import db from "../db.server";
import { haversineDistanceKm, isPostalCodeListed, type Coordinates } from "../lib/geo";

// I/O orchestration around the pure math in lib/geo.ts. Geocoding results
// are cached permanently per IMPLEMENTATION_PLAN.md §9 ("cache geocode
// results per address; don't call the maps API on every availability
// request") — addresses don't move, so there's no cache invalidation to
// worry about, only cache growth, which is fine for this volume.

export interface ZoneLike {
  id: string;
  locationId: string;
  type: string; // "postal" | "radius" | "driving"
  postalCodes: string[];
  radiusKm: number | null; // for "driving" zones, this is the max driving distance in km
  minOrders: number | null;
  active: boolean;
}

function normalizeAddressKey(address: string): string {
  return address.trim().toLowerCase().replace(/\s+/g, " ");
}

/**
 * Geocodes an address via the Google Maps Geocoding API, using
 * GOOGLE_MAPS_API_KEY. Returns null (rather than throwing) when no key is
 * configured or the address can't be resolved — callers should treat that
 * as "can't determine eligibility," not a hard error, since a merchant may
 * not have set up Maps yet.
 */
export async function geocodeAddress(address: string): Promise<Coordinates | null> {
  const key = normalizeAddressKey(address);

  const cached = await db.geocodeCache.findUnique({ where: { normalizedKey: key } });
  if (cached) return { lat: cached.lat, lng: cached.lng };

  const apiKey = process.env.GOOGLE_MAPS_API_KEY;
  if (!apiKey) return null;

  const url = new URL("https://maps.googleapis.com/maps/api/geocode/json");
  url.searchParams.set("address", address);
  url.searchParams.set("key", apiKey);

  const res = await fetch(url.toString());
  if (!res.ok) return null;

  const body = (await res.json()) as {
    status: string;
    results: Array<{ geometry: { location: { lat: number; lng: number } } }>;
  };
  if (body.status !== "OK" || body.results.length === 0) return null;

  const { lat, lng } = body.results[0].geometry.location;
  await db.geocodeCache.upsert({
    where: { normalizedKey: key },
    create: { normalizedKey: key, lat, lng },
    update: { lat, lng },
  });

  return { lat, lng };
}

/**
 * Radius zones use the location's own lat/lng as the center — postal zones
 * need no coordinates at all. This is why isZoneEligible takes the
 * location's coordinates separately rather than assuming the zone carries
 * its own center point.
 *
 * "driving" zones need a road-network distance, which is an API call (see
 * resolveDrivingDistanceKm) — this function stays pure/synchronous (no I/O
 * in the math, CLAUDE.md), so the caller resolves that distance first and
 * passes it in via `customer.drivingDistanceKm`, exactly the way it already
 * resolves geocoding before calling this for radius zones.
 */
export function isZoneEligible(
  zone: ZoneLike,
  locationCoordinates: Coordinates | null,
  customer: { coordinates?: Coordinates; postalCode?: string; drivingDistanceKm?: number },
): boolean {
  if (!zone.active) return false;

  if (zone.type === "postal") {
    return customer.postalCode ? isPostalCodeListed(customer.postalCode, zone.postalCodes) : false;
  }

  if (zone.type === "radius") {
    if (!locationCoordinates || !customer.coordinates || zone.radiusKm == null) return false;
    return haversineDistanceKm(customer.coordinates, locationCoordinates) <= zone.radiusKm;
  }

  if (zone.type === "driving") {
    if (zone.radiusKm == null || customer.drivingDistanceKm == null) return false;
    return customer.drivingDistanceKm <= zone.radiusKm;
  }

  return false;
}

function roundCoord(n: number): number {
  return Math.round(n * 10000) / 10000; // ~11m precision — plenty for a zone-eligibility cache key
}

function routeKey(origin: Coordinates, destination: Coordinates): string {
  return `${roundCoord(origin.lat)},${roundCoord(origin.lng)}|${roundCoord(destination.lat)},${roundCoord(destination.lng)}`;
}

/**
 * Road distance between two points via Google's Distance Matrix API, using
 * the same GOOGLE_MAPS_API_KEY as geocodeAddress. Returns null (not a throw)
 * when there's no key or the API can't route between the points — callers
 * must treat that as "can't determine eligibility" (isZoneEligible's driving
 * branch already fails closed on null), the same permissive-to-the-API,
 * fail-closed-on-eligibility posture as the rest of this file.
 */
export async function resolveDrivingDistanceKm(origin: Coordinates, destination: Coordinates): Promise<number | null> {
  const key = routeKey(origin, destination);

  const cached = await db.drivingDistanceCache.findUnique({ where: { routeKey: key } });
  if (cached) return cached.distanceKm;

  const apiKey = process.env.GOOGLE_MAPS_API_KEY;
  if (!apiKey) return null;

  const url = new URL("https://maps.googleapis.com/maps/api/distancematrix/json");
  url.searchParams.set("origins", `${origin.lat},${origin.lng}`);
  url.searchParams.set("destinations", `${destination.lat},${destination.lng}`);
  url.searchParams.set("key", apiKey);

  const res = await fetch(url.toString());
  if (!res.ok) return null;

  const body = (await res.json()) as {
    status: string;
    rows: Array<{ elements: Array<{ status: string; distance?: { value: number } }> }>;
  };
  const element = body.rows?.[0]?.elements?.[0];
  if (body.status !== "OK" || !element || element.status !== "OK" || !element.distance) return null;

  const distanceKm = element.distance.value / 1000;
  await db.drivingDistanceCache.upsert({
    where: { routeKey: key },
    create: { routeKey: key, distanceKm },
    update: { distanceKm },
  });

  return distanceKm;
}

export interface EligibleLocationMatch {
  locationId: string;
  zoneId: string;
  distanceKm: number | null;
}

/**
 * Nearest-location auto-assign (PRODUCT_STRATEGY.md §2 "Auto location
 * assignment"): given a shopper's address, finds every active zone across
 * the shop's locations that covers it, ranked nearest-first when distance
 * is known (radius zones) — postal zones without location coordinates sort
 * after distance-ranked ones, in the order returned by the query.
 */
export async function findEligibleLocationsForDelivery(
  shopDomain: string,
  customer: { address?: string; postalCode?: string },
): Promise<EligibleLocationMatch[]> {
  const customerCoordinates = customer.address ? await geocodeAddress(customer.address) : null;

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

  const matches: EligibleLocationMatch[] = [];

  for (const location of locations) {
    const locationCoordinates = location.lat != null && location.lng != null ? { lat: location.lat, lng: location.lng } : null;

    for (const zone of location.zones) {
      // "driving" zones need a road-distance lookup before isZoneEligible can
      // even evaluate them — resolved (and cached) here, not inside the pure
      // eligibility check itself.
      let drivingDistanceKm: number | undefined;
      if (zone.type === "driving" && locationCoordinates && customerCoordinates) {
        // eslint-disable-next-line no-await-in-loop -- one cached lookup per candidate zone; there's no batch API to move this out of the loop
        drivingDistanceKm = (await resolveDrivingDistanceKm(customerCoordinates, locationCoordinates)) ?? undefined;
      }

      const eligible = isZoneEligible(zone, locationCoordinates, {
        coordinates: customerCoordinates ?? undefined,
        postalCode: customer.postalCode,
        drivingDistanceKm,
      });
      if (!eligible) continue;

      const distanceKm =
        drivingDistanceKm ??
        (locationCoordinates && customerCoordinates ? haversineDistanceKm(customerCoordinates, locationCoordinates) : null);

      matches.push({ locationId: location.id, zoneId: zone.id, distanceKm });
    }
  }

  return matches.sort((a, b) => {
    if (a.distanceKm == null && b.distanceKm == null) return 0;
    if (a.distanceKm == null) return 1;
    if (b.distanceKm == null) return -1;
    return a.distanceKm - b.distanceKm;
  });
}

/**
 * Delivery-density threshold (PRODUCT_STRATEGY.md §3.2): a sparse zone
 * shouldn't unlock delivery capacity until `minOrders` bookings have
 * already routed through it — cuts delivery cost on routes that wouldn't
 * be worth a driver trip for just one or two orders. A zone with no
 * minOrders set (or 0) always passes.
 */
export async function meetsDeliveryDensity(shopDomain: string, zone: ZoneLike): Promise<boolean> {
  if (!zone.minOrders || zone.minOrders <= 0) return true;

  const count = await db.booking.count({
    where: { shopDomain, zoneId: zone.id, status: { in: ["confirmed", "fulfilled"] } },
  });

  return count >= zone.minOrders;
}

export interface AdminGraphQLClient {
  graphql(query: string, options?: { variables?: Record<string, unknown> }): Promise<Response>;
}

/**
 * Inventory-based location exclusion (PRODUCT_STRATEGY.md §2): drops any
 * candidate location that doesn't stock at least one of the cart's
 * products, per Shopify's InventoryLevel API. Locations without a
 * shopifyLocationId mapping are left in (can't check what we can't query —
 * excluding them would be a false negative, not a safe default) and this
 * whole check is a no-op when productIds is empty (nothing to check stock
 * for, e.g. availability requests made before a cart exists).
 */
export async function excludeLocationsWithoutStock(
  admin: AdminGraphQLClient,
  locationIds: string[],
  productVariantGids: string[],
): Promise<Set<string>> {
  if (productVariantGids.length === 0) return new Set(locationIds);

  const locations = await db.location.findMany({
    where: { id: { in: locationIds } },
    select: { id: true, shopifyLocationId: true },
  });

  const inStock = new Set<string>();

  for (const location of locations) {
    if (!location.shopifyLocationId) {
      inStock.add(location.id); // unmapped — can't verify, don't exclude
      continue;
    }

    const response = await admin.graphql(
      `#graphql
      query LocationStock($locationId: ID!, $variantIds: [ID!]!) {
        location(id: $locationId) {
          id
        }
        nodes(ids: $variantIds) {
          ... on ProductVariant {
            inventoryItem {
              inventoryLevel(locationId: $locationId) {
                quantities(names: ["available"]) {
                  quantity
                }
              }
            }
          }
        }
      }`,
      { variables: { locationId: location.shopifyLocationId, variantIds: productVariantGids } },
    );

    const body = (await response.json()) as {
      data?: {
        nodes: Array<{ inventoryItem?: { inventoryLevel?: { quantities: Array<{ quantity: number }> } | null } } | null>;
      };
    };

    const hasStock = (body.data?.nodes ?? []).some((node) =>
      (node?.inventoryItem?.inventoryLevel?.quantities ?? []).some((q) => q.quantity > 0),
    );

    if (hasStock) inStock.add(location.id);
  }

  return inStock;
}