using DiskAccessLibrary;
using DiskAccessLibrary.Mod;
using ISCSI.Server;
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Diagnostics;
using System.Linq;
using System.Xml;

namespace ISCSIConsole.Mods
{
    public class AutoLoadEntrySection : IConfigurationSectionHandler
    {
        public object Create(object parent, object configContext, XmlNode section)
        {
            var entries = new List<AutoLoadEntry>();

            foreach (XmlNode entryNode in section.ChildNodes)
            {
                Debug.Assert(entryNode.Attributes != null, "childNode.Attributes != null");

                var entry = new AutoLoadEntry
                {
                    Iqn = entryNode.Attributes[nameof(AutoLoadEntry.Iqn)].Value,
                    Enable = entryNode.Attributes[nameof(AutoLoadEntry.Enable)].Value == "true",
                };

                entry.Disks = new List<AutoLoadDisk>();

                foreach (XmlNode diskNode in entryNode.ChildNodes)
                {
                    Debug.Assert(diskNode.Attributes != null, "diskNode.Attributes != null");

                    var disk = new AutoLoadDisk
                    {
                        Type = (AutoLoadDiskType)Enum.Parse(typeof(AutoLoadDiskType), diskNode.Attributes[nameof(AutoLoadDisk.Type)].Value),
                        FilePath = diskNode.Attributes[nameof(AutoLoadDisk.FilePath)].Value,
                        ReadOnly = "true" == diskNode.Attributes[nameof(AutoLoadDisk.ReadOnly)]?.Value,
                        Enable = "true" == diskNode.Attributes[nameof(AutoLoadDisk.Enable)]?.Value
                    };

                    entry.Disks.Add(disk);
                }

                entries.Add(entry);
            }
            return entries;
        }
    }

    internal class AutoLoadEntry
    {
        public bool Enable { get; set; }

        public string Iqn { get; set; }

        public List<AutoLoadDisk> Disks { get; set; }

        public ISCSITarget CreateTarget()
        {
            var disks = new List<Disk>();
            var target = new ISCSITarget(Iqn, disks);
            foreach (var disk in Disks.Where(p=>p.Enable))
            {
                disks.Add(disk.CreateDisk());
            }

            return target;
        }
    }

    internal class AutoLoadDisk
    {
        public bool Enable { get; set; }
        public AutoLoadDiskType Type { get; set; }
        public string FilePath { get; set; }
        public bool ReadOnly { get; set; }

        public Disk CreateDisk()
        {
            switch (Type)
            {
                case AutoLoadDiskType.RamDiskFromFile:
                    var bdd = new BlockDifferencingDiskImage(FilePath, true);
                    try
                    {
                        bdd.OpenForRead();
                        if (false == bdd.IsNoBaseImage) throw new ConfigurationErrorsException("RamDiskFromFile: Only ** No Base Image Mode ** supported");

                        var ramDisk = new UnmanagedGigabyteBlockSeparatedRamDisk((int)Math.Ceiling(bdd.Size / (float)Consts.Gigabyte));
                        ramDisk.Allocate();

                        var buffer = new byte[bdd.BlockSize];
                        for (var i = 0; i < bdd.NumberOfBlocks; i++)
                        {
                            if (false == bdd.IsBlockAllocated[i]) continue;

                            bdd.ReadBlock(buffer, 0, buffer.Length, i, 0);
                            ramDisk.WriteData((long)i * bdd.BlockSize, buffer);
                        }
                        return ramDisk;
                    }
                    finally
                    {
                        bdd.CloseForRead();
                    }

                case AutoLoadDiskType.AttachFile:
                    var diskImage = DiskImage.GetDiskImage(FilePath, ReadOnly);
                    diskImage.ExclusiveLock();
                    return diskImage;

                default:
                    throw new ArgumentOutOfRangeException($"Unknown type: {Type}");
            }
        }
    }

    internal enum AutoLoadDiskType
    {
        RamDiskFromFile,
        AttachFile
    }
}