"use strict"

var buildPathname = require("../pathname/build")

module.exports = function($window, Promise) {
	var callbackCount = 0
	var oncompletion

	function makeRequest(factory) {
		return function(url, args) {
			if (typeof url !== "string") { args = url; url = url.url }
			else if (args == null) args = {}
			var promise = new Promise(function(resolve, reject) {
				factory(buildPathname(url, args.params), args, function (data) {
					if (typeof args.type === "function") {
						if (Array.isArray(data)) {
							for (var i = 0; i < data.length; i++) {
								data[i] = new args.type(data[i])
							}
						}
						else data = new args.type(data)
					}
					resolve(data)
				}, reject)
			})
			if (args.background === true) return promise
			var count = 0
			function complete() {
				if (--count === 0 && typeof oncompletion === "function") oncompletion()
			}

			return wrap(promise)

			function wrap(promise) {
				var then = promise.then
				promise.then = function() {
					count++
					var next = then.apply(promise, arguments)
					next.then(complete, function(e) {
						complete()
						if (count === 0) throw e
					})
					return wrap(next)
				}
				return promise
			}
		}
	}

	function hasHeader(args, name) {
		for (var key in args.headers) {
			if ({}.hasOwnProperty.call(args.headers, key) && name.test(key)) return true
		}
		return false
	}

	return {
		request: makeRequest(function(url, args, resolve, reject) {
			var method = args.method != null ? args.method.toUpperCase() : "GET"
			var body = args.body
			var assumeJSON = (args.serialize == null || args.serialize === JSON.serialize) && !(body instanceof $window.FormData)

			var xhr = new $window.XMLHttpRequest(),
				aborted = false,
				_abort = xhr.abort

			xhr.abort = function abort() {
				aborted = true
				_abort.call(xhr)
			}

			xhr.open(method, url, args.async !== false, typeof args.user === "string" ? args.user : undefined, typeof args.password === "string" ? args.password : undefined)

			if (assumeJSON && !hasHeader(args, /^content-type$/i)) {
				xhr.setRequestHeader("Content-Type", "application/json; charset=utf-8")
			}
			if (typeof args.deserialize !== "function" && !hasHeader(args, /^accept$/i)) {
				xhr.setRequestHeader("Accept", "application/json, text/*")
			}
			if (args.withCredentials) xhr.withCredentials = args.withCredentials
			if (args.timeout) xhr.timeout = args.timeout
			xhr.responseType = args.responseType || (typeof args.extract === "function" ? "" : "json")

			for (var key in args.headers) {
				if ({}.hasOwnProperty.call(args.headers, key)) {
					xhr.setRequestHeader(key, args.headers[key])
				}
			}

			if (typeof args.config === "function") xhr = args.config(xhr, args) || xhr

			xhr.onreadystatechange = function() {
				// Don't throw errors on xhr.abort().
				if(aborted) return

				if (xhr.readyState === 4) {
					try {
						var success = (xhr.status >= 200 && xhr.status < 300) || xhr.status === 304 || (/^file:\/\//i).test(url)
						// When the response type isn't "" or "text",
						// `xhr.responseText` is the wrong thing to use.
						// Browsers do the right thing and throw here, and we
						// should honor that and do the right thing by
						// preferring `xhr.response` where possible/practical.
						var response = xhr.response, message

						if (response == null) {
							try {
								response = xhr.responseText
								// Note: this snippet is intentionally *after*
								// `xhr.responseText` is accessed, since the
								// above will throw in modern browsers (thus
								// skipping the rest of this section). It's an
								// IE hack to detect and work around the lack of
								// native `responseType: "json"` support there.
								if (typeof args.extract !== "function" && xhr.responseType === "json") response = JSON.parse(response)
							}
							catch (e) { response = null }
						}

						if (typeof args.extract === "function") {
							response = args.extract(xhr, args)
							success = true
						} else if (typeof args.deserialize === "function") {
							response = args.deserialize(response)
						}
						if (success) resolve(response)
						else {
							try { message = xhr.responseText }
							catch (e) { message = response }
							var error = new Error(message)
							error.code = xhr.status
							error.response = response
							reject(error)
						}
					}
					catch (e) {
						reject(e)
					}
				}
			}

			if (body == null) xhr.send()
			else if (typeof args.serialize === "function") xhr.send(args.serialize(body))
			else if (body instanceof $window.FormData) xhr.send(body)
			else xhr.send(JSON.stringify(body))
		}),
		jsonp: makeRequest(function(url, args, resolve, reject) {
			var callbackName = args.callbackName || "_mithril_" + Math.round(Math.random() * 1e16) + "_" + callbackCount++
			var script = $window.document.createElement("script")
			$window[callbackName] = function(data) {
				delete $window[callbackName]
				script.parentNode.removeChild(script)
				resolve(data)
			}
			script.onerror = function() {
				delete $window[callbackName]
				script.parentNode.removeChild(script)
				reject(new Error("JSONP request failed"))
			}
			script.src = url + (url.indexOf("?") < 0 ? "?" : "&") +
				encodeURIComponent(args.callbackKey || "callback") + "=" +
				encodeURIComponent(callbackName)
			$window.document.documentElement.appendChild(script)
		}),
		setCompletionCallback: function(callback) {
			oncompletion = callback
		},
	}
}