// ==========================================================================
//  Squidex Headless CMS
// ==========================================================================
//  Copyright (c) Squidex UG (haftungsbeschraenkt)
//  All rights reserved. Licensed under the MIT license.
// ==========================================================================

using System.Runtime.CompilerServices;
using Squidex.Domain.Apps.Core.HandleRules;
using Squidex.Domain.Apps.Core.Rules.EnrichedEvents;
using Squidex.Domain.Apps.Core.Rules.Triggers;
using Squidex.Domain.Apps.Core.Scripting;
using Squidex.Domain.Apps.Events;
using Squidex.Domain.Apps.Events.Comments;
using Squidex.Infrastructure.EventSourcing;
using Squidex.Infrastructure.Reflection;
using Squidex.Shared.Users;

namespace Squidex.Domain.Apps.Entities.Comments
{
    public sealed class CommentTriggerHandler : IRuleTriggerHandler
    {
        private readonly IScriptEngine scriptEngine;
        private readonly IUserResolver userResolver;

        public Type TriggerType => typeof(CommentTrigger);

        public CommentTriggerHandler(IScriptEngine scriptEngine, IUserResolver userResolver)
        {
            this.scriptEngine = scriptEngine;

            this.userResolver = userResolver;
        }

        public bool Handles(AppEvent @event)
        {
            return @event is CommentCreated;
        }

        public async IAsyncEnumerable<EnrichedEvent> CreateEnrichedEventsAsync(Envelope<AppEvent> @event, RuleContext context,
            [EnumeratorCancellation] CancellationToken ct)
        {
            var commentCreated = (CommentCreated)@event.Payload;

            if (!(commentCreated.Mentions?.Length > 0))
            {
                yield break;
            }

            var users = await userResolver.QueryManyAsync(commentCreated.Mentions, ct);

            if (users.Count <= 0)
            {
                yield break;
            }

            foreach (var user in users.Values)
            {
                var enrichedEvent = new EnrichedCommentEvent
                {
                    MentionedUser = user
                };

                enrichedEvent.Name = "UserMentioned";

                // Use the concrete event to map properties that are not part of app event.
                SimpleMapper.Map(commentCreated, enrichedEvent);

                yield return enrichedEvent;
            }
        }

        public bool Trigger(EnrichedEvent @event, RuleContext context)
        {
            var trigger = (CommentTrigger)context.Rule.Trigger;

            if (string.IsNullOrWhiteSpace(trigger.Condition))
            {
                return true;
            }

            // Script vars are just wrappers over dictionaries for better performance.
            var vars = new EventScriptVars
            {
                Event = @event
            };

            return scriptEngine.Evaluate(vars, trigger.Condition);
        }
    }
}