using System;
using System.IO;
using System.Threading;
using System.Threading.Tasks;

namespace FlowScope.Config
{
    public sealed class FileConfigSource : IConfigSource
    {
        private readonly string _rootPath;

        public FileConfigSource(string rootPath, string name = "File")
        {
            _rootPath = string.IsNullOrWhiteSpace(rootPath)
                ? throw new ArgumentException("Config root path is required.", nameof(rootPath))
                : rootPath;
            Name = string.IsNullOrWhiteSpace(name)
                ? throw new ArgumentException("Config source name is required.", nameof(name))
                : name;
        }

        public string Name { get; }

        public Task<string> LoadTextAsync(string fileName, CancellationToken cancellationToken)
        {
            cancellationToken.ThrowIfCancellationRequested();
            var path = Path.Combine(_rootPath, fileName);
            return Task.Run(() => File.ReadAllText(path), cancellationToken);
        }
    }
}