using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Tango.Telemetry
{
    /// <summary>
    /// Represents the result of publishing a telemetry package to one or more destinations.
    /// Contains the status and metrics per destination and total publish time.
    /// </summary>
    public class TelemetryPublishResult
    {
        /// <summary>
        /// Defines the outcome of an attempt to publish to a specific destination.
        /// </summary>
        public enum DestinationStatus
        {
            None,
            Passed,
            Unavailable,
            Failed,
            Postponed
        }

        /// <summary>
        /// Contains information about the result of publishing telemetry to a specific destination.
        /// </summary>
        public class DestinationResult
        {
            /// <summary>
            /// The destination to which the telemetry was attempted to be published.
            /// </summary>
            public ITelemetryDestination Destination { get; set; }

            /// <summary>
            /// The result status of the publish attempt.
            /// </summary>
            public DestinationStatus Status { get; set; }

            /// <summary>
            /// Any error that occurred during the publish attempt.
            /// </summary>
            public Exception Error { get; set; }

            /// <summary>
            /// The amount of time it took to attempt publishing to this destination.
            /// </summary>
            public TimeSpan ElapsedTime { get; set; }

            /// <summary>
            /// Number of retry attempts for this destination.
            /// </summary>
            public int RetryCount { get; internal set; }

            /// <summary>
            /// Time until the next eligible retry attempt.
            /// </summary>
            public TimeSpan RetryDelay { get; internal set; }
        }

        /// <summary>
        /// Gets or sets the telemetry source that generated the package associated with this publish result.
        /// </summary>
        public ITelemetrySource Source { get; set; }

        /// <summary>
        /// Gets or sets the source type of the telemetry (e.g., Streaming, ExternalStorage, PendingStorage).
        /// </summary>
        public TelemetrySourceTypes SourceType { get; set; }

        /// <summary>
        /// List of results for each destination that was part of the publish process.
        /// </summary>
        public List<DestinationResult> DestinationsResults { get; set; }

        /// <summary>
        /// Total elapsed time taken to publish the telemetry package across all destinations.
        /// </summary>
        public TimeSpan TotalElapsedTime { get; set; }

        /// <summary>
        /// Time spent outside of destination publishing, typically system overhead or coordination.
        /// </summary>
        public TimeSpan OverheadTime
        {
            get { return TimeSpan.FromMilliseconds(TotalElapsedTime.TotalMilliseconds - DestinationsResults.Sum(x => x.ElapsedTime.TotalMilliseconds)); }
        }

        /// <summary>
        /// Initializes a new instance of the TelemetryPublishResult class.
        /// </summary>
        public TelemetryPublishResult()
        {
            DestinationsResults = new List<DestinationResult>();
        }

        public override string ToString()
        {
            var sb = new StringBuilder();

            sb.AppendLine($"Source: {Source?.Name ?? "Unknown"} ({SourceType})");
            sb.AppendLine($"Total Elapsed Time: {TotalElapsedTime.TotalMilliseconds:F1} ms");
            sb.AppendLine($"Overhead Time: {OverheadTime.TotalMilliseconds:F1} ms");
            sb.AppendLine("Destination Results:");

            foreach (var result in DestinationsResults ?? Enumerable.Empty<DestinationResult>())
            {
                sb.Append($"  - {result.Destination.Name}: {result.Status}, {result.ElapsedTime.TotalMilliseconds:F1} ms");
                if (!string.IsNullOrWhiteSpace(result.Error.ToStringSafe()))
                    sb.Append($" (Error: {result.Error})");

                sb.AppendLine();
            }

            return sb.ToString();
        }
    }
}