using System;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
using Microsoft.Win32;

namespace QuickClaude
{
    // Decides which "open ..." shell commands skip the confirm box. Only a command that is a
    // single open of ONE target, with no arguments and nothing chained on, qualifies:
    //   Start-Process "https://x.com"        a website (http/https only)
    //   Start-Process "C:\wallpapers"        a folder that exists (no network paths)
    //   Start-Process mspaint                a program: an .exe in Program Files, Windows,
    //   Start-Process "C:\...\mirc.exe"      AppData\Local\Programs or the Store app aliases,
    //   Start-Process "...\mIRC.lnk"         or a shortcut in the Start Menu or on the Desktop
    // Scripts (.bat, .ps1 and so on) and programs anywhere else still get the confirm box.
    public static class OpenRules
    {
        public enum Verdict { Ask, Allow, Hint }

        // verb, optional "" title (cmd start), optional -FilePath/-Path, then ONE target.
        // Quoted targets may contain spaces and ( ) for "Program Files (x86)", but never quotes,
        // ` $ % or line breaks (PowerShell and cmd expand those). Unquoted targets are stricter.
        static readonly Regex OpenCmd = new Regex(
            @"^\s*(?:cmd(?:\.exe)?\s+/c\s+)?(?:Start-Process|saps|start|explorer(?:\.exe)?|Invoke-Item|ii)\s+" +
            @"(?:""""\s+)?(?:-(?:FilePath|Path|LiteralPath)\s+)?" +
            @"(?:""(?<t>[^""'`$%\r\n;&|<>^]+)""|'(?<t>[^""'`$%\r\n;&|<>^]+)'|(?<t>[^\s""'`$%;&|<>()^]+))\s*$",
            RegexOptions.IgnoreCase | RegexOptions.CultureInvariant);

        static readonly Regex Url = new Regex(@"^https?://[^\s""'`;&|<>$()^%]+$", RegexOptions.IgnoreCase);
        static readonly Regex BareName = new Regex(@"^[A-Za-z0-9_.\-]+$");

        public static Verdict Check(string command, string cwd, out string hint)
        {
            hint = null;
            if (string.IsNullOrEmpty(command) || command.IndexOfAny(new[] { '\n', '\r' }) >= 0) return Verdict.Ask;
            var m = OpenCmd.Match(command);
            if (!m.Success) return Verdict.Ask;
            var target = m.Groups["t"].Value.Trim();
            if (target.Length == 0) return Verdict.Ask;

            if (Url.IsMatch(target)) return Verdict.Allow;

            try
            {
                if (Path.IsPathFullyQualified(target))
                {
                    if (target.StartsWith(@"\\")) return Verdict.Ask;          // no network paths
                    var full = Path.GetFullPath(target);
                    if (Directory.Exists(full)) return Verdict.Allow;
                    if (File.Exists(full) && TrustedProgram(full)) return Verdict.Allow;
                    return Verdict.Ask;
                }

                if (BareName.IsMatch(target))
                {
                    // A bare name could also pick up a file sitting in the work folder; never allow that
                    if (!string.IsNullOrEmpty(cwd) && Directory.Exists(cwd) &&
                        (File.Exists(Path.Combine(cwd, target)) || Directory.EnumerateFiles(cwd, target + ".*").Any())) return Verdict.Ask;

                    if (FindProgram(target) != null) return Verdict.Allow;

                    var lnk = FindShortcut(target);
                    if (lnk != null)
                    {
                        hint = "\"" + target + "\" isn't on the PATH, so that command wouldn't find it. " +
                               "Its Start Menu shortcut is " + lnk + ". Run Start-Process \"" + lnk + "\" instead " +
                               "(that one opens without a confirm box).";
                        return Verdict.Hint;
                    }
                }
            }
            catch { }
            return Verdict.Ask;
        }

        static string Env(string name) => Environment.GetEnvironmentVariable(name) ?? "";
        static string Special(Environment.SpecialFolder f) => Environment.GetFolderPath(f);

        static string[] ProgramDirs => new[]
        {
            Env("ProgramFiles"), Env("ProgramFiles(x86)"), Env("ProgramW6432"),
            Env("WINDIR"),
            Path.Combine(Special(Environment.SpecialFolder.LocalApplicationData), "Programs"),
            Path.Combine(Special(Environment.SpecialFolder.LocalApplicationData), "Microsoft", "WindowsApps"),
        }.Where(d => d.Length > 0).ToArray();

        static string[] ShortcutDirs => new[]
        {
            Path.Combine(Special(Environment.SpecialFolder.CommonApplicationData), "Microsoft", "Windows", "Start Menu"),
            Path.Combine(Special(Environment.SpecialFolder.ApplicationData), "Microsoft", "Windows", "Start Menu"),
            Special(Environment.SpecialFolder.DesktopDirectory),
            Special(Environment.SpecialFolder.CommonDesktopDirectory),
        }.Where(d => d.Length > 0).ToArray();

        static bool Under(string path, string dir)
        {
            var d = Path.GetFullPath(dir).TrimEnd('\\') + "\\";
            return path.StartsWith(d, StringComparison.OrdinalIgnoreCase);
        }

        static bool TrustedProgram(string full)
        {
            var ext = Path.GetExtension(full).ToLowerInvariant();
            if (ext == ".exe") return ProgramDirs.Any(d => Under(full, d));
            if (ext == ".lnk") return ShortcutDirs.Any(d => Under(full, d));
            return false;
        }

        // Where Windows itself would find a bare program name: the Windows folders, the Store app
        // aliases, and the App Paths registry (how "mspaint" and friends resolve).
        static string FindProgram(string name)
        {
            var exe = name.EndsWith(".exe", StringComparison.OrdinalIgnoreCase) ? name : name + ".exe";
            var win = Env("WINDIR");
            foreach (var dir in new[]
            {
                Path.Combine(win, "System32"), win,
                Path.Combine(Special(Environment.SpecialFolder.LocalApplicationData), "Microsoft", "WindowsApps"),
            })
            {
                var p = Path.Combine(dir, exe);
                if (File.Exists(p)) return p;
            }
            foreach (var hive in new[] { Registry.CurrentUser, Registry.LocalMachine })
            {
                using var key = hive.OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\App Paths\" + exe);
                var val = (key?.GetValue(null) as string)?.Trim('"');
                if (!string.IsNullOrEmpty(val) && File.Exists(val) && TrustedProgram(Path.GetFullPath(val))) return val;
            }
            return null;
        }

        // A Start Menu or Desktop shortcut named like the program ("mirc" finds "mIRC.lnk").
        // Exact name first, then the shortest name that starts with it.
        static string FindShortcut(string name)
        {
            var all = ShortcutDirs.Where(Directory.Exists)
                .SelectMany(d => { try { return Directory.EnumerateFiles(d, "*.lnk", SearchOption.AllDirectories); } catch { return Enumerable.Empty<string>(); } })
                .ToList();
            var exact = all.FirstOrDefault(f => string.Equals(Path.GetFileNameWithoutExtension(f), name, StringComparison.OrdinalIgnoreCase));
            if (exact != null) return exact;
            return all.Where(f => Path.GetFileNameWithoutExtension(f).StartsWith(name, StringComparison.OrdinalIgnoreCase))
                      .OrderBy(f => Path.GetFileNameWithoutExtension(f).Length).FirstOrDefault();
        }
    }
}