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urlManager.js
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urlManager.js
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const ShortUrl = require("./schemas/ShortUrl");
const Settings = require("./schemas/Settings");
const urlManager = () => {
let current = 0;
let max = 2 ** 16;
let coprime = 7931;
// Lazy initialize settings. (Check DB first)
Settings.findOne()
.then(settings => {
if (settings) {
console.log(`Settings found ${settings}`);
current = settings.current;
max = settings.max;
coprime = settings.coprime;
} else {
const settings = new Settings({
current, max, coprime
})
settings.save()
.then(console.log("Saved settings"))
.catch(err => console.log(err))
}
})
.catch(err => console.log(err))
// Get Base64 number for up to 16 bits
const getBase64 = (num) => {
return Buffer.from([num >> 8, num]).toString('base64').substr(0, 3);
};
// URL Manager object
return {
// Given a URL create a shortened version
setUrl: async (url) => {
console.log("setUrl called with " + url);
current = (coprime + current) % max;
console.log(max, current)
// New database starts with current of (0 + coprime) % max
// If we repeat this, we eventually go all the way around back to 0
// This means that the database is full (or has one more slot technically)
if (current == 0) throw "Database is Full";
let b64 = getBase64(current);
// Replace URL unfriendly characters with dash and underscore
b64 = b64.replace('/', '-');
b64 = b64.replace('+', '_');
const shortUrl = new ShortUrl({
code: b64, url: url
})
// Insert shortUrl record into database
try {
await shortUrl.save();
console.log(`Saved ${b64} as ${url}`);
const newSettings = { max, coprime, current }
await Settings.findOneAndUpdate({}, newSettings, { upsert: true, new: true, setDefaultsOnInsert: true, findOneAndUpdate: false })
console.log(`Settings modified to: ${newSettings}`)
return b64
}
catch (err) {
console.log(err);
process.exit(1);
}
},
getUrl: async (ascii) => {
console.log(ascii);
let shortUrl;
try {
shortUrl = await ShortUrl.findOne({ code: ascii }).exec();
if (shortUrl) {
console.log(`Found match: ${shortUrl.code} -> ${shortUrl.url}`);
return shortUrl.url;
} else {
return undefined;
}
} catch (err) {
console.log(err);
process.exit(1);
}
}
}
}
module.exports = urlManager;