using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;

namespace Notify.Interop;

/// <summary>
/// 沿父进程上溯，跳过 shell/运行时，找到真正的调用方 App（编辑器/终端）
/// </summary>
internal static partial class ProcessTree
{
    // 这些进程是 shell / 运行时 / 包装器，不是用户面对的 App，跳过继续上溯
    private static readonly HashSet<string> SkipNames = new(StringComparer.OrdinalIgnoreCase)
    {
        "cmd", "powershell", "pwsh", "bash", "sh", "zsh", "fish",
        "wsl", "wslhost", "conhost", "openconsole",
        "node", "deno", "bun", "python", "python3", "py",
        "uv", "uvx", "npm", "npx", "yarn", "pnpm",
        "claude", "dotnet", "git", "env", "busybox", "winpty", "sudo",
        "notify",
    };

    public static string FindCallerExePath()
    {
        try
        {
            var parents = BuildParentMap();
            var pid = GetCurrentProcessId();

            for (var i = 0; i < 16; i++)
            {
                if (!parents.TryGetValue(pid, out var info))
                {
                    break;
                }

                pid = info.Parent;
                if (pid == 0 || !parents.TryGetValue(pid, out var anc))
                {
                    break;
                }

                var name = anc.Name;
                if (name.EndsWith(".exe", StringComparison.OrdinalIgnoreCase))
                {
                    name = name[..^4];
                }

                if (SkipNames.Contains(name))
                {
                    continue;
                }

                // 第一个非 shell/运行时的祖先即调用方 App
                return GetFullPath(pid);
            }
        }
        catch
        {
            // 取不到就回退默认图标
        }

        return "";
    }

    private static Dictionary<uint, (uint Parent, string Name)> BuildParentMap()
    {
        var map = new Dictionary<uint, (uint, string)>();
        var snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
        if (snapshot == IntPtr.Zero || snapshot == new IntPtr(-1))
        {
            return map;
        }

        try
        {
            var entry = default(PROCESSENTRY32W);
            entry.dwSize = (uint)Marshal.SizeOf<PROCESSENTRY32W>();

            if (Process32FirstW(snapshot, ref entry))
            {
                do
                {
                    map[entry.th32ProcessID] = (entry.th32ParentProcessID, ReadExeName(ref entry));
                }
                while (Process32NextW(snapshot, ref entry));
            }
        }
        finally
        {
            CloseHandle(snapshot);
        }

        return map;
    }

    private static unsafe string ReadExeName(ref PROCESSENTRY32W entry)
    {
        fixed (char* p = entry.szExeFile)
        {
            return new string(p);
        }
    }

    private static string GetFullPath(uint pid)
    {
        var h = OpenProcess(PROCESS_QUERY_LIMITED_INFORMATION, false, pid);
        if (h == IntPtr.Zero)
        {
            return "";
        }

        try
        {
            var buf = new char[1024];
            var size = (uint)buf.Length;
            return QueryFullProcessImageName(h, 0, ref buf[0], ref size) ? new string(buf, 0, (int)size) : "";
        }
        finally
        {
            CloseHandle(h);
        }
    }

    private const uint TH32CS_SNAPPROCESS = 0x00000002;
    private const uint PROCESS_QUERY_LIMITED_INFORMATION = 0x1000;

    [LibraryImport("kernel32.dll")]
    private static partial uint GetCurrentProcessId();

    [LibraryImport("kernel32.dll")]
    private static partial IntPtr CreateToolhelp32Snapshot(uint dwFlags, uint th32ProcessID);

    [LibraryImport("kernel32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static partial bool Process32FirstW(IntPtr hSnapshot, ref PROCESSENTRY32W lppe);

    [LibraryImport("kernel32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static partial bool Process32NextW(IntPtr hSnapshot, ref PROCESSENTRY32W lppe);

    [LibraryImport("kernel32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static partial bool CloseHandle(IntPtr hObject);

    [LibraryImport("kernel32.dll")]
    private static partial IntPtr OpenProcess(uint dwDesiredAccess, [MarshalAs(UnmanagedType.Bool)] bool bInheritHandle, uint dwProcessId);

    [LibraryImport("kernel32.dll", EntryPoint = "QueryFullProcessImageNameW", StringMarshalling = StringMarshalling.Utf16)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static partial bool QueryFullProcessImageName(IntPtr hProcess, uint dwFlags, ref char lpExeName, ref uint lpdwSize);
}

[StructLayout(LayoutKind.Sequential)]
internal unsafe struct PROCESSENTRY32W
{
    public uint dwSize;
    public uint cntUsage;
    public uint th32ProcessID;
    public nint th32DefaultHeapID;
    public uint th32ModuleID;
    public uint cntThreads;
    public uint th32ParentProcessID;
    public int pcPriClassBase;
    public uint dwFlags;
    public fixed char szExeFile[260];
}