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 *     following disclaimer. 
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 *     following disclaimer in the documentation and/or other 
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 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
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 */

using System;
using XenAPI;


namespace XenAdmin.Actions
{
    public class VMSnapshotRevertAction : PureAsyncAction
    {
        private VM m_Snapshot;
        private Host previousHost; // The host the VM was running on before the snapshot

        public VMSnapshotRevertAction(VM snapshot)
            : base(snapshot.Connection, String.Format(Messages.ACTION_VM_REVERT_SNAPSHOT_TITLE, snapshot.Name()))
        {
            this.VM = Connection.Resolve<VM>(snapshot.snapshot_of);
            previousHost = Connection.Resolve<Host>(VM.resident_on);
            this.m_Snapshot = snapshot;
            Description = String.Format(Messages.VM_REVERTING, m_Snapshot.Name());

        }
        private bool _finished = false;
        protected override void Run()
        {


            Description = String.Format(Messages.VM_REVERTING, m_Snapshot.Name());
            RelatedTask = XenAPI.VM.async_revert(Session, m_Snapshot.opaque_ref);
            PollToCompletion();
            _finished = true;
            Tick(90, string.Format(Messages.REVERTING_POWER_STATE, VM.Name()));

            try
            {
                RevertPowerState(m_Snapshot, VM);
            }
            catch (Exception)
            {
                // ignored
            }

            Tick(100, string.Format(Messages.VM_REVERTED, m_Snapshot.Name()));
        }

        public override int PercentComplete
        {
            get
            {
                return base.PercentComplete;
            }
            set
            {
                if ((value < 90 && !_finished) || (value >= 90 && _finished))
                    base.PercentComplete = value;
            }
        }


        private void RevertPowerState(VM snapshot, VM vm)
        {
            string state;
            if (snapshot.snapshot_info.TryGetValue("power-state-at-snapshot",
                                                   out state))
            {
                if (state == vm_power_state.Running.ToString())
                {
                    if (vm.power_state == vm_power_state.Halted)
                    {
                        if (previousHost != null && VMCanBootOnHost(vm, previousHost))
                        {
                            RelatedTask = XenAPI.VM.async_start_on(Session,
                                vm.opaque_ref, previousHost.opaque_ref, false, false);
                        }
                        else
                        {
                            RelatedTask = XenAPI.VM.async_start(Session,
                                vm.opaque_ref, false, false);
                        }

                    }
                    else if (vm.power_state == vm_power_state.Suspended)
                    {
                        if (previousHost != null && VMCanBootOnHost(vm, previousHost))
                        {
                            RelatedTask = XenAPI.VM.async_resume_on(Session, vm.opaque_ref, previousHost.opaque_ref,
                                false, false);
                        }
                        else
                        {
                            RelatedTask = XenAPI.VM.async_resume(Session, vm.opaque_ref, false, false);
                        }

                    }
                    PollToCompletion();
                }
            }
        }

        private bool VMCanBootOnHost(VM vm, Host host)
        {
            try
            {
                VM.assert_can_boot_here(Session, vm.opaque_ref, host.opaque_ref);
            }
            catch
            {
                return false;
            }

            return true;
        }
    }
}