using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using Svrnty.CQRS.Events.Abstractions.Projections;

namespace Svrnty.CQRS.Events.Projections;

/// <summary>
/// In-memory registry for projection definitions.
/// </summary>
/// <remarks>
/// Thread-safe implementation using ConcurrentDictionary.
/// </remarks>
public sealed class ProjectionRegistry : IProjectionRegistry
{
    private readonly ConcurrentDictionary<string, ProjectionDefinition> _projections = new();

    /// <inheritdoc />
    public void Register(ProjectionDefinition definition)
    {
        if (definition == null)
            throw new ArgumentNullException(nameof(definition));

        if (string.IsNullOrWhiteSpace(definition.ProjectionName))
            throw new ArgumentException("Projection name cannot be null or empty", nameof(definition));

        if (!_projections.TryAdd(definition.ProjectionName, definition))
        {
            throw new InvalidOperationException(
                $"A projection with name '{definition.ProjectionName}' is already registered");
        }
    }

    /// <inheritdoc />
    public ProjectionDefinition? GetProjection(string projectionName)
    {
        return _projections.TryGetValue(projectionName, out var definition) ? definition : null;
    }

    /// <inheritdoc />
    public IEnumerable<ProjectionDefinition> GetAllProjections()
    {
        return _projections.Values.ToList();
    }

    /// <inheritdoc />
    public IEnumerable<ProjectionDefinition> GetProjectionsForStream(string streamName)
    {
        return _projections.Values.Where(p => p.StreamName == streamName).ToList();
    }
}