SSR and hydration agree.
 *
 * ── Removing it ──────────────────────────────────────────────────────────
 * See `shared/mocks/withSample.ts` — one procedure for every mock folder.
 */

import type {
  ConversionReport,
  FootfallReport,
  ReportBucket,
} from '@/features/dashboard/types/reports';

const MONTHS = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];

/** A smooth, repeatable wave: weekly rhythm plus a gentle upward drift. */
function wave(i: number, base: number, amp: number): number {
  const weekly = Math.sin((i / 7) * Math.PI * 2 - 1.2);
  const drift = i * 0.012;
  const ripple = Math.sin(i * 1.7) * 0.18;
  return Math.max(0, Math.round(base * (1 + drift) + amp * (weekly + ripple)));
}

function dayBuckets(days: number): ReportBucket[] {
  // Fixed anchor so the labels are stable across renders and runtimes.
  const start = Date.UTC(2026, 7, 27);
  return Array.from({length: days}, (_, i) => {
    const d = new Date(start + i * 86_400_000);
    const visitors = wave(i, 140, 42);
    const newVisitors = Math.round(visitors * (0.38 + 0.06 * Math.sin(i / 3)));
    const purchases = Math.round(visitors * (0.22 + 0.04 * Math.sin(i / 4 + 1)));
    const revenue = purchases * (620 + Math.round(90 * Math.sin(i / 5)));
    return {
      label: `${MONTHS[d.getUTCMonth()]} ${String(d.getUTCDate()).padStart(2, '0')}`,
      visitors,
      newVisitors,
      returningVisitors: visitors - newVisitors,
      purchases,
      revenue,
      conversion: Number(((purchases / visitors) * 100).toFixed(1)),
    };
  });
}

function weekBuckets(days: ReportBucket[]): ReportBucket[] {
  const weeks: ReportBucket[] = [];
  for (let i = 0; i < days.length; i += 7) {
    const slice = days.slice(i, i + 7);
    const sum = (k: keyof ReportBucket) =>
      slice.reduce((acc, b) => acc + (b[k] as number), 0);
    const visitors = sum('visitors');
    const purchases = sum('purchases');
    weeks.push({
      label: `W${Math.floor(i / 7) + 1}`,
      visitors,
      newVisitors: sum('newVisitors'),
      returningVisitors: sum('returningVisitors'),
      purchases,
      revenue: sum('revenue'),
      conversion: Number(((purchases / visitors) * 100).toFixed(1)),
    });
  }
  return weeks;
}

const DAYS = dayBuckets(30);
const WEEKS = weekBuckets(DAYS);

function footfallFrom(buckets: ReportBucket[]): FootfallReport {
  const visits = buckets.reduce((a, b) => a + b.visitors, 0);
  const newVisitors = buckets.reduce((a, b) => a + b.newVisitors, 0);
  // Unique people < visit events: regulars come more than once.
  const total = Math.round(visits * 0.46);
  return {
    total,
    newVisitors,
    returningVisitors: Math.max(0, Math.round(total * 0.9) - newVisitors),
    visits,
    buckets,
    timezone: null,
    previousTotal: Math.round(total * 0.88),
  };
}

function conversionFrom(buckets: ReportBucket[], total: number): ConversionReport {
  const purchases = buckets.reduce((a, b) => a + b.purchases, 0);
  const revenue = buckets.reduce((a, b) => a + b.revenue, 0);
  return {
    purchases,
    revenue,
    conversionPct: Number(((purchases / total) * 100).toFixed(1)),
    basketSize: Math.round(revenue / purchases),
    buckets,
    timezone: null,
    previousPurchases: Math.round(purchases * 0.91),
    previousRevenue: Math.round(revenue * 0.86),
  };
}

export const MOCK_FOOTFALL_DAILY = footfallFrom(DAYS);
export const MOCK_FOOTFALL_WEEKLY = footfallFrom(WEEKS);
export const MOCK_CONVERSION_DAILY = conversionFrom(DAYS, MOCK_FOOTFALL_DAILY.total);
export const MOCK_CONVERSION_WEEKLY = conversionFrom(WEEKS, MOCK_FOOTFALL_WEEKLY.total);

/** True when the report carries at least one non-zero value for `key`. */
export function hasSignal(
  report: {buckets: ReportBucket[]} | undefined,
  key: keyof Omit<ReportBucket, 'label'>,
): boolean {
  return !!report && report.buckets.some((b) => b[key] > 0);
}

export {withSample} from '@/shared/mocks/withSample';