using System;
using System.Collections.Generic;

namespace Svrnty.CQRS.Events.ConsumerGroups.Abstractions;

/// <summary>
/// Configuration options for consumer group behavior.
/// </summary>
public class ConsumerGroupOptions
{
    /// <summary>
    /// Number of events to fetch in each batch from the stream.
    /// Higher values improve throughput but increase memory usage.
    /// Default: 100.
    /// </summary>
    public int BatchSize { get; set; } = 100;

    /// <summary>
    /// Polling interval when no events are available in the stream.
    /// The consumer will sleep for this duration before checking for new events.
    /// Default: 1 second.
    /// </summary>
    public TimeSpan PollingInterval { get; set; } = TimeSpan.FromSeconds(1);

    /// <summary>
    /// Offset commit strategy.
    /// Determines when and how offsets are committed.
    /// Default: AfterBatch.
    /// </summary>
    public OffsetCommitStrategy CommitStrategy { get; set; } = OffsetCommitStrategy.AfterBatch;

    /// <summary>
    /// Interval for periodic offset commits when using OffsetCommitStrategy.Periodic.
    /// Ignored for other commit strategies.
    /// Default: 5 seconds.
    /// </summary>
    public TimeSpan PeriodicCommitInterval { get; set; } = TimeSpan.FromSeconds(5);

    /// <summary>
    /// Heartbeat interval for consumer liveness.
    /// The consumer will send heartbeats at this interval to signal it's alive.
    /// Must be less than SessionTimeout.
    /// Default: 10 seconds.
    /// </summary>
    public TimeSpan HeartbeatInterval { get; set; } = TimeSpan.FromSeconds(10);

    /// <summary>
    /// Consumer session timeout.
    /// If a consumer doesn't send a heartbeat within this period, it's considered dead
    /// and will be removed from the group.
    /// Must be greater than HeartbeatInterval.
    /// Default: 30 seconds.
    /// </summary>
    public TimeSpan SessionTimeout { get; set; } = TimeSpan.FromSeconds(30);

    /// <summary>
    /// Whether to start from the beginning of the stream if no offset has been committed.
    /// If false, starts from the current end of the stream (only new events).
    /// Default: true (start from beginning).
    /// </summary>
    public bool StartFromBeginning { get; set; } = true;

    /// <summary>
    /// Optional metadata to include with consumer registration.
    /// Useful for debugging and monitoring (e.g., hostname, version, environment).
    /// </summary>
    public IReadOnlyDictionary<string, string>? Metadata { get; set; }

    /// <summary>
    /// Validates the options and throws if invalid.
    /// </summary>
    /// <exception cref="ArgumentException">Thrown if options are invalid.</exception>
    public void Validate()
    {
        if (BatchSize <= 0)
            throw new ArgumentException("BatchSize must be greater than 0", nameof(BatchSize));

        if (PollingInterval <= TimeSpan.Zero)
            throw new ArgumentException("PollingInterval must be greater than 0", nameof(PollingInterval));

        if (HeartbeatInterval <= TimeSpan.Zero)
            throw new ArgumentException("HeartbeatInterval must be greater than 0", nameof(HeartbeatInterval));

        if (SessionTimeout <= HeartbeatInterval)
            throw new ArgumentException(
                "SessionTimeout must be greater than HeartbeatInterval",
                nameof(SessionTimeout));

        if (CommitStrategy == OffsetCommitStrategy.Periodic && PeriodicCommitInterval <= TimeSpan.Zero)
            throw new ArgumentException(
                "PeriodicCommitInterval must be greater than 0 when using Periodic commit strategy",
                nameof(PeriodicCommitInterval));
    }
}