list.js

import { BaseFormat} from './base';
import { deconstructPattern } from '../utils';

export function constructParts(pattern, list) {
  if (list.length === 1) {
    return [{type: 'element', value: list[0]}];
  }

  const elem0 = typeof list[0] === 'string' ?
    {type: 'element', value: list[0]} : list[0];

  let elem1;

  if (list.length === 2) {
    if (typeof list[1] === 'string') {
      elem1 = {type: 'element', value: list[1]}; 
    } else {
      elem1 = list[1];
    }
  } else {
    elem1 = constructParts(pattern, list.slice(1));
  }

  return deconstructPattern(pattern, {
    '0': elem0,
    '1': elem1
  });
}

function FormatToParts(type, style, list) {
  if (!Array.isArray(list)) {
    return Promise.resolve([
      {type: 'element', value: list}
    ]);
  }

  const length = list.length;

  if (length === 0) {
    return Promise.resolve([
      {type: 'element', value: ''}
    ]);
  }

  if (length === 1) {
    return Promise.resolve([
      {type: 'element', value: list[0]}
    ]);
  }

  if (type === 'unit' || type === 'number') {
    return document.l10n.formatValue(`listformat-${type}`).then(pattern => {
      return constructParts(pattern, list);
    });
  }

  const strid = `listformat-${type}-${style}`;

  if (length === 2) {
    return document.l10n.formatValue(`${strid}-2`).then(pattern => {
      return constructParts(pattern, list);
    });
  }

  return document.l10n.formatValues(
    `${strid}-start`,
    `${strid}-middle`,
    `${strid}-end`).then(([start, middle, end]) => {
      let parts = list[length - 1];

      for (let i = length - 2; i >= 0; i--) {
        let template = middle;
        if (i === length - 2) {
          template = end;
        } else if (i === 0) {
          template = start;
        }

        parts = constructParts(template, [
          list[i],
          parts
        ]);
      }

      return parts;
    }
  );
}

export class ListFormat extends BaseFormat {
  constructor(locales, options) {
    super(locales, options, {
      type: 'regular',
      style: 'long'
    });
  }

  format(list) {
    const type = this['[[Type]]'];
    const style = this['[[Style]]'];
    return FormatToParts(type, style, list).then(parts => {
      return parts.reduce((string, part) => string + part.value, '');
    });
  }

  formatToParts(list) {
    const type = this['[[Type]]'];
    const style = this['[[Style]]'];
    return FormatToParts(type, style, list);
  }
}