import { DateTime } from "luxon";
import type { Method } from "@prisma/client";
import db from "../db.server";
import { getAvailability, type AvailableSlot } from "./scheduling.server";
import {
  findEligibleLocationsForDelivery,
  meetsDeliveryDensity,
  excludeLocationsWithoutStock,
  type AdminGraphQLClient,
} from "./zones.server";
import { resolveRate } from "./rates.server";
import { formatPriceLabel } from "../lib/currency";
import { resolveProductRuleConstraints, productRefsFromCartLines, type ProductRef } from "./product-rules.server";
import { resolvePickupLocations, type PickupLocationDto } from "./pickup-locations.server";

// The single availability resolver every surface calls — storefront widget
// (via apps.scheduling.availability.tsx, app-proxy auth), POS (via
// pos.scheduling.availability.tsx, session-token auth), and eventually
// Checkout UI. CLAUDE.md's non-negotiable: "One Scheduling Service + one
// capacity pool feeds every surface... behavior must never diverge between
// channels" — this is that single point, not just a shared convention each
// route re-implements.

const MAX_DAYS = 60;
const DEFAULT_DAYS = 14;

export interface AvailabilityRequestParams {
  method: Method;
  locationId?: string;
  postalCode?: string;
  address?: string;
  days?: number;
  /**
   * Cart contents for ProductRule scoping (PRODUCT_STRATEGY.md §2). `cartLines`
   * (vendor/productType, straight from the storefront's /cart.js — no extra
   * round-trip) covers vendor/type-scoped rules for free; `productRefs` (already
   * resolved via the Admin API by the caller — see product-rules.server.ts's
   * resolveProductRefs) additionally covers product/collection/tag-scoped rules.
   * Both are optional so existing callers (POS, pre-cart availability checks)
   * keep working unchanged.
   */
  cartLines?: Array<{ vendor?: string; productType?: string }>;
  productRefs?: ProductRef[];
  /**
   * Cart variant GIDs + an Admin API client — when both are supplied, any
   * candidate location that stocks none of them is dropped from selection
   * (study §3.4 "product-inventory-based location choice"). Only the
   * app-proxy surface has an Admin client; POS/checkout pass neither and
   * skip the check.
   */
  productVariantGids?: string[];
  admin?: AdminGraphQLClient;
}

export interface AvailabilityResult {
  locationId: string | null;
  locationName?: string;
  locationLat?: number | null;
  locationLng?: number | null;
  timezone?: string;
  method: Method;
  dates: Record<string, AvailableSlot[]>;
  zoneId: string | null;
  distanceKm: number | null;
  rate: { name: string; priceCents: number; label: string } | null;
  /**
   * All eligible pickup points, for the multi-pin selector (study §3.4).
   * Present only for `method === "PICKUP"`. `dates` above is for whichever
   * one is currently active (`locationId` / `locationName`); the caller
   * re-requests with `locationId` when the shopper picks a different pin.
   */
  pickupLocations?: PickupLocationDto[];
  error?: string;
}

function toIsoDate(date: Date): string {
  return date.toISOString().slice(0, 10);
}

/** getAvailability's consumed-capacity map key — must match scheduling.server.ts's slotKey() exactly. */
function slotKey(date: string, startMin: number): string {
  return `${date}|${startMin}`;
}

export async function resolveAvailabilityRequest(
  shopDomain: string,
  params: AvailabilityRequestParams,
): Promise<AvailabilityResult> {
  const { method, locationId: locationIdParam, postalCode, address } = params;
  const days = params.days && params.days > 0 ? Math.min(params.days, MAX_DAYS) : DEFAULT_DAYS;

  // ProductRule scoping (PRODUCT_STRATEGY.md §2): resolve before touching
  // locations, since an allowedLocationIds restriction narrows which
  // locations are even eligible to be picked, not just which one filters
  // through afterward.
  const productRules = await db.productRule.findMany({ where: { shopDomain, active: true } });
  const cartProductRefs = [...(params.productRefs ?? []), ...productRefsFromCartLines(params.cartLines ?? [])];
  const ruleConstraints = resolveProductRuleConstraints(productRules, cartProductRefs);

  if (ruleConstraints.allowedMethods != null && !ruleConstraints.allowedMethods.includes(method)) {
    return {
      locationId: null,
      method,
      dates: {},
      zoneId: null,
      distanceKm: null,
      rate: null,
      error: "One or more items in your cart aren't available with this fulfillment method.",
    };
  }

  let location: Awaited<ReturnType<typeof db.location.findFirst>> = null;
  let zoneId: string | null = null;
  let distanceKm: number | null = null;
  let pickupLocations: PickupLocationDto[] | undefined;

  // Inventory-based location exclusion (study §3.4): only runs on the
  // app-proxy surface, which is the only one that hands us an Admin client
  // plus the cart's variant GIDs. `inStock` is the identity set otherwise.
  const stockCheckEnabled = Boolean(params.admin) && (params.productVariantGids?.length ?? 0) > 0;
  const inStock = async (locationIds: string[]): Promise<Set<string>> =>
    stockCheckEnabled
      ? excludeLocationsWithoutStock(params.admin!, locationIds, params.productVariantGids!)
      : new Set(locationIds);

  // Delivery-zone auto-assignment (IMPLEMENTATION_PLAN.md Phase 5): route to
  // the nearest eligible, density-qualified zone for the shopper's address.
  // Falls through to the plain location lookup below for PICKUP/SHIPPING,
  // or when no address was supplied yet, so the picker can still show
  // something before that input exists.
  if (method === "LOCAL_DELIVERY" && (postalCode || address)) {
    const matches = await findEligibleLocationsForDelivery(shopDomain, { postalCode, address });
    const zones = matches.length
      ? await db.zone.findMany({ where: { id: { in: matches.map((m) => m.zoneId) } } })
      : [];
    const zoneById = new Map(zones.map((z) => [z.id, z]));
    const stockedLocationIds = await inStock([...new Set(matches.map((m) => m.locationId))]);

    for (const match of matches) {
      if (locationIdParam && match.locationId !== locationIdParam) continue;
      if (ruleConstraints.allowedLocationIds != null && !ruleConstraints.allowedLocationIds.includes(match.locationId)) continue;
      if (!stockedLocationIds.has(match.locationId)) continue; // location doesn't stock the cart
      const zone = zoneById.get(match.zoneId);
      if (!zone) continue;
      // eslint-disable-next-line no-await-in-loop -- checked in nearest-first order; stop at the first that qualifies
      if (!(await meetsDeliveryDensity(shopDomain, zone))) continue;

      zoneId = match.zoneId;
      distanceKm = match.distanceKm;
      location = await db.location.findFirst({ where: { id: match.locationId, shopDomain, active: true } });
      break;
    }

    if (!location) {
      return {
        locationId: null,
        method,
        dates: {},
        zoneId: null,
        distanceKm: null,
        rate: null,
        error: "This address is outside our delivery area right now.",
      };
    }
  } else if (method === "PICKUP") {
    // Multi-pin pickup (study §3.4): resolve every eligible pickup point so
    // the widget/checkout can offer a chooser, then narrow the date picker
    // to the shopper's pick (or the first eligible one).
    pickupLocations = await resolvePickupLocations(shopDomain, {
      allowedLocationIds: ruleConstraints.allowedLocationIds,
      admin: params.admin,
      productVariantGids: params.productVariantGids,
    });
    const activeId =
      locationIdParam && pickupLocations.some((l) => l.id === locationIdParam)
        ? locationIdParam
        : pickupLocations[0]?.id;
    location = activeId ? await db.location.findFirst({ where: { id: activeId, shopDomain, active: true } }) : null;
  } else {
    const locationWhere =
      ruleConstraints.allowedLocationIds != null ? { id: { in: ruleConstraints.allowedLocationIds } } : {};
    const candidates = await db.location.findMany({
      where: locationIdParam
        ? { id: locationIdParam, shopDomain, active: true, ...locationWhere }
        : { shopDomain, active: true, ...locationWhere },
      orderBy: { createdAt: "asc" },
    });
    const stocked = await inStock(candidates.map((c) => c.id));
    location = candidates.find((c) => stocked.has(c.id)) ?? null;
  }

  if (!location) {
    return {
      locationId: null,
      method,
      dates: {},
      zoneId: null,
      distanceKm: null,
      rate: null,
      pickupLocations: method === "PICKUP" ? [] : undefined,
      error:
        ruleConstraints.allowedLocationIds != null
          ? "One or more items in your cart aren't available at this location."
          : stockCheckEnabled
            ? "No location currently stocks every item in your cart."
            : method === "PICKUP"
              ? "No pickup location is available right now."
              : "No active location configured",
    };
  }

  const now = DateTime.now().setZone(location.timezone);
  const startDate = now.toISODate()!;
  const endDate = now.plus({ days }).toISODate()!;
  const rangeStart = DateTime.fromISO(startDate, { zone: "utc" }).toJSDate();
  const rangeEnd = DateTime.fromISO(endDate, { zone: "utc" }).toJSDate();
  // Bookings are keyed by exact instant; widen the window by a day on each
  // side so a slot near midnight UTC-offset boundaries isn't miscounted.
  const bookingRangeStart = DateTime.fromISO(startDate, { zone: "utc" }).minus({ days: 1 }).toJSDate();
  const bookingRangeEnd = DateTime.fromISO(endDate, { zone: "utc" }).plus({ days: 1 }).toJSDate();

  const [slotTemplates, overrides, blackouts, bookings, rates] = await Promise.all([
    db.slotTemplate.findMany({ where: { shopDomain, locationId: location.id, method } }),
    db.slotOverride.findMany({
      where: { shopDomain, locationId: location.id, method, date: { gte: rangeStart, lte: rangeEnd } },
    }),
    db.blackoutDate.findMany({
      where: {
        shopDomain,
        date: { gte: rangeStart, lte: rangeEnd },
        AND: [{ OR: [{ locationId: location.id }, { locationId: null }] }, { OR: [{ method }, { method: null }] }],
      },
    }),
    db.booking.findMany({
      where: {
        shopDomain,
        locationId: location.id,
        // Per-day cap (study §3.3) counts every method at the location, so the
        // daily tally can't be filtered to one method — the per-slot tally
        // below still keys by exact start instant, which is method-specific
        // enough on its own.
        status: { in: ["confirmed", "fulfilled"] },
        slotStart: { gte: bookingRangeStart, lte: bookingRangeEnd },
      },
      select: { slotStart: true, method: true },
    }),
    db.rate.findMany({ where: { shopDomain, method } }),
  ]);

  const consumed = new Map<string, number>();
  const consumedPerDate = new Map<string, number>();
  for (const booking of bookings) {
    const local = DateTime.fromJSDate(booking.slotStart, { zone: "utc" }).setZone(location.timezone);
    const isoDate = local.toISODate()!;
    consumedPerDate.set(isoDate, (consumedPerDate.get(isoDate) ?? 0) + 1);
    if (booking.method !== method) continue; // per-slot capacity is for this method's picker only
    const key = slotKey(isoDate, local.hour * 60 + local.minute);
    consumed.set(key, (consumed.get(key) ?? 0) + 1);
  }

  const availability = getAvailability({
    timezone: location.timezone,
    dateRange: { startDate, endDate },
    slotTemplates: slotTemplates.map((t) => ({
      weekday: t.weekday,
      startMin: t.startMin,
      endMin: t.endMin,
      capacity: t.capacity,
      cutoffMin: t.cutoffMin,
      // ProductRule-driven prep-time floor (per-product/vendor/collection lead
      // time and cart-content-based slot blocking, PRODUCT_STRATEGY.md §2)
      // stacks with the slot's own leadTimeMin — getAvailability already takes
      // the max of leadTimeMin/cutoffMin, so folding it in here keeps that
      // function's signature and purity guarantee untouched.
      leadTimeMin: Math.max(t.leadTimeMin, ruleConstraints.minLeadTimeMin),
      transitMinDays: t.transitMinDays,
      transitMaxDays: t.transitMaxDays,
    })),
    overrides: overrides.map((o) => ({
      date: toIsoDate(o.date),
      closed: o.closed,
      startMin: o.startMin,
      endMin: o.endMin,
      capacity: o.capacity,
    })),
    blackoutDates: blackouts.map((b) => ({ date: toIsoDate(b.date) })),
    now,
    consumed,
    dailyCap: location.dailyOrderCap,
    consumedPerDate,
    blockedStartMins: ruleConstraints.blockedStartMins,
  });

  const matchedRate = resolveRate(rates, { method, zoneId: zoneId ?? undefined, distanceKm: distanceKm ?? undefined });

  return {
    locationId: location.id,
    locationName: location.name,
    locationLat: location.lat,
    locationLng: location.lng,
    timezone: location.timezone,
    method,
    dates: availability,
    zoneId,
    distanceKm,
    rate: matchedRate
      ? { name: matchedRate.name, priceCents: matchedRate.priceCents, label: formatPriceLabel(matchedRate.priceCents) }
      : null,
    pickupLocations,
  };
}