com.google.gwt.inject.rebind.resolution.RequiredKeySet Maven / Gradle / Ivy

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package com.google.gwt.inject.rebind.resolution;

import com.google.gwt.inject.rebind.binding.Dependency;
import com.google.inject.Key;

import java.util.LinkedHashSet;
import java.util.Set;

/**
 * Computes the set of required keys in a given {@link DependencyGraph}.  A key is considered 
 * required if there exists a path from the dependencies of the origin Ginjector to the key that
 *  only passes through required edges.
 */
public class RequiredKeySet {
  
  private Set> requiredKeys;
  private final DependencyGraph graph;
  
  public RequiredKeySet(DependencyGraph graph) {
    this.graph = graph;
  }
  
  public boolean isRequired(Key key) {
    if (requiredKeys == null) {
      computeRequiredKeys();
    }
    return requiredKeys.contains(key);
  }
  
  private void computeRequiredKeys() {
    requiredKeys = new LinkedHashSet>(graph.size());
    
    Set> newKeys = new LinkedHashSet>();
    addRequiredKeysFor(graph.getOrigin().getDependencies(), newKeys);
    
    while (!newKeys.isEmpty()) {
      requiredKeys.addAll(newKeys);
      Set> discoveredKeys = new LinkedHashSet>();
      for (Key key : newKeys) {
        addRequiredKeysFor(graph.getDependenciesOf(key), discoveredKeys);
      }
      newKeys = discoveredKeys;
      newKeys.removeAll(requiredKeys);
    }
  }
  
  private void addRequiredKeysFor(Iterable edges, Set> discoveredKeys) {
    for (Dependency edge : edges) {
      if (!edge.isOptional()) {
        discoveredKeys.add(edge.getTarget());
      }
    }
  }
}