// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

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

namespace Microsoft.Arcade.Common
{
    public class CommandFactory : ICommandFactory
    {
        public ICommand Create(string executable, params string[] args)
        {
            return Create(executable, ArgumentEscaper.EscapeAndConcatenateArgArrayForProcessStart(args));
        }

        public ICommand Create(string executable, IEnumerable<string> args)
        {
            return Create(executable, ArgumentEscaper.EscapeAndConcatenateArgArrayForProcessStart(args));
        }

        public ICommand Create(string executable, string args)
        {
            ResolveExecutablePath(ref executable, ref args);

            return new Command(executable, args);
        }

        private static void ResolveExecutablePath(ref string executable, ref string args)
        {
            // On Windows, we want to avoid using "cmd" if possible (it mangles the colors, and a bunch of other things)
            // So, do a quick path search to see if we can just directly invoke it
            var useCmd = ShouldUseCmd(executable);

            if (useCmd)
            {
                var comSpec = System.Environment.GetEnvironmentVariable("ComSpec");

                // cmd doesn't like "foo.exe ", so we need to ensure that if
                // args is empty, we just run "foo.exe"
                if (!string.IsNullOrEmpty(args))
                {
                    executable = (executable + " " + args).Replace("\"", "\\\"");
                }
                args = $"/C \"{executable}\"";
                executable = comSpec;
            }
        }

        private static bool ShouldUseCmd(string executable)
        {
            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
            {
                var extension = Path.GetExtension(executable);
                if (!string.IsNullOrEmpty(extension))
                {
                    return !string.Equals(extension, ".exe", StringComparison.Ordinal);
                }
                else if (executable.Contains(Path.DirectorySeparatorChar))
                {
                    // It's a relative path without an extension
                    if (File.Exists(executable + ".exe"))
                    {
                        // It refers to an exe!
                        return false;
                    }
                }
                else
                {
                    // Search the path to see if we can find it 
                    foreach (var path in System.Environment.GetEnvironmentVariable("PATH").Split(Path.PathSeparator))
                    {
                        var candidate = Path.Combine(path, executable + ".exe");
                        if (File.Exists(candidate))
                        {
                            // We found an exe!
                            return false;
                        }
                    }
                }

                // It's a non-exe :(
                return true;
            }

            // Non-windows never uses cmd
            return false;
        }
    }
}