using System;
using Svrnty.CQRS.Events.Abstractions.Delivery;
using Svrnty.CQRS.Events.Abstractions.Streaming;
using Svrnty.CQRS.Events.Abstractions.Configuration;
using Svrnty.CQRS.Events.Abstractions;

namespace Svrnty.CQRS.Events.Configuration;

/// <summary>
/// Default implementation of <see cref="IStreamConfiguration"/>.
/// Provides configuration for an event stream's storage, delivery, and retention behavior.
/// </summary>
public class StreamConfiguration : IStreamConfiguration
{
    /// <summary>
    /// Initializes a new instance of the <see cref="StreamConfiguration"/> class.
    /// </summary>
    /// <param name="streamName">Name of the stream. Must not be null or whitespace.</param>
    /// <exception cref="ArgumentException">Thrown if <paramref name="streamName"/> is null or whitespace.</exception>
    public StreamConfiguration(string streamName)
    {
        if (string.IsNullOrWhiteSpace(streamName))
            throw new ArgumentException("Stream name cannot be null or whitespace.", nameof(streamName));

        StreamName = streamName;

        // Set defaults
        Type = StreamType.Ephemeral;
        DeliverySemantics = DeliverySemantics.AtLeastOnce;
        Scope = StreamScope.Internal;
        Retention = null;
        EnableReplay = false;
    }

    /// <inheritdoc />
    public string StreamName { get; }

    /// <inheritdoc />
    public StreamType Type { get; set; }

    /// <inheritdoc />
    public DeliverySemantics DeliverySemantics { get; set; }

    /// <inheritdoc />
    public StreamScope Scope { get; set; }

    /// <inheritdoc />
    public TimeSpan? Retention { get; set; }

    /// <inheritdoc />
    public bool EnableReplay { get; set; }

    /// <summary>
    /// Validates the configuration settings.
    /// </summary>
    /// <exception cref="InvalidOperationException">
    /// Thrown if configuration is invalid (e.g., ephemeral stream with replay enabled).
    /// </exception>
    public void Validate()
    {
        // Ephemeral streams cannot have replay enabled
        if (Type == StreamType.Ephemeral && EnableReplay)
        {
            throw new InvalidOperationException(
                $"Stream '{StreamName}': Ephemeral streams cannot have replay enabled. " +
                "Set Type = StreamType.Persistent to enable replay.");
        }

        // Ephemeral streams shouldn't have retention policies
        if (Type == StreamType.Ephemeral && Retention.HasValue)
        {
            throw new InvalidOperationException(
                $"Stream '{StreamName}': Ephemeral streams do not support retention policies. " +
                "Retention only applies to persistent streams.");
        }

        // Retention must be positive if set
        if (Retention.HasValue && Retention.Value <= TimeSpan.Zero)
        {
            throw new InvalidOperationException(
                $"Stream '{StreamName}': Retention period must be positive. " +
                $"Got: {Retention.Value}");
        }
    }
}