using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Web.Script.Serialization;

namespace FileInterface.Scheduler
{
    public sealed class CronJobRepository
    {
        private readonly object _sync = new object();
        private readonly string _fileName;
        private readonly JavaScriptSerializer _serializer = new JavaScriptSerializer();
        private List<CronJobConfig> _jobs;

        public CronJobRepository(string fileName)
        {
            _fileName = Path.GetFullPath(fileName);
            _serializer.MaxJsonLength = Int32.MaxValue;
            _jobs = LoadInternal();
        }

        public IList<CronJobConfig> GetAll()
        {
            lock (_sync)
            {
                // Clone through JSON so callers cannot mutate repository state behind our lock.
                return Clone(_jobs);
            }
        }

        public CronJobConfig GetById(string id)
        {
            lock (_sync)
            {
                CronJobConfig job = _jobs.FirstOrDefault(j => String.Equals(j.Id, id, StringComparison.OrdinalIgnoreCase));
                return job == null ? null : Clone(job);
            }
        }

        public CronJobConfig Save(CronJobConfig job)
        {
            if (job == null) throw new ArgumentNullException("job");
            Validate(job);

            lock (_sync)
            {
                if (String.IsNullOrWhiteSpace(job.Id))
                    job.Id = Guid.NewGuid().ToString("N");

                int index = _jobs.FindIndex(j => String.Equals(j.Id, job.Id, StringComparison.OrdinalIgnoreCase));
                if (index >= 0) _jobs[index] = Clone(job);
                else _jobs.Add(Clone(job));

                SaveInternal();
                return Clone(job);
            }
        }

        public bool Delete(string id)
        {
            lock (_sync)
            {
                int count = _jobs.RemoveAll(j => String.Equals(j.Id, id, StringComparison.OrdinalIgnoreCase));
                if (count > 0) SaveInternal();
                return count > 0;
            }
        }

        private List<CronJobConfig> LoadInternal()
        {
            if (!File.Exists(_fileName)) return new List<CronJobConfig>();
            string json = File.ReadAllText(_fileName, Encoding.UTF8);
            if (String.IsNullOrWhiteSpace(json)) return new List<CronJobConfig>();
            return _serializer.Deserialize<List<CronJobConfig>>(json) ?? new List<CronJobConfig>();
        }

        private void SaveInternal()
        {
            string dir = Path.GetDirectoryName(_fileName);
            if (!String.IsNullOrWhiteSpace(dir)) Directory.CreateDirectory(dir);

            string json = _serializer.Serialize(_jobs);
            string tmp = _fileName + ".tmp";
            File.WriteAllText(tmp, json, new UTF8Encoding(false));

            if (File.Exists(_fileName))
            {
                string backup = _fileName + ".bak";
                try { File.Replace(tmp, _fileName, backup, true); }
                catch
                {
                    File.Delete(_fileName);
                    File.Move(tmp, _fileName);
                }
            }
            else File.Move(tmp, _fileName);
        }

        private static void Validate(CronJobConfig job)
        {
            if (String.IsNullOrWhiteSpace(job.Name)) throw new InvalidOperationException("Name is required.");
            CronExpression.Parse(job.Cron);
            if (String.IsNullOrWhiteSpace(job.CustomFunction)) throw new InvalidOperationException("CustomFunction is required.");
            if (!job.CallOnceWithoutFile && String.IsNullOrWhiteSpace(job.SourceDirectory))
                throw new InvalidOperationException("SourceDirectory is required for file jobs.");
            if (job.MoveFileAfterSuccess && String.IsNullOrWhiteSpace(job.MoveTargetDirectory))
                throw new InvalidOperationException("MoveTargetDirectory is required when MoveFileAfterSuccess=true.");
            if (job.InArgs == null) job.InArgs = new List<string>();
            if (String.IsNullOrWhiteSpace(job.SearchPattern)) job.SearchPattern = "*.*";
            if (job.JoinSeparator == null) job.JoinSeparator = ";";
        }

        private T Clone<T>(T value)
        {
            return _serializer.Deserialize<T>(_serializer.Serialize(value));
        }
    }
}