using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using Unity.Properties;
using UnityEngine.UIElements;

namespace Uigenx.Binding
{
    /// <summary>
    /// Base class for hand written data sources. Derive from it, mark bindable members with
    /// <c>[CreateProperty]</c> and call <see cref="Notify"/> from every setter. Unity's runtime
    /// binding reads the members directly; <see cref="IUgxDataSource"/> is what the studio bridge
    /// and the UI Creator binder use.
    /// </summary>
    public abstract class UgxDataSource : IUgxDataSource, INotifyBindablePropertyChanged, IDataSourceViewHashProvider
    {
        long _version;

        public event EventHandler<BindablePropertyChangedEventArgs> propertyChanged;

        public long GetViewHashCode() => _version;

        /// <summary>Raises the change notification for the calling property and bumps the view hash.</summary>
        protected void Notify([CallerMemberName] string property = null)
        {
            if (string.IsNullOrEmpty(property)) return;
            _version++;
            // Bindings are foreign code from the source's point of view.
            try
            {
                propertyChanged?.Invoke(this, new BindablePropertyChangedEventArgs(property));
            }
            catch (Exception e)
            {
                UnityEngine.Debug.LogError("[ugx] a property change listener threw: " + e);
            }
        }

        /// <summary>
        /// Announces that everything changed. Listeners read the empty path as "refresh all", so
        /// this cannot go through <see cref="Notify"/>, which ignores an empty name.
        /// </summary>
        protected void NotifyAll()
        {
            _version++;
            try
            {
                propertyChanged?.Invoke(this, new BindablePropertyChangedEventArgs(string.Empty));
            }
            catch (Exception e)
            {
                UnityEngine.Debug.LogError("[ugx] a property change listener threw: " + e);
            }
        }

        public virtual bool TryGet(string path, out object value)
        {
            var container = (object)this;
            return PropertyContainer.TryGetValue(ref container, UgxPropertyPaths.Get(path), out value);
        }

        public virtual bool TrySet(string path, object value)
        {
            var container = (object)this;
            if (!PropertyContainer.TrySetValue(ref container, UgxPropertyPaths.Get(path), value)) return false;
            _version++;
            Notify(path);
            return true;
        }

        public virtual IEnumerable<string> Paths
        {
            get
            {
                foreach (var entry in UgxSchemaWalker.Collect(GetType())) yield return entry.Path;
            }
        }
    }
}