using Microsoft.Extensions.Logging;

namespace VFXReviewWorker;

/// <summary>
/// Minimal rolling file logger (§7.9): one file per day under
/// %ProgramData%\VFXReviewWorker\logs, files older than 14 days pruned on
/// startup and at midnight rollover. No external logging dependencies.
/// </summary>
public sealed class FileLoggerProvider : ILoggerProvider
{
    private readonly object _lock = new();
    private StreamWriter? _writer;
    private DateOnly _currentDay;

    public FileLoggerProvider()
    {
        Directory.CreateDirectory(WorkerOptions.LogsDir);
        Prune();
    }

    public ILogger CreateLogger(string categoryName) => new FileLogger(this, categoryName);

    internal void Write(string category, LogLevel level, string message, Exception? ex)
    {
        lock (_lock)
        {
            var today = DateOnly.FromDateTime(DateTime.Now);
            if (_writer is null || today != _currentDay)
            {
                _writer?.Dispose();
                _currentDay = today;
                _writer = new StreamWriter(
                    Path.Combine(WorkerOptions.LogsDir, $"worker_{today:yyyyMMdd}.log"),
                    append: true) { AutoFlush = true };
                Prune();
            }
            _writer.WriteLine($"{DateTime.Now:HH:mm:ss.fff} [{level,-5}] {Shorten(category)}: {message}{(ex is null ? "" : $"\n{ex}")}");
        }
    }

    private static string Shorten(string category) => category[(category.LastIndexOf('.') + 1)..];

    private static void Prune()
    {
        try
        {
            var cutoff = DateTime.Now.AddDays(-14);
            foreach (var f in Directory.EnumerateFiles(WorkerOptions.LogsDir, "*.log"))
            {
                if (File.GetLastWriteTime(f) < cutoff) File.Delete(f);
            }
        }
        catch { /* best effort */ }
    }

    public void Dispose()
    {
        lock (_lock) { _writer?.Dispose(); _writer = null; }
    }

    private sealed class FileLogger : ILogger
    {
        private readonly FileLoggerProvider _provider;
        private readonly string _category;

        public FileLogger(FileLoggerProvider provider, string category)
        {
            _provider = provider;
            _category = category;
        }

        public IDisposable? BeginScope<TState>(TState state) where TState : notnull => null;
        public bool IsEnabled(LogLevel logLevel) => logLevel >= LogLevel.Information;

        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
        {
            if (!IsEnabled(logLevel)) return;
            _provider.Write(_category, logLevel, formatter(state, exception), exception);
        }
    }
}