using System;
using System.Collections.Generic;
using System.Reflection;
using Golems.Attributes;

namespace Golems
{
    public partial class AttributesEditor
    {
        const BindingFlags k_OnValChangedFlags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic;

        private Dictionary<string, object> m_Fields = new Dictionary<string, object>();

        private void OnInspectorGUIOnValueChangedAttribute()
        {
            var targetType = target.GetType();
            var fields = targetType.GetFields(k_OnValChangedFlags);
            //
            // Search for OnValueChanged Attribute on Each Field on this Object
            //
            for (int i = 0, counti = fields.Length; i < counti; ++i)
            {
                var field = fields[i];
                var onValueChangedAttribute = field.GetCustomAttribute<OnValueChanged>();

                //
                // If we find an attribute and haven't already included it in m_Fields, include it!
                //
                if (onValueChangedAttribute == null || m_Fields.TryGetValue(field.Name, out var fieldValue)) continue;
                var method = targetType.GetMethod(onValueChangedAttribute.Method, k_ButtonBindingFlags);

                if (method != null)
                {
                    m_Fields.Add(field.Name, field.GetValue(this.target));
                }
            }

            var changed = new List<Action>();

            //
            // Now check all our found Fields and see if a value has changed
            //
            foreach (var fieldValueKeypair in m_Fields)
            {
                //
                // Retrieve the FieldInfo for the cached field name
                //
                var fieldInfo = targetType.GetField(fieldValueKeypair.Key, k_OnValChangedFlags);
                if (fieldInfo == null) continue;

                //
                // Detect any change?
                //
                var currentValue = fieldInfo.GetValue(target);
                if (currentValue != null && currentValue.Equals(fieldValueKeypair.Value) || 
                    currentValue == null && fieldValueKeypair.Value == null) continue;

                var key = fieldValueKeypair.Key;
                changed.Add(() => { m_Fields[key] = currentValue; });

                // ...a bit lazy, probably should cache this stuff but here we are :( 
                var onValueChangedAttribute = fieldInfo.GetCustomAttribute<OnValueChanged>();
                if (onValueChangedAttribute == null) continue;

                var method = targetType.GetMethod(onValueChangedAttribute.Method, k_ButtonBindingFlags);
                method?.Invoke(target, null);
            }

            //
            // Update m_Fields which have been changed
            //
            changed.ForEach(x => x.Invoke());
        }
    }
}