express.js

var express = require('express');
var qs = require('qs');
var config = require('grant/lib/config');
var flows = {
	1: require('grant/lib/flow/oauth1'),
	2: require('grant/lib/flow/oauth2'),
	getpocket: require('grant/lib/flow/getpocket')
};

function Grant (_config, configOverride) {
	var app = express()
	app.config = config.init(_config)
	app._config = config

	if (typeof configOverride !== 'function') {
		configOverride = function (config, provider, req, done) {
			done(config);
		};
	}

	app.all('/connect/:provider/:override?', function (req, res, next) {
		if (!req.session) {
			throw new Error('Grant: mount session middleware first')
		}
		if (req.method === 'POST' && !req.body) {
			throw new Error('Grant: mount body parser middleware first')
		}
		next()
	})

	app.get('/connect/:provider/:override?', function (req, res, next) {
		if (req.params.override === 'callback') {
			next()
			return
		}

		req.session.grant = {
			provider: req.params.provider
		}
		if (req.params.override) {
			req.session.grant.override = req.params.override
		}

		if (Object.keys(req.query || {}).length) {
			req.session.grant.dynamic = req.query
		}

		connect(req, res)
	})

	app.post('/connect/:provider/:override?', function (req, res) {
		req.session.grant = {
			provider: req.params.provider
		}
		if (req.params.override) {
			req.session.grant.override = req.params.override
		}
		if (Object.keys(req.body || {}).length) {
			req.session.grant.dynamic = req.body
		}

		connect(req, res)
	})

	function connect (req, res) {
		var appConfig = app.config;
		var grant = req.session.grant

    // Pass original config, the 'req' object to access the session data and a callback.
    // Use the configOverride function to manipulate the config dynamically from within the backend code
    configOverride(app.config, req, function (appConfig) {
			var provider = config.provider(appConfig, grant)
			var flow = flows[provider.oauth]

			function callback (err, url) {
				var path = (provider.callback || '')
				if (err) {
					path ? res.redirect(path + '?' + err) : res.end(err)
				}
				else {
					res.redirect(url)
				}
			}

			if (/^1$/.test(provider.oauth)) {
				flow.step1(provider, function (err, data) {
					if (err) {
						callback(err)
					}
					else {
						grant.step1 = data
						var url = flow.step2(provider, data)
						var error = !/^http|\//.test(url) ? url : null
						callback(error, url)
					}
				})
			}

			else if (/^2$/.test(provider.oauth)) {
				grant.state = provider.state
				var url = flow.step1(provider)
				callback(null, url)
			}

			else if (flow) {
				flow.step1(provider, function (err, data) {
					if (err) {
						callback(err)
					}
					else {
						grant.step1 = data
						var url = flow.step2(provider, data)
						callback(null, url)
					}
				})
			}

			else {
				var err = {error: 'Grant: missing or misconfigured provider'}
				callback(qs.stringify(err))
			}
		});
	}

	app.get('/connect/:provider/callback', function (req, res) {
		var grant = req.session.grant || {}
		var provider = config.provider(app.config, grant)
		var flow = flows[provider.oauth]

		function callback (err, response) {
			var path = (provider.callback || '')
			if (err) {
				path ? res.redirect(path + '?' + err) : res.end(err)
			}
			else if (!provider.transport || provider.transport === 'querystring') {
				res.redirect(path + '?' + response)
			}
			else if (provider.transport === 'session') {
				req.session.grant.response = qs.parse(response)
				res.redirect(path)
			}
		}

		if (/^1$/.test(provider.oauth)) {
			flow.step3(provider, grant.step1, req.query, callback)
		}

		else if (/^2$/.test(provider.oauth)) {
			flow.step2(provider, req.query, grant, function (err, data) {
				if (err) {
					callback(err)
				}
				else {
					var response = flow.step3(provider, data)
					callback(null, response)
				}
			})
		}

		else if (flow) {
			flow.step3(provider, grant.step1, callback)
		}

		else {
			var err = {error: 'Grant: missing session or misconfigured provider'}
			callback(qs.stringify(err))
		}
	})

	return app
}

exports = module.exports = Grant