// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
namespace Aspire.Hosting.Python;
 
/// <summary>
/// Handles location of files within the virtual environment of a python app.
/// </summary>
/// <param name="virtualEnvironmentPath">The path to the directory containing the python app files.</param>
internal sealed class VirtualEnvironment(string virtualEnvironmentPath)
{
    /// <summary>
    /// Locates an executable in the virtual environment.
    /// </summary>
    /// <param name="name">The name of the executable.</param>
    /// <returns>Returns the path to the executable if it exists in the virtual environment.</returns>
    public string? GetExecutable(string name)
    {
        if(OperatingSystem.IsWindows())
        {
            string[] allowedExtensions = [".exe", ".cmd", ".bat"];
 
            foreach(var allowedExtension in allowedExtensions)
            {
                string executablePath = Path.Join(virtualEnvironmentPath, "Scripts", name + allowedExtension);
 
                if(File.Exists(executablePath))
                {
                    return executablePath;
                }
            }
        }
        else
        {
            var executablePath = Path.Join(virtualEnvironmentPath, "bin", name);
 
            if (File.Exists(executablePath))
            {
                return executablePath;
            }
        }
 
        return null;
    }
 
    /// <summary>
    /// Locates a required executable in the virtual environment.
    /// </summary>
    /// <param name="name">The name of the executable.</param>
    /// <returns>The path to the executable in the virtual environment.</returns>
    /// <exception cref="DistributedApplicationException">Gets thrown when the executable couldn't be located.</exception>
    public string GetRequiredExecutable(string name)
    {
        return GetExecutable(name) ?? throw new DistributedApplicationException(
            $"The executable {name} could not be found in the virtual environment at '{virtualEnvironmentPath}' . " +
            "Make sure the virtual environment is initialized and the executable is installed.");
    }
}