using System.Text;
using Microsoft.Extensions.Logging;

namespace WxAgent.Service;

public static class RuntimeLog
{
    private static readonly object Gate = new();

    public static void Append(string path, LogLevel level, string category, string message, Exception? exception = null)
    {
        try
        {
            var fullPath = Path.GetFullPath(path);
            var directory = Path.GetDirectoryName(fullPath);
            if (!string.IsNullOrEmpty(directory)) Directory.CreateDirectory(directory);
            var line = Format(level, category, message, exception);
            lock (Gate)
            {
                using var stream = new FileStream(fullPath, FileMode.Append, FileAccess.Write, FileShare.ReadWrite | FileShare.Delete);
                using var writer = new StreamWriter(stream, new UTF8Encoding(false));
                writer.WriteLine(line);
            }
        }
        catch
        {
            // Logging must not prevent the agent from starting or serving requests.
        }
    }

    internal static string Format(LogLevel level, string category, string message, Exception? exception)
    {
        var line = $"{DateTimeOffset.Now:O} [{level}] {category}: {message}";
        return exception is null ? line : $"{line}{Environment.NewLine}{exception}";
    }
}

internal sealed class FileLoggerProvider(string path) : ILoggerProvider
{
    private readonly string path = Path.GetFullPath(path);

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

    public void Dispose() { }

    private sealed class FileLogger(FileLoggerProvider provider, string categoryName) : ILogger
    {
        public IDisposable BeginScope<TState>(TState state) where TState : notnull => NoopScope.Instance;

        public bool IsEnabled(LogLevel logLevel) => logLevel != LogLevel.None;

        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception,
            Func<TState, Exception?, string> formatter)
        {
            if (!IsEnabled(logLevel)) return;
            RuntimeLog.Append(provider.path, logLevel, categoryName, formatter(state, exception), exception);
        }

        private sealed class NoopScope : IDisposable
        {
            public static readonly NoopScope Instance = new();
            public void Dispose() { }
        }
    }
}