// ReSharper disable once RedundantUsingDirective
using System.Linq;

namespace SRF
{
    using System;
    using System.Collections.Generic;
    using System.Reflection;
    using Helpers;
    using Service;
    using UnityEngine;

    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Field)]
    public sealed class RequiredFieldAttribute : Attribute
    {
        private bool _autoCreate;
        private bool _autoSearch;
        private bool _editorOnly = true;

        public RequiredFieldAttribute(bool autoSearch)
        {
            AutoSearch = autoSearch;
        }

        public RequiredFieldAttribute() {}

        public bool AutoSearch
        {
            get { return _autoSearch; }
            set { _autoSearch = value; }
        }

        public bool AutoCreate
        {
            get { return _autoCreate; }
            set { _autoCreate = value; }
        }

        [Obsolete]
        public bool EditorOnly
        {
            get { return _editorOnly; }
            set { _editorOnly = value; }
        }
    }

    /// <summary>
    /// Add to a field to attempt to use SRServiceManager to get an instance of the field type
    /// </summary>
    [AttributeUsage(AttributeTargets.Field)]
    public class ImportAttribute : Attribute
    {
        public readonly Type Service;
        public ImportAttribute() {}

        public ImportAttribute(Type serviceType)
        {
            Service = serviceType;
        }
    }

    public abstract class SRMonoBehaviourEx : SRMonoBehaviour
    {
        private static Dictionary<Type, IList<FieldInfo>> _checkedFields;

        private static void CheckFields(SRMonoBehaviourEx instance, bool justSet = false)
        {
            if (_checkedFields == null)
            {
                _checkedFields = new Dictionary<Type, IList<FieldInfo>>();
            }

            var t = instance.GetType();

            IList<FieldInfo> cache;

            if (!_checkedFields.TryGetValue(instance.GetType(), out cache))
            {
                cache = ScanType(t);

                _checkedFields.Add(t, cache);
            }

            PopulateObject(cache, instance, justSet);
        }

        private static void PopulateObject(IList<FieldInfo> cache, SRMonoBehaviourEx instance, bool justSet)
        {
            for (var i = 0; i < cache.Count; i++)
            {
                var f = cache[i];

                if (!EqualityComparer<object>.Default.Equals(f.Field.GetValue(instance), null))
                {
                    continue;
                }

                // If import is enabled, use SRServiceManager to import the reference
                if (f.Import)
                {
                    var t = f.ImportType ?? f.Field.FieldType;

                    var service = SRServiceManager.GetService(t);

                    if (service == null)
                    {
                        Debug.LogWarning("Field {0} import failed (Type {1})".Fmt(f.Field.Name, t));
                        continue;
                    }

                    f.Field.SetValue(instance, service);

                    continue;
                }

                // If autoset is enabled on field, try and find the component on the GameObject

                if (f.AutoSet)
                {
                    var newValue = instance.GetComponent(f.Field.FieldType);

                    if (!EqualityComparer<object>.Default.Equals(newValue, null))
                    {
                        f.Field.SetValue(instance, newValue);
                        continue;
                    }
                }

                if (justSet)
                {
                    continue;
                }

                if (f.AutoCreate)
                {
                    var newValue = instance.CachedGameObject.AddComponent(f.Field.FieldType);
                    f.Field.SetValue(instance, newValue);
                }

                throw new UnassignedReferenceException(
                    "Field {0} is unassigned, but marked with RequiredFieldAttribute".Fmt(f.Field.Name));
            }
        }

        private static List<FieldInfo> ScanType(Type t)
        {
            var cache = new List<FieldInfo>();

            // Check for attribute added to the class
            var globalAttr = SRReflection.GetAttribute<RequiredFieldAttribute>(t);

#if NETFX_CORE
		var fields = t.GetTypeInfo().DeclaredFields.Where(f => !f.IsStatic);
#else
            // Check each field for the attribute
            var fields = t.GetFields(BindingFlags.Public | BindingFlags.Instance | BindingFlags.NonPublic);
#endif

            foreach (var f in fields)
            {
                var requiredFieldAttribute = SRReflection.GetAttribute<RequiredFieldAttribute>(f);
                var importAttribute = SRReflection.GetAttribute<ImportAttribute>(f);

                if (globalAttr == null && requiredFieldAttribute == null && importAttribute == null)
                {
                    continue; // Early out if no attributes found.
                }

                var info = new FieldInfo();
                info.Field = f;

                if (importAttribute != null)
                {
                    info.Import = true;
                    info.ImportType = importAttribute.Service;
                }
                else if (requiredFieldAttribute != null)
                {
                    info.AutoSet = requiredFieldAttribute.AutoSearch;
                    info.AutoCreate = requiredFieldAttribute.AutoCreate;
                }
                else
                {
                    info.AutoSet = globalAttr.AutoSearch;
                    info.AutoCreate = globalAttr.AutoCreate;
                }

                cache.Add(info);
            }

            return cache;
        }

        protected virtual void Awake()
        {
            CheckFields(this);
        }

        protected virtual void Start() {}
        protected virtual void Update() {}
        protected virtual void FixedUpdate() {}
        protected virtual void OnEnable() {}
        protected virtual void OnDisable() {}
        protected virtual void OnDestroy() {}

        private struct FieldInfo
        {
            public bool AutoCreate;
            public bool AutoSet;
            public System.Reflection.FieldInfo Field;
            public bool Import;
            public Type ImportType;
        }
    }
}