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

using Jint;
using Squidex.Infrastructure.Tasks;
using Squidex.Text;

namespace Squidex.Domain.Apps.Core.Scripting
{
    public abstract class ScriptExecutionContext : ScriptContext
    {
        public Engine Engine { get; }

        protected ScriptExecutionContext(Engine engine)
        {
            Engine = engine;
        }

        public abstract void Schedule(Func<IScheduler, CancellationToken, Task> action);
    }

#pragma warning disable MA0048 // File name must match type name
    public interface IScheduler
#pragma warning restore MA0048 // File name must match type name
    {
        void Run(Action? action);

        void Run<T>(Action<T>? action, T argument);
    }

    public sealed class ScriptExecutionContext<T> : ScriptExecutionContext, IScheduler
    {
        private readonly TaskCompletionSource<T?> tcs = new TaskCompletionSource<T?>();
        private readonly CancellationToken cancellationToken;
        private int pendingTasks;

        public bool IsCompleted
        {
            get => tcs.Task.Status == TaskStatus.RanToCompletion || tcs.Task.Status == TaskStatus.Faulted;
        }

        internal ScriptExecutionContext(Engine engine, CancellationToken cancellationToken)
            : base(engine)
        {
            this.cancellationToken = cancellationToken;
        }

        public Task<T?> CompleteAsync()
        {
            if (pendingTasks <= 0)
            {
                tcs.TrySetResult(default);
            }

            return tcs.Task.WithCancellation(cancellationToken);
        }

        public void Complete(T value)
        {
            tcs.TrySetResult(value);
        }

        public override void Schedule(Func<IScheduler, CancellationToken, Task> action)
        {
            if (IsCompleted)
            {
                return;
            }

            async Task ScheduleAsync()
            {
                try
                {
                    Interlocked.Increment(ref pendingTasks);

                    await action(this, cancellationToken);

                    if (Interlocked.Decrement(ref pendingTasks) <= 0)
                    {
                        tcs.TrySetResult(default);
                    }
                }
                catch (Exception ex)
                {
                    tcs.TrySetException(ex);
                }
            }

            ScheduleAsync().Forget();
        }

        public ScriptExecutionContext<T> ExtendAsync(IEnumerable<IJintExtension> extensions)
        {
            foreach (var extension in extensions)
            {
                extension.ExtendAsync(this);
            }

            return this;
        }

        public ScriptExecutionContext<T> Extend(IEnumerable<IJintExtension> extensions)
        {
            foreach (var extension in extensions)
            {
                extension.Extend(this);
            }

            return this;
        }

        public ScriptExecutionContext<T> Extend(ScriptVars vars, ScriptOptions options)
        {
            var engine = Engine;

            if (options.AsContext)
            {
                var contextInstance = new WritableContext(engine, vars);

                foreach (var (key, value) in vars.Where(x => x.Value != null))
                {
                    this[key.ToCamelCase()] = value;
                }

                engine.SetValue("ctx", contextInstance);
                engine.SetValue("context", contextInstance);
            }
            else
            {
                foreach (var (key, value) in vars)
                {
                    var property = key.ToCamelCase();

                    if (value != null)
                    {
                        engine.SetValue(property, value);

                        this[property] = value;
                    }
                }
            }

            engine.SetValue("async", true);

            return this;
        }

        void IScheduler.Run(Action? action)
        {
            if (IsCompleted || action == null)
            {
                return;
            }

            Engine.ResetConstraints();
            action();
        }

        void IScheduler.Run<TArg>(Action<TArg>? action, TArg argument)
        {
            if (IsCompleted || action == null)
            {
                return;
            }

            Engine.ResetConstraints();
            action(argument);
        }
    }
}