let _cache = {};

export function lookupCachedUploadUrl(shortUrl) {
  return _cache[shortUrl] || {};
}

const MISSING = "missing";

export function lookupUncachedUploadUrls(urls, ajax) {
  return ajax("/uploads/lookup-urls", {
    method: "POST",
    data: { short_urls: urls }
  }).then(uploads => {
    uploads.forEach(upload => {
      cacheShortUploadUrl(upload.short_url, {
        url: upload.url,
        short_path: upload.short_path
      });
    });

    urls.forEach(url =>
      cacheShortUploadUrl(url, {
        url: lookupCachedUploadUrl(url).url || MISSING,
        short_path: lookupCachedUploadUrl(url).short_path || MISSING
      })
    );

    return uploads;
  });
}

export function cacheShortUploadUrl(shortUrl, value) {
  _cache[shortUrl] = value;
}

export function resetCache() {
  _cache = {};
}

export const ATTACHMENT_CSS_CLASS = "attachment";

function _loadCachedShortUrls($uploads) {
  $uploads.each((idx, upload) => {
    const $upload = $(upload);
    let url;

    switch (upload.tagName) {
      case "A":
        url = lookupCachedUploadUrl($upload.data("orig-href")).short_path;

        if (url) {
          $upload.removeAttr("data-orig-href");

          if (url !== MISSING) {
            $upload.attr("href", url);
            const content = $upload.text().split("|");

            if (content[1] === ATTACHMENT_CSS_CLASS) {
              $upload.addClass(ATTACHMENT_CSS_CLASS);
              $upload.text(content[0]);
            }
          }
        }

        break;
      case "IMG":
        url = lookupCachedUploadUrl($upload.data("orig-src")).url;

        if (url) {
          $upload.removeAttr("data-orig-src");

          if (url !== MISSING) {
            $upload.attr("src", url);
          }
        }

        break;
    }
  });
}

function _loadShortUrls($uploads, ajax) {
  const urls = $uploads.toArray().map(upload => {
    const $upload = $(upload);
    return $upload.data("orig-src") || $upload.data("orig-href");
  });

  return lookupUncachedUploadUrls(urls, ajax).then(() =>
    _loadCachedShortUrls($uploads)
  );
}

export function resolveAllShortUrls(ajax) {
  const attributes = "img[data-orig-src], a[data-orig-href]";
  let $shortUploadUrls = $(attributes);

  if ($shortUploadUrls.length > 0) {
    _loadCachedShortUrls($shortUploadUrls);

    $shortUploadUrls = $(attributes);
    if ($shortUploadUrls.length > 0) {
      // this is carefully batched so we can do a leading debounce (trigger right away)
      return Ember.run.debounce(
        null,
        () => _loadShortUrls($shortUploadUrls, ajax),
        450,
        true
      );
    }
  }
}