path: root/src/data/things/language.js

import { Temporal, toTemporalInstant } from '@js-temporal/polyfill';

import {withAggregate} from '#aggregate';
import CacheableObject from '#cacheable-object';
import {logWarn} from '#cli';
import * as html from '#html';
import {empty} from '#sugar';
import {isLanguageCode} from '#validators';
import Thing from '#thing';

import {
  getExternalLinkStringOfStyleFromDescriptors,
  getExternalLinkStringsFromDescriptors,
  isExternalLinkContext,
  isExternalLinkSpec,
  isExternalLinkStyle,
} from '#external-links';

import {externalFunction, flag, name} from '#composite/wiki-properties';

export const languageOptionRegex = /{(?<name>[A-Z0-9_]+)}/g;

export class Language extends Thing {
  static [Thing.getPropertyDescriptors] = () => ({
    // Update & expose

    // General language code. This is used to identify the language distinctly
    // from other languages (similar to how "Directory" operates in many data
    // objects).
    code: {
      flags: {update: true, expose: true},
      update: {validate: isLanguageCode},
    },

    // Human-readable name. This should be the language's own native name, not
    // localized to any other language.
    name: name(`Unnamed Language`),

    // Language code specific to JavaScript's Internationalization (Intl) API.
    // Usually this will be the same as the language's general code, but it
    // may be overridden to provide Intl constructors an alternative value.
    intlCode: {
      flags: {update: true, expose: true},
      update: {validate: isLanguageCode},
      expose: {
        dependencies: ['code'],
        transform: (intlCode, {code}) => intlCode ?? code,
      },
    },

    // Flag which represents whether or not to hide a language from general
    // access. If a language is hidden, its portion of the website will still
    // be built (with all strings localized to the language), but it won't be
    // included in controls for switching languages or the <link rel=alternate>
    // tags used for search engine optimization. This flag is intended for use
    // with languages that are currently in development and not ready for
    // formal release, or which are just kept hidden as "experimental zones"
    // for wiki development or content testing.
    hidden: flag(false),

    // Mapping of translation keys to values (strings). Generally, don't
    // access this object directly - use methods instead.
    strings: {
      flags: {update: true, expose: true},
      update: {validate: (t) => typeof t === 'object'},

      expose: {
        dependencies: ['inheritedStrings', 'code'],
        transform(strings, {inheritedStrings, code}) {
          if (!strings && !inheritedStrings) return null;
          if (!inheritedStrings) return strings;

          const validStrings = {
            ...inheritedStrings,
            ...strings,
          };

          const optionsFromTemplate = template =>
            Array.from(template.matchAll(languageOptionRegex))
              .map(({groups}) => groups.name);

          for (const [key, providedTemplate] of Object.entries(strings)) {
            const inheritedTemplate = inheritedStrings[key];
            if (!inheritedTemplate) continue;

            const providedOptions = optionsFromTemplate(providedTemplate);
            const inheritedOptions = optionsFromTemplate(inheritedTemplate);

            const missingOptionNames =
              inheritedOptions.filter(name => !providedOptions.includes(name));

            const misplacedOptionNames =
              providedOptions.filter(name => !inheritedOptions.includes(name));

            if (!empty(missingOptionNames) || !empty(misplacedOptionNames)) {
              logWarn`Not using ${code ?? '(no code)'} string ${key}:`;
              if (!empty(missingOptionNames))
                logWarn`- Missing options: ${missingOptionNames.join(', ')}`;
              if (!empty(misplacedOptionNames))
                logWarn`- Unexpected options: ${misplacedOptionNames.join(', ')}`;
              validStrings[key] = inheritedStrings[key];
            }
          }

          return validStrings;
        },
      },
    },

    // May be provided to specify "default" strings, generally (but not
    // necessarily) inherited from another Language object.
    inheritedStrings: {
      flags: {update: true, expose: true},
      update: {validate: (t) => typeof t === 'object'},
    },

    // List of descriptors for providing to external link utilities when using
    // language.formatExternalLink - refer to util/external-links.js for info.
    externalLinkSpec: {
      flags: {update: true, expose: true},
      update: {validate: isExternalLinkSpec},
    },

    // Update only

    escapeHTML: externalFunction(),

    // Expose only

    onlyIfOptions: {
      flags: {expose: true},
      expose: {
        compute: () => Symbol.for(`language.onlyIfOptions`),
      },
    },

    intl_date: this.#intlHelper(Intl.DateTimeFormat, {full: true}),
    intl_number: this.#intlHelper(Intl.NumberFormat),
    intl_listConjunction: this.#intlHelper(Intl.ListFormat, {type: 'conjunction'}),
    intl_listDisjunction: this.#intlHelper(Intl.ListFormat, {type: 'disjunction'}),
    intl_listUnit: this.#intlHelper(Intl.ListFormat, {type: 'unit'}),
    intl_pluralCardinal: this.#intlHelper(Intl.PluralRules, {type: 'cardinal'}),
    intl_pluralOrdinal: this.#intlHelper(Intl.PluralRules, {type: 'ordinal'}),

    validKeys: {
      flags: {expose: true},

      expose: {
        dependencies: ['strings', 'inheritedStrings'],
        compute: ({strings, inheritedStrings}) =>
          Array.from(
            new Set([
              ...Object.keys(inheritedStrings ?? {}),
              ...Object.keys(strings ?? {}),
            ])
          ),
      },
    },

    // TODO: This currently isn't used. Is it still needed?
    strings_htmlEscaped: {
      flags: {expose: true},
      expose: {
        dependencies: ['strings', 'inheritedStrings', 'escapeHTML'],
        compute({strings, inheritedStrings, escapeHTML}) {
          if (!(strings || inheritedStrings) || !escapeHTML) return null;
          const allStrings = {...inheritedStrings, ...strings};
          return Object.fromEntries(
            Object.entries(allStrings).map(([k, v]) => [k, escapeHTML(v)])
          );
        },
      },
    },
  });

  static #intlHelper (constructor, opts) {
    return {
      flags: {expose: true},
      expose: {
        dependencies: ['code', 'intlCode'],
        compute: ({code, intlCode}) => {
          const constructCode = intlCode ?? code;
          if (!constructCode) return null;
          return Reflect.construct(constructor, [constructCode, opts]);
        },
      },
    };
  }

  $(...args) {
    return this.formatString(...args);
  }

  assertIntlAvailable(property) {
    if (!this[property]) {
      throw new Error(`Intl API ${property} unavailable`);
    }
  }

  getUnitForm(value) {
    this.assertIntlAvailable('intl_pluralCardinal');
    return this.intl_pluralCardinal.select(value);
  }

  formatString(...args) {
    const hasOptions =
      typeof args.at(-1) === 'object' &&
      args.at(-1) !== null;

    const key =
      this.#joinKeyParts(hasOptions ? args.slice(0, -1) : args);

    const options =
      (hasOptions
        ? args.at(-1)
        : {});

    if (!this.strings) {
      throw new Error(`Strings unavailable`);
    }

    if (!this.validKeys.includes(key)) {
      throw new Error(`Invalid key ${key} accessed`);
    }

    const constantCasify = name =>
      name
        .replace(/[A-Z]/g, '_$&')
        .toUpperCase();

    // These will be filled up as we iterate over the template, slotting in
    // each option (if it's present).
    const missingOptionNames = new Set();

    // These will also be filled. It's a bit different of an error, indicating
    // a provided option was *expected,* but its value was null, undefined, or
    // blank HTML content.
    const valuelessOptionNames = new Set();

    // These *might* be missing, and if they are, that's OK!! Instead of adding
    // to the valueless set above, we'll just mark to return a blank for the
    // whole string.
    const expectedValuelessOptionNames =
      new Set(
        (options[this.onlyIfOptions] ?? [])
          .map(constantCasify));

    let seenExpectedValuelessOption = false;

    const isValueless =
      value =>
        value === null ||
        value === undefined ||
        html.isBlank(value);

    // And this will have entries deleted as they're encountered in the
    // template. Leftover entries are misplaced.
    const optionsMap =
      new Map(
        Object.entries(options).map(([name, value]) => [
          constantCasify(name),
          value,
        ]));

    const output = this.#iterateOverTemplate({
      template: this.strings[key],

      match: languageOptionRegex,

      insert: ({name: optionName}, canceledForming) => {
        if (!optionsMap.has(optionName)) {
          missingOptionNames.add(optionName);

          // We don't need to continue forming the output if we've hit a
          // missing option name, since the end result of this formatString
          // call will be a thrown error, and formed output won't be needed.
          // Return undefined to mark canceledForming for the following
          // iterations (and exit early out of this iteration).
          return undefined;
        }

        // Even if we're not actually forming the output anymore, we'll still
        // have to access this option's value to check if it is invalid.
        const optionValue = optionsMap.get(optionName);

        // We always have to delete expected options off the provided option
        // map, since the leftovers are what will be used to tell which are
        // misplaced - information you want even (or doubly so) if we've
        // already stopped forming the output thanks to missing options.
        optionsMap.delete(optionName);

        // Just like if an option is missing, a valueless option cancels
        // forming the rest of the output.
        if (isValueless(optionValue)) {
          // It's also an error, *except* if this option is one of the ones
          // that we're indicated to *expect* might be valueless! In that case,
          // we still need to stop forming the string (and mark a separate flag
          // so that we return a blank), but it's not an error.
          if (expectedValuelessOptionNames.has(optionName)) {
            seenExpectedValuelessOption = true;
          } else {
            valuelessOptionNames.add(optionName);
          }

          return undefined;
        }

        if (canceledForming) {
          return undefined;
        }

        return optionValue;
      },
    });

    const misplacedOptionNames =
      Array.from(optionsMap.keys());

    withAggregate({message: `Errors in options for string "${key}"`}, ({push}) => {
      const names = set => Array.from(set).join(', ');

      if (!empty(missingOptionNames)) {
        push(new Error(
          `Missing options: ${names(missingOptionNames)}`));
      }

      if (!empty(valuelessOptionNames)) {
        push(new Error(
          `Valueless options: ${names(valuelessOptionNames)}`));
      }

      if (!empty(misplacedOptionNames)) {
        push(new Error(
          `Unexpected options: ${names(misplacedOptionNames)}`));
      }
    });

    // If an option was valueless as marked to expect, then that indicates
    // the whole string should be treated as blank content.
    if (seenExpectedValuelessOption) {
      return html.blank();
    }

    return output;
  }

  #iterateOverTemplate({
    template,
    match: regexp,
    insert: insertFn,
  }) {
    const outputParts = [];

    let canceledForming = false;

    let lastIndex = 0;
    let partInProgress = '';

    for (const match of template.matchAll(regexp)) {
      const insertion =
        insertFn(match.groups, canceledForming);

      if (insertion === undefined) {
        canceledForming = true;
      }

      // Don't proceed with forming logic if the insertion function has
      // indicated that's not needed anymore - but continue iterating over
      // the rest of the template's matches, so other iteration logic (with
      // side effects) gets to process everything.
      if (canceledForming) {
        continue;
      }

      partInProgress += template.slice(lastIndex, match.index);

      // Sanitize string arguments in particular. These are taken to come from
      // (raw) data and may include special characters that aren't meant to be
      // rendered as HTML markup.
      const sanitizedInsertion =
        this.#sanitizeValueForInsertion(insertion);

      if (typeof sanitizedInsertion === 'string') {
        // Join consecutive strings together.
        partInProgress += sanitizedInsertion;
      } else if (
        sanitizedInsertion instanceof html.Tag &&
        sanitizedInsertion.contentOnly
      ) {
        // Collapse string-only tag contents onto the current string part.
        partInProgress += sanitizedInsertion.toString();
      } else {
        // Push the string part in progress, then the insertion as-is.
        outputParts.push(partInProgress);
        outputParts.push(sanitizedInsertion);
        partInProgress = '';
      }

      lastIndex = match.index + match[0].length;
    }

    if (canceledForming) {
      return undefined;
    }

    // Tack onto the final partInProgress, which may still have a value by this
    // point, if the final inserted value was a string. (Otherwise, it'll just
    // be equal to the remaining template text.)
    if (lastIndex < template.length) {
      partInProgress += template.slice(lastIndex);
    }

    if (partInProgress) {
      outputParts.push(partInProgress);
    }

    return this.#wrapSanitized(outputParts);
  }

  // Processes a value so that it's suitable to be inserted into a template.
  // For strings, this escapes HTML special characters, displaying them as-are
  // instead of representing HTML markup. For numbers and booleans, this turns
  // them into string values, so they never accidentally get caught as falsy
  // by #html stringification. Everything else - most importantly including
  // html.Tag objects - gets left as-is, preserving the value exactly as it's
  // provided.
  #sanitizeValueForInsertion(value) {
    const escapeHTML = CacheableObject.getUpdateValue(this, 'escapeHTML');
    if (!escapeHTML) {
      throw new Error(`escapeHTML unavailable`);
    }

    switch (typeof value) {
      case 'string':
        return escapeHTML(value);

      case 'number':
      case 'boolean':
        return value.toString();

      default:
        return value;
    }
  }

  // Wraps the output of a formatting function in a no-name-nor-attributes
  // HTML tag, which will indicate to other calls to formatString that this
  // content is a string *that may contain HTML* and doesn't need to
  // sanitized any further. It'll still .toString() to just the string
  // contents, if needed.
  #wrapSanitized(content) {
    return html.tags(content, {
      [html.blessAttributes]: true,
      [html.joinChildren]: '',
      [html.noEdgeWhitespace]: true,
    });
  }

  // Similar to the above internal methods, but this one is public.
  // It should be used when embedding content that may not have previously
  // been sanitized directly into an HTML tag or template's contents.
  // The templating engine usually handles this on its own, as does passing
  // a value (sanitized or not) directly for inserting into formatting
  // functions, but if you used a custom slot validation function (for example,
  // {validate: v => v.isHTML} instead of {type: 'string'} / {type: 'html'})
  // and are embedding the contents of the slot as a direct child of another
  // tag, you should manually sanitize those contents with this function.
  sanitize(value) {
    if (typeof value === 'string') {
      return this.#wrapSanitized(this.#sanitizeValueForInsertion(value));
    } else {
      return value;
    }
  }

  formatDate(date) {
    // Null or undefined date is blank content.
    if (date === null || date === undefined) {
      return html.blank();
    }

    this.assertIntlAvailable('intl_date');
    return this.intl_date.format(date);
  }

  formatDateRange(startDate, endDate) {
    // formatDateRange expects both values to be present, but if both are null
    // or both are undefined, that's just blank content.
    const hasStart = startDate !== null && startDate !== undefined;
    const hasEnd = endDate !== null && endDate !== undefined;
    if (!hasStart || !hasEnd) {
      if (startDate === endDate) {
        return html.blank();
      } else if (hasStart) {
        throw new Error(`Expected both start and end of date range, got only start`);
      } else if (hasEnd) {
        throw new Error(`Expected both start and end of date range, got only end`);
      } else {
        throw new Error(`Got mismatched ${startDate}/${endDate} for start and end`);
      }
    }

    this.assertIntlAvailable('intl_date');
    return this.intl_date.formatRange(startDate, endDate);
  }

  formatDateDuration({
    years: numYears = 0,
    months: numMonths = 0,
    days: numDays = 0,
    approximate = false,
  }) {
    // Give up if any of years, months, or days is null or undefined.
    // These default to zero, so something's gone pretty badly wrong to
    // pass in all or partial missing values.
    if (
      numYears === undefined || numYears === null ||
      numMonths === undefined || numMonths === null ||
      numDays === undefined || numDays === null
    ) {
      throw new Error(`Expected values or default zero for years, months, and days`);
    }

    let basis;

    const years = this.countYears(numYears, {unit: true});
    const months = this.countMonths(numMonths, {unit: true});
    const days = this.countDays(numDays, {unit: true});

    if (numYears && numMonths && numDays)
      basis = this.formatString('count.dateDuration.yearsMonthsDays', {years, months, days});
    else if (numYears && numMonths)
      basis = this.formatString('count.dateDuration.yearsMonths', {years, months});
    else if (numYears && numDays)
      basis = this.formatString('count.dateDuration.yearsDays', {years, days});
    else if (numYears)
      basis = this.formatString('count.dateDuration.years', {years});
    else if (numMonths && numDays)
      basis = this.formatString('count.dateDuration.monthsDays', {months, days});
    else if (numMonths)
      basis = this.formatString('count.dateDuration.months', {months});
    else if (numDays)
      basis = this.formatString('count.dateDuration.days', {days});
    else
      return this.formatString('count.dateDuration.zero');

    if (approximate) {
      return this.formatString('count.dateDuration.approximate', {
        duration: basis,
      });
    } else {
      return basis;
    }
  }

  formatRelativeDate(currentDate, referenceDate, {
    considerRoundingDays = false,
    approximate = true,
    absolute = true,
  } = {}) {
    // Give up if current and/or reference date is null or undefined.
    if (
      currentDate === undefined || currentDate === null ||
      referenceDate === undefined || referenceDate === null
    ) {
      throw new Error(`Expected values for currentDate and referenceDate`);
    }

    const currentInstant = toTemporalInstant.apply(currentDate);
    const referenceInstant = toTemporalInstant.apply(referenceDate);

    const comparison =
      Temporal.Instant.compare(currentInstant, referenceInstant);

    if (comparison === 0) {
      return this.formatString('count.dateDuration.same');
    }

    const currentTDZ = currentInstant.toZonedDateTimeISO('Etc/UTC');
    const referenceTDZ = referenceInstant.toZonedDateTimeISO('Etc/UTC');

    const earlierTDZ = (comparison === -1 ? currentTDZ : referenceTDZ);
    const laterTDZ = (comparison === 1 ? currentTDZ : referenceTDZ);

    const {years, months, days} =
      laterTDZ.since(earlierTDZ, {
        largestUnit: 'year',
        smallestUnit:
          (considerRoundingDays
            ? (laterTDZ.since(earlierTDZ, {
                largestUnit: 'year',
                smallestUnit: 'day',
              }).years
                ? 'month'
                : 'day')
            : 'day'),
        roundingMode: 'halfCeil',
      });

    const duration =
      this.formatDateDuration({
        years, months, days,
        approximate: false,
      });

    const relative =
      this.formatString(
        'count.dateDuration',
        (approximate && (years || months || days)
          ? (comparison === -1
              ? 'approximateEarlier'
              : 'approximateLater')
          : (comparison === -1
              ? 'earlier'
              : 'later')),
        {duration});

    if (absolute) {
      return this.formatString('count.dateDuration.relativeAbsolute', {
        relative,
        absolute: this.formatDate(currentDate),
      });
    } else {
      return relative;
    }
  }

  formatDuration(secTotal, {approximate = false, unit = false} = {}) {
    // Null or undefined duration is blank content.
    if (secTotal === null || secTotal === undefined) {
      return html.blank();
    }

    // Zero duration is a "missing" string.
    if (secTotal === 0) {
      return this.formatString('count.duration.missing');
    }

    const hour = Math.floor(secTotal / 3600);
    const min = Math.floor((secTotal - hour * 3600) / 60);
    const sec = Math.floor(secTotal - hour * 3600 - min * 60);

    const pad = (val) => val.toString().padStart(2, '0');

    const stringSubkey = unit ? '.withUnit' : '';

    const duration =
      hour > 0
        ? this.formatString('count.duration.hours' + stringSubkey, {
            hours: hour,
            minutes: pad(min),
            seconds: pad(sec),
          })
        : this.formatString('count.duration.minutes' + stringSubkey, {
            minutes: min,
            seconds: pad(sec),
          });

    return approximate
      ? this.formatString('count.duration.approximate', {duration})
      : duration;
  }

  formatExternalLink(url, {
    style = 'platform',
    context = 'generic',
  } = {}) {
    if (!this.externalLinkSpec) {
      throw new TypeError(`externalLinkSpec unavailable`);
    }

    // Null or undefined url is blank content.
    if (url === null || url === undefined) {
      return html.blank();
    }

    isExternalLinkContext(context);

    if (style === 'all') {
      return getExternalLinkStringsFromDescriptors(url, this.externalLinkSpec, {
        language: this,
        context,
      });
    }

    isExternalLinkStyle(style);

    const result =
      getExternalLinkStringOfStyleFromDescriptors(url, style, this.externalLinkSpec, {
        language: this,
        context,
      });

    // It's possible for there to not actually be any string available for the
    // given URL, style, and context, and we want this to be detectable via
    // html.blank().
    return result ?? html.blank();
  }

  formatIndex(value) {
    // Null or undefined value is blank content.
    if (value === null || value === undefined) {
      return html.blank();
    }

    this.assertIntlAvailable('intl_pluralOrdinal');
    return this.formatString('count.index.' + this.intl_pluralOrdinal.select(value), {index: value});
  }

  formatNumber(value) {
    // Null or undefined value is blank content.
    if (value === null || value === undefined) {
      return html.blank();
    }

    this.assertIntlAvailable('intl_number');
    return this.intl_number.format(value);
  }

  formatWordCount(value) {
    // Null or undefined value is blank content.
    if (value === null || value === undefined) {
      return html.blank();
    }

    const num = this.formatNumber(
      value > 1000 ? Math.floor(value / 100) / 10 : value
    );

    const words =
      value > 1000
        ? this.formatString('count.words.thousand', {words: num})
        : this.formatString('count.words', {words: num});

    return this.formatString('count.words.withUnit.' + this.getUnitForm(value), {words});
  }

  #formatListHelper(array, processFn) {
    // Empty lists, null, and undefined are blank content.
    if (empty(array) || array === null || array === undefined) {
      return html.blank();
    }

    // Operate on "insertion markers" instead of the actual contents of the
    // array, because the process function (likely an Intl operation) is taken
    // to only operate on strings. We'll insert the contents of the array back
    // at these points afterwards.

    const insertionMarkers =
      Array.from(
        {length: array.length},
        (_item, index) => `<::insertion_${index}>`);

    // Basically the same insertion logic as in formatString. Like there, we
    // can't assume that insertion markers were kept in the same order as they
    // were provided, so we'll refer to the marked index. But we don't need to
    // worry about some of the indices *not* corresponding to a provided source
    // item, like we do in formatString, so that cuts out a lot of the
    // validation logic.

    return this.#iterateOverTemplate({
      template: processFn(insertionMarkers),

      match: /<::insertion_(?<index>[0-9]+)>/g,

      insert: ({index: markerIndex}) => {
        return array[markerIndex];
      },
    });
  }

  // Conjunction list: A, B, and C
  formatConjunctionList(array) {
    this.assertIntlAvailable('intl_listConjunction');
    return this.#formatListHelper(
      array,
      array => this.intl_listConjunction.format(array));
  }

  // Disjunction lists: A, B, or C
  formatDisjunctionList(array) {
    this.assertIntlAvailable('intl_listDisjunction');
    return this.#formatListHelper(
      array,
      array => this.intl_listDisjunction.format(array));
  }

  // Unit lists: A, B, C
  formatUnitList(array) {
    this.assertIntlAvailable('intl_listUnit');
    return this.#formatListHelper(
      array,
      array => this.intl_listUnit.format(array));
  }

  // Lists without separator: A B C
  formatListWithoutSeparator(array) {
    return this.#formatListHelper(
      array,
      array => array.join(' '));
  }

  // File sizes: 42.5 kB, 127.2 MB, 4.13 GB, 998.82 TB
  formatFileSize(bytes) {
    // Null or undefined bytes is blank content.
    if (bytes === null || bytes === undefined) {
      return html.blank();
    }

    // Zero bytes is blank content.
    if (bytes === 0) {
      return html.blank();
    }

    bytes = parseInt(bytes);

    // Non-number bytes is blank content! Wow.
    if (isNaN(bytes)) {
      return html.blank();
    }

    const round = (exp) => Math.round(bytes / 10 ** (exp - 1)) / 10;

    if (bytes >= 10 ** 12) {
      return this.formatString('count.fileSize.terabytes', {
        terabytes: round(12),
      });
    } else if (bytes >= 10 ** 9) {
      return this.formatString('count.fileSize.gigabytes', {
        gigabytes: round(9),
      });
    } else if (bytes >= 10 ** 6) {
      return this.formatString('count.fileSize.megabytes', {
        megabytes: round(6),
      });
    } else if (bytes >= 10 ** 3) {
      return this.formatString('count.fileSize.kilobytes', {
        kilobytes: round(3),
      });
    } else {
      return this.formatString('count.fileSize.bytes', {bytes});
    }
  }

  // Utility function to quickly provide a useful string key
  // (generally a prefix) to stuff nested beneath it.
  encapsulate(...args) {
    const fn =
      (typeof args.at(-1) === 'function'
        ? args.at(-1)
        : null);

    const parts =
      (fn
        ? args.slice(0, -1)
        : args);

    const capsule =
      this.#joinKeyParts(parts);

    if (fn) {
      return fn(capsule);
    } else {
      return capsule;
    }
  }

  #joinKeyParts(parts) {
    return parts.filter(Boolean).join('.');
  }
}

const countHelper = (stringKey, optionName = stringKey) =>
  function(value, {
    unit = false,
    blankIfZero = false,
  } = {}) {
    // Null or undefined value is blank content.
    if (value === null || value === undefined) {
      return html.blank();
    }

    // Zero is blank content, if that option is set.
    if (value === 0 && blankIfZero) {
      return html.blank();
    }

    return this.formatString(
      unit
        ? `count.${stringKey}.withUnit.` + this.getUnitForm(value)
        : `count.${stringKey}`,
      {[optionName]: this.formatNumber(value)});
  };

// TODO: These are hard-coded. Is there a better way?
Object.assign(Language.prototype, {
  countAdditionalFiles: countHelper('additionalFiles', 'files'),
  countAlbums: countHelper('albums'),
  countArtworks: countHelper('artworks'),
  countCommentaryEntries: countHelper('commentaryEntries', 'entries'),
  countContributions: countHelper('contributions'),
  countCoverArts: countHelper('coverArts'),
  countDays: countHelper('days'),
  countFlashes: countHelper('flashes'),
  countMonths: countHelper('months'),
  countTimesReferenced: countHelper('timesReferenced'),
  countTimesUsed: countHelper('timesUsed'),
  countTracks: countHelper('tracks'),
  countWeeks: countHelper('weeks'),
  countYears: countHelper('years'),
});