server.js

var http = require("http")
var url = require("url")
var qs = require("querystring")
var sqlite3 = require("sqlite3").verbose()
var config = require("./config.js")
var port = config.port || 8000
var host = config.host || "0.0.0.0"

console.log("Starting app")

var db = new sqlite3.Database(
	`${process.env.DATA_PATH}links.db`,
	sqlite3.OPEN_READWRITE | sqlite3.OPEN_CREATE,
	function (err) {
		if (err) {
			console.log(err)
			process.exit(1)
		}
		console.log("Starting DB")

		db.serialize(function () {
			db.run(
				"CREATE TABLE IF NOT EXISTS links (path TEXT PRIMARY KEY NOT NULL, destination TEXT NOT NULL, used INT NOT NULL)",
				function (err) {
					if (err) {
						console.log(err)
						process.exit(2)
					}
					console.log("Started DB")
				}
			)
		})
	}
)

http
	.createServer(function (req, res) {
		var url_params = url.parse(req.url)
		var query = qs.parse(url_params.query)
		console.log(url_params)
		console.log(query)
		if (
			url_params.pathname &&
			url_params.pathname.length > 2 &&
			url_params.pathname[2] == "."
		) {
			res.writeHead(404, { "Content-Type": "text/plain" })
			res.end("Not found")
		} else if (query.secret == config.secret) {
			switch (url_params.pathname) {
				case "":
				case "/":
					res.writeHead(200, { "Content-Type": "text/html" })
					getFrontPageHtml(function (html) {
						res.end(html)
					})
					break
				case "/new":
					if (typeof query.target === "undefined" || query.target.length == 0) {
						returnError(res, 400, "Bad Request: Target must be specified")
					} else {
						var path,
							target = query.target
						if (typeof query.path !== "undefined" && query.path.length > 0) {
							path = query.path
							newLink(res, path, target)
						} else {
							db.get(
								"SELECT path FROM links WHERE destination = $destination",
								{
									$destination: target,
								},
								function (err, row) {
									if (err) {
										returnError(res, 500, "SQL Error")
									} else {
										console.log("Existing " + (row ? row.path : "none"))
										if (row && row.path) {
											res.writeHead(200, { "Content-Type": "application/json" })
											res.end(
												JSON.stringify({
													status: 200,
													short: config.base_url + row.path,
													destination: target,
												})
											)
										} else {
											generateNewLinkPath(res, target)
										}
									}
								}
							)
						}
					}
					break
				default:
					returnError(res, 404, "Not Found")
					break
			}
		} else if (url_params.pathname.length < 2) {
			returnError(res, 200, "Forbidden to access /")
		} else {
			var path = url_params.pathname.substring(1)
			// Follow redirect
			db.get(
				"SELECT destination FROM links WHERE path = $path",
				{
					$path: path,
				},
				function (err, row) {
					if (err) {
						console.log(err)
						returnError(res, 500, "SQL Error")
					} else if (!row || !row.destination) {
						returnError(res, 404, "Not Found")
					} else {
						res.writeHead(301, {
							"Content-Type": "text/html",
							Location: row.destination,
						})
						res.end(
							'<script type="text/javascript">window.location.href="' +
								row.destination +
								'";</script><a href="' +
								row.destination +
								'">Click here to follow redirect.</a>'
						)
						db.run("UPDATE links SET used = used + 1 WHERE path = $path", {
							$path: path,
						})
					}
				}
			)
		}
	})
	.listen(port, host)
console.log("Starting HTTP")

function generateNewLinkPath(res, target) {
	var path = numToPath(Math.floor(Math.random() * (Math.pow(64, 5) - 1) + 1))
	db.get(
		"SELECT COUNT(1) AS amount FROM links WHERE path = $path",
		{
			$path: path,
		},
		function (err, row) {
			if (err) {
				returnError(res, 500, "SQL Error")
			} else {
				if (row && row.amount) {
					generateNewLinkPath(res)
				} else {
					newLink(res, path, target)
				}
			}
		}
	)
}

var validChars =
	"qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM1234567890_-"

function numToPath(num) {
	if (num < validChars.length) return validChars[num]
	return (
		numToPath(Math.floor(num / validChars.length)) +
		numToPath(num % validChars.length)
	)
}

function returnError(res, code, message) {
	res.writeHead(code, { "Content-Type": "application/json" })
	res.end(
		JSON.stringify({
			status: code,
			msg: message,
		})
	)
}

function newLink(res, path, target) {
	if (config.includeHostInPath) {
		if (!/^[a-z0-9]+:\/\//.test(target)) {
			target = "http://" + target
		}
		var targetparts = url.parse(target)
		console.log(target, JSON.stringify(targetparts))
		path = targetparts.hostname + "/" + path
	}
	db.run(
		"INSERT OR IGNORE INTO links VALUES ($path, $destination, 0)",
		{
			$path: path,
			$destination: target,
		},
		function (err) {
			if (err) {
				console.log(err)
				returnError(res, 500, "SQL Error")
			} else {
				db.run(
					"UPDATE links SET destination = $destination WHERE path = $path",
					{
						$path: path,
						$destination: target,
					},
					function (err) {
						if (err) {
							console.log(err)
							returnError(res, 500, "SQL Error")
						} else {
							res.writeHead(200, { "Content-Type": "application/json" })
							res.end(
								JSON.stringify({
									status: 200,
									short: config.base_url + path,
									destination: target,
								})
							)
						}
					}
				)
			}
		}
	)
}

function HtmlReplacer(c) {
	return (
		{
			'"': "&quot;",
			"&": "&amp;",
			"'": "&#39;",
			"/": "&#47;",
			"<": "&lt;",
			">": "&gt;",
		}[c] || "[UNKNOWN]"
	)
}

function escapeHtml(text) {
	return text.toString().replace(/["&'\/<>]/g, HtmlReplacer)
}

function getFrontPageHtml(callback) {
	var html =
		'<!DOCTYPE html><html><head><meta charset="utf-8" /><title>Shorten Link</title></head><body>' +
		'<form  action="' +
		config.base_url +
		'new" method="GET"><input type="hidden" name="secret" value="' +
		config.secret +
		'" /><input type="text" name="path" placeholder="(optional) path" /><input type="url" name="target" placeholder="target" /><input name="submit" type="submit" value="Create" /></form><ul>'

	db.each(
		"SELECT rowid AS id, path, destination, used FROM links",
		function (err, row) {
			if (err) {
				console.log(err)
			} else {
				console.log(
					row.id + " (" + row.used + ") " + row.path + ": " + row.destination
				)
				html +=
					"<li>" +
					row.id +
					" (" +
					row.used +
					") " +
					escapeHtml(row.path) +
					": " +
					escapeHtml(row.destination) +
					"</li>"
			}
		},
		function (err) {
			if (err) {
				console.log(err)
			}
			html += "</ul></body></html>"
			callback(html)
		}
	)
}

function exitHandler() {
	console.log("Closing db connection")
	db.close(function (err) {
		if (err) {
			console.log(err)
			process.exit(3)
		} else process.exit(0)
	})
}

process.on("SIGINT", exitHandler)