gray-matter-from-file/lib/index.js

Extracts only the front matter from a file stream, and passes to the well known gray-matter library for parsing.

'use strict';

Object.defineProperty(exports, "__esModule", {
    value: true
});

var _readline = require('readline');

var _readline2 = _interopRequireDefault(_readline);

var _fs = require('fs');

var _fs2 = _interopRequireDefault(_fs);

var _os = require('os');

var _os2 = _interopRequireDefault(_os);

var _grayMatter = require('gray-matter');

var _grayMatter2 = _interopRequireDefault(_grayMatter);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

const readFrontMatter = filepath => {
    return new Promise((resolve, reject) => {
        let frontMatter = '';
        const fileReader = _fs2.default.createReadStream(filepath);
        const lineReader = _readline2.default.createInterface({ input: fileReader });

        lineReader.on('line', line => {
            // first line / last line / mid lines
            if (!frontMatter && line === '---') {
                frontMatter = frontMatter + line;
            } else if (frontMatter && line === '---') {
                frontMatter = frontMatter + _os2.default.EOL + line;
                lineReader.close();
            } else {
                frontMatter = frontMatter + _os2.default.EOL + line;
            }
        });

        lineReader.on('close', () => {
            resolve(frontMatter);
        });

        fileReader.on('error', error => {
            reject(error);
        });
    });
};

exports.default = filepath => {
    return new Promise((resolve, reject) => {
        readFrontMatter(filepath).then(frontMatter => {
            const parsedFrontMatter = (0, _grayMatter2.default)(frontMatter);
            resolve(parsedFrontMatter.data);
        }).catch(e => reject(e));
    });
};