using System;

using System.Collections.Generic;

using System.Linq;

using System.Reactive.Linq;

using System.Text;

using System.Windows.Input;

using ReactiveUI;

namespace MobileSample_Android.ViewModels

{

// borrowed from https://github.com/SignalR/SignalR-StockTicker/blob/master/SignalR.StockTicker/SignalR.StockTicker/SignalR.StockTicker/StockTicker.cs

public class WatchListViewModel : ReactiveObject

{

private readonly object marketStateLock = new object();

private readonly double rangePercent = 0.002;

private readonly ReactiveList<WatchListItemViewModel> stocks = new ReactiveList<WatchListItemViewModel>();

private readonly TimeSpan updateInterval = TimeSpan.FromMilliseconds(250);

private readonly Random updateOrNotRandom = new Random();

private readonly object updateStockPricesLock = new object();

private volatile MarketState marketState = MarketState.Closed;

private IDisposable timer;

private volatile bool updatingStockPrices;

public ICommand OpenMarketCommand { get; private set; }

public ICommand CloseMarketCommand { get; private set; }

public ICommand ResetCommand { get; private set; }

public WatchListViewModel()

{

var openCmd = ReactiveCommand.CreateAsyncObservable(this.WhenAnyValue(vm => vm.MarketState, m => m == MarketState.Closed),

_ => Observable.Start(OpenMarket), RxApp.MainThreadScheduler);

OpenMarketCommand = openCmd;

var closeCmd = ReactiveCommand.CreateAsyncObservable(

this.WhenAnyValue(vm => vm.MarketState, m => m == MarketState.Open),

_ => Observable.Start(CloseMarket), RxApp.MainThreadScheduler);

CloseMarketCommand = closeCmd;

var resetCmd = ReactiveCommand.CreateAsyncObservable(

this.WhenAnyValue(vm => vm.MarketState, m => m == MarketState.Closed),

_ => Observable.Start(Reset), RxApp.MainThreadScheduler);

ResetCommand = resetCmd;

LoadDefaultStocks();

}

public IReadOnlyReactiveList<WatchListItemViewModel> Stocks

{

get { return stocks; }

}

public MarketState MarketState

{

get { return marketState; }

private set

{

marketState = value;

this.RaisePropertyChanged(); // can't use ref as it's volatile

}

}

private bool TryUpdateStockPrice(WatchListItemViewModel stock)

{

// Randomly choose whether to udpate this stock or not

var r = updateOrNotRandom.NextDouble();

if (r > 0.1)

{

return false;

}

// Update the stock price by a random factor of the range percent

var random = new Random((int)Math.Floor(stock.Price));

var percentChange = random.NextDouble()*rangePercent;

var pos = random.NextDouble() > 0.51;

var change = Math.Round(stock.Price*(decimal)percentChange, 2);

change = pos ? change : -change;

stock.Price += change;

return true;

}

private void UpdateStockPrices()

{

// This function must be re-entrant as it's running as a timer interval handler

lock (updateStockPricesLock)

{

if (!updatingStockPrices)

{

updatingStockPrices = true;

foreach (var stock in stocks)

{

if (TryUpdateStockPrice(stock))

{

//BroadcastStockPrice(stock);

}

}

updatingStockPrices = false;

}

}

}

public void OpenMarket()

{

lock (marketStateLock)

{

if (MarketState != MarketState.Open)

{

timer = Observable.Timer(updateInterval, updateInterval, RxApp.MainThreadScheduler)

.Subscribe(_ => UpdateStockPrices());

MarketState = MarketState.Open;

}

}

}

public void CloseMarket()

{

lock (marketStateLock)

{

if (MarketState == MarketState.Open)

{

if (timer != null)

{

timer.Dispose();

}

MarketState = MarketState.Closed;

}

}

}

public void Reset()

{

lock (marketStateLock)

{

if (MarketState != MarketState.Closed)

{

throw new InvalidOperationException("Market must be closed before it can be reset.");

}

LoadDefaultStocks();

}

}

private void LoadDefaultStocks()

{

using (stocks.SuppressChangeNotifications())

{

stocks.Clear();

stocks.Add(new WatchListItemViewModel("MSFT") {Price = 36.91m});

stocks.Add(new WatchListItemViewModel("AAPL") {Price = 545.09m});

stocks.Add(new WatchListItemViewModel("GOOG") {Price = 1107.32m});

stocks.Add(new WatchListItemViewModel("FB") {Price = 54.77m});

}

}

}

public enum MarketState

{

Closed,

Open

}

}