using System;
using System.Workflow.Runtime.Hosting;
using System.Workflow.ComponentModel;
using System.IO;

namespace FilePersisetenceService
{
    public class FileWorkFlowPersisetenceService: WorkflowPersistenceService
    {
        private string fBaseDir;

        public FileWorkFlowPersisetenceService(string basedir)
        {
            this.fBaseDir = basedir;
        }
        
        protected override Activity LoadCompletedContextActivity(Guid scopeId, Activity outerActivity)
        {
            object obj = DeserializeActivity(outerActivity, scopeId);
            return (Activity)obj;
        }

        protected override Activity LoadWorkflowInstanceState(Guid instanceId)
        {
            object obj = DeserializeActivity(null, instanceId);
            return (Activity)obj;
        }

        protected override void SaveCompletedContextActivity(Activity activity)
        {
            Guid contextGuid = (Guid)activity.GetValue(Activity.ActivityContextGuidProperty);
            SerializeActivity(activity, contextGuid);
        }

        protected override void SaveWorkflowInstanceState(Activity rootActivity, bool unlock)
        {
            Guid contextGuid = (Guid)rootActivity.GetValue(Activity.ActivityContextGuidProperty);
            SerializeActivity(rootActivity, contextGuid);
        }

        protected override bool UnloadOnIdle(Activity activity)
        {
            return true;
        }

        protected override void UnlockWorkflowInstanceState(Activity rootActivity)
        {
            //empty
        }

        private void SerializeActivity(Activity RootActivity, Guid id)
        {
            string filename = GetFileName(id);
            using (FileStream stream = new FileStream(filename, FileMode.OpenOrCreate))
            {
                RootActivity.Save(stream);
                stream.Close();
            }
        }

        private object DeserializeActivity(Activity RootActivity, Guid id)
        {
            string filename = GetFileName(id);
            object result;
            using (FileStream stream = new FileStream(filename, FileMode.Open))
            {
                result = Activity.Load(stream, RootActivity);
                stream.Close();
            }
            return result;
        }

        private string GetFileName(Guid id)
        {
            return Path.Combine(this.fBaseDir, id.ToString() + ".bin");
        }        
    }
}