using System;
using System.Collections.Generic;
using System.Linq;
using Svrnty.CQRS.Abstractions.Discovery;

namespace Svrnty.CQRS.Discovery;

public sealed class CommandDiscovery : ICommandDiscovery
{
    private readonly List<ICommandMeta> _commandMetas;
    private readonly Dictionary<string, ICommandMeta> _commandsByName;
    private readonly Dictionary<Type, ICommandMeta> _commandsByType;

    public CommandDiscovery(IEnumerable<ICommandMeta> commandMetas)
    {
        // Materialize the enumerable to a list once
        _commandMetas = commandMetas.ToList();

        // Build lookup dictionaries for O(1) access
        _commandsByName = new Dictionary<string, ICommandMeta>(_commandMetas.Count);
        _commandsByType = new Dictionary<Type, ICommandMeta>(_commandMetas.Count);

        foreach (var meta in _commandMetas)
        {
            _commandsByName[meta.Name] = meta;
            _commandsByType[meta.CommandType] = meta;
        }
    }

    public IEnumerable<ICommandMeta> GetCommands() => _commandMetas;

    public ICommandMeta FindCommand(string name) =>
        _commandsByName.TryGetValue(name, out var meta) ? meta : null;

    public ICommandMeta FindCommand(Type commandType) =>
        _commandsByType.TryGetValue(commandType, out var meta) ? meta : null;

    public bool CommandExists(string name) =>
        _commandsByName.ContainsKey(name);

    public bool CommandExists(Type commandType) =>
        _commandsByType.ContainsKey(commandType);
}