using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Runtime.InteropServices;
using WhiteMagic.Native;
using WhiteMagic.Windows;

namespace WhiteMagic.ProcessDiscovery;

/// <summary>
/// Discovers running processes by name, window title, or window handle so they can be
/// attached through a <see cref="Magic"/> session.
/// </summary>
public static class ApplicationFinder
{
    /// <summary>
    /// Enumerates processes whose image name matches <paramref name="processName"/>
    /// (extension optional).
    /// </summary>
    public static IEnumerable<Process> Enumerate(string processName)
    {
        ArgumentException.ThrowIfNullOrEmpty(processName);

        return Process.GetProcessesByName(GetNameWithoutExtension(processName));
    }

    /// <summary>
    /// Returns the unique process whose image name matches <paramref name="processName"/>.
    /// </summary>
    /// <exception cref="InvalidOperationException">Zero or multiple processes match.</exception>
    public static Process OpenProcess(string processName)
    {
        Process[] candidates = Enumerate(processName).ToArray();

        if (candidates.Length == 0)
        {
            throw new InvalidOperationException(
                $"No process named '{processName}' was found.");
        }

        if (candidates.Length > 1)
        {
            string list = string.Join(", ", candidates.Select(p => $"{p.ProcessName}:{p.Id}"));
            foreach (Process candidate in candidates)
                candidate.Dispose();

            throw new InvalidOperationException(
                $"Process name '{processName}' is ambiguous ({candidates.Length} matches): {list}");
        }

        Process result = candidates[0];
        for (int i = 1; i < candidates.Length; i++)
            candidates[i].Dispose();

        return result;
    }

    /// <summary>
    /// Enumerates processes that own a top-level window whose title equals
    /// <paramref name="title"/>.
    /// </summary>
    public static IEnumerable<Process> FindByWindowTitle(string title)
    {
        ArgumentException.ThrowIfNullOrEmpty(title);

        var seen = new HashSet<int>();
        foreach (RemoteWindow window in WindowFactory.GetWindows())
        {
            if (!string.Equals(window.Text, title, StringComparison.Ordinal))
                continue;

            uint pid = window.ProcessId;
            if (pid == 0 || !seen.Add((int)pid))
                continue;

            Process? process;
            try
            {
                process = global::System.Diagnostics.Process.GetProcessById((int)pid);
            }
            catch
            {
                continue;
            }

            yield return process;
        }
    }

    /// <summary>
    /// Returns the unique process that owns a top-level window titled <paramref name="title"/>.
    /// </summary>
    /// <exception cref="InvalidOperationException">Zero or multiple windows match.</exception>
    public static Process OpenByWindowTitle(string title)
    {
        Process[] candidates = FindByWindowTitle(title).ToArray();

        if (candidates.Length == 0)
        {
            throw new InvalidOperationException(
                $"No top-level window titled '{title}' was found.");
        }

        if (candidates.Length > 1)
        {
            throw new InvalidOperationException(
                $"Window title '{title}' is ambiguous ({candidates.Length} matches): " +
                string.Join(", ", candidates.Select(p => $"{p.ProcessName}:{p.Id}")));
        }

        return candidates[0];
    }

    /// <summary>
    /// Returns the process that owns the specified window handle.
    /// </summary>
    public static Process OpenByWindowHandle(IntPtr handle)
    {
        if (handle == IntPtr.Zero)
            throw new ArgumentException("Window handle cannot be zero.", nameof(handle));

        uint tid = NativeMethods.GetWindowThreadProcessId(handle, out uint processId);
        if (tid == 0 || processId == 0)
        {
            int error = Marshal.GetLastPInvokeError();
            throw new InvalidOperationException(
                $"GetWindowThreadProcessId failed for handle {handle:X}: error {error}.");
        }

        try
        {
            return global::System.Diagnostics.Process.GetProcessById((int)processId);
        }
        catch (ArgumentException)
        {
            throw new InvalidOperationException(
                $"Process {processId} owning window {handle:X} is no longer running.");
        }
    }

    private static string GetNameWithoutExtension(string name)
    {
        if (name.EndsWith(".exe", StringComparison.OrdinalIgnoreCase))
            return name[..^4];

        return name;
    }
}