salix/modules/invoiceOut/back/methods/invoiceOut/download.js

const fs = require('fs-extra');
const path = require('path');
const isProduction = require('vn-loopback/server/boot/isProduction');

module.exports = Self => {
    Self.remoteMethodCtx('download', {
        description: 'Download an invoice PDF',
        accessType: 'READ',
        accepts: [
            {
                arg: 'id',
                type: 'string',
                description: 'The invoice id',
                http: {source: 'path'}
            }
        ],
        returns: [
            {
                arg: 'body',
                type: 'file',
                root: true
            }, {
                arg: 'Content-Type',
                type: 'string',
                http: {target: 'header'}
            }, {
                arg: 'Content-Disposition',
                type: 'string',
                http: {target: 'header'}
            }
        ],
        http: {
            path: '/:id/download',
            verb: 'GET'
        },
        accessScopes: ['DEFAULT', 'read:multimedia']
    });

    Self.download = async function(ctx, id, options) {
        const models = Self.app.models;
        options = typeof options == 'object'
            ? Object.assign({}, options) : {};

        const pdfFile = await Self.filePath(id, options);

        const container = await models.InvoiceContainer.container(pdfFile.year);
        const rootPath = container.client.root;

        const file = {
            path: path.join(rootPath, pdfFile.path, pdfFile.name),
            contentType: 'application/pdf',
            name: pdfFile.name
        };

        try {
            await fs.access(file.path);
        } catch (error) {
            await Self.createPdf(ctx, id, options);
        }

        let stream = await fs.createReadStream(file.path);
        // XXX: To prevent unhandled ENOENT error
        // https://stackoverflow.com/questions/17136536/is-enoent-from-fs-createreadstream-uncatchable
        stream.on('error', err => {
            const e = new Error(err.message);
            err.stack = e.stack;
            console.error(err);
        });

        if (!isProduction()) {
            try {
                await fs.access(file.path);
            } catch (error) {
                stream = null;
            }
        }

        return [stream, file.contentType, `filename="${pdfFile.name}"`];
    };
};