using System;
using System.Collections.Generic;
using System.IO;

namespace StellaOps.Interop;

internal sealed class ToolPathResolver : IToolPathResolver
{
    private readonly IReadOnlyDictionary<string, string> _toolPaths;

    public ToolPathResolver(IReadOnlyDictionary<string, string> toolPaths)
    {
        _toolPaths = toolPaths ?? throw new ArgumentNullException(nameof(toolPaths));
    }

    public string? ResolveToolPath(string tool)
    {
        if (_toolPaths.TryGetValue(tool, out var configured) && File.Exists(configured))
        {
            return configured;
        }

        return FindOnPath(tool);
    }

    public static string? FindOnPath(string tool)
    {
        if (File.Exists(tool))
        {
            return Path.GetFullPath(tool);
        }

        var path = Environment.GetEnvironmentVariable("PATH");
        if (string.IsNullOrWhiteSpace(path))
        {
            return null;
        }

        foreach (var dir in path.Split(Path.PathSeparator))
        {
            if (string.IsNullOrWhiteSpace(dir))
            {
                continue;
            }

            var candidate = Path.Combine(dir, tool);
            if (File.Exists(candidate))
            {
                return candidate;
            }

            if (OperatingSystem.IsWindows())
            {
                var exeCandidate = candidate + ".exe";
                if (File.Exists(exeCandidate))
                {
                    return exeCandidate;
                }
            }
        }

        return null;
    }
}