using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Text;
using ytLive.Models;

namespace ytLive.Services;

/// <summary>
/// Win32 implementation of <see cref="IWindowEnumerator"/>. Enumerates visible
/// top-level windows for the "Capture Window…" submenu, mirroring the style of
/// <see cref="Win32FullScreenDetector"/>: visible, non-cloaked, zero-rect
/// excluded, and windows belonging to this process excluded (the app must never
/// offer itself for pinning). Ordered by process name, then title.
/// </summary>
public sealed class Win32WindowEnumerator : IWindowEnumerator
{
    private static readonly IntPtr OwnProcessId = new(Environment.ProcessId);

    public IReadOnlyList<WindowInfo> Enumerate()
    {
        var results = new List<WindowInfo>();
        EnumWindows((hwnd, _) =>
        {
            if (TryDescribe(hwnd, out var info))
                results.Add(info);
            return true; // keep enumerating
        }, IntPtr.Zero);

        results.Sort(static (a, b) =>
        {
            var byProcess = string.Compare(a.ProcessName, b.ProcessName, StringComparison.OrdinalIgnoreCase);
            return byProcess != 0 ? byProcess
                : string.Compare(a.Title, b.Title, StringComparison.OrdinalIgnoreCase);
        });
        return results;
    }

    private static bool TryDescribe(IntPtr hwnd, out WindowInfo info)
    {
        info = null!;
        if (GetWindowThreadProcessId(hwnd, out var pid) == 0) return false;
        if (pid == 0 || new IntPtr((long)pid) == OwnProcessId) return false;
        if (!IsWindowVisible(hwnd)) return false;
        if (IsCloaked(hwnd)) return false;
        if (!TryGetRect(hwnd, out var rect) || rect.Right <= rect.Left || rect.Bottom <= rect.Top) return false;

        var title = GetTitle(hwnd);
        if (string.IsNullOrWhiteSpace(title)) return false;

        var processName = ProcessName((int)pid);
        if (string.IsNullOrWhiteSpace(processName)) return false;

        info = new WindowInfo(title, processName, hwnd.ToInt64(), (int)pid);
        return true;
    }

    private static string ProcessName(int pid)
    {
        try
        {
            using var process = Process.GetProcessById(pid);
            return process.ProcessName;
        }
        catch { return string.Empty; }
    }

    private static string GetTitle(IntPtr hwnd)
    {
        var length = GetWindowTextLength(hwnd);
        if (length <= 0) return string.Empty;
        var sb = new StringBuilder(length + 1);
        GetWindowText(hwnd, sb, sb.Capacity);
        return sb.ToString();
    }

    private static bool IsCloaked(IntPtr hwnd)
    {
        const int DWMWA_CLOAKED = 14;
        var cloaked = 0;
        return DwmGetWindowAttribute(hwnd, DWMWA_CLOAKED, out cloaked, sizeof(int)) == 0 && cloaked != 0;
    }

    private static bool TryGetRect(IntPtr hwnd, out Rect rect)
    {
        rect = default;
        return GetWindowRect(hwnd, out rect);
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct Rect
    {
        public int Left;
        public int Top;
        public int Right;
        public int Bottom;
    }

    private delegate bool EnumWindowsProc(IntPtr hwnd, IntPtr lParam);

    [DllImport("user32.dll")]
    private static extern bool EnumWindows(EnumWindowsProc lpEnumFunc, IntPtr lParam);

    [DllImport("user32.dll")]
    private static extern bool IsWindowVisible(IntPtr hWnd);

    [DllImport("user32.dll", CharSet = CharSet.Unicode)]
    private static extern int GetWindowText(IntPtr hWnd, StringBuilder lpString, int nMaxCount);

    [DllImport("user32.dll", CharSet = CharSet.Unicode)]
    private static extern int GetWindowTextLength(IntPtr hWnd);

    [DllImport("user32.dll")]
    private static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);

    [DllImport("user32.dll")]
    private static extern bool GetWindowRect(IntPtr hWnd, out Rect lpRect);

    [DllImport("dwmapi.dll")]
    private static extern int DwmGetWindowAttribute(IntPtr hwnd, int dwAttribute, out int pvAttribute, int cbAttribute);
}