using System;
using System.Collections.Generic;
using System.Xml;
using System.Xml.Schema;
using SabreTools.Core;
using SabreTools.Core.Tools;
using SabreTools.DatItems;
using SabreTools.DatItems.Formats;

namespace SabreTools.DatFiles.Formats
{
    /// <summary>
    /// Represents parsing an OfflineList XML DAT
    /// </summary>
    internal partial class OfflineList : DatFile
    {
        /// <inheritdoc/>
        public override void ParseFile(string filename, int indexId, bool keep, bool statsOnly = false, bool throwOnError = false)
        {
            XmlReader xtr = XmlReader.Create(filename, new XmlReaderSettings
            {
                CheckCharacters = false,
                DtdProcessing = DtdProcessing.Ignore,
                IgnoreComments = true,
                IgnoreWhitespace = true,
                ValidationFlags = XmlSchemaValidationFlags.None,
                ValidationType = ValidationType.None,
            });

            // If we got a null reader, just return
            if (xtr == null)
                return;

            // Otherwise, read the file to the end
            try
            {
                xtr.MoveToContent();
                while (!xtr.EOF)
                {
                    // We only want elements
                    if (xtr.NodeType != XmlNodeType.Element)
                    {
                        xtr.Read();
                        continue;
                    }

                    switch (xtr.Name)
                    {
                        case "configuration":
                            ReadConfiguration(xtr.ReadSubtree(), keep);

                            // Skip the configuration node now that we've processed it
                            xtr.Skip();
                            break;

                        case "games":
                            ReadGames(xtr.ReadSubtree(), statsOnly, filename, indexId);

                            // Skip the games node now that we've processed it
                            xtr.Skip();
                            break;

                        default:
                            xtr.Read();
                            break;
                    }
                }
            }
            catch (Exception ex) when (!throwOnError)
            {
                logger.Warning(ex, $"Exception found while parsing '{filename}'");

                // For XML errors, just skip the affected node
                xtr?.Read();
            }

            xtr.Dispose();
        }

        /// <summary>
        /// Read configuration information
        /// </summary>
        /// <param name="reader">XmlReader to use to parse the header</param>
        /// <param name="keep">True if full pathnames are to be kept, false otherwise (default)</param>
        private void ReadConfiguration(XmlReader reader, bool keep)
        {
            bool superdat = false;

            // If there's no subtree to the configuration, skip it
            if (reader == null)
                return;

            // Otherwise, add what is possible
            reader.MoveToContent();

            // Otherwise, read what we can from the header
            while (!reader.EOF)
            {
                // We only want elements
                if (reader.NodeType != XmlNodeType.Element)
                {
                    reader.Read();
                    continue;
                }

                // Get all configuration items (ONLY OVERWRITE IF THERE'S NO DATA)
                string content;
                switch (reader.Name.ToLowerInvariant())
                {
                    case "datname":
                        content = reader.ReadElementContentAsString();
                        Header.Name ??= content;
                        superdat |= content.Contains(" - SuperDAT");
                        if (keep && superdat)
                        {
                            Header.Type ??= "SuperDAT";
                        }
                        break;

                    case "datversion":
                        content = reader.ReadElementContentAsString();
                        Header.Version ??= content;
                        break;

                    case "system":
                        content = reader.ReadElementContentAsString();
                        Header.System ??= content;
                        break;

                    // TODO: Int32?
                    case "screenshotswidth":
                        content = reader.ReadElementContentAsString();
                        Header.ScreenshotsWidth ??= content;
                        break;

                    // TODO: Int32?
                    case "screenshotsheight":
                        content = reader.ReadElementContentAsString();
                        Header.ScreenshotsHeight ??= content;
                        break;

                    case "infos":
                        ReadInfos(reader.ReadSubtree());

                        // Skip the infos node now that we've processed it
                        reader.Skip();
                        break;

                    case "canopen":
                        ReadCanOpen(reader.ReadSubtree());

                        // Skip the canopen node now that we've processed it
                        reader.Skip();
                        break;

                    // TODO: Use all header values
                    case "newdat":
                        ReadNewDat(reader.ReadSubtree());

                        // Skip the newdat node now that we've processed it
                        reader.Skip();
                        break;

                    // TODO: Use header values
                    case "search":
                        ReadSearch(reader.ReadSubtree());

                        // Skip the search node now that we've processed it
                        reader.Skip();
                        break;

                    case "romtitle":
                        content = reader.ReadElementContentAsString();
                        Header.RomTitle ??= content;
                        break;

                    default:
                        reader.Read();
                        break;
                }
            }
        }

        /// <summary>
        /// Read infos information
        /// </summary>
        /// <param name="reader">XmlReader to use to parse the header</param>
        private void ReadInfos(XmlReader reader)
        {
            // If there's no subtree to the configuration, skip it
            if (reader == null)
                return;

            // Setup the infos object
            Header.Infos = new List<OfflineListInfo>();

            // Otherwise, add what is possible
            reader.MoveToContent();

            // Otherwise, read what we can from the header
            while (!reader.EOF)
            {
                // We only want elements
                if (reader.NodeType != XmlNodeType.Element)
                {
                    reader.Read();
                    continue;
                }

                // Add all infos to the info list
                switch (reader.Name.ToLowerInvariant())
                {
                    default:
                        var info = new OfflineListInfo
                        {
                            Name = reader.Name.ToLowerInvariant(),
                            Visible = reader.GetAttribute("visible").AsYesNo(),
                            InNamingOption = reader.GetAttribute("inNamingOption").AsYesNo(),
                            Default = reader.GetAttribute("default").AsYesNo()
                        };

                        Header.Infos.Add(info);

                        reader.Read();
                        break;
                }
            }
        }

        /// <summary>
        /// Read canopen information
        /// </summary>
        /// <param name="reader">XmlReader to use to parse the header</param>
        private void ReadCanOpen(XmlReader reader)
        {
            // Prepare all internal variables
            Header.CanOpen = new List<string>();

            // If there's no subtree to the configuration, skip it
            if (reader == null)
                return;

            // Otherwise, add what is possible
            reader.MoveToContent();

            // Otherwise, read what we can from the header
            while (!reader.EOF)
            {
                // We only want elements
                if (reader.NodeType != XmlNodeType.Element)
                {
                    reader.Read();
                    continue;
                }

                // Get all canopen items
                switch (reader.Name.ToLowerInvariant())
                {
                    case "extension":
                        Header.CanOpen.Add(reader.ReadElementContentAsString());
                        break;

                    default:
                        reader.Read();
                        break;
                }
            }
        }

        /// <summary>
        /// Read newdat information
        /// </summary>
        /// <param name="reader">XmlReader to use to parse the header</param>
        private void ReadNewDat(XmlReader reader)
        {
            // If there's no subtree to the configuration, skip it
            if (reader == null)
                return;

            // Otherwise, add what is possible
            reader.MoveToContent();

            // Otherwise, read what we can from the header
            while (!reader.EOF)
            {
                // We only want elements
                if (reader.NodeType != XmlNodeType.Element)
                {
                    reader.Read();
                    continue;
                }

                // Get all newdat items
                string content;
                switch (reader.Name.ToLowerInvariant())
                {
                    case "datversionurl":
                        // TODO: Read this into an appropriate field
                        content = reader.ReadElementContentAsString();
                        Header.Url ??= content;
                        break;

                    case "daturl":
                        // TODO: Read this into an appropriate structure
                        reader.GetAttribute("fileName");
                        reader.ReadElementContentAsString();
                        break;

                    case "imurl":
                        // TODO: Read this into an appropriate field
                        reader.ReadElementContentAsString();
                        break;

                    default:
                        reader.Read();
                        break;
                }
            }
        }

        /// <summary>
        /// Read search information
        /// </summary>
        /// <param name="reader">XmlReader to use to parse the header</param>
        private void ReadSearch(XmlReader reader)
        {
            // If there's no subtree to the configuration, skip it
            if (reader == null)
                return;

            // Otherwise, add what is possible
            reader.MoveToContent();

            // Otherwise, read what we can from the header
            while (!reader.EOF)
            {
                // We only want elements
                if (reader.NodeType != XmlNodeType.Element)
                {
                    reader.Read();
                    continue;
                }

                // Get all search items
                switch (reader.Name.ToLowerInvariant())
                {
                    case "to":
                        // TODO: Read this into an appropriate structure
                        reader.GetAttribute("value");
                        reader.GetAttribute("default"); // (true|false)
                        reader.GetAttribute("auto"); // (true|false)

                        ReadTo(reader.ReadSubtree());

                        // Skip the to node now that we've processed it
                        reader.Skip();
                        break;

                    default:
                        reader.Read();
                        break;
                }
            }
        }

        /// <summary>
        /// Read to information
        /// </summary>
        /// <param name="reader">XmlReader to use to parse the header</param>
        private void ReadTo(XmlReader reader)
        {
            // If there's no subtree to the configuration, skip it
            if (reader == null)
                return;

            // Otherwise, add what is possible
            reader.MoveToContent();

            // Otherwise, read what we can from the header
            while (!reader.EOF)
            {
                // We only want elements
                if (reader.NodeType != XmlNodeType.Element)
                {
                    reader.Read();
                    continue;
                }

                // Get all search items
                switch (reader.Name.ToLowerInvariant())
                {
                    case "find":
                        // TODO: Read this into an appropriate structure
                        reader.GetAttribute("operation");
                        reader.GetAttribute("value"); // Int32?
                        reader.ReadElementContentAsString();
                        break;

                    default:
                        reader.Read();
                        break;
                }
            }
        }

        /// <summary>
        /// Read games information
        /// </summary>
        /// <param name="reader">XmlReader to use to parse the header</param>
        /// <param name="statsOnly">True to only add item statistics while parsing, false otherwise</param>
        /// <param name="filename">Name of the file to be parsed</param>
        /// <param name="indexId">Index ID for the DAT</param>
        private void ReadGames(XmlReader reader, bool statsOnly, string filename, int indexId)
        {
            // If there's no subtree to the configuration, skip it
            if (reader == null)
                return;

            // Otherwise, add what is possible
            reader.MoveToContent();

            // Otherwise, read what we can from the header
            while (!reader.EOF)
            {
                // We only want elements
                if (reader.NodeType != XmlNodeType.Element)
                {
                    reader.Read();
                    continue;
                }

                // Get all games items (ONLY OVERWRITE IF THERE'S NO DATA)
                switch (reader.Name.ToLowerInvariant())
                {
                    case "game":
                        ReadGame(reader.ReadSubtree(), statsOnly, filename, indexId);

                        // Skip the game node now that we've processed it
                        reader.Skip();
                        break;

                    default:
                        reader.Read();
                        break;
                }
            }
        }

        /// <summary>
        /// Read game information
        /// </summary>
        /// <param name="reader">XmlReader to use to parse the header</param>
        /// <param name="statsOnly">True to only add item statistics while parsing, false otherwise</param>
        /// <param name="filename">Name of the file to be parsed</param>
        /// <param name="indexId">Index ID for the DAT</param>
        private void ReadGame(XmlReader reader, bool statsOnly, string filename, int indexId)
        {
            // Prepare all internal variables
            string releaseNumber = string.Empty, duplicateid;
            long? size = null;
            List<Rom> datItems = new();
            Machine machine = new();

            // If there's no subtree to the configuration, skip it
            if (reader == null)
                return;

            // Otherwise, add what is possible
            reader.MoveToContent();

            // Otherwise, read what we can from the header
            while (!reader.EOF)
            {
                // We only want elements
                if (reader.NodeType != XmlNodeType.Element)
                {
                    reader.Read();
                    continue;
                }

                // Get all games items
                switch (reader.Name.ToLowerInvariant())
                {
                    case "imagenumber":
                        // TODO: Read this into a field
                        reader.ReadElementContentAsString();
                        break;

                    case "releasenumber":
                        // TODO: Read this into a field
                        releaseNumber = reader.ReadElementContentAsString();
                        break;

                    case "title":
                        machine.Name = reader.ReadElementContentAsString();
                        break;

                    case "savetype":
                        // TODO: Read this into a field
                        reader.ReadElementContentAsString();
                        break;

                    case "romsize":
                        size = Utilities.CleanLong(reader.ReadElementContentAsString());
                        break;

                    case "publisher":
                        machine.Publisher = reader.ReadElementContentAsString();
                        break;

                    case "location":
                        // TODO: Read this into a field
                        reader.ReadElementContentAsString();
                        break;

                    case "sourcerom":
                        // TODO: Read this into a field
                        reader.ReadElementContentAsString();
                        break;

                    case "language":
                        // TODO: Read this into a field
                        reader.ReadElementContentAsString();
                        break;

                    case "files":
                        datItems = ReadFiles(reader.ReadSubtree(), releaseNumber, machine.Name, filename, indexId);
                        
                        // Skip the files node now that we've processed it
                        reader.Skip();
                        break;

                    case "im1crc":
                        // TODO: Read this into a field
                        reader.ReadElementContentAsString();
                        break;

                    case "im2crc":
                        // TODO: Read this into a field
                        reader.ReadElementContentAsString();
                        break;

                    case "comment":
                        machine.Comment = reader.ReadElementContentAsString();
                        break;

                    case "duplicateid":
                        duplicateid = reader.ReadElementContentAsString();
                        if (duplicateid != "0")
                            machine.CloneOf = duplicateid;

                        break;

                    default:
                        reader.Read();
                        break;
                }
            }

            // Add information accordingly for each rom
            for (int i = 0; i < datItems.Count; i++)
            {
                datItems[i].Size = size;
                datItems[i].CopyMachineInformation(machine);

                // Now process and add the rom
                ParseAddHelper(datItems[i], statsOnly);
            }
        }

        /// <summary>
        /// Read files information
        /// </summary>
        /// <param name="reader">XmlReader to use to parse the header</param>
        /// <param name="releaseNumber">Release number from the parent game</param>
        /// <param name="machineName">Name of the parent game to use</param>
        /// <param name="filename">Name of the file to be parsed</param>
        /// <param name="indexId">Index ID for the DAT</param>
        private List<Rom> ReadFiles(
            XmlReader reader,
            string releaseNumber,
            string machineName,

            // Standard Dat parsing
            string filename,
            int indexId)
        {
            // Prepare all internal variables
            var extensionToCrc = new List<KeyValuePair<string, string>>();
            var roms = new List<Rom>();

            // If there's no subtree to the configuration, skip it
            if (reader == null)
                return roms;

            // Otherwise, add what is possible
            reader.MoveToContent();

            // Otherwise, read what we can from the header
            while (!reader.EOF)
            {
                // We only want elements
                if (reader.NodeType != XmlNodeType.Element)
                {
                    reader.Read();
                    continue;
                }

                // Get all romCRC items
                switch (reader.Name.ToLowerInvariant())
                {
                    case "romcrc":
                        extensionToCrc.Add(
                            new KeyValuePair<string, string>(
                                reader.GetAttribute("extension") ?? string.Empty,
                                reader.ReadElementContentAsString().ToLowerInvariant()));
                        break;

                    default:
                        reader.Read();
                        break;
                }
            }

            // Now process the roms with the proper information
            foreach (KeyValuePair<string, string> pair in extensionToCrc)
            {
                roms.Add(new Rom()
                {
                    Name = (releaseNumber != "0" ? releaseNumber + " - " : string.Empty) + machineName + pair.Key,
                    CRC = pair.Value,

                    ItemStatus = ItemStatus.None,

                    Source = new Source
                    {
                        Index = indexId,
                        Name = filename,
                    },
                });
            }

            return roms;
        }
    }
}