index.js

const namedQueue = require('named-queue');
const helpers = require('./helpers');

var providers = {
    metadata: require('./providers/cinemeta'),
    imdbFind: require('./providers/imdbFind'),
}

var defaultProviders = ['metadata', 'imdbFind']

// Constants
var CACHE_TTL = 12 * 60 * 60 * 1000; // if we don't find an item, how long does it stay in the cache as 'not found' before we retry it 

// In-memory cache for matched items, to avoid flooding Google (or whatever search api we use)
var cache = {};
var cacheLastSet = {};

// Named queue, means that we're not working on one name more than once at a time
// and a total of 3 names at once
var queue = new namedQueue(worker, 3)

// Outside API
function nameToImdb(args, cb) {

    if (!cb)
        return new Promise(function (resolve, reject) {
            nameToImdb(args, function (error, res, inf) {
                if (error)
                    return reject(error)
                resolve({ res, inf })
            })
        })

    args = typeof (args) == 'string' ? { name: args } : args

    var q = { name: helpers.parseSearchTerm(args.name) }
    if (args.year) q.year = args.year
    if (args.type) q.type = args.type

    if (!q.name)
        return cb(new Error('empty name'))

    if (q.year && typeof (q.year) == 'string') q.year = parseInt(q.year.split('-')[0])

    if (q.year && isNaN(q.year))
        return cb(new Error('invalid year'))

    if (q.type && !(q.type == 'movie' || q.type == 'series'))
        return cb(null, null) // no match for other types
    var key = new Buffer.from(args.hintUrl || Object.values(q).join(':')).toString('ascii') // convert to ASCII since EventEmitter bugs with UTF8

    if (cache.hasOwnProperty(key) && Date.now() - cacheLastSet[key] < CACHE_TTL) {
        return cb(null, cache[key][0], { match: cache[key][1].match, isCached: true })
    }

    queue.push({
        id: key,
        q: q,
        providers: args.providers || defaultProviders,
    }, function (err, res, match) {
        if (err)
            return cb(err)

        if (res && res.id) {
            cache[key] = [res.id, match]
            cacheLastSet[key] = Date.now()
        }

        cb(null, (res || {}).id, { ...match, meta: res })
    })
};

function worker(task, cb) {
    var prov = [].concat(task.providers)

    nextProv()

    function nextProv() {
        var n = prov.shift()
        if (!n)
            return cb(null, null)

        var provider = providers[n]
        if (!provider)
            return cb(new Error('unknown provider: ' + n))

        provider(task.q, function (err, res) {
            if (err)
                return cb(err)

            if (res)
                return cb(null, res, { match: n })
            else
                nextProv()
        })
    }
}

module.exports = nameToImdb;