using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using Azure.Storage.Blobs;
using Azure.Storage.Blobs.Models;
using Azure.Storage.Blobs.Specialized;
using gehGassi.Core.Interfaces;
using gehGassi.Core.Services;

namespace gehGassi.External.Services
{
    /// <summary>
    /// Service der die Verwaltung von Dateien mittels Azure ermöglicht.
    /// Verwendet das neue Azure-Interface
    /// </summary>
    public class AzureBlobFileService : IFileService
    {
        internal BlobServiceClient BlobServiceClient;

        /// <summary>
        /// Erstellt eine Instanz
        /// </summary>
        /// <param name="connectionString">Connectionstring für Azure-Storage</param>
        public AzureBlobFileService(string connectionString)
        {
            BlobServiceClient = new BlobServiceClient(connectionString);
            InitContainers();
        }

        /// <summary>
        /// Initialisieren der Container
        /// </summary>
        /// <returns>Task</returns>
        private void InitContainers()
        {
            var container = BlobServiceClient.GetBlobContainerClient(FileServiceHelper.DocumentContainer);
            container.CreateIfNotExists();
            container = BlobServiceClient.GetBlobContainerClient(FileServiceHelper.TempContainer);
            container.CreateIfNotExists();
        }

        /// <summary>
        /// Speichern einer Datei in einen Container
        /// </summary>
        /// <param name="containerName">Name des Containers</param>
        /// <param name="filename">Dateiname (inkl. Pfad, wenn gewünscht)</param>
        /// <param name="file">Datei als Byte-Array</param>
        /// <param name="overwrite">Überschreiben vorhandener Daten</param>
        /// <returns>Absoluter Dateiname</returns>
        public async Task<string> StoreAsync(string containerName, string filename, byte[] file, bool overwrite = true)
        {
            var container = BlobServiceClient.GetBlobContainerClient(containerName);
            var blob = container.GetBlockBlobClient(filename);
            await using var stream = new MemoryStream(file);
            await blob.UploadAsync(stream);
            return blob.Name;
        }

        /// <summary>
        /// Speichern einer Datei in einen Container
        /// </summary>
        /// <param name="containerName">Name des Containers</param>
        /// <param name="filename">Dateiname (inkl. Pfad, wenn gewünscht)</param>
        /// <param name="fileStream">Datei als Stream</param>
        /// <param name="overwrite">Überschreiben vorhandener Daten</param>
        /// <returns>Absoluter Dateiname</returns>
        public async Task<string> StoreAsync(string containerName, string filename, Stream fileStream, bool overwrite = true)
        {
            var container = BlobServiceClient.GetBlobContainerClient(containerName);
            var blob = container.GetBlockBlobClient(filename);
            await blob.UploadAsync(fileStream);
            return blob.Name;
        }

        /// <summary>
        /// Umbenennen einer Datei in einem Container
        /// </summary>
        /// <param name="containerName">Name des Containers</param>
        /// <param name="filename">Dateiname (inkl. Pfad, wenn gewünscht)</param>
        /// <param name="newFilename">Neuer Dateiname</param>
        public async Task RenameAsync(string containerName, string filename, string newFilename)
        {
            var container = BlobServiceClient.GetBlobContainerClient(containerName);
            var blob = container.GetBlockBlobClient(filename);
            var newBlob = container.GetBlockBlobClient(newFilename);
            await newBlob.StartCopyFromUriAsync(blob.Uri);
            await blob.DeleteIfExistsAsync();
        }

        /// <summary>
        /// Gibt eine Datei zurück
        /// </summary>
        /// <param name="containerName">Name des Containers</param>
        /// <param name="filename">Dateiname (inkl. Pfad, wenn gewünscht)</param>
        /// <returns>Datei als Byte-Array</returns>
        public async Task<byte[]> GetAsync(string containerName, string filename)
        {
            var container = BlobServiceClient.GetBlobContainerClient(containerName);
            var blob = container.GetBlockBlobClient(filename);
            // Save blob contents to a file.
            byte[] result = null;
            if (await blob.ExistsAsync())
            {
                await using var memoryStream = new MemoryStream();
                await blob.DownloadToAsync(memoryStream);
                result = memoryStream.ToArray();
            }
            return result;
        }

        /// <summary>
        /// Gibt eine Datei zurück
        /// </summary>
        /// <param name="containerName">Name des Containers</param>
        /// <param name="filename">Dateiname (inkl. Pfad, wenn gewünscht)</param>
        /// <returns>Datei als Stream</returns>
        public async Task<Stream> GetAsStreamAsync(string containerName, string filename)
        {
            var container = BlobServiceClient.GetBlobContainerClient(containerName);
            var blob = container.GetBlockBlobClient(filename);
            var memoryStream = new MemoryStream();
            await blob.DownloadToAsync(memoryStream);
            memoryStream.Position = 0;
            return memoryStream;
        }

        /// <summary>
        /// Löschen einer Datei in einem Container
        /// </summary>
        /// <param name="containerName">Name des Containers</param>
        /// <param name="filename">Dateiname (inkl. Pfad, wenn gewünscht)</param>
        public async Task DeleteAsync(string containerName, string filename)
        {
            var container = BlobServiceClient.GetBlobContainerClient(containerName);
            var blob = container.GetBlockBlobClient(filename);
            await blob.DeleteIfExistsAsync();
        }

        /// <summary>
        /// Gibt eine Liste aller Dateien eines Containers zurück die sich in einem Directory befinden
        /// </summary>
        /// <param name="containerName">Name des Containers</param>
        /// <param name="directory">Verzeichnis.</param>
        /// <param name="fileNamePart">Teil eines Dateinamens für die suche</param>
        /// <returns>Liste von Dateien</returns>
        public async Task<List<string>> ListFilesAsync(string containerName, string directory = "", string fileNamePart = "")
        {
            var result = new List<string>();

            Wildcard wildCard = null;
            if (!string.IsNullOrWhiteSpace(fileNamePart))
                wildCard = new Wildcard(fileNamePart, RegexOptions.IgnoreCase);

            var container = BlobServiceClient.GetBlobContainerClient(containerName);

            await foreach (var blobPage in container.GetBlobsByHierarchyAsync(BlobTraits.None, BlobStates.None, prefix: directory).AsPages())
            {
                // A hierarchical listing may return both virtual directories and blobs.
                foreach (var item in blobPage.Values)
                {
                    if (item.IsPrefix)
                        continue;
                    if (!item.IsBlob)
                        continue;
                    if (wildCard != null)
                    {
                        if (wildCard.IsMatch(GetFilename(item.Blob.Name)))
                            result.Add(item.Blob.Name);
                    }
                    else
                        result.Add(item.Blob.Name);
                }
            }
            return result;
        }

        /// <summary>
        /// Gibt eine Liste aller Verzeichnise zurück die sich im Container befindne
        /// </summary>
        /// <param name="containerName">Name des Containers</param>
        /// <param name="root">wenn angegeben, wird von dem Verzeihnis als root ausgegangen</param>
        /// <returns></returns>
        public async Task<List<string>> ListDirectoriesAsync(string containerName, string root = "")
        {
            var result = new List<string>();

            var container = BlobServiceClient.GetBlobContainerClient(containerName);

            await foreach (var blobPage in container.GetBlobsByHierarchyAsync(delimiter: "/", prefix: root).AsPages())
            {
                result.AddRange(from item in blobPage.Values where item.IsPrefix select item.Prefix);
            }
            return result;
        }

        /// <summary>
        /// Koperien von Dateinen eines Containers in einen anderen
        /// </summary>
        /// <param name="sourceContainer">Quellcontainer</param>
        /// <param name="sourceDirectory">Quellpfad</param>
        /// <param name="targetContainer">ZielContainer</param>
        /// <param name="targetDirectory">ZielPfad</param>
        public async Task CopyFilesAsync(string sourceContainer, string sourceDirectory, string targetContainer, string targetDirectory)
        {
            var cloudSourceContainer = BlobServiceClient.GetBlobContainerClient(sourceContainer);
            var cloudTargetContainer = BlobServiceClient.GetBlobContainerClient(targetContainer);

            var blobs = new List<BlobItem>();
            await foreach (var blobPage in cloudSourceContainer.GetBlobsByHierarchyAsync(BlobTraits.None, BlobStates.None, prefix: sourceDirectory).AsPages())
            {
                blobs.AddRange(from item in blobPage.Values where item.IsBlob select item.Blob);
            }

            foreach (var blobItem in blobs)
            {
                var sourceClient = cloudSourceContainer.GetBlockBlobClient(blobItem.Name);
                var copyClient = cloudTargetContainer.GetBlockBlobClient(blobItem.Name.Replace(sourceDirectory, targetDirectory));
                await copyClient.StartCopyFromUriAsync(sourceClient.Uri);
            }
        }

        /// <summary>
        /// Koperien von Dateien eines Pfades in einen anderen
        /// </summary>
        /// <param name="containerName">Name des Containers</param>
        /// <param name="sourceDirectory">Quellpfad</param>
        /// <param name="targetDirectory">ZielPfad</param>
        public async Task CopyFilesAsync(string containerName, string sourceDirectory, string targetDirectory)
        {
            await CopyFilesAsync(containerName, sourceDirectory, containerName, targetDirectory);
        }

        /// <summary>
        /// Verschieben von Dateien eines Containers in einen anderen
        /// </summary>
        /// <param name="sourceContainer">Quellcontainer</param>
        /// <param name="sourceDirectory">Quellpfad</param>
        /// <param name="targetContainer">ZielContainer</param>
        /// <param name="targetDirectory">ZielPfad</param>
        public async Task MoveFilesAsync(string sourceContainer, string sourceDirectory, string targetContainer, string targetDirectory)
        {
            var cloudSourceContainer = BlobServiceClient.GetBlobContainerClient(sourceContainer);
            var cloudTargetContainer = BlobServiceClient.GetBlobContainerClient(targetContainer);

            var blobs = new List<BlobItem>();
            await foreach (var blobPage in cloudSourceContainer.GetBlobsByHierarchyAsync(BlobTraits.None, BlobStates.None, prefix: sourceDirectory).AsPages())
            {
                blobs.AddRange(from item in blobPage.Values where item.IsBlob select item.Blob);
            }

            foreach (var blobItem in blobs)
            {
                var sourceClient = cloudSourceContainer.GetBlockBlobClient(blobItem.Name);
                var copyClient = cloudTargetContainer.GetBlockBlobClient(blobItem.Name.Replace(sourceDirectory, targetDirectory));
                await copyClient.StartCopyFromUriAsync(sourceClient.Uri);
                await sourceClient.DeleteAsync();
            }
        }

        /// <summary>
        /// Verschieben von Dateien eines Pfades in einen anderen
        /// </summary>
        /// <param name="containerName">Name des Containers</param>
        /// <param name="sourceDirectory">Quellpfad</param>
        /// <param name="targetDirectory">ZielPfad</param>
        public async Task MoveFilesAsync(string containerName, string sourceDirectory, string targetDirectory)
        {
            await MoveFilesAsync(containerName, sourceDirectory, containerName, targetDirectory);
        }

        /// <summary>
        /// Löschen des Inhalts eines Verzeichnises
        /// </summary>
        /// <param name="containerName">Name des Containers</param>
        /// <param name="directory">Verzeichnis</param>
        /// <param name="fileNamePart">Optional: Dateinamen Wildcard</param>
        public async Task ClearDirectoryAsync(string containerName, string directory, string fileNamePart = "")
        {
            Wildcard wildCard = null;
            if (!string.IsNullOrWhiteSpace(fileNamePart))
                wildCard = new Wildcard(fileNamePart, RegexOptions.IgnoreCase);

            var container = BlobServiceClient.GetBlobContainerClient(containerName);

            await foreach (var blobPage in container.GetBlobsByHierarchyAsync(BlobTraits.None, BlobStates.None, prefix: directory).AsPages())
            {
                // A hierarchical listing may return both virtual directories and blobs.
                foreach (var item in blobPage.Values)
                {
                    if (item.IsPrefix)
                        continue;
                    if (!item.IsBlob)
                        continue;
                    if (wildCard != null)
                    {
                        if (wildCard.IsMatch(GetFilename(item.Blob.Name)))
                        {
                            var client = container.GetBlockBlobClient(item.Blob.Name);
                            await client.DeleteAsync();
                        }
                    }
                    else
                    {
                        var client = container.GetBlockBlobClient(item.Blob.Name);
                        await client.DeleteAsync();
                    }
                }
            }
        }

        /// <summary>
        /// Löscht einen Container und den Inhalt
        /// </summary>
        /// <param name="containerName">Name des Containers</param>
        public async Task DeleteContainerAsync(string containerName)
        {
            var container = BlobServiceClient.GetBlobContainerClient(containerName);
            await container.DeleteAsync();
        }

        /// <summary>
        /// Löscht Dateien aus einem Ordner auf welche
        /// vor dem Datum das letzte mal zugegriffen wurde
        /// </summary>
        /// <param name="containerName">Name des Containers</param>
        /// <param name="directory">Verzeichnis</param>
        /// <param name="date">Datum</param>
        public async Task DeleteOldFilesAsync(string containerName, string directory, DateTimeOffset date)
        {
            var container = BlobServiceClient.GetBlobContainerClient(containerName);

            await foreach (var blobPage in container.GetBlobsByHierarchyAsync(BlobTraits.None, BlobStates.None, prefix: directory).AsPages())
            {
                foreach (var item in blobPage.Values)
                {
                    if (item.IsPrefix)
                        continue;
                    if (!item.IsBlob)
                        continue;
                    var client = container.GetBlockBlobClient(item.Blob.Name);
                    if (item.Blob.Properties.LastModified < date)
                        await client.DeleteAsync();
                }
            }
        }

        /// <summary>
        /// Gibt den reinen Dateinamen eines Files zurück (Ohne Directories usw)
        /// </summary>
        /// <param name="fileName">Dateiname</param>
        /// <returns>Reiner Dateiname</returns>
        public string GetFlatFilename(string fileName)
        {
            return GetFilename(fileName);
        }

        #region private

        /// <summary>
        /// Gibt den Dateinamen einer Datei ohne lokale Pfadangaben zurück
        /// </summary>
        /// <param name="path">Pfad + Dateinamen</param>
        /// <returns>Dateiname ohne Pfadangaben</returns>
        private string GetFilename(string path)
        {
            var fileName = path.Split(new[] { "/" }, StringSplitOptions.None).Last();
            return fileName;
        }

        #endregion
    }

    /// <summary>
    /// Hilfsklasse für das Finden von Dateien mittels Wildcards
    /// </summary>
    [ExcludeFromCodeCoverage]
    internal class Wildcard : Regex
    {
        /// <summary>
        /// Erstellt eine instanz
        /// </summary>
        /// <param name="pattern">Wildcard-Ausdruck</param>
        public Wildcard(string pattern) : base(ToRegex(pattern))
        {
        }

        /// <summary>
        /// Erstellt eine Instanz
        /// </summary>
        /// <param name="pattern">Wildcard-Ausdruck</param>
        /// <param name="options">Optionen</param>
        public Wildcard(string pattern, RegexOptions options) : base(ToRegex(pattern), options)
        {
        }

        /// <summary>
        /// Erstellt einen regulären Ausdruck aus dem Wildcard-Ausdruck
        /// </summary>
        /// <param name="pattern">Wildcard-Ausdruck</param>
        /// <returns>Wildcard-Ausdruck in Regex konvertiert</returns>
        public static string ToRegex(string pattern)
        {
            return "^" + Escape(pattern).Replace("\\*", ".*").Replace("\\?", ".") + "$";
        }
    }
}