import { DateTime } from "luxon";
import type { Method } from "@prisma/client";

// Pure aggregation for the ops/dispatch dashboard (IMPLEMENTATION_PLAN.md
// Phase 6). No DB calls — the route loader fetches Bookings/SlotTemplates
// and passes plain data in here, per CLAUDE.md's "inject data" rule.

export interface BookingSummary {
  id: string;
  orderName: string | null;
  locationId: string;
  locationName: string;
  method: Method;
  slotStart: Date; // UTC instant
  slotEnd: Date;
  timezone: string; // the booking's location's timezone, for local-date bucketing
  status: string;
  totalPriceCents: number | null;
  customerEmail: string | null;
}

export interface CapacitySummary {
  locationId: string;
  method: Method;
  weekday: number;
  capacity: number;
}

export interface DailyLocationUtilization {
  date: string; // location-local ISO date
  locationId: string;
  locationName: string;
  method: Method;
  booked: number;
  capacity: number;
  utilizationPct: number; // 0-100, capped even if overbooked past capacity
}

function localDate(booking: BookingSummary): string {
  return DateTime.fromJSDate(booking.slotStart, { zone: "utc" }).setZone(booking.timezone).toISODate()!;
}

function localWeekday(booking: BookingSummary): number {
  return DateTime.fromJSDate(booking.slotStart, { zone: "utc" }).setZone(booking.timezone).weekday % 7;
}

/** Groups bookings by their own location's local calendar date — the basis for "bookings by day/slot/location". */
export function bucketByLocalDate(bookings: BookingSummary[]): Record<string, BookingSummary[]> {
  const buckets: Record<string, BookingSummary[]> = {};
  for (const booking of bookings) {
    const key = localDate(booking);
    (buckets[key] ??= []).push(booking);
  }
  for (const list of Object.values(buckets)) {
    list.sort((a, b) => a.slotStart.getTime() - b.slotStart.getTime());
  }
  return buckets;
}

/** Confirmed/fulfilled revenue, summed per method — cancelled/no_show bookings never counted. */
export function revenueByMethod(bookings: BookingSummary[]): Record<Method, number> {
  const totals: Record<Method, number> = { SHIPPING: 0, LOCAL_DELIVERY: 0, PICKUP: 0 };
  for (const booking of bookings) {
    if (booking.status !== "confirmed" && booking.status !== "fulfilled") continue;
    totals[booking.method] += booking.totalPriceCents ?? 0;
  }
  return totals;
}

/**
 * Capacity-utilization view: for each date/location/method that has at
 * least one booking, what fraction of that weekday's total slot capacity
 * (summed across every matching SlotTemplate) is booked. Dates/locations
 * with zero bookings are omitted — there's nothing to show a merchant for
 * an empty day.
 */
export function utilizationByDateLocation(
  bookings: BookingSummary[],
  capacities: CapacitySummary[],
): DailyLocationUtilization[] {
  const capacityByKey = new Map<string, number>();
  for (const c of capacities) {
    const key = `${c.locationId}|${c.method}|${c.weekday}`;
    capacityByKey.set(key, (capacityByKey.get(key) ?? 0) + c.capacity);
  }

  const bookedByKey = new Map<
    string,
    { date: string; locationId: string; locationName: string; method: Method; weekday: number; count: number }
  >();

  for (const booking of bookings) {
    if (booking.status === "cancelled") continue;
    const date = localDate(booking);
    const weekday = localWeekday(booking);
    const key = `${date}|${booking.locationId}|${booking.method}`;
    const existing = bookedByKey.get(key);
    if (existing) {
      existing.count += 1;
    } else {
      bookedByKey.set(key, {
        date,
        locationId: booking.locationId,
        locationName: booking.locationName,
        method: booking.method,
        weekday,
        count: 1,
      });
    }
  }

  return [...bookedByKey.values()]
    .map((entry) => {
      const capacity = capacityByKey.get(`${entry.locationId}|${entry.method}|${entry.weekday}`) ?? 0;
      const utilizationPct = capacity > 0 ? Math.min(100, Math.round((entry.count / capacity) * 100)) : 0;
      return {
        date: entry.date,
        locationId: entry.locationId,
        locationName: entry.locationName,
        method: entry.method,
        booked: entry.count,
        capacity,
        utilizationPct,
      };
    })
    .sort((a, b) => a.date.localeCompare(b.date) || a.locationName.localeCompare(b.locationName));
}

/** Nearest-first list of not-yet-fulfilled bookings, for the "upcoming fulfillment" panel. */
export function upcomingFulfillments(bookings: BookingSummary[], limit = 25): BookingSummary[] {
  return bookings
    .filter((b) => b.status === "confirmed")
    .sort((a, b) => a.slotStart.getTime() - b.slotStart.getTime())
    .slice(0, limit);
}

export function toCsvRow(values: Array<string | number>): string {
  return values
    .map((v) => {
      const s = String(v);
      return /[",\n]/.test(s) ? `"${s.replace(/"/g, '""')}"` : s;
    })
    .join(",");
}

export function bookingsToCsv(bookings: BookingSummary[]): string {
  const header = toCsvRow([
    "Order",
    "Date",
    "Time",
    "Method",
    "Location",
    "Status",
    "Customer email",
    "Total",
  ]);
  const rows = bookings.map((b) => {
    const local = DateTime.fromJSDate(b.slotStart, { zone: "utc" }).setZone(b.timezone);
    return toCsvRow([
      b.orderName ?? "",
      local.toISODate() ?? "",
      local.toFormat("h:mm a"),
      b.method,
      b.locationName,
      b.status,
      b.customerEmail ?? "",
      b.totalPriceCents != null ? (b.totalPriceCents / 100).toFixed(2) : "",
    ]);
  });
  return [header, ...rows].join("\n");
}