@messageformat/fluent/lib/fluent-to-resource.js

Conversion & compatibility tools for using Fluent with MessageFormat 2

import * as Fluent from '@fluent/syntax';
import { MessageFormat } from 'messageformat';
import { DraftFunctions } from 'messageformat/functions';
import { fluentToMessage } from "./fluent-to-message.js";
import { getMessageFunction } from "./functions.js";
/**
 * Compile a Fluent resource (i.e. an FTL file) into a Map of
 * {@link MessageFormat} instances.
 *
 * Uses {@link DraftFunctions.currency}, {@link DraftFunctions.unit}, as well as
 * a custom `fluent:message` function provided by {@link getMessageFunction}.
 *
 * @param source - A Fluent resource,
 *   as the string contents of an FTL file,
 *   as a {@link https://projectfluent.org/fluent.js/syntax/classes/resource.html | Fluent.Resource},
 *   or in the shape output by {@link fluentToResourceData} as `data`.
 * @param locales - The locale code or codes to use for all of the resource's messages.
 * @param options - The MessageFormat constructor options to use for all of the resource's messages.
 * @param options.detectNumberSelection - Set `false` to disable number selector detection based on keys.
 */
export function fluentToResource(locales, source, options) {
    const res = new Map();
    const { detectNumberSelection, ...opt } = options ?? {};
    opt.functions = Object.assign({
        currency: DraftFunctions.currency,
        datetime: DraftFunctions.datetime,
        unit: DraftFunctions.unit,
        'fluent:message': getMessageFunction(res)
    }, options?.functions);
    const data = typeof source === 'string' || source instanceof Fluent.Resource
        ? fluentToResourceData(source, { detectNumberSelection }).data
        : source;
    for (const [id, group] of data) {
        let rg = res.get(id);
        if (!rg) {
            rg = new Map();
            res.set(id, rg);
        }
        for (const [attr, msg] of group) {
            rg.set(attr, new MessageFormat(locales, msg, opt));
        }
    }
    return res;
}
/**
 * Compile a Fluent resource (i.e. an FTL file) into a Map of
 * {@link MF.Message | Model.Message} data objects.
 *
 * @param source - A Fluent resource,
 *   as the string contents of an FTL file or
 *   as a {@link https://projectfluent.org/fluent.js/syntax/classes/resource.html | Fluent.Resource}
 * @param options.detectNumberSelection - Set `false` to disable number selector detection based on keys.
 * @returns An object containing the messages as `data` and any resource-level
 *   `comments` of the resource.
 */
export function fluentToResourceData(source, options) {
    const ast = typeof source === 'string'
        ? Fluent.parse(source, { withSpans: false })
        : source;
    const data = new Map();
    let groupComment = '';
    const resourceComments = [];
    for (const msg of ast.body) {
        switch (msg.type) {
            case 'Message':
            case 'Term': {
                const id = msg.type === 'Term' ? `-${msg.id.name}` : msg.id.name;
                const group = new Map();
                if (msg.value) {
                    const entry = fluentToMessage(msg.value, options);
                    if (msg.comment)
                        entry.comment = msg.comment.content;
                    if (groupComment) {
                        entry.comment = entry.comment
                            ? `${groupComment}\n\n${entry.comment}`
                            : groupComment;
                    }
                    group.set('', entry);
                }
                for (const attr of msg.attributes) {
                    group.set(attr.id.name, fluentToMessage(attr.value, options));
                }
                data.set(id, group);
                break;
            }
            case 'GroupComment':
                groupComment = msg.content;
                break;
            case 'ResourceComment':
                resourceComments.push(msg.content);
                break;
        }
    }
    return { data, comments: resourceComments.join('\n\n') };
}