using System;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

namespace Sony.Filtr.Tasks.Tasks.Spotify.Analytics
{
    public static class ScheduledTaskLogFileParser
    {
        private static Regex jobStartRegex = new Regex(@"^(\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}\.\d{3,5}) \|.* \| Begin processing for argument .+");
        public static DateTime GetPreviousLaunchTime()
        {
            string[] logFiles = FindScheduledTaskLogFiles();
            if (logFiles == null || logFiles.Any() == false) { return DateTime.MinValue; }

            foreach (var file in logFiles)
            {
                Nullable<DateTime> latestLogTime = GetFileLatestLaunchTime(file);

                if (latestLogTime.HasValue) { return latestLogTime.Value; }
            }

            return DateTime.MinValue;
        }

        private static Nullable<DateTime> GetFileLatestLaunchTime(string filePath)
        {
            var fileDateRegex = new Regex(@"^ScheduledTask-(\d{4}-\d{2}-\d{2})\.txt$");

            var match = fileDateRegex.Match(Path.GetFileName(filePath));
            if (match.Success == false) { return null; }
            var logFileDate = DateTime.Parse(match.Groups[1].Value);

            var sequence = File.ReadAllLines(filePath).Reverse().Where(line => jobStartRegex.IsMatch(line));

            //To skip current launch log
            if (logFileDate == DateTime.Now.Date)
            {
                sequence = sequence.Skip(1);
            }

            var latestJobStartLog = sequence.FirstOrDefault();
            if (latestJobStartLog == null) { return null; }

            return DateTime.Parse(jobStartRegex.Match(latestJobStartLog).Groups[1].Value);
        }

        private static string[] FindScheduledTaskLogFiles()
        {
            if (Directory.Exists("logs") == false)
            {
                return Array.Empty<string>();
            }

            var dir = new DirectoryInfo("logs");
            var latestLogs = dir.EnumerateFiles("ScheduledTask*.txt")
                .OrderByDescending(f => f.LastWriteTime)
                .ToArray();

            return latestLogs
                .Select(fi => fi.FullName)
                .ToArray();
        }
    }
}