// Alamofire.swift
//
// Copyright (c) 2014–2015 Alamofire Software Foundation (http://alamofire.org/)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

import Foundation

/**
    Responsible for sending a request and receiving the response and associated data from the server, as well as managing its underlying `NSURLSessionTask`.
*/
public class Request {
    let delegate: TaskDelegate
    
    /// The underlying task.
    public var task: NSURLSessionTask { return delegate.task }
    
    /// The session belonging to the underlying task.
    public let session: NSURLSession
    
    /// The request sent or to be sent to the server.
    public var request: NSURLRequest { return task.originalRequest }
    
    /// The response received from the server, if any.
    public var response: NSHTTPURLResponse? { return task.response as? NSHTTPURLResponse }
    
    /// The progress of the request lifecycle.
    public var progress: NSProgress { return delegate.progress }
    
    init(session: NSURLSession, task: NSURLSessionTask) {
        self.session = session
        
        switch task {
        case is NSURLSessionUploadTask:
            self.delegate = UploadTaskDelegate(task: task)
        case is NSURLSessionDataTask:
            self.delegate = DataTaskDelegate(task: task)
        case is NSURLSessionDownloadTask:
            self.delegate = DownloadTaskDelegate(task: task)
        default:
            self.delegate = TaskDelegate(task: task)
        }
    }
    
    // MARK: - Authentication
    
    /**
        Associates an HTTP Basic credential with the request.
    
        :param: user The user.
        :param: password The password.
    
        :returns: The request.
    */
    public func authenticate(#user: String, password: String) -> Self {
        let credential = NSURLCredential(user: user, password: password, persistence: .ForSession)
        
        return authenticate(usingCredential: credential)
    }
    
    /**
        Associates a specified credential with the request.
        
        :param: credential The credential.
        
        :returns: The request.
    */
    public func authenticate(usingCredential credential: NSURLCredential) -> Self {
        delegate.credential = credential
        
        return self
    }
    
    // MARK: - Progress
    
    /**
        Sets a closure to be called periodically during the lifecycle of the request as data is written to or read from the server.
        
        - For uploads, the progress closure returns the bytes written, total bytes written, and total bytes expected to write.
        - For downloads, the progress closure returns the bytes read, total bytes read, and total bytes expected to write.
        
        :param: closure The code to be executed periodically during the lifecycle of the request.
        
        :returns: The request.
    */
    public func progress(closure: ((Int64, Int64, Int64) -> Void)? = nil) -> Self {
        if let uploadDelegate = delegate as? UploadTaskDelegate {
            uploadDelegate.uploadProgress = closure
        } else if let dataDelegate = delegate as? DataTaskDelegate {
            dataDelegate.dataProgress = closure
        } else if let downloadDelegate = delegate as? DownloadTaskDelegate {
            downloadDelegate.downloadProgress = closure
        }
        
        return self
    }
    
    // MARK: - Response
    
    /**
        A closure used by response handlers that takes a request, response, and data and returns a serialized object and any error that occured in the process.
    */
    public typealias Serializer = (NSURLRequest, NSHTTPURLResponse?, NSData?) -> (AnyObject?, NSError?)
    
    /**
        Creates a response serializer that returns the associated data as-is.
        
        :returns: A data response serializer.
    */
    public class func responseDataSerializer() -> Serializer {
        return { (request, response, data) in
            return (data, nil)
        }
    }
    
    /**
        Adds a handler to be called once the request has finished.
        
        :param: completionHandler The code to be executed once the request has finished.
        
        :returns: The request.
    */
    public func response(completionHandler: (NSURLRequest, NSHTTPURLResponse?, AnyObject?, NSError?) -> Void) -> Self {
        return response(serializer: Request.responseDataSerializer(), completionHandler: completionHandler)
    }
    
    /**
        Adds a handler to be called once the request has finished.
        
        :param: queue The queue on which the completion handler is dispatched.
        :param: serializer The closure responsible for serializing the request, response, and data.
        :param: completionHandler The code to be executed once the request has finished.
        
        :returns: The request.
    */
    public func response(queue: dispatch_queue_t? = nil, serializer: Serializer, completionHandler: (NSURLRequest, NSHTTPURLResponse?, AnyObject?, NSError?) -> Void) -> Self {
        delegate.queue.addOperationWithBlock {
            let (responseObject: AnyObject?, serializationError: NSError?) = serializer(self.request, self.response, self.delegate.data)
            
            dispatch_async(queue ?? dispatch_get_main_queue()) {
                completionHandler(self.request, self.response, responseObject, self.delegate.error ?? serializationError)
            }
        }
        
        return self
    }
    
    // MARK: - State
    
    /**
        Suspends the request.
    */
    public func suspend() {
        task.suspend()
    }
    
    /**
        Resumes the request.
    */
    public func resume() {
        task.resume()
    }
    
    /**
        Cancels the request.
    */
    public func cancel() {
        if let downloadDelegate = delegate as? DownloadTaskDelegate {
            downloadDelegate.downloadTask.cancelByProducingResumeData { (data) in
                downloadDelegate.resumeData = data
            }
        } else {
            task.cancel()
        }
    }
    
    // MARK: - TaskDelegate
    
    class TaskDelegate: NSObject, NSURLSessionTaskDelegate {
        let task: NSURLSessionTask
        let queue: NSOperationQueue
        let progress: NSProgress
        
        var data: NSData? { return nil }
        var error: NSError?
        
        var credential: NSURLCredential?
        
        var taskWillPerformHTTPRedirection: ((NSURLSession!, NSURLSessionTask!, NSHTTPURLResponse!, NSURLRequest!) -> (NSURLRequest!))?
        var taskDidReceiveChallenge: ((NSURLSession!, NSURLSessionTask!, NSURLAuthenticationChallenge) -> (NSURLSessionAuthChallengeDisposition, NSURLCredential?))?
        var taskDidSendBodyData: ((NSURLSession!, NSURLSessionTask!, Int64, Int64, Int64) -> Void)?
        var taskNeedNewBodyStream: ((NSURLSession!, NSURLSessionTask!) -> (NSInputStream!))?
        
        init(task: NSURLSessionTask) {
            self.task = task
            self.progress = NSProgress(totalUnitCount: 0)
            self.queue = {
                let operationQueue = NSOperationQueue()
                operationQueue.maxConcurrentOperationCount = 1
                operationQueue.qualityOfService = NSQualityOfService.Utility
                operationQueue.suspended = true
                
                return operationQueue
            }()
        }
        
        deinit {
            queue.cancelAllOperations()
            queue.suspended = true
        }
        
        // MARK: - NSURLSessionTaskDelegate
        
        func URLSession(session: NSURLSession, task: NSURLSessionTask, willPerformHTTPRedirection response: NSHTTPURLResponse, newRequest request: NSURLRequest, completionHandler: ((NSURLRequest!) -> Void)) {
            var redirectRequest = request
            if taskWillPerformHTTPRedirection != nil {
                redirectRequest = taskWillPerformHTTPRedirection!(session, task, response, request)
            }
            
            completionHandler(redirectRequest)
        }
        
        func URLSession(session: NSURLSession, task: NSURLSessionTask, didReceiveChallenge challenge: NSURLAuthenticationChallenge, completionHandler: ((NSURLSessionAuthChallengeDisposition, NSURLCredential!) -> Void)) {
            var disposition: NSURLSessionAuthChallengeDisposition = .PerformDefaultHandling
            var credential: NSURLCredential?
            
            if taskDidReceiveChallenge != nil {
                (disposition, credential) = taskDidReceiveChallenge!(session, task, challenge)
            } else {
                if challenge.previousFailureCount > 0 {
                    disposition = .CancelAuthenticationChallenge
                } else {
                    credential = self.credential ?? session.configuration.URLCredentialStorage?.defaultCredentialForProtectionSpace(challenge.protectionSpace)
                    if credential != nil {
                        disposition = .UseCredential
                    }
                }
            }
            
            completionHandler(disposition, credential)
        }
        
        func URLSession(session: NSURLSession, task: NSURLSessionTask, needNewBodyStream completionHandler: ((NSInputStream!) -> Void)) {
            var bodyStream: NSInputStream?
            if taskNeedNewBodyStream != nil {
                bodyStream = taskNeedNewBodyStream!(session, task)
            }
            
            completionHandler(bodyStream)
        }
        
        func URLSession(session: NSURLSession, task: NSURLSessionTask, didCompleteWithError error: NSError?) {
            if error != nil {
                self.error = error
            }
            
            queue.suspended = false
        }
    }
    
    // MARK: - DataTaskDelegate
    
    class DataTaskDelegate: TaskDelegate, NSURLSessionDataDelegate {
        var dataTask: NSURLSessionDataTask! { return task as! NSURLSessionDataTask }
        
        private var mutableData: NSMutableData
        override var data: NSData? {
            return mutableData
        }
        
        private var expectedContentLength: Int64?
        
        var dataTaskDidReceiveResponse: ((NSURLSession!, NSURLSessionDataTask!, NSURLResponse!) -> (NSURLSessionResponseDisposition))?
        var dataTaskDidBecomeDownloadTask: ((NSURLSession!, NSURLSessionDataTask!) -> Void)?
        var dataTaskDidReceiveData: ((NSURLSession!, NSURLSessionDataTask!, NSData!) -> Void)?
        var dataTaskWillCacheResponse: ((NSURLSession!, NSURLSessionDataTask!, NSCachedURLResponse!) -> (NSCachedURLResponse))?
        var dataProgress: ((bytesReceived: Int64, totalBytesReceived: Int64, totalBytesExpectedToReceive: Int64) -> Void)?
        
        override init(task: NSURLSessionTask) {
            self.mutableData = NSMutableData()
            super.init(task: task)
        }
        
        // MARK: - NSURLSessionDataDelegate
        
        func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didReceiveResponse response: NSURLResponse, completionHandler: ((NSURLSessionResponseDisposition) -> Void)) {
            var disposition: NSURLSessionResponseDisposition = .Allow
            
            expectedContentLength = response.expectedContentLength
            
            if dataTaskDidReceiveResponse != nil {
                disposition = dataTaskDidReceiveResponse!(session, dataTask, response)
            }
            
            completionHandler(disposition)
        }
        
        func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didBecomeDownloadTask downloadTask: NSURLSessionDownloadTask) {
            dataTaskDidBecomeDownloadTask?(session, dataTask)
        }
        
        func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didReceiveData data: NSData) {
            dataTaskDidReceiveData?(session, dataTask, data)
            
            mutableData.appendData(data)
            
            if let expectedContentLength = dataTask.response?.expectedContentLength {
                dataProgress?(bytesReceived: Int64(data.length), totalBytesReceived: Int64(mutableData.length), totalBytesExpectedToReceive: expectedContentLength)
            }
        }
        
        func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, willCacheResponse proposedResponse: NSCachedURLResponse, completionHandler: ((NSCachedURLResponse!) -> Void)) {
            var cachedResponse = proposedResponse
            
            if dataTaskWillCacheResponse != nil {
                cachedResponse = dataTaskWillCacheResponse!(session, dataTask, proposedResponse)
            }
            
            completionHandler(cachedResponse)
        }
    }
}

// MARK: - Printable

extension Request: Printable {
    /// The textual representation used when written to an output stream, which includes the HTTP method and URL, as well as the response status code if a response has been received.
    public var description: String {
        var components: [String] = []
        if request.HTTPMethod != nil {
            components.append(request.HTTPMethod!)
        }
        
        components.append(request.URL!.absoluteString!)
        
        if response != nil {
            components.append("(\(response!.statusCode))")
        }
        
        return join(" ", components)
    }
}

// MARK: - DebugPrintable

extension Request: DebugPrintable {
    func cURLRepresentation() -> String {
        var components: [String] = ["$ curl -i"]
        
        let URL = request.URL
        
        if request.HTTPMethod != nil && request.HTTPMethod != "GET" {
            components.append("-X \(request.HTTPMethod!)")
        }
        
        if let credentialStorage = self.session.configuration.URLCredentialStorage {
            let protectionSpace = NSURLProtectionSpace(host: URL!.host!, port: URL!.port?.integerValue ?? 0, `protocol`: URL!.scheme!, realm: URL!.host!, authenticationMethod: NSURLAuthenticationMethodHTTPBasic)
            if let credentials = credentialStorage.credentialsForProtectionSpace(protectionSpace)?.values.array {
                for credential: NSURLCredential in (credentials as! [NSURLCredential]) {
                    components.append("-u \(credential.user!):\(credential.password!)")
                }
            } else {
                if let credential = delegate.credential {
                    components.append("-u \(credential.user!):\(credential.password!)")
                }
            }
        }
        
        // Temporarily disabled on OS X due to build failure for CocoaPods
        // See https://github.com/CocoaPods/swift/issues/24
        #if !os(OSX)
            if let cookieStorage = session.configuration.HTTPCookieStorage,
                cookies = cookieStorage.cookiesForURL(URL!) as? [NSHTTPCookie]
                where !cookies.isEmpty
            {
                let string = cookies.reduce(""){ $0 + "\($1.name)=\($1.value ?? String());" }
                components.append("-b \"\(string.substringToIndex(string.endIndex.predecessor()))\"")
            }
        #endif
        
        if request.allHTTPHeaderFields != nil {
            for (field, value) in request.allHTTPHeaderFields! {
                switch field {
                case "Cookie":
                    continue
                default:
                    components.append("-H \"\(field): \(value)\"")
                }
            }
        }
        
        if session.configuration.HTTPAdditionalHeaders != nil {
            for (field, value) in session.configuration.HTTPAdditionalHeaders! {
                switch field {
                case "Cookie":
                    continue
                default:
                    components.append("-H \"\(field): \(value)\"")
                }
            }
        }
        
        if let HTTPBody = request.HTTPBody,
            escapedBody = NSString(data: HTTPBody, encoding: NSUTF8StringEncoding)?.stringByReplacingOccurrencesOfString("\"", withString: "\\\"")
        {
            components.append("-d \"\(escapedBody)\"")
        }
        
        components.append("\"\(URL!.absoluteString!)\"")
        
        return join(" \\\n\t", components)
    }
    
    /// The textual representation used when written to an output stream, in the form of a cURL command.
    public var debugDescription: String {
        return cURLRepresentation()
    }
}