namespace Caliburn.Micro.Core {
using System;
using System.Collections.Generic;
///
/// Used to gather the results from multiple child elements which may or may not prevent closing.
///
/// The type of child element.
public class DefaultCloseStrategy : ICloseStrategy {
readonly bool closeConductedItemsWhenConductorCannotClose;
///
/// Creates an instance of the class.
///
/// Indicates that even if all conducted items are not closable, those that are should be closed. The default is FALSE.
public DefaultCloseStrategy(bool closeConductedItemsWhenConductorCannotClose = false) {
this.closeConductedItemsWhenConductorCannotClose = closeConductedItemsWhenConductorCannotClose;
}
///
/// Executes the strategy.
///
/// Items that are requesting close.
/// The action to call when all enumeration is complete and the close results are aggregated.
/// The bool indicates whether close can occur. The enumerable indicates which children should close if the parent cannot.
public void Execute(IEnumerable toClose, Action> callback) {
using (var enumerator = toClose.GetEnumerator()) {
Evaluate(new EvaluationState(), enumerator, callback);
}
}
void Evaluate(EvaluationState state, IEnumerator enumerator, Action> callback) {
var guardPending = false;
do {
if (!enumerator.MoveNext()) {
callback(state.FinalResult, closeConductedItemsWhenConductorCannotClose ? state.Closable : new List());
break;
}
var current = enumerator.Current;
var guard = current as IGuardClose;
if (guard != null) {
guardPending = true;
guard.CanClose(canClose => {
guardPending = false;
if (canClose) {
state.Closable.Add(current);
}
state.FinalResult = state.FinalResult && canClose;
if (state.GuardMustCallEvaluate) {
state.GuardMustCallEvaluate = false;
Evaluate(state, enumerator, callback);
}
});
state.GuardMustCallEvaluate = state.GuardMustCallEvaluate || guardPending;
} else {
state.Closable.Add(current);
}
} while (!guardPending);
}
class EvaluationState {
public readonly List Closable = new List();
public bool FinalResult = true;
public bool GuardMustCallEvaluate;
}
}
}