using System;
using System.IO;

namespace PKHeX.Core;

/// <summary>
/// Tracks information about where the <see cref="SAV"/> originated from, and provides logic for saving to a file.
/// </summary>
public sealed record SaveFileMetadata(SaveFile SAV)
{
    public SaveFile SAV { private get; init; } = SAV;

    /// <summary>
    /// Full path where the <see cref="SAV"/> originated from.
    /// </summary>
    public string? FilePath { get; private set; }

    /// <summary>
    /// File Name of the <see cref="SAV"/>.
    /// </summary>
    /// <remarks>This is not always the original file name. We try to strip out the Backup name markings to get the original filename.</remarks>
    public string? FileName { get; private set; }

    /// <summary>
    /// Directory in which the <see cref="SAV"/> was saved in.
    /// </summary>
    public string? FileFolder { get; private set; }

    private byte[] Footer = []; // .dsv
    private byte[] Header = []; // .gci

    private string BAKSuffix => $" [{SAV.ShortSummary}].bak";

    /// <summary>
    /// Simple summary of the save file, to help differentiate it from other save files with the same filename.
    /// </summary>
    public string BAKName => FileName + BAKSuffix;

    public bool HasHeader => Header.Length != 0;
    public bool HasFooter => Footer.Length != 0;

    /// <summary>
    /// File Dialog filter to help save the file.
    /// </summary>
    public string Filter => $"{SAV.GetType().Name}|{GetSuggestedExtension()}|All Files|*.*";

    /// <summary>
    /// Writes the input <see cref="data"/> and appends the <see cref="Header"/> and <see cref="Footer"/> if requested.
    /// </summary>
    /// <param name="data">Finalized save file data (with fixed checksums) to be written to a file</param>
    /// <param name="setting">Toggle flags </param>
    /// <returns>Final save file data.</returns>
    public byte[] Finalize(byte[] data, BinaryExportSetting setting)
    {
        if (Footer.Length > 0 && setting.HasFlag(BinaryExportSetting.IncludeFooter))
            return [..data, ..Footer];
        if (Header.Length > 0 && setting.HasFlag(BinaryExportSetting.IncludeHeader))
            return [..Header, ..data];
        return data;
    }

    /// <summary>
    /// Sets the details of any trimmed header and footer arrays to a <see cref="SaveFile"/> object.
    /// </summary>
    public void SetExtraInfo(byte[] header, byte[] footer)
    {
        Header = header;
        Footer = footer;
    }

    /// <summary>
    /// Sets the details of a path to a <see cref="SaveFile"/> object.
    /// </summary>
    /// <param name="path">Full Path of the file</param>
    public void SetExtraInfo(string path)
    {
        var sav = SAV;
        if (!sav.State.Exportable || string.IsNullOrWhiteSpace(path)) // Blank save file
        {
            sav.Metadata.SetAsBlank();
            return;
        }

        SetAsLoadedFile(path);
    }

    private void SetAsLoadedFile(string path)
    {
        FilePath = path;
        FileFolder = Path.GetDirectoryName(path);
        FileName = GetFileName(path, BAKSuffix);
    }

    private static string GetFileName(string path, string bak)
    {
        var bakName = Util.CleanFileName(bak);
        var fn = Path.GetFileName(path);
        return fn.EndsWith(bakName, StringComparison.Ordinal) ? fn[..^bakName.Length] : fn;
    }

    private void SetAsBlank()
    {
        FileFolder = FilePath = string.Empty;
        FileName = "Blank Save File";
    }

    /// <summary>
    /// Gets the suggested file extension when writing to a saved file.
    /// </summary>
    public string GetSuggestedExtension()
    {
        var sav = SAV;
        var fn = sav.Metadata.FileName;
        if (fn != null)
            return Path.GetExtension(fn);

        if ((sav.Generation is 4 or 5) && sav.Metadata.HasFooter)
            return ".dsv";
        return sav.Extension;
    }

    /// <summary>
    /// Gets suggested export options for the save file.
    /// </summary>
    /// <param name="ext">Selected export extension</param>
    public BinaryExportSetting GetSuggestedFlags(string? ext = null)
    {
        var flags = BinaryExportSetting.None;
        if (ext == ".dsv")
            flags |= BinaryExportSetting.IncludeFooter;
        if (ext == ".gci" || SAV is IGCSaveFile {MemoryCard: null})
            flags |= BinaryExportSetting.IncludeHeader;
        return flags;
    }
}