// @flow
import type { Node } from 'react';
import React from 'react';
import ClaimPreviewTile from 'component/claimPreviewTile';
import useFetchViewCount from 'effects/use-fetch-view-count';
import useLastVisibleItem from 'effects/use-last-visible-item';

function urisEqual(prev: ?Array<string>, next: ?Array<string>) {
  if (!prev || !next) {
    // ClaimList: "null" and "undefined" have special meaning,
    // so we can't just compare array length here.
    //   - null = "timed out"
    //   - undefined = "no result".
    return prev === next;
  }

  // $FlowFixMe - already checked for null above.
  return prev.length === next.length && prev.every((value, index) => value === next[index]);
}

// ****************************************************************************
// ClaimTilesDiscover
// ****************************************************************************

type Props = {
  prefixUris?: Array<string>,
  pinUrls?: Array<string>,
  uris: Array<string>,
  injectedItem?: { node: Node, index?: number, replace?: boolean },
  showNoSourceClaims?: boolean,
  renderProperties?: (Claim) => ?Node,
  fetchViewCount?: boolean,
  // claim search options are below
  tags: Array<string>,
  claimIds?: Array<string>,
  channelIds?: Array<string>,
  pageSize: number,
  orderBy?: Array<string>,
  releaseTime?: string,
  languages?: Array<string>,
  claimType?: string | Array<string>,
  streamTypes?: Array<string>,
  timestamp?: string,
  feeAmount?: string,
  limitClaimsPerChannel?: number,
  hasSource?: boolean,
  hasNoSource?: boolean,
  // --- select ---
  location: { search: string },
  claimSearchResults: Array<string>,
  claimsByUri: { [string]: any },
  fetchingClaimSearch: boolean,
  showNsfw: boolean,
  hideReposts: boolean,
  optionsStringified: string,
  // --- perform ---
  doClaimSearch: ({}) => void,
  doFetchViewCount: (claimIdCsv: string) => void,
};

function ClaimTilesDiscover(props: Props) {
  const {
    doClaimSearch,
    claimSearchResults,
    claimsByUri,
    fetchViewCount,
    fetchingClaimSearch,
    hasNoSource,
    renderProperties,
    pinUrls,
    prefixUris,
    injectedItem,
    showNoSourceClaims,
    doFetchViewCount,
    pageSize = 8,
    optionsStringified,
  } = props;

  // reference to the claim-grid
  const sectionRef = React.useRef();
  // determine the index where the ad should be injected
  const injectedIndex = useLastVisibleItem(injectedItem, sectionRef);

  const prevUris = React.useRef();
  const claimSearchUris = claimSearchResults || [];
  const isUnfetchedClaimSearch = claimSearchResults === undefined;

  const shouldPerformSearch = !fetchingClaimSearch && claimSearchUris.length === 0;

  const uris = (prefixUris || []).concat(claimSearchUris);
  if (prefixUris && prefixUris.length) uris.splice(prefixUris.length * -1, prefixUris.length);

  if (pinUrls && uris && uris.length > 2 && window.location.pathname === '/') {
    pinUrls.forEach((pin) => {
      if (uris.indexOf(pin) !== -1) {
        uris.splice(uris.indexOf(pin), 1);
      } else {
        uris.pop();
      }
    });
    uris.splice(2, 0, ...pinUrls);
  }

  if (uris.length > 0 && uris.length < pageSize && shouldPerformSearch) {
    // prefixUri and pinUrls might already be present while waiting for the
    // remaining claim_search results. Fill the space to prevent layout shifts.
    uris.push(...Array(pageSize - uris.length).fill(''));
  }

  // Show previous results while we fetch to avoid blinkies and poor CLS.
  const finalUris = isUnfetchedClaimSearch && prevUris.current ? prevUris.current : uris;
  prevUris.current = finalUris;

  // --------------------------------------------------------------------------
  // --------------------------------------------------------------------------

  // populate the view counts for the current claim uris
  useFetchViewCount(fetchViewCount, uris, claimsByUri, doFetchViewCount);

  // Run `doClaimSearch`
  React.useEffect(() => {
    if (shouldPerformSearch) {
      const searchOptions = JSON.parse(optionsStringified);
      doClaimSearch(searchOptions);
    }
  }, [doClaimSearch, shouldPerformSearch, optionsStringified]);

  return (
    <ul ref={sectionRef} className="claim-grid">
      {finalUris && finalUris.length
        ? finalUris.map((uri, i) => {
            if (uri) {
              // if indexes match, inject ad in place of tile (aka replace it)
              if (injectedIndex === i && injectedItem && injectedItem.replace) {
                return <React.Fragment key={uri}>{injectedItem.node}</React.Fragment>;
              }

              return (
                <React.Fragment key={uri}>
                  {injectedIndex === i && injectedItem && injectedItem.node}
                  {/* inject ad */}
                  <ClaimPreviewTile
                    showNoSourceClaims={hasNoSource || showNoSourceClaims}
                    uri={uri}
                    properties={renderProperties}
                  />
                </React.Fragment>
              );
            } else {
              return <ClaimPreviewTile showNoSourceClaims={hasNoSource || showNoSourceClaims} key={i} placeholder />;
            }
          })
        : new Array(pageSize)
            .fill(1)
            .map((x, i) => (
              <ClaimPreviewTile showNoSourceClaims={hasNoSource || showNoSourceClaims} key={i} placeholder />
            ))}
    </ul>
  );
}

export default React.memo<Props>(ClaimTilesDiscover, areEqual);

// ****************************************************************************
// ****************************************************************************

function trace(key, value) {
  // @if process.env.DEBUG_TILE_RENDER
  // $FlowFixMe "cannot coerce certain types".
  console.log(`[claimTilesDiscover] ${key}: ${value}`); // eslint-disable-line no-console
  // @endif
}

function areEqual(prev: Props, next: Props) {
  // --- Deep-compare ---
  // These are props that are hard to memoize from where it is passed.

  if (prev.claimType !== next.claimType) {
    // Array<string>: confirm the contents are actually different.
    if (prev.claimType && next.claimType && JSON.stringify(prev.claimType) !== JSON.stringify(next.claimType)) {
      trace('claimType', next.claimType);
      return false;
    }
  }

  const ARRAY_KEYS = ['prefixUris', 'channelIds'];
  for (let i = 0; i < ARRAY_KEYS.length; ++i) {
    const key = ARRAY_KEYS[i];
    if (!urisEqual(prev[key], next[key])) {
      trace(key, next[key]);
      return false;
    }
  }

  // --- Default the rest(*) to shallow-compare ---
  // (*) including new props introduced in the future, in case developer forgets
  // to update this function. Better to render more than miss an important one.
  const KEYS_TO_IGNORE = [
    ...ARRAY_KEYS,
    'claimType', // Handled above.
    'claimsByUri', // Used for view-count. Just ignore it for now.
    'location',
    'history',
    'match',
    'doClaimSearch',
  ];

  const propKeys = Object.keys(next);
  for (let i = 0; i < propKeys.length; ++i) {
    const pk = propKeys[i];
    if (!KEYS_TO_IGNORE.includes(pk) && prev[pk] !== next[pk]) {
      trace(pk, next[pk]);
      return false;
    }
  }

  return true;
}