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 WatcherJobRepository
    {
        private readonly object _sync = new object();
        private readonly string _fileName;
        private readonly JavaScriptSerializer _serializer = new JavaScriptSerializer();
        private List<WatcherJobConfig> _jobs;

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

        public IList<WatcherJobConfig> GetAll()
        {
            lock (_sync) return Clone(_jobs);
        }

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

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

        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(WatcherJobConfig job)
        {
            if (String.IsNullOrWhiteSpace(job.Name)) throw new InvalidOperationException("Name is required.");
            if (String.IsNullOrWhiteSpace(job.SourceDirectory)) throw new InvalidOperationException("SourceDirectory is required.");
            if (String.IsNullOrWhiteSpace(job.CustomFunction)) throw new InvalidOperationException("CustomFunction is required.");
            if (!job.WatchCreated && !job.WatchChanged && !job.WatchRenamed)
                throw new InvalidOperationException("At least one watcher event (Created, Changed, Renamed) must be enabled.");
            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 = ";";
            if (job.DebounceMilliseconds < 0) job.DebounceMilliseconds = 0;
            if (job.FileReadyRetries < 1) job.FileReadyRetries = 1;
            if (job.FileReadyRetries > 1000) job.FileReadyRetries = 1000;
            if (job.FileReadyDelayMilliseconds < 10) job.FileReadyDelayMilliseconds = 10;
        }

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