using System;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
using System.Xml;
using System.Xml.Schema;
using System.Xml.Serialization;
using SabreTools.Models.Logiqx;
using SabreTools.Models.PIC;
using SabreTools.RedumpLib.Data;

namespace MPF.Processors
{
    /// <summary>
    /// Includes processing-specific utility functionality
    /// </summary>
    public static class ProcessingTool
    {
        #region Information Extraction

        /// <summary>
        /// Generate the proper datfile from the input Datafile, if possible
        /// </summary>
        /// <param name="datafile">.dat file location</param>
        /// <returns>Relevant pieces of the datfile, null on error</returns>
        public static string? GenerateDatfile(Datafile? datafile)
        {
            // If we don't have a valid datafile, we can't do anything
            if (datafile?.Game == null || datafile.Game.Length == 0)
                return null;

            var roms = datafile.Game[0].Rom;
            if (roms == null || roms.Length == 0)
                return null;

            // Otherwise, reconstruct the hash data with only the required info
            try
            {
                string datString = string.Empty;
                for (int i = 0; i < roms.Length; i++)
                {
                    var rom = roms[i];
                    datString += $"<rom name=\"{rom.Name}\" size=\"{rom.Size}\" crc=\"{rom.CRC}\" md5=\"{rom.MD5}\" sha1=\"{rom.SHA1}\" />\n";
                }

                return datString.TrimEnd('\n');
            }
            catch
            {
                // We don't care what the exception is right now
                return null;
            }
        }

        /// <summary>
        /// Get the Base64 representation of a string
        /// </summary>
        /// <param name="content">String content to encode</param>
        /// <returns>Base64-encoded contents, if possible</returns>
        public static string? GetBase64(string? content)
        {
            if (string.IsNullOrEmpty(content))
                return null;

            byte[] temp = Encoding.UTF8.GetBytes(content);
            return Convert.ToBase64String(temp);
        }

        /// <summary>
        /// Get Datafile from a standard DAT
        /// </summary>
        /// <param name="dat">Path to the DAT file to parse</param>
        /// <returns>Filled Datafile on success, null on error</returns>
        public static Datafile? GetDatafile(string? dat)
        {
            // If there's no path, we can't read the file
            if (string.IsNullOrEmpty(dat))
                return null;

            // If the file doesn't exist, we can't read it
            if (!File.Exists(dat))
                return null;

            try
            {
                // Open and read in the XML file
                XmlReader xtr = XmlReader.Create(dat, new XmlReaderSettings
                {
                    CheckCharacters = false,
#if NET40_OR_GREATER || NETCOREAPP
                    DtdProcessing = DtdProcessing.Ignore,
#endif
                    IgnoreComments = true,
                    IgnoreWhitespace = true,
                    ValidationFlags = XmlSchemaValidationFlags.None,
                    ValidationType = ValidationType.None,
                });

                // If the reader is null for some reason, we can't do anything
                if (xtr == null)
                    return null;

                var serializer = new XmlSerializer(typeof(Datafile));
                return serializer.Deserialize(xtr) as Datafile;
            }
            catch
            {
                // We don't care what the exception is right now
                return null;
            }
        }

        /// <summary>
        /// Gets disc information from a PIC file
        /// </summary>
        /// <param name="pic">Path to a PIC.bin file</param>
        /// <returns>Filled DiscInformation on success, null on error</returns>
        /// <remarks>This omits the emergency brake information, if it exists</remarks>
        public static DiscInformation? GetDiscInformation(string pic)
        {
            try
            {
                return SabreTools.Serialization.Deserializers.PIC.DeserializeFile(pic);
            }
            catch
            {
                // We don't care what the error was
                return null;
            }
        }

        /// <summary>
        /// Get the last modified date from a file path, if possible
        /// </summary>
        /// <param name="filename">Path to the input file</param>
        /// <returns>Filled DateTime on success, null on failure</returns>
        public static DateTime? GetFileModifiedDate(string? filename, bool fallback = false)
        {
            if (string.IsNullOrEmpty(filename))
                return fallback ? (DateTime?)DateTime.UtcNow : null;
            else if (!File.Exists(filename))
                return fallback ? (DateTime?)DateTime.UtcNow : null;

            var fi = new FileInfo(filename);
            return fi.LastWriteTimeUtc;
        }

        /// <summary>
        /// Get the full lines from the input file, if possible
        /// </summary>
        /// <param name="filename">file location</param>
        /// <param name="binary">True if should read as binary, false otherwise (default)</param>
        /// <returns>Full text of the file, null on error</returns>
        public static string? GetFullFile(string filename, bool binary = false)
        {
            // If the file doesn't exist, we can't get info from it
            if (!File.Exists(filename))
                return null;

            // If we're reading as binary
            if (binary)
            {
                byte[] bytes = File.ReadAllBytes(filename);
                return BitConverter.ToString(bytes).Replace("-", string.Empty);
            }

            return File.ReadAllText(filename);
        }

        /// <summary>
        /// Get the split values for ISO-based media
        /// </summary>
        /// <param name="datafile">Datafile represenging the hash data</param>
        /// <returns>True if extraction was successful, false otherwise</returns>
        public static bool GetISOHashValues(Datafile? datafile, out long size, out string? crc32, out string? md5, out string? sha1)
        {
            size = -1; crc32 = null; md5 = null; sha1 = null;

            if (datafile?.Game == null || datafile.Game.Length == 0)
                return false;

            var roms = datafile.Game[0].Rom;
            if (roms == null || roms.Length == 0)
                return false;

            var rom = roms[0];

            _ = Int64.TryParse(rom.Size, out size);
            crc32 = rom.CRC;
            md5 = rom.MD5;
            sha1 = rom.SHA1;

            return true;
        }

        /// <summary>
        /// Get the split values for ISO-based media
        /// </summary>
        /// <param name="hashData">String representing the combined hash data</param>
        /// <returns>True if extraction was successful, false otherwise</returns>
        public static bool GetISOHashValues(string? hashData, out long size, out string? crc32, out string? md5, out string? sha1)
        {
            size = -1; crc32 = null; md5 = null; sha1 = null;

            if (string.IsNullOrEmpty(hashData))
                return false;

            var hashreg = new Regex(@"<rom name="".*?"" size=""(.*?)"" crc=""(.*?)"" md5=""(.*?)"" sha1=""(.*?)""", RegexOptions.Compiled);
            Match m = hashreg.Match(hashData);
            if (m.Success)
            {
                _ = Int64.TryParse(m.Groups[1].Value, out size);
                crc32 = m.Groups[2].Value;
                md5 = m.Groups[3].Value;
                sha1 = m.Groups[4].Value;
                return true;
            }
            else
            {
                return false;
            }
        }

        /// <summary>
        /// Get the layerbreak info associated from the disc information
        /// </summary>
        /// <param name="di">Disc information containing unformatted data</param>
        /// <returns>True if layerbreak info was set, false otherwise</returns>
        public static bool GetLayerbreaks(DiscInformation? di, out long? layerbreak1, out long? layerbreak2, out long? layerbreak3)
        {
            // Set the default values
            layerbreak1 = null; layerbreak2 = null; layerbreak3 = null;

            // If we don't have valid disc information, we can't do anything
            if (di?.Units == null || di.Units.Length <= 1)
                return false;

            static int ReadFromArrayBigEndian(byte[]? bytes, int offset)
            {
                if (bytes == null)
                    return default;

#if NET20 || NET35 || NET40
                byte[] rev = new byte[0x04];
                Array.Copy(bytes, offset, rev, 0, 0x04);
#else
                var span = new ReadOnlySpan<byte>(bytes, offset, 0x04);
                byte[] rev = span.ToArray();
#endif
                Array.Reverse(rev);
                return BitConverter.ToInt32(rev, 0);
            }

            // Layerbreak 1 (2+ layers)
            if (di.Units.Length >= 2)
            {
                long offset = ReadFromArrayBigEndian(di.Units[0]?.Body?.FormatDependentContents, 0x0C);
                long value = ReadFromArrayBigEndian(di.Units[0]?.Body?.FormatDependentContents, 0x10);
                layerbreak1 = value - offset + 2;
            }

            // Layerbreak 2 (3+ layers)
            if (di.Units.Length >= 3)
            {
                long offset = ReadFromArrayBigEndian(di.Units[1]?.Body?.FormatDependentContents, 0x0C);
                long value = ReadFromArrayBigEndian(di.Units[1]?.Body?.FormatDependentContents, 0x10);
                layerbreak2 = layerbreak1 + value - offset + 2;
            }

            // Layerbreak 3 (4 layers)
            if (di.Units.Length >= 4)
            {
                long offset = ReadFromArrayBigEndian(di.Units[2]?.Body?.FormatDependentContents, 0x0C);
                long value = ReadFromArrayBigEndian(di.Units[2]?.Body?.FormatDependentContents, 0x10);
                layerbreak3 = layerbreak2 + value - offset + 2;
            }

            return true;
        }

        /// <summary>
        /// Get the PIC identifier from the first disc information unit, if possible
        /// </summary>
        /// <param name="di">Disc information containing the data</param>
        /// <returns>String representing the PIC identifier, null on error</returns>
        public static string? GetPICIdentifier(DiscInformation? di)
        {
            // If we don't have valid disc information, we can't do anything
            if (di?.Units == null || di.Units.Length <= 1)
                return null;

            // We assume the identifier is consistent across all units
            return di.Units[0]?.Body?.DiscTypeIdentifier;
        }

        #endregion

        #region Category Extraction

        /// <summary>
        /// Determine the category based on the UMDImageCreator string
        /// </summary>
        /// <param name="region">String representing the category</param>
        /// <returns>Category, if possible</returns>
        public static DiscCategory? GetUMDCategory(string? category)
        {
            return category switch
            {
                "GAME" => DiscCategory.Games,
                "VIDEO" => DiscCategory.Video,
                "AUDIO" => DiscCategory.Audio,
                _ => null,
            };
        }

        #endregion

        #region Region Extraction

        /// <summary>
        /// Determine the region based on the XGD serial character
        /// </summary>
        /// <param name="region">Character denoting the region</param>
        /// <returns>Region, if possible</returns>
        public static Region? GetXGDRegion(char? region)
        {
            return region switch
            {
                'W' => (Region?)Region.World,
                'A' => (Region?)Region.UnitedStatesOfAmerica,
                'J' => (Region?)Region.JapanAsia,
                'E' => (Region?)Region.Europe,
                'K' => (Region?)Region.USAJapan,
                'L' => (Region?)Region.USAEurope,
                'H' => (Region?)Region.JapanEurope,
                _ => null,
            };
        }

        #endregion
    }
}