using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;

namespace FileInterface.Scheduler
{
    public sealed class WatcherJobExecutor
    {
        private readonly ICustomFunctionInvoker _invoker;
        private readonly JobLog _log;

        public WatcherJobExecutor(ICustomFunctionInvoker invoker, JobLog log)
        {
            _invoker = invoker;
            _log = log;
        }

        public void ExecuteFile(WatcherJobConfig job, string file, string reason)
        {
            if (job == null) throw new ArgumentNullException("job");
            if (String.IsNullOrWhiteSpace(file)) return;
            if (!WaitUntilReadable(file, job.FileReadyRetries, job.FileReadyDelayMilliseconds))
            {
                _log.Error(job, "File is not readable after retries: " + file);
                return;
            }

            string rawContent;
            using (var stream = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
            using (var reader = new StreamReader(stream, Encoding.UTF8, true))
                rawContent = reader.ReadToEnd();

            string processedContent = ProcessContent(rawContent, job.RemoveEmptyLines, job.JoinSeparator);
            string[] inArgs = (job.InArgs ?? new List<string>())
                .Select(arg => Expand(arg, job, file, rawContent, processedContent, reason))
                .ToArray();

            _log.Info(job, "Calling CustomFunction '" + job.CustomFunction + "' with " + inArgs.Length + " inArg(s) for " + Path.GetFileName(file) + " (" + reason + ").");
            CustomFunctionCallResult result = _invoker.Invoke(job.CustomFunction, inArgs);
            if (result == null) result = CustomFunctionCallResult.Fail("Invoker returned null.");

            if (!result.Success)
            {
                _log.Error(job, "CustomFunction failed: " + result.Message);
                return;
            }

            _log.Info(job, "CustomFunction succeeded: " + result.Message);
            if (job.MoveFileAfterSuccess && File.Exists(file))
            {
                string movedTo = MoveProcessedFile(file, job.MoveTargetDirectory, job.OverwriteTargetFile);
                _log.Info(job, "Moved file to: " + movedTo);
            }
        }

        private static bool WaitUntilReadable(string file, int retries, int delayMs)
        {
            retries = Math.Max(2, retries);
            delayMs = Math.Max(10, delayMs);
            long previousLength = -1;
            DateTime previousWrite = DateTime.MinValue;
            int stableChecks = 0;

            for (int i = 0; i < retries; i++)
            {
                if (!File.Exists(file)) return false;
                try
                {
                    var info = new FileInfo(file);
                    long length = info.Length;
                    DateTime lastWrite = info.LastWriteTimeUtc;
                    using (var stream = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
                    {
                        if (stream.Length != length) length = stream.Length;
                    }

                    if (length == previousLength && lastWrite == previousWrite)
                    {
                        stableChecks++;
                        if (stableChecks >= 1) return true;
                    }
                    else
                    {
                        stableChecks = 0;
                        previousLength = length;
                        previousWrite = lastWrite;
                    }
                }
                catch (IOException) { stableChecks = 0; }
                catch (UnauthorizedAccessException) { stableChecks = 0; }

                Thread.Sleep(delayMs);
            }
            return false;
        }

        private static string ProcessContent(string text, bool removeEmptyLines, string separator)
        {
            if (!removeEmptyLines) return text ?? "";
            string[] lines = (text ?? "").Replace("\r\n", "\n").Replace('\r', '\n').Split('\n');
            return String.Join(separator ?? ";", lines.Where(l => !String.IsNullOrWhiteSpace(l)).Select(l => l.Trim()));
        }

        private static string Expand(string template, WatcherJobConfig job, string file, string rawContent, string processedContent, string reason)
        {
            string value = template ?? "";
            string fileName = Path.GetFileName(file) ?? "";
            string extension = Path.GetExtension(file) ?? "";
            string directory = Path.GetDirectoryName(file) ?? "";
            return value
                .Replace("{{CONTENT}}", processedContent ?? "")
                .Replace("{{RAW_CONTENT}}", rawContent ?? "")
                .Replace("{{FILE_NAME}}", fileName)
                .Replace("{{FILE_PATH}}", file ?? "")
                .Replace("{{FILE_DIR}}", directory)
                .Replace("{{FILE_EXT}}", extension)
                .Replace("{{JOB_NAME}}", job.Name ?? "")
                .Replace("{{EVENT}}", reason ?? "")
                .Replace("{{NOW}}", DateTime.Now.ToString("yyyy-MM-ddTHH:mm:ss.fffK"));
        }

        private static string MoveProcessedFile(string source, string targetDirectory, bool overwrite)
        {
            Directory.CreateDirectory(targetDirectory);
            string target = Path.Combine(targetDirectory, Path.GetFileName(source));
            if (File.Exists(target))
            {
                if (overwrite) File.Delete(target);
                else
                {
                    string name = Path.GetFileNameWithoutExtension(source);
                    string ext = Path.GetExtension(source);
                    target = Path.Combine(targetDirectory, name + "_" + DateTime.Now.ToString("yyyyMMdd_HHmmss_fff") + ext);
                    int i = 1;
                    while (File.Exists(target))
                    {
                        target = Path.Combine(targetDirectory, name + "_" + DateTime.Now.ToString("yyyyMMdd_HHmmss_fff") + "_" + i + ext);
                        i++;
                    }
                }
            }
            File.Move(source, target);
            return target;
        }
    }
}