ChatBot/ChatBot/Services/FileSystemPromptProvider.cs

using System.Text;
using ChatBot.Models.Configuration;
using ChatBot.Services.Interfaces;
using Microsoft.Extensions.Options;

namespace ChatBot.Services
{
    /// <summary>
    /// System prompt provider that loads prompt from file
    /// </summary>
    public class FileSystemPromptProvider : ISystemPromptProvider
    {
        private readonly string _filePath;
        private readonly ILogger<FileSystemPromptProvider> _logger;
        private readonly Lazy<string> _cachedPrompt;

        public FileSystemPromptProvider(
            IOptions<OllamaSettings> settings,
            ILogger<FileSystemPromptProvider> logger
        )
        {
            _filePath = settings.Value.SystemPromptFilePath;
            _logger = logger;
            _cachedPrompt = new Lazy<string>(LoadPrompt);
        }

        public string GetSystemPrompt() => _cachedPrompt.Value;

        private string LoadPrompt()
        {
            if (!File.Exists(_filePath))
            {
                var error = $"System prompt file not found: {_filePath}";
                _logger.LogError(error);
                throw new FileNotFoundException(error);
            }

            try
            {
                var prompt = File.ReadAllText(_filePath, Encoding.UTF8);
                _logger.LogInformation(
                    "System prompt loaded from {FilePath} ({Length} characters)",
                    _filePath,
                    prompt.Length
                );
                return prompt;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Failed to read system prompt file: {FilePath}", _filePath);
                throw new InvalidOperationException(
                    $"Failed to read system prompt file '{_filePath}': {ex.Message}",
                    ex
                );
            }
        }
    }
}