import { DateTime } from "luxon";
import type { Method } from "@prisma/client";
import db from "../db.server";
import { getAvailability } from "./scheduling.server";
import type { AdminGraphQLClient } from "./zones.server";

// Denormalized capacity + enforcement snapshot that the Cart/Checkout
// Validation Function reads from a shop metafield. Shopify Functions can't
// query this app's database, so anything the Function needs to enforce
// "the slot has since become invalid" (study §5.2) or "only enforce for
// tagged products" (study §3.5) has to be pushed into a metafield it can
// read directly. This module builds and writes that metafield; it's
// refreshed whenever bookings or scheduling config change (order webhooks,
// slot/blackout admin edits) and on a periodic worker sweep so the rolling
// horizon keeps advancing.

export const SNAPSHOT_NAMESPACE = "delivery_datetime";
export const SNAPSHOT_KEY = "checkout_snapshot";

const HORIZON_DAYS = 30;
const METHODS: Method[] = ["SHIPPING", "LOCAL_DELIVERY", "PICKUP"];

// A fixed instant far in the past, so getAvailability's cutoff/lead-time
// filters never hide a slot here — the snapshot captures *capacity and
// calendar* state (blackout, closed override, daily cap, bookings), not the
// time-of-day cutoff, which is inherently second-sensitive and already
// covered by the hold TTL and the widget.
const EPOCH = DateTime.fromISO("1970-01-01T00:00:00Z");

export interface CheckoutSnapshot {
  version: 1;
  generatedAt: string;
  /** Slots whose date is after this (UTC calendar date) aren't covered — the Function stays permissive past the horizon. */
  horizonDate: string;
  enforcement: { mode: "all" | "tagged" | "off" };
  /** Product GIDs that trigger enforcement when mode = "tagged". Ignored otherwise. */
  schedulableProductIds: string[];
  /** `${locationId}|${METHOD}|${YYYY-MM-DD}|${startMin}` -> remaining capacity. */
  slots: Record<string, number>;
  /** `${locationId}|${METHOD}|${YYYY-MM-DD}` -> true when that day has no bookable slot (blackout / closed / daily cap / no template). */
  closedDates: Record<string, true>;
}

export function slotSnapshotKey(locationId: string, method: Method, date: string, startMin: number): string {
  return `${locationId}|${method}|${date}|${startMin}`;
}

export function closedDateKey(locationId: string, method: Method, date: string): string {
  return `${locationId}|${method}|${date}`;
}

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

/**
 * Builds the capacity/calendar half of the snapshot from the database.
 * Enforcement config and tagged-product resolution are layered on by
 * writeCheckoutSnapshot (they need the Admin API / are cheap to add there).
 */
export async function buildCheckoutSnapshot(shopDomain: string): Promise<Omit<CheckoutSnapshot, "enforcement" | "schedulableProductIds">> {
  const nowUtc = DateTime.utc();
  const startDate = nowUtc.toISODate()!;
  const endDate = nowUtc.plus({ days: HORIZON_DAYS }).toISODate()!;
  const rangeStart = DateTime.fromISO(startDate, { zone: "utc" }).minus({ days: 1 }).toJSDate();
  const rangeEnd = DateTime.fromISO(endDate, { zone: "utc" }).plus({ days: 1 }).toJSDate();

  const locations = await db.location.findMany({ where: { shopDomain, active: true } });

  const slots: Record<string, number> = {};
  const closedDates: Record<string, true> = {};

  for (const location of locations) {
    const [templates, overrides, blackouts, bookings] = await Promise.all([
      db.slotTemplate.findMany({ where: { shopDomain, locationId: location.id } }),
      db.slotOverride.findMany({
        where: { shopDomain, locationId: location.id, date: { gte: rangeStart, lte: rangeEnd } },
      }),
      db.blackoutDate.findMany({
        where: { shopDomain, date: { gte: rangeStart, lte: rangeEnd }, OR: [{ locationId: location.id }, { locationId: null }] },
      }),
      db.booking.findMany({
        where: {
          shopDomain,
          locationId: location.id,
          status: { in: ["confirmed", "fulfilled"] },
          slotStart: { gte: rangeStart, lte: rangeEnd },
        },
        select: { slotStart: true, method: true },
      }),
    ]);

    // Per-date booking tally (all methods) drives the daily cap; per-slot
    // tally is method-specific.
    const consumedPerDate = new Map<string, number>();
    const consumedBySlot = new Map<string, Map<string, number>>(); // method -> (date|startMin -> n)
    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);
      const perMethod = consumedBySlot.get(booking.method) ?? new Map<string, number>();
      const key = `${isoDate}|${local.hour * 60 + local.minute}`;
      perMethod.set(key, (perMethod.get(key) ?? 0) + 1);
      consumedBySlot.set(booking.method, perMethod);
    }

    for (const method of METHODS) {
      const availability = getAvailability({
        timezone: location.timezone,
        dateRange: { startDate, endDate },
        slotTemplates: templates
          .filter((t) => t.method === method)
          .map((t) => ({
            weekday: t.weekday,
            startMin: t.startMin,
            endMin: t.endMin,
            capacity: t.capacity,
            cutoffMin: null, // deliberately ignored here — see EPOCH note
            leadTimeMin: 0,
            transitMinDays: t.transitMinDays,
            transitMaxDays: t.transitMaxDays,
          })),
        overrides: overrides
          .filter((o) => o.method === method)
          .map((o) => ({ date: toIsoDate(o.date), closed: o.closed, startMin: o.startMin, endMin: o.endMin, capacity: o.capacity })),
        blackoutDates: blackouts
          .filter((b) => b.method === null || b.method === method)
          .map((b) => ({ date: toIsoDate(b.date) })),
        now: EPOCH,
        consumed: consumedBySlot.get(method) ?? new Map(),
        dailyCap: location.dailyOrderCap,
        consumedPerDate,
      });

      // Walk every calendar day in the horizon: present -> record each slot's
      // remaining capacity; absent -> the day is closed for this method.
      let cursor = DateTime.fromISO(startDate, { zone: "utc" });
      const last = DateTime.fromISO(endDate, { zone: "utc" });
      for (; cursor <= last; cursor = cursor.plus({ days: 1 })) {
        const date = cursor.toISODate()!;
        const daySlots = availability[date];
        if (!daySlots || daySlots.length === 0) {
          closedDates[closedDateKey(location.id, method, date)] = true;
          continue;
        }
        for (const slot of daySlots) {
          slots[slotSnapshotKey(location.id, method, date, slot.startMin)] = slot.remainingCapacity;
        }
      }
    }
  }

  return { version: 1, generatedAt: nowUtc.toISO()!, horizonDate: endDate, slots, closedDates };
}

/** Resolves the Product GIDs carrying `tag` via the Admin API (paged). */
async function resolveTaggedProductIds(admin: AdminGraphQLClient, tag: string): Promise<string[]> {
  const ids: string[] = [];
  let cursor: string | null = null;
  // Cap the sweep so a huge catalog can't stall a webhook — 2000 tagged
  // products is already an extreme case for this feature.
  for (let page = 0; page < 8; page += 1) {
    const response: Response = await admin.graphql(
      `#graphql
      query TaggedProducts($query: String!, $after: String) {
        products(first: 250, query: $query, after: $after) {
          nodes { id }
          pageInfo { hasNextPage endCursor }
        }
      }`,
      { variables: { query: `tag:'${tag.replace(/'/g, "")}'`, after: cursor } },
    );
    const body = (await response.json()) as {
      data?: { products: { nodes: Array<{ id: string }>; pageInfo: { hasNextPage: boolean; endCursor: string | null } } };
    };
    const products = body.data?.products;
    if (!products) break;
    for (const node of products.nodes) ids.push(node.id);
    if (!products.pageInfo.hasNextPage) break;
    cursor = products.pageInfo.endCursor;
  }
  return ids;
}

/**
 * Builds the snapshot and writes it to the shop metafield the Validation
 * Function reads. Safe to call from a webhook handler — failures are logged,
 * not thrown, so a metafield hiccup never fails order processing.
 */
export async function writeCheckoutSnapshot(admin: AdminGraphQLClient, shopDomain: string): Promise<void> {
  try {
    const shop = await db.shop.findUnique({
      where: { shopDomain },
      select: { enforcementMode: true, enforcementTag: true },
    });
    const mode = (shop?.enforcementMode as CheckoutSnapshot["enforcement"]["mode"]) ?? "all";

    const base = await buildCheckoutSnapshot(shopDomain);

    const schedulableProductIds =
      mode === "tagged" && shop?.enforcementTag ? await resolveTaggedProductIds(admin, shop.enforcementTag) : [];

    const snapshot: CheckoutSnapshot = { ...base, enforcement: { mode }, schedulableProductIds };

    const response = await admin.graphql(
      `#graphql
      mutation WriteCheckoutSnapshot($metafields: [MetafieldsSetInput!]!) {
        metafieldsSet(metafields: $metafields) {
          userErrors { field message }
        }
      }`,
      {
        variables: {
          metafields: [
            {
              ownerId: await currentShopGid(admin),
              namespace: SNAPSHOT_NAMESPACE,
              key: SNAPSHOT_KEY,
              type: "json",
              value: JSON.stringify(snapshot),
            },
          ],
        },
      },
    );
    const body = (await response.json()) as { data?: { metafieldsSet?: { userErrors: Array<{ message: string }> } } };
    const errors = body.data?.metafieldsSet?.userErrors ?? [];
    if (errors.length > 0) {
      console.error("writeCheckoutSnapshot userErrors", errors);
    }
  } catch (error) {
    console.error("writeCheckoutSnapshot failed", error);
  }
}

async function currentShopGid(admin: AdminGraphQLClient): Promise<string> {
  const response = await admin.graphql(`#graphql
    query CurrentShopId { shop { id } }`);
  const body = (await response.json()) as { data?: { shop?: { id: string } } };
  return body.data?.shop?.id ?? "";
}