using System;
using Svrnty.CQRS.Events.Abstractions.Storage;

namespace Svrnty.CQRS.Events.Abstractions.Configuration;

/// <summary>
/// Configuration for event stream retention policy.
/// Supports time-based and/or size-based retention.
/// </summary>
public record RetentionPolicyConfig : IRetentionPolicy
{
    /// <summary>
    /// Stream name this policy applies to.
    /// Use "*" for default policy.
    /// </summary>
    public required string StreamName { get; init; }

    /// <summary>
    /// Maximum age for events (null = no time-based retention).
    /// Example: TimeSpan.FromDays(30) keeps events for 30 days.
    /// </summary>
    public TimeSpan? MaxAge { get; init; }

    /// <summary>
    /// Maximum number of events to retain (null = no size-based retention).
    /// Example: 1000000 keeps only the last 1 million events.
    /// </summary>
    public long? MaxEventCount { get; init; }

    /// <summary>
    /// Whether this policy is enabled.
    /// Default: true
    /// </summary>
    public bool Enabled { get; init; } = true;

    /// <summary>
    /// Validates the retention policy configuration.
    /// </summary>
    /// <exception cref="ArgumentException">Thrown when configuration is invalid.</exception>
    public void Validate()
    {
        if (string.IsNullOrWhiteSpace(StreamName))
            throw new ArgumentException("StreamName cannot be null or whitespace", nameof(StreamName));

        if (MaxAge.HasValue && MaxAge.Value <= TimeSpan.Zero)
            throw new ArgumentException("MaxAge must be positive", nameof(MaxAge));

        if (MaxEventCount.HasValue && MaxEventCount.Value <= 0)
            throw new ArgumentException("MaxEventCount must be positive", nameof(MaxEventCount));

        if (!MaxAge.HasValue && !MaxEventCount.HasValue)
            throw new ArgumentException("At least one of MaxAge or MaxEventCount must be specified");
    }
}