socket.io-client-swift/Source/SocketEnginePollable.swift

//
//  SocketEnginePollable.swift
//  Socket.IO-Client-Swift
//
//  Created by Erik Little on 1/15/16.
//
//  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

/// Protocol that is used to implement socket.io polling support
public protocol SocketEnginePollable : SocketEngineSpec {
    var invalidated: Bool { get }
    /// Holds strings waiting to be sent over polling. 
    /// You shouldn't need to mess with this.
    var postWait: [String] { get set }
    var session: URLSession? { get }
    /// Because socket.io doesn't let you send two polling request at the same time
    /// we have to keep track if there's an outstanding poll
    var waitingForPoll: Bool { get set }
    /// Because socket.io doesn't let you send two post request at the same time
    /// we have to keep track if there's an outstanding post
    var waitingForPost: Bool { get set }
    
    func doPoll()
    func sendPollMessage(_ message: String, withType type: SocketEnginePacketType, withData datas: [Data])
    func stopPolling()
}

// Default polling methods
extension SocketEnginePollable {
    private func addHeaders(for req: URLRequest) -> URLRequest {
        var req = req
        
        if cookies != nil {
            let headers = HTTPCookie.requestHeaderFields(with: cookies!)
            req.allHTTPHeaderFields = headers
        }
        
        if extraHeaders != nil {
            for (headerName, value) in extraHeaders! {
                req.setValue(value, forHTTPHeaderField: headerName)
            }
        }
        
        return req
    }
    
    func createRequestForPostWithPostWait() -> URLRequest {
        defer { postWait.removeAll(keepingCapacity: true) }

        var postStr = ""
        
        for packet in postWait {
            let len = packet.characters.count
            
            postStr += "\(len):\(packet)"
        }
        
        DefaultSocketLogger.Logger.log("Created POST string: %@", type: "SocketEnginePolling", args: postStr)
        
        var req = URLRequest(url: urlPollingWithSid)
        let postData = postStr.data(using: .utf8, allowLossyConversion: false)!
        
        req = addHeaders(for: req)
        
        req.httpMethod = "POST"
        req.setValue("text/plain; charset=UTF-8", forHTTPHeaderField: "Content-Type")

        req.httpBody = postData
        req.setValue(String(postData.count), forHTTPHeaderField: "Content-Length")
        
        return req as URLRequest
    }
    
    public func doPoll() {
        if websocket || waitingForPoll || !connected || closed { return }
        
        waitingForPoll = true
        
        var req = URLRequest(url: urlPollingWithSid)
        
        req = addHeaders(for: req)
        doLongPoll(for: req )
    }
    
    func doRequest(for req: URLRequest, callbackWith callback: @escaping (Data?, URLResponse?, Error?) -> Void) {
        if !polling || closed || invalidated || fastUpgrade {
            return
        }
        
        DefaultSocketLogger.Logger.log("Doing polling request", type: "SocketEnginePolling")
        
        session?.dataTask(with: req, completionHandler: callback).resume()
    }
    
    func doLongPoll(for req: URLRequest) {
        doRequest(for: req) {[weak self] data, res, err in
            guard let this = self, this.polling else { return }
            
            if err != nil || data == nil {
                DefaultSocketLogger.Logger.error(err?.localizedDescription ?? "Error", type: "SocketEnginePolling")
                
                if this.polling {
                    this.didError(reason: err?.localizedDescription ?? "Error")
                }
                
                return
            }
            
            DefaultSocketLogger.Logger.log("Got polling response", type: "SocketEnginePolling")
            
            if let str = String(data: data!, encoding: String.Encoding.utf8) {
                this.parseQueue.async {
                    this.parsePollingMessage(str)
                }
            }
            
            this.waitingForPoll = false
            
            if this.fastUpgrade {
                this.doFastUpgrade()
            } else if !this.closed && this.polling {
                this.doPoll()
            }
        }
    }
    
    private func flushWaitingForPost() {
        if postWait.count == 0 || !connected {
            return
        } else if websocket {
            flushWaitingForPostToWebSocket()
            return
        }
        
        let req = createRequestForPostWithPostWait()
        
        waitingForPost = true
        
        DefaultSocketLogger.Logger.log("POSTing", type: "SocketEnginePolling")
        
        doRequest(for: req) {[weak self] data, res, err in
            guard let this = self else { return }
            
            if err != nil {
                DefaultSocketLogger.Logger.error(err?.localizedDescription ?? "Error", type: "SocketEnginePolling")
                
                if this.polling {
                    this.didError(reason: err?.localizedDescription ?? "Error")
                }
                
                return
            }
            
            this.waitingForPost = false
            
            this.emitQueue.async {
                if !this.fastUpgrade {
                    this.flushWaitingForPost()
                    this.doPoll()
                }
            }
        }
    }
    
    func parsePollingMessage(_ str: String) {
        guard str.characters.count != 1 else { return }
        
        var reader = SocketStringReader(message: str)
        
        while reader.hasNext {
            if let n = Int(reader.readUntilOccurence(of: ":")) {
                let str = reader.read(count: n)
                
                handleQueue.async { self.parseEngineMessage(str, fromPolling: true) }
            } else {
                handleQueue.async { self.parseEngineMessage(str, fromPolling: true) }
                break
            }
        }
    }
    
    /// Send polling message.
    /// Only call on emitQueue
    public func sendPollMessage(_ message: String, withType type: SocketEnginePacketType, withData datas: [Data]) {
        DefaultSocketLogger.Logger.log("Sending poll: %@ as type: %@", type: "SocketEnginePolling", args: message, type.rawValue)
        let fixedMessage: String
        
        if doubleEncodeUTF8 {
            fixedMessage = doubleEncodeUTF8(message)
        } else {
            fixedMessage = message
        }
        
        postWait.append(String(type.rawValue) + fixedMessage)
        
        for data in datas {
            if case let .right(bin) = createBinaryDataForSend(using: data) {
                postWait.append(bin)
            }
        }
        
        if !waitingForPost {
            flushWaitingForPost()
        }
    }
    
    public func stopPolling() {
        waitingForPoll = false
        waitingForPost = false
        session?.finishTasksAndInvalidate()
    }
}