using System.Runtime.InteropServices;

namespace Robovoice.App;

internal static class IconExtractor
{
    private const string Source = @"%SystemRoot%\System32\mmres.dll";
    private static readonly int[] CandidateIndices = { 5, 12 };

    public static Icon? TryExtractMicrophone(int size = 32)
    {
        string path = Environment.ExpandEnvironmentVariables(Source);
        if (!File.Exists(path)) return null;

        foreach (int index in CandidateIndices)
        {
            if (ExtractIconAt(path, index, size, size) is { } icon)
                return icon;
        }
        return null;
    }

    private static Icon? ExtractIconAt(string path, int index, int width, int height)
    {
        IntPtr[] hicons = new IntPtr[1];
        IntPtr[] ids = new IntPtr[1];

        int count = PrivateExtractIcons(path, index, width, height, hicons, ids, 1, 0);
        if (count <= 0 || hicons[0] == IntPtr.Zero) return null;

        try
        {
            return Icon.FromHandle(hicons[0]);
        }
        catch
        {
            DestroyIcon(hicons[0]);
            return null;
        }
    }

    [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
    private static extern int PrivateExtractIcons(
        string lpszFile,
        int nIconIndex,
        int cxIcon,
        int cyIcon,
        IntPtr[] phicon,
        IntPtr[] phiconId,
        int nIcons,
        int flags);

    [DllImport("user32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool DestroyIcon(IntPtr hIcon);
}