render-mail.js

const LANG_SCORE = 128;
const FORMAT_SCORE = 64;

const weighTemplate = curry((format, lang, item) =>
  (item.lang   === lang   ? LANG_SCORE   : 0) +
  (item.format === format ? FORMAT_SCORE : 0));

const filterMatchingTemplates = curry((templates, format, lang, type) =>
  pipe(
    // First, find the template items that match the type, lang and format,
    // or where lang and format are 'ANY', i.e. wildcards
    filter(where({
      type   : equals(type),
      lang   : equalOrAny(lang),
      // markdown is a special format that acts like ANY
      format : anyPass([ equalOrAny(format), equals('md') ])
    })),
    // Group by name, and pick the values that are most appropriate for
    // given format and lang
    groupBy(prop('name')),
    mapObj(maximumBy(weighTemplate(format, lang))),
    values
  )(templates));