using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using NDB.Infrastructure.DatabaseMigration.Models;
using NDB.Infrastructure.DatabaseMigration.Repositories;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Xml;
using System.Xml.Serialization;

namespace NDB.Infrastructure.DatabaseMigration.Services
{
    internal class MigrationService : IMigrationService
    {
        private readonly string _migrationSignaturesFilePath;
        private const string _migrationSignaturesFileName = "MigrationSignatures.xml";
        private readonly ILogger<MigrationService> _logger;
        private readonly IServiceProvider _serviceProvider;
        private readonly ServiceConfiguration _configuration;

        public MigrationService(ILogger<MigrationService> logger, IServiceProvider serviceProvider, ServiceConfiguration configuration)
        {
            _migrationSignaturesFilePath = Path.Combine(configuration.Workspace, _migrationSignaturesFileName);
            _logger = logger;
            _serviceProvider = serviceProvider;
            _configuration = configuration;
        }

        private void CheckWorkspace()
        {
            if (string.IsNullOrEmpty(_configuration.Workspace))
                throw new Exception($"Workspace path is empty! Check 'Workspace' parameter.");

            if (!Directory.Exists(_configuration.Workspace))
                Directory.CreateDirectory(_configuration.Workspace);
        }

        private MigrationSignature[] GetMigrationSignatures()
        {
            if (!File.Exists(_migrationSignaturesFilePath))
                return null;

            var serializer = new XmlSerializer(typeof(MigrationThumbprint));
            using (var reader = XmlReader.Create(_migrationSignaturesFilePath))
            {
                var migrationSignatureRoot = (MigrationThumbprint)serializer.Deserialize(reader);
                return migrationSignatureRoot.MigrationSignatures;
            }
        }

        private void SaveMigrationSignatures(MigrationSignature[] migrationSignatures)
        {
            var root = new MigrationThumbprint() { MigrationSignatures = migrationSignatures };
            var serializer = new XmlSerializer(root.GetType());
            var settings = new XmlWriterSettings() { Indent = true };
            using (var writer = XmlWriter.Create(_migrationSignaturesFilePath, settings))
            {
                serializer.Serialize(writer, root);
            }
        }

        public void Execute()
        {
            _logger.LogInformation("Starting migration...");

            CheckWorkspace();

            var localSignatures = GetMigrationSignatures();
            var lastInstalledVersion = localSignatures?.OrderByDescending(z => z.MigrationDate).FirstOrDefault()?.LastVersion ?? "0.0.0";
            var targetVersion = new Version(lastInstalledVersion);
            var scriptPacks = GetScriptPacks();
            var packsToInstall = scriptPacks.Where(p => p.Version > targetVersion);

            if (!packsToInstall.Any())
            {
                _logger.LogInformation("Nothing to migrate.");
                return;
            }

            var signature = new MigrationSignature() { MachineName = System.Environment.MachineName, MigrationDate = DateTime.Now };
            var migratedVersions = new List<MigratedVersion>();

            foreach (var pack in packsToInstall.OrderBy(p => p.Version))
            {
                var scripts = Directory.GetFiles(pack.Path);
                if (!scripts.Any())
                    continue;

                _logger.LogInformation($"Running script pack: '{pack.Version}'");

                Array.ForEach(scripts, s => RunScript(s));
                var migratedVersion = new MigratedVersion() { Version = pack.Version.ToString(), Scripts = scripts.Select(z => Path.GetFileName(z)).ToArray() };
                migratedVersions.Add(migratedVersion);
            }

            signature.MigratedVersions = migratedVersions.ToArray();
            signature.LastVersion = packsToInstall.OrderByDescending(z => z.Version).First().Version.ToString();

            var signatures = localSignatures != null ? new List<MigrationSignature>(localSignatures) : new List<MigrationSignature>();
            signatures.Add(signature);

            SaveMigrationSignatures(signatures.ToArray());
        }

        private ScriptPack[] GetScriptPacks()
        {
            var scripts = Directory.GetDirectories(_configuration.ScriptsDirectory);
            var packs = scripts.Select(z => new ScriptPack() { Path = z, Version = new Version(new DirectoryInfo(z).Name) });

            return packs.ToArray();
        }

        private void RunScript(string path)
        {
            _logger.LogInformation($"Running sql script: '{path}'");
            var sqlContent = File.ReadAllText(path);
            if (string.IsNullOrEmpty(sqlContent))
                return;

            using (var scope = _serviceProvider.CreateScope())
            {
                var _repository = scope.ServiceProvider.GetRequiredService<IMigrationRepository>();
                _repository.ExecuteSqlRaw(sqlContent);
            }
        }
    }
}