PromptFileReader.cs

namespace MultiCliLauncher;

/// <summary>
/// Result of reading a prompts file, including parsed prompts and optional model override
/// </summary>
public class PromptsFileResult
{
    public List<string> Prompts { get; set; } = new();
    public string? ModelOverride { get; set; }
}

/// <summary>
/// Reads prompts from a file with support for multi-line prompts and directives
/// </summary>
public static class PromptFileReader
{
    private const string PromptDelimiter = "---";
    private const string ModelDirectivePrefix = "#model:";

    /// <summary>
    /// Reads prompts from a file asynchronously
    /// </summary>
    /// <param name="filePath">Path to the prompts file</param>
    /// <returns>PromptsFileResult containing prompts and optional model override</returns>
    public static async Task<PromptsFileResult> ReadPromptsAsync(string filePath)
    {
        var content = await File.ReadAllTextAsync(filePath);
        return ParseContent(content);
    }

    /// <summary>
    /// Reads prompts from a file synchronously
    /// </summary>
    /// <param name="filePath">Path to the prompts file</param>
    /// <returns>PromptsFileResult containing prompts and optional model override</returns>
    public static PromptsFileResult ReadPrompts(string filePath)
    {
        var content = File.ReadAllText(filePath);
        return ParseContent(content);
    }

    /// <summary>
    /// Parses content string into prompts (useful for testing)
    /// </summary>
    /// <param name="content">Raw file content</param>
    /// <returns>PromptsFileResult containing prompts and optional model override</returns>
    public static PromptsFileResult ParseContent(string content)
    {
        var result = new PromptsFileResult();
        
        if (string.IsNullOrWhiteSpace(content))
        {
            return result;
        }

        // Split by delimiter
        var sections = content.Split(PromptDelimiter, StringSplitOptions.None);
        
        foreach (var section in sections)
        {
            var processedSection = ProcessSection(section, result);
            
            if (!string.IsNullOrWhiteSpace(processedSection))
            {
                result.Prompts.Add(processedSection);
            }
        }

        return result;
    }

    /// <summary>
    /// Processes a section of the file, extracting directives and filtering comments
    /// </summary>
    private static string ProcessSection(string section, PromptsFileResult result)
    {
        var lines = section.Split('\n');
        var promptLines = new List<string>();

        foreach (var rawLine in lines)
        {
            var line = rawLine.TrimEnd('\r'); // Handle CRLF
            var trimmedLine = line.TrimStart();

            // Check for model directive (only if not already set)
            if (result.ModelOverride == null && 
                trimmedLine.StartsWith(ModelDirectivePrefix, StringComparison.OrdinalIgnoreCase))
            {
                var modelValue = trimmedLine[ModelDirectivePrefix.Length..].Trim();
                if (!string.IsNullOrWhiteSpace(modelValue))
                {
                    result.ModelOverride = modelValue;
                }
                continue;
            }

            // Skip comment lines (lines starting with #)
            if (trimmedLine.StartsWith('#'))
            {
                continue;
            }

            // Add non-comment lines to prompt
            promptLines.Add(line);
        }

        // Join lines and trim the result
        var prompt = string.Join('\n', promptLines).Trim();
        return prompt;
    }
}