Kitten Cache

kittens.js

var fs = require('fs'),
    http = require('http'),
    path = require('path');

var CACHE_DIR = '.kitten_cache';

if (!path.existsSync(CACHE_DIR)) {
    fs.mkdirSync('.kitten_cache', 0755);
} else if (!fs.statSync(CACHE_DIR).isDirectory()) {
    console.error('Cache dir `%s` must be a directory.', CACHE_DIR)
    process.exit(1);
}

http.createServer(function (req, res) {
    var match = req.url.match(/^\/(\d+)\/(\d+)\/?$/), filename, cache_in;
    if (!match) {
        res.writeHead(404);
        res.end('404 Image not found\r\n');
        return;
    }

    // Try to read from cache
    filename = '.kitten_cache/' + match[1] + '_' + match[2];
    cache_in = fs.createReadStream(filename);
    cache_in.pipe(res, {end: false});
    cache_in.on('end', function () {
        res.end();
        console.log('From cache ' + req.url);
    });
    
    // Otherwise pull from web
    cache_in.on('error', function (e) {
        var cache_out, img_req;
        cache_out = fs.createWriteStream(filename, {mode: 0644});
        cache_out.on('error', function (e) {
            console.log('Could not write to cache: ' + e.message);
        });
        img_req = http.get({
            host: 'placekitten.com',
            port: 80,
            path: req.url
        });
        img_req.on('all', function () {
            console.log('all', arguments);
        });
        img_req.on('response', function (img_res) {
            console.log('From web ' + req.url);
            img_res.pipe(res);
            if (cache_out.writable) {
                img_res.pipe(cache_out);
            }
        });
        img_req.on('close', function () {
            console.log('From web ' + req.url);
        });
        img_req.on('error', function (e) {
            res.writeHead(500);
            res.end('500 could not fetch image from placekitten.com: ' +
                    e.message);
            console.log('Failed web ' + req.url);
        });
    });
}).listen(1337, '127.0.0.1');

console.log('Server running at http://127.0.0.1:1337/');