using System.Collections.Concurrent;

namespace StellaOps.Scheduler.Plugin;

/// <summary>
/// Thread-safe in-memory registry for scheduler job plugins.
/// </summary>
public sealed class SchedulerPluginRegistry : ISchedulerPluginRegistry
{
    private readonly ConcurrentDictionary<string, ISchedulerJobPlugin> _plugins = new(StringComparer.OrdinalIgnoreCase);

    /// <inheritdoc />
    public void Register(ISchedulerJobPlugin plugin)
    {
        ArgumentNullException.ThrowIfNull(plugin);

        if (string.IsNullOrWhiteSpace(plugin.JobKind))
        {
            throw new ArgumentException("Plugin JobKind must not be null or whitespace.", nameof(plugin));
        }

        if (!_plugins.TryAdd(plugin.JobKind, plugin))
        {
            throw new InvalidOperationException(
                $"A plugin with JobKind '{plugin.JobKind}' is already registered. " +
                $"Existing: '{_plugins[plugin.JobKind].DisplayName}', " +
                $"Attempted: '{plugin.DisplayName}'.");
        }
    }

    /// <inheritdoc />
    public ISchedulerJobPlugin? Resolve(string jobKind)
    {
        if (string.IsNullOrWhiteSpace(jobKind))
        {
            return null;
        }

        return _plugins.TryGetValue(jobKind, out var plugin) ? plugin : null;
    }

    /// <inheritdoc />
    public IReadOnlyList<(string JobKind, string DisplayName)> ListRegistered()
    {
        return _plugins.Values
            .OrderBy(p => p.JobKind, StringComparer.OrdinalIgnoreCase)
            .Select(p => (p.JobKind, p.DisplayName))
            .ToArray();
    }
}