using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Text;
using Microsoft.Win32.SafeHandles;

namespace Agc.Unity.Attach;

public static class ProjectIdentity
{
    public static string Normalize(string projectPath)
    {
        if (string.IsNullOrWhiteSpace(projectPath) || projectPath.Contains('\0') || !Path.IsPathFullyQualified(projectPath))
            throw new HostException("UnityProjectInvalid", "An absolute Unity project path is required.");
        var supplied = new DirectoryInfo(WithoutDevicePrefix(Path.GetFullPath(projectPath)));
        if (!supplied.Exists || IsLink(supplied))
            throw new HostException("UnityProjectInvalid", "The Unity project root must be an existing ordinary directory.");
        var root = Canonical(projectPath);
        var directory = new DirectoryInfo(root);
        if (!directory.Exists || IsLink(directory))
            throw new HostException("UnityProjectInvalid", "The Unity project root must be an existing ordinary directory.");
        foreach (var child in new[] { "Assets", "Packages", "ProjectSettings" })
        {
            var info = new DirectoryInfo(Path.Combine(root, child));
            if (!info.Exists || IsLink(info))
                throw new HostException("UnityProjectInvalid", "The Unity project directories must be ordinary directories.");
        }
        var version = new FileInfo(Path.Combine(root, "ProjectSettings", "ProjectVersion.txt"));
        if (!version.Exists || IsLink(version))
            throw new HostException("UnityProjectInvalid", "ProjectVersion.txt must be an existing ordinary file.");
        return root;
    }

    public static bool Same(string? first, string? second)
    {
        if (string.IsNullOrWhiteSpace(first) || string.IsNullOrWhiteSpace(second)) return false;
        try
        {
            return string.Equals(Canonical(first), Canonical(second),
                OperatingSystem.IsWindows() ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal);
        }
        catch (Exception error) when (error is ArgumentException or NotSupportedException or IOException or Win32Exception or UnauthorizedAccessException) { return false; }
    }

    private static bool IsLink(FileSystemInfo info) => (info.Attributes & FileAttributes.ReparsePoint) != 0 || info.LinkTarget != null;
    internal static string Canonical(string path)
    {
        var full = Path.TrimEndingDirectorySeparator(Path.GetFullPath(WithoutDevicePrefix(path)));
        if (OperatingSystem.IsWindows() && Directory.Exists(full))
        {
            // A directory handle resolves 8.3 aliases and junction ancestors to the
            // same physical identity used by Rust canonicalize before any attach.
            using var handle = CreateFileW(full, 0, 7, IntPtr.Zero, 3, 0x02000000, IntPtr.Zero);
            if (handle.IsInvalid) throw new Win32Exception(Marshal.GetLastWin32Error());
            var buffer = new StringBuilder(512);
            var length = GetFinalPathNameByHandleW(handle, buffer, (uint)buffer.Capacity, 0);
            if (length == 0) throw new Win32Exception(Marshal.GetLastWin32Error());
            if (length >= buffer.Capacity)
            {
                if (length > 32768) throw new PathTooLongException();
                buffer = new StringBuilder((int)length + 1);
                length = GetFinalPathNameByHandleW(handle, buffer, (uint)buffer.Capacity, 0);
                if (length == 0 || length >= buffer.Capacity) throw new Win32Exception(Marshal.GetLastWin32Error());
            }
            full = WithoutDevicePrefix(buffer.ToString());
        }
        return Path.TrimEndingDirectorySeparator(full);
    }

    private static string WithoutDevicePrefix(string path)
    {
        if (!OperatingSystem.IsWindows()) return path;
        if (path.StartsWith(@"\\?\UNC\", StringComparison.OrdinalIgnoreCase)) return @"\\" + path[8..];
        return path.StartsWith(@"\\?\", StringComparison.Ordinal) ? path[4..] : path;
    }

    [DllImport("kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    private static extern SafeFileHandle CreateFileW(string path, uint access, uint share, IntPtr security, uint creation, uint flags, IntPtr template);
    [DllImport("kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    private static extern uint GetFinalPathNameByHandleW(SafeFileHandle file, StringBuilder path, uint length, uint flags);
}