using System;
using System.Threading.Tasks;

namespace ProjectI.Sessions
{
    public sealed class SessionLifecycle
    {
        private Func<Task> pendingCleanup;
        private Func<bool> cleanupAlreadyRemoved;
        private Func<Task> finishLocalNetwork;
        private Func<Exception, bool> terminalCleanupError;
        public bool Busy { get; private set; }
        public bool ConnectionLossPending { get; private set; }
        public bool HasPendingCleanup => pendingCleanup != null;

        public void BeginOperation()
        {
            if (Busy) throw new InvalidOperationException("A session operation is already pending.");
            Busy = true;
        }

        public void RequestConnectionLoss() { ConnectionLossPending = true; }

        public bool EndOperation()
        {
            Busy = false;
            bool lost = ConnectionLossPending;
            ConnectionLossPending = false;
            return lost;
        }

        public void PreserveCleanup(Func<Task> cleanup, Func<bool> alreadyRemoved = null, Func<Task> finishNetwork = null,
            Func<Exception, bool> isTerminalError = null)
        {
            pendingCleanup = cleanup;
            cleanupAlreadyRemoved = alreadyRemoved;
            finishLocalNetwork = finishNetwork;
            terminalCleanupError = isTerminalError;
        }

        public async Task RetryCleanupAsync()
        {
            var cleanup = pendingCleanup;
            if (cleanup == null) return;
            var alreadyRemoved = cleanupAlreadyRemoved;
            var finishNetwork = finishLocalNetwork;
            var isTerminalError = terminalCleanupError;
            bool completeLocally = alreadyRemoved?.Invoke() ?? false;
            if (!completeLocally)
            {
                try { await cleanup(); }
                catch (Exception exception) when ((alreadyRemoved?.Invoke() ?? false) || (isTerminalError?.Invoke(exception) ?? false))
                {
                    // The remote game/membership is gone; retrying a cloud leave cannot restore it.
                    completeLocally = true;
                }
            }
            if (completeLocally && finishNetwork != null) await finishNetwork();
            if (pendingCleanup == cleanup)
            {
                pendingCleanup = null;
                cleanupAlreadyRemoved = null;
                finishLocalNetwork = null;
                terminalCleanupError = null;
            }
        }
    }
}