using System.Text;

namespace Luna.Memory;

public class MemoryStore : IMemoryStore
{
    private const string FileNamePrefix = "Luna_Conversation_Log_";
    private const string TimestampFormat = "yyyyMMddHHmmss";
    
    private readonly string memoryStorePath = "/home/erik/.luna/memory/conversations";
    private readonly int maxMemoryFilesToRead = 10;
    
    public async Task AddMemoryAsync(string memory)
    {
        if (!Directory.Exists(memoryStorePath))
        {
            Directory.CreateDirectory(memoryStorePath);
        }

        var fileName = $"{FileNamePrefix}{DateTime.UtcNow.ToString(TimestampFormat)}";
        var filePath = Path.Combine(memoryStorePath, fileName);

        await using var writer = new StreamWriter(File.Create(filePath));
        await writer.WriteAsync(memory);
    }

    public async Task<string> GetMemoriesAsync()
    {
        if (!Directory.Exists(memoryStorePath))
        {
            return string.Empty;
        }

        var files = Directory.GetFiles(memoryStorePath)
            .OrderByDescending(GetTimeFromFileName)
            .ToArray();

        if (files.Length == 0)
        {
            return string.Empty;
        }

        var filesToRead = files.Take(maxMemoryFilesToRead);
        var memoryBuilder = new StringBuilder();

        foreach (var file in filesToRead)
        {
            var content = await File.ReadAllTextAsync(file);
            memoryBuilder.Append(content);
        }
        
        return memoryBuilder.ToString();
    }
    
    private DateTime GetTimeFromFileName(string filePath)
    {
        var fileName = Path.GetFileName(filePath);
        var timestamp = fileName[FileNamePrefix.Length..];
        return DateTime.ParseExact(timestamp, TimestampFormat, null);
    } 
}