// import { useSWR } from "sswr";
import { useSWR } from "../util/fetch";
import { derived, Readable, readable, writable } from "svelte/store";
import type { IEntry, ListingResult, OrderedListing } from "upend/types";
import { listingAsOrdered } from "upend";
import LRU from "lru-cache";

export function useEntity(
  address: string | (() => string),
  condition?: () => Boolean
) {
  const { data, error, revalidate } = useSWR<ListingResult, unknown>(() =>
    condition === undefined || condition()
      ? `/api/obj/${typeof address === "string" ? address : address()}`
      : null
  );

  const entries = derived(data, ($values) =>
    $values ? listingAsOrdered($values) : []
  );
  const attributes = derived(entries, ($entries) => {
    const addr = typeof address === "string" ? address : address();
    return $entries.filter(([_, e]) => e.entity === addr);
  });
  const backlinks = derived(entries, ($entries) => {
    const addr = typeof address === "string" ? address : address();
    return $entries.filter(([_, e]) => e.entity !== addr);
  });

  return {
    entries,
    attributes,
    backlinks,
    data,
    error,
    revalidate,
  };
}

export function query(query: () => string) {
  let queryString = typeof query === "string" ? query : query();
  console.debug(`Querying: ${queryString}`);
  const { data, error, revalidate } = useSWR<ListingResult, unknown>(
    () => `/api/obj?query=${query()}`
  );

  const result = derived(data, ($values) => {
    return $values ? listingAsOrdered($values) : [];
  });

  return {
    result,
    data,
    error,
    revalidate,
  };
}

const queryOnceLRU = new LRU<string, OrderedListing>(128);
const inFlightRequests: { [key: string]: Promise<OrderedListing> } = {};

export async function queryOnce(query: string): Promise<OrderedListing> {
  const cacheResult = queryOnceLRU.get(query);
  if (!cacheResult) {
    const url = `/api/obj?query=${query}`;
    let response;
    if (!inFlightRequests[url]) {
      console.debug(`Querying: ${query}`);
      inFlightRequests[url] = new Promise(async (resolve, reject) => {
        const response = await fetch(url);
        resolve(listingAsOrdered(await response.json()));
      });
    } else {
      console.debug(`Chaining request for ${query}...`);
    }
    return await inFlightRequests[url];
  } else {
    console.debug(`Returning cached: ${query}`);
    return cacheResult;
  }
}

interface EntityIdentification {
  type: string;
  value: string;
}

export async function identify(
  attributes: OrderedListing,
  backlinks: OrderedListing
): Promise<EntityIdentification[]> {
  // Get all entries where the object is linked
  const hasEntries = backlinks
    .filter(([_, entry]) => entry.attribute === "HAS")
    .map(([addr, _]) => addr);

  // Out of those relations, retrieve their ALIAS attrs
  const hasAliases = hasEntries.length
    ? await queryOnce(
        `(matches (in ${hasEntries.map((e) => `"${e}"`).join(" ")}) "ALIAS" ?)`
      )
    : [];

  const aliasValues = hasAliases.map(([_, entry]) => {
    return entry.value.c;
  });

  // Get all identities of the object
  const isEntries = attributes
    .filter(([_, entry]) => entry.attribute === "IS")
    .map(([_, entry]) => entry.value.c);

  // Out of those, retrieve their TYPE_ID entries
  const typeIdListing = isEntries.length
    ? await queryOnce(
        `(matches (in ${isEntries.map((e) => `"${e}"`).join(" ")}) "TYPE_ID" ?)`
      )
    : [];

  const typeIdAttributes = typeIdListing.map(([_, entry]) => {
    return [entry.entity, entry.value.c];
  });

  // Finally, filter own object's attributes according to TYPE_IDs
  // For each identity/TYPE_ID pair
  return typeIdAttributes
    .map(([type, attrName]) => {
      // And each associated TYPE_ID attribute...
      // return own matchin attributes
      return attributes
        .filter(([_, e]) => e.attribute === attrName)
        .map(([_, attr]) => {
          return {
            type,
            value: attr.value.c,
          };
        });
    })
    .flat()
    .concat(
      aliasValues.map((value) => {
        return {
          type: "ALIAS",
          value,
        };
      })
    );
}