import defaults from '~assets/default.strings.json';

let i18n;

function BaseStringService (namespace) {
    const ERROR_NO_NAMESPACE = 'BaseString cannot be extended without providing a namespace';
    const ERROR_NO_STRING = 'No string exists with this name';

    if (!namespace) {
        throw new Error(ERROR_NO_NAMESPACE);
    }

    this[namespace] = {};
    this.t = {};

    /**
     * To translate a singular string by itself or a string with context data, use `translate`.
     * For brevity, this is renamed as `t.s` (as in "translate singular"). `t.s` serves a dual
     * purpose -- it's to mark strings for translation so they appear in the `.pot` file after
     * the grunt-angular-gettext task is run AND it's used to fetch the translated string at
     * runtime.
     *
     * NOTE: View ui/src/i18n.js for where these i18n methods are defined. i18n is a wrapper around
     * the library angular-gettext.
     *
     * @arg {string} string - The string to be translated
     * @arg {object=} context - A data object used to populate dynamic context data in a string.
     *
     * @returns {string} The translated string or the original string in the even the translation
     * does not exist.
     */
    this.t.s = i18n.translate;

    /**
     * To translate a plural string use `t.p`. The `count` supplied will determine whether the
     * singular or plural string is returned.
     *
     * @arg {number} count - The count of the plural object
     * @arg {string} singular - The singular version of the string to be translated
     * @arg {string} plural - The plural version of the string to be translated
     * @arg {object=} context - A data object used to populate dynamic context data in a string.
     *
     * @returns {string} The translated string or the original string in the even the translation
     * does not exist.
     */
    this.t.p = i18n.translatePlural;

    const { t } = this;

    /*
     * These strings are globally relevant and configured to give priority to values in
     * default.strings.json and fall back to defaults defined inline.
     */
    this.BRAND_NAME = defaults.BRAND_NAME || 'AWX';
    this.PENDO_API_KEY = defaults.PENDO_API_KEY || '';

    /*
     * Globally relevant strings should be defined here to avoid duplication of content across the
     * the project.
     */
    this.CANCEL = t.s('CANCEL');
    this.SAVE = t.s('SAVE');
    this.OK = t.s('OK');

    /**
     * This getter searches the extending class' namespace first for a match then falls back to
     * the more globally relevant strings defined here. Strings with with dots as delimeters are
     * supported to give flexibility to extending classes to nest strings as necessary.
     *
     * If no match is found, an error is thrown to alert the developer immediately instead of
     * failing silently.
     *
     * The `t.s` and `t.p` calls should only be used where strings are defined in
     * <name>.strings.js` files. To use translated strings elsewhere, access them through this
     * common interface.
     *
     * @arg {string} name - The property name of the string (e.g. 'CANCEL')
     * @arg {number=} count - A count of objects referenced in your plural string
     * @arg {object=} context - An object containing data to use in the interpolation of the string
     */
    this.get = (name, ...args) => {
        const keys = name.split('.');
        let value;

        keys.forEach(key => {
            if (!value) {
                value = this[namespace][key] || this[key];
            } else {
                value = value[key];
            }

            if (!value) {
                throw new Error(`${ERROR_NO_STRING}: ${name}`);
            }
        });

        return typeof value === 'string' ? value : value(...args);
    };
}

function BaseStringServiceLoader (_i18n_) {
    i18n = _i18n_;

    return BaseStringService;
}

BaseStringServiceLoader.$inject = ['i18n'];

export default BaseStringServiceLoader;