namespace Eto.Forms;

/// <summary>
/// Base interface for an indirect binding.
/// </summary>
/// <remarks>
/// An indirect binding is passed the data item to get/set values on the object.
/// This is used for things like the <see cref="Forms.Grid"/>, <see cref="Forms.ListBox"/>, etc when
/// binding to values for each item in the data store.
/// </remarks>
public interface IIndirectBinding<T> : IBinding
{
	/// <summary>
	/// Gets the value from the specified object using this binding
	/// </summary>
	/// <remarks>
	/// When values are needed from this binding, this method will be called.
	/// </remarks>
	/// <param name="dataItem">object to retrieve the value from</param>
	/// <returns>value from the specified object</returns>
	T GetValue(object dataItem);

	/// <summary>
	/// Sets the specified value to an object using this binding
	/// </summary>
	/// <remarks>
	/// This is called to set the value to the object.
	/// </remarks>
	/// <param name="dataItem">object to set the value to</param>
	/// <param name="value">value to set to the object</param>
	void SetValue(object dataItem, T value);
}

/// <summary>
/// Provides an indirect binding to an indeterminate source/destination
/// </summary>
/// <remarks>
/// This binding does not directly bind to an object - you must pass the
/// object to get/set the value.  The <see cref="DirectBinding{T}"/> differs in 
/// that it binds directly to an object.
/// 
/// The IndirectBinding is useful when you want to use the same binding on multiple
/// objects, such as when binding cells in a <see cref="Forms.Grid"/>.
/// 
/// Typically one would use <see cref="PropertyBinding{T}"/> or <see cref="ColumnBinding{T}"/>
/// which are ways to retrieve either a property value or column/index-based value.
/// </remarks>
/// <copyright>(c) 2014 by Curtis Wensley</copyright>
/// <license type="BSD-3">See LICENSE for full terms</license>
public abstract class IndirectBinding<T> : Binding, IIndirectBinding<T>
{
	/// <summary>
	/// Gets the value from the specified object using this binding
	/// </summary>
	/// <remarks>
	/// When values are needed from this binding, this method will be called.
	/// Implementors of this binding would implement logic in <see cref="InternalGetValue"/>
	/// </remarks>
	/// <param name="dataItem">object to retrieve the value from</param>
	/// <returns>value from the specified object</returns>
	public T GetValue(object dataItem)
	{
		return InternalGetValue(dataItem);
	}

	/// <summary>
	/// Sets the specified value to an object using this binding
	/// </summary>
	/// <remarks>
	/// This is called to set the value to the object. Implementors of this binding
	/// woulc implement logic in <see cref="InternalSetValue"/>.
	/// </remarks>
	/// <param name="dataItem">object to set the value to</param>
	/// <param name="value">value to set to the object</param>
	public void SetValue(object dataItem, T value)
	{
		var args = new BindingChangingEventArgs(value);
		OnChanging(args);
		if (!args.Cancel)
		{
			InternalSetValue(dataItem, (T)args.Value);
			OnChanged(new BindingChangedEventArgs(args.Value));
		}
	}

	/// <summary>
	/// Implements the logic to get the value from the specified object
	/// </summary>
	/// <remarks>
	/// Implementors of this binding must implement this method to get the value from the specified object
	/// </remarks>
	/// <param name="dataItem">object to get the value from</param>
	/// <returns>value from this binding of the specified object</returns>
	protected abstract T InternalGetValue(object dataItem);

	/// <summary>
	/// Implements the logic to set the value to the specified object
	/// </summary>
	/// <param name="dataItem">object to set the value to</param>
	/// <param name="value">value to set on the dataItem for this binding</param>
	protected abstract void InternalSetValue(object dataItem, T value);


	/// <summary>
	/// Adds a handler to trap when the value of this binding changes for the specified object
	/// </summary>
	/// <remarks>
	/// This is used to wire up events (or other mechanisms) to detect if the value is changed for a particular
	/// object.
	/// 
	/// This is typically used to fire the <see cref="DirectBinding{T}.DataValueChanged"/> event (which is wired up automatically)
	/// </remarks>
	/// <param name="dataItem">object to hook up the value changed event for</param>
	/// <param name="handler">handler for when the value of this binding changes for the specified object</param>
	/// <returns>object to track the changed handler (must be passed to <see cref="RemoveValueChangedHandler"/> to remove)</returns>
	public virtual object AddValueChangedHandler(object dataItem, EventHandler<EventArgs> handler)
	{
		return null;
	}

	/// <summary>
	/// Removes the handler for the specified reference from <see cref="AddValueChangedHandler"/>
	/// </summary>
	/// <param name="bindingReference">Reference from the call to <see cref="AddValueChangedHandler"/></param>
	/// <param name="handler">Same handler that was set up during the <see cref="AddValueChangedHandler"/> call</param>
	public virtual void RemoveValueChangedHandler(object bindingReference, EventHandler<EventArgs> handler)
	{
	}

	/// <summary>
	/// Converts this binding's value to another value using delegates.
	/// </summary>
	/// <remarks>
	/// This is useful when you want to cast one binding to another, perform logic when getting/setting a value from a particular
	/// binding, or get/set a preoperty of the value.
	/// </remarks>
	/// <param name="toValue">Delegate to convert to the new value type.</param>
	/// <param name="fromValue">Delegate to convert from the value to the original binding's type.</param>
	/// <typeparam name="TValue">The type to convert to.</typeparam>
	public IndirectBinding<TValue> Convert<TValue>(Func<T, TValue> toValue, Func<TValue, T> fromValue = null)
	{
		return new DelegateBinding<object, TValue>(
			m => toValue != null ? toValue(GetValue(m)) : default(TValue),
			(m, val) => { if (fromValue != null) SetValue(m, fromValue(val)); },
			addChangeEvent: AddValueChangedHandler,
			removeChangeEvent: RemoveValueChangedHandler
		);
	}

	/// <summary>
	/// Converts the binding using the specified <paramref name="converter"/> object.
	/// </summary>
	/// <returns>A new binding that will be converted using the specified IValueConverter.</returns>
	/// <param name="converter">Converter object to use when converting to/from the value</param>
	/// <param name="conveterParameter">Parameter to pass to the converter.</param>
	/// <param name="culture">Culture to use for conversion, null to use invariant culture.</param>
	public IndirectBinding<TValue> Convert<TValue>(IValueConverter converter, object conveterParameter = null, CultureInfo culture = null)
	{
		culture = culture ?? CultureInfo.InvariantCulture;
		return Convert(
			val => (TValue)converter.Convert(val, typeof(TValue), conveterParameter, culture),
			val => (T)converter.ConvertBack(val, typeof(T), conveterParameter, culture)
		);
	}

	/// <summary>
	/// Converts the binding using the specified <paramref name="converter"/> object.
	/// </summary>
	/// <returns>A new binding that will be converted using the specified IValueConverter.</returns>
	/// <param name="converter">Converter object to use when converting to/from the value</param>
	/// <param name="propertyType">Type for the converter to convert to</param>
	/// <param name="conveterParameter">Parameter to pass to the converter.</param>
	/// <param name="culture">Culture to use for conversion, null to use invariant culture.</param>
	public IndirectBinding<object> Convert(IValueConverter converter, Type propertyType, object conveterParameter = null, CultureInfo culture = null)
	{
		culture = culture ?? CultureInfo.InvariantCulture;
		return Convert(
			val => converter.Convert(val, propertyType, conveterParameter, culture),
			val => (T)converter.ConvertBack(val, typeof(T), conveterParameter, culture)
		);
	}

	/// <summary>
	/// Casts this binding value to another (compatible) type.
	/// </summary>
	/// <typeparam name="TValue">The type to cast the values of this binding to.</typeparam>
	public IndirectBinding<TValue> Cast<TValue>()
	{
		return new DelegateBinding<object, TValue>(
			m =>
			{
				var value = (object)GetValue(m);
				if (value == null)
					return default(TValue);
				return (TValue)value;
			},
			(m, val) => SetValue(m, (T)(object)val),
			addChangeEvent: AddValueChangedHandler,
			removeChangeEvent: RemoveValueChangedHandler
		);
	}

	/// <summary>
	/// Binds to the specified child <paramref name="property"/> expression.
	/// </summary>
	/// <remarks>
	/// This can be used to bind to properties of child objects of your view model, for example
	/// <code>model.SomeProperty.ChildProperty</code>.
	/// 
	/// This will automatically look up the changed event either by a [Property]Changed event or INotifyPropertyChanged implementation
	/// for each object in the heirarchy.
	/// 
	/// Note that you only really need to use this when you have an existing binding that you cannot change.
	/// See <see cref="Binding.Property{T,TValue}(Expression{Func{T,TValue}})"/> for an example of how to bind to child property values
	/// more directly.
	/// </remarks>
	/// <example>
	/// Use this like so:
	/// <code>
	/// 	public class MyChild { public SomeChildProperty { get; set; } }
	/// 	public class MyModel { public ChildObject { get; set; } }
	/// 
	/// 	Binding.Property((MyModel m) => m.ChildObject).Child(c => c.SomeChildProperty);
	///		// or:
	/// 	Binding.Property((MyModel m) => m.ChildObject.SomeChildProperty);
	/// </code>
	/// </example>
	/// <returns>The binding to the child property accessed through the current binding.</returns>
	/// <param name="property">Property to bind to.</param>
	/// <typeparam name="TNewValue">The type of the child property value.</typeparam>
	public IndirectBinding<TNewValue> Child<TNewValue>(Expression<Func<T, TNewValue>> property)
	{
		return Child(Property(property));
	}

	/// <summary>
	/// Binds to the specified child <paramref name="binding"/> of this binding.
	/// </summary>
	/// <remarks>
	/// This can be used to bind to child objects of your view model, for example
	/// <code>model.SomeProperty.ChildProperty</code>.
	/// </remarks>
	/// <example>
	/// Use this like so:
	/// <code>
	/// 	public class MyChild { public SomeChildProperty { get; set; } }
	/// 	public class MyModel { public ChildObject { get; set; } }
	/// 
	/// 	Binding.Property((MyModel m) => m.ChildObject).Child(Binding.Property("SomeChildProperty"));
	/// </code>
	/// </example>
	/// <returns>The binding to the child property accessed through the current binding.</returns>
	/// <param name="binding">Binding to get the child value from this binding.</param>
	/// <typeparam name="TNewValue">The type of the child property value.</typeparam>
	public IndirectBinding<TNewValue> Child<TNewValue>(IndirectBinding<TNewValue> binding)
	{
		return new IndirectChildBinding<T, TNewValue>(this, binding);
	}

	/// <summary>
	/// Casts this binding value to another (compatible) type, or returns the default if the types do not match.
	/// </summary>
	/// <typeparam name="TValue">The type to cast the values of this binding to.</typeparam>
	public IndirectBinding<TValue> OfType<TValue>(TValue defaultConvertedValue = default(TValue), T defaultValue = default(T))
	{
		return new DelegateBinding<object, TValue>(
			m =>
			{
				var val = GetValue(m);
				return val is TValue ? (TValue)(object)val : defaultConvertedValue;
			},
			(m, val) => SetValue(m, val is T ? (T)(object)val : defaultValue),
			addChangeEvent: AddValueChangedHandler,
			removeChangeEvent: RemoveValueChangedHandler
		);
	}

	/// <summary>
	/// Converts this binding to return a nullable boolean binding
	/// </summary>
	/// <remarks>
	/// This is useful when converting a binding to be used for a checkbox's Checked binding for example.
	/// When the binding's value matches the <paramref name="trueValue"/>, it will return true.
	/// </remarks>
	/// <returns>Boolean binding.</returns>
	/// <param name="trueValue">Value when the binding is true.</param>
	/// <param name="falseValue">Value when the binding is false.</param>
	/// <param name="nullValue">Value when the binding is null.</param>
	public IndirectBinding<bool?> ToBool(T trueValue, T falseValue, T nullValue)
	{
		return new DelegateBinding<object, bool?>(
			m =>
			{
				var val = GetValue(m);
				if (Equals(val, trueValue))
					return true;
				if (Equals(val, falseValue))
					return false;
				return null;
			},
			(m, val) =>
			{
				var typedVal = val == true ? trueValue : val == false ? falseValue : nullValue;
				SetValue(m, typedVal);
			},
			addChangeEvent: AddValueChangedHandler,
			removeChangeEvent: RemoveValueChangedHandler
		);
	}

	/// <summary>
	/// Converts this binding to return a nullable boolean binding
	/// </summary>
	/// <remarks>
	/// This is useful when converting a binding to be used for a checkbox's Checked binding for example.
	/// When the binding's value matches the <paramref name="trueValue"/>, it will return true.
	/// </remarks>
	/// <returns>Boolean binding.</returns>
	/// <param name="trueValue">Value when the binding is true.</param>
	/// <param name="falseValue">Value when the binding is false.</param>
	public IndirectBinding<bool?> ToBool(T trueValue, T falseValue)
	{
		return new DelegateBinding<object, bool?>(
			m =>
			{
				var val = GetValue(m);
				if (Equals(val, trueValue))
					return true;
				if (Equals(val, falseValue))
					return false;
				return null;
			},
			(m, val) =>
			{
				if (val == true)
					SetValue(m, trueValue);
				else if (val == false)
					SetValue(m, falseValue);
			},
			addChangeEvent: AddValueChangedHandler,
			removeChangeEvent: RemoveValueChangedHandler
		);
	}

	/// <summary>
	/// Converts this binding to return a nullable boolean binding
	/// </summary>
	/// <remarks>
	/// This is useful when converting a binding to be used for a checkbox's Checked binding for example.
	/// When the binding's value matches the <paramref name="trueValue"/>, it will return true.
	/// </remarks>
	/// <returns>Boolean binding.</returns>
	/// <param name="trueValue">Value when the binding is true.</param>
	public IndirectBinding<bool?> ToBool(T trueValue)
	{
		return new DelegateBinding<object, bool?>(
			m =>
			{
				var val = GetValue(m);
				if (Equals(val, trueValue))
					return true;
				return false;
			},
			(m, val) =>
			{
				if (val == true)
					SetValue(m, trueValue);
			},
			addChangeEvent: AddValueChangedHandler,
			removeChangeEvent: RemoveValueChangedHandler
		);
	}

	/// <summary>
	/// Converts the a binding to an enumeration to/from its string representation
	/// </summary>
	/// <returns>Binding to the string value of the enumeration.</returns>
	/// <param name="defaultValue">Default if the value is not valid or empty.</param>
	public IndirectBinding<string> EnumToString(T defaultValue = default(T))
	{
		var enumType = Nullable.GetUnderlyingType(typeof(T)) ?? typeof(T);
		if (!enumType.IsEnum)
			throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, "Type of T ({0}) must be an enumeration type", typeof(T)));
		return new DelegateBinding<object, string>(
			m => System.Convert.ToString(GetValue(m)),
			(m, val) =>
			{
				var value = (!string.IsNullOrEmpty(val) && Enum.IsDefined(enumType, val))
					? (T)Enum.Parse(enumType, val)
					: defaultValue;
				SetValue(m, value);
			},
			addChangeEvent: AddValueChangedHandler,
			removeChangeEvent: RemoveValueChangedHandler
		);
	}

	/// <summary>
	/// Uses System.Convert.ChangeType to change the value of the binding to the specified type.
	/// </summary>
	/// <remarks>
	/// This has additional logic to deal with nullable types so they can be converted properly as well.
	/// </remarks>
	/// <param name="invalidGetValue">Delegate to get a value when it cannot be converted to the specified <typeparamref name="TType"/>. When null, an exception will be thrown when the value cannot be converted.</param>
	/// <param name="invalidSetValue">Delegate to set a value when it cannot be converted from the specified <typeparamref name="TType"/>. When null, an exception will be thrown when the value cannot be converted.</param>
	/// <typeparam name="TType">Type to convert the value to</typeparam>
	/// <returns>A binding of the new type that is a converted version of this binding</returns>
	public IndirectBinding<TType> ToType<TType>(Func<T, TType> invalidGetValue = null, Func<TType, T> invalidSetValue = null)
	{
		return new DelegateBinding<object, TType>(
			o =>
			{
				var val = GetValue(o);
				try
				{
					var type = Nullable.GetUnderlyingType(typeof(TType)) ?? typeof(TType);
					return (TType)System.Convert.ChangeType(val, type);
				}
				catch
				{
					if (invalidGetValue == null)
						throw;
					return invalidGetValue(val);
				}
			},
			(o, val) =>
			{
				try
				{
					var type = Nullable.GetUnderlyingType(typeof(T)) ?? typeof(T);
					SetValue(o, (T)System.Convert.ChangeType(val, type));
				}
				catch
				{
					if (invalidSetValue == null)
						throw;
					SetValue(o, invalidSetValue(val));
				}
			},
			addChangeEvent: (o, eh) => AddValueChangedHandler(o, eh),
			removeChangeEvent: (o, eh) => RemoveValueChangedHandler(o, eh)
		);
	}

	/// <summary>
	/// Specifies that the binding should only respond to change events after a delay.
	/// </summary>
	/// <remarks>
	/// This is useful if the property/delegate that is bound is expensive to retrieve the new value,
	/// for example to dynamically generate a bitmap based on the state of the model, etc. 
	/// 
	/// The <paramref name="reset"/> boolean allows you to ensure that the binding is updated periodically when <c>false</c> (default), 
	/// or <c>true</c> to wait for the delay period after the last change event.
	/// </remarks>
	/// <param name="delay">The delay time span to wait after the value has changed before updating the binding.</param>
	/// <param name="reset"><c>true</c> to reset the delay every time the event is fired, <c>false</c> to trigger the change at least by the delay interval since the last time it was triggered</param>
	/// <returns>A binding that will delay the change event</returns>
	public IndirectBinding<T> AfterDelay(TimeSpan delay, bool reset = false)
	{
		return AfterDelay(delay.TotalSeconds, reset);
	}

	/// <summary>
	/// Specifies that the binding should only respond to change events after a delay.
	/// </summary>
	/// <remarks>
	/// This is useful if the property/delegate that is bound is expensive to retrieve the new value,
	/// for example to dynamically generate a bitmap based on the state of the model, etc. 
	/// 
	/// The <paramref name="reset"/> boolean allows you to ensure that the binding is updated periodically when <c>false</c> (default), 
	/// or <c>true</c> to wait for the delay period after the last change event.
	/// </remarks>
	/// <param name="delay">The delay, in seconds to wait after the value has changed before updating the binding.</param>
	/// <param name="reset"><c>true</c> to reset the delay every time the event is fired, <c>false</c> to trigger the change at least by the delay interval since the last time it was triggered</param>
	/// <returns>A binding that will delay the change event</returns>
	public IndirectBinding<T> AfterDelay(double delay, bool reset = false)
	{
		UITimer timer = null;
		EventArgs args = null;
		object sender = null;
		return new DelegateBinding<object, T>(
			m => GetValue(m),
			(m, val) => SetValue(m, val),
			addChangeEvent: (m, ev) =>
			{
				EventHandler<EventArgs> ev2 = (s, e) =>
				{
					args = e;
					sender = s;
					if (timer == null)
					{
						timer = new UITimer { Interval = delay };
						timer.Elapsed += (s2, e2) =>
						{
							timer.Stop();
							ev(sender, args);
						};
					}
					if (reset || !timer.Started)
						timer.Start();
				};
				AddValueChangedHandler(m, ev2);
			},
			removeChangeEvent: RemoveValueChangedHandler
		);
	}

	/// <summary>
	/// Catches any exceptions when setting the value of the binding
	/// </summary>
	/// <param name="exceptionHandler">Handler to call when setting the value, regardless of whether an exception occurs. Return true when the exception is handled, false to throw an exception.</param>
	/// <returns>The binding that catches any exception.</returns>
	public IndirectBinding<T> CatchException(Func<Exception, bool> exceptionHandler = null) => CatchException<Exception>(exceptionHandler);

	/// <summary>
	/// Catches any exceptions of the specified <typeparamref name="TException"/> when setting the value of the binding.
	/// </summary>
	/// <typeparam name="TException">Type of the exception to catch</typeparam>
	/// <param name="exceptionHandler">Handler to call when setting the value, regardless of whether an exception occurs. Return true when the exception is handled, false to throw an exception.</param>
	/// <returns>The binding that catches the specified exception.</returns>
	public IndirectBinding<T> CatchException<TException>(Func<TException, bool> exceptionHandler = null)
		where TException : Exception
	{
		return new DelegateBinding<object, T>(
			m => GetValue(m),
			(m, val) =>
			{
				try
				{
					SetValue(m, val);
					exceptionHandler?.Invoke(null);
				}
				catch (TException ex)
				{
					if (exceptionHandler?.Invoke(ex) == false)
						throw;
				}
			},
			addChangeEvent: AddValueChangedHandler,
			removeChangeEvent: RemoveValueChangedHandler
		);
	}
}