Takari incremental build context with indirect dependency support

IndirectBuildContext.java

package io.takari.incrementalbuild.spi;

import java.io.File;
import java.util.HashSet;

import javax.inject.Inject;
import javax.inject.Named;

import org.apache.maven.execution.scope.MojoExecutionScoped;

import io.takari.incrementalbuild.Resource;
import io.takari.incrementalbuild.ResourceMetadata;
import io.takari.incrementalbuild.ResourceStatus;

/**
 * Provides a build context that allows detection of modified dependencies
 * of an input file.
 * 
 * Usage:
 * 
 *  for (resource: buildContext.registerInputs(..)) {
 *      if (!buildContext.isResourceDirty(resource))
 *          continue;
 *          
 *      // do something to file
 *      
 *      // for each indirect input file that is included by input:
 *          buildContext.associateIndirectInput(resource, indirectInputFile)
 *  }
 */
@Named
@MojoExecutionScoped
public class IndirectBuildContext extends DefaultBuildContext {

    static final String INDIRECT_KEY = "indirect-resource";
    
    @Inject
    public IndirectBuildContext(BuildContextEnvironment configuration) {
        super(configuration);
    }
    
    public boolean isResourceDirty(ResourceMetadata<File> resource) {
        return resource.getStatus() != ResourceStatus.UNMODIFIED ||
                areIndirectInputsModified(resource.getResource());
    }
    
    
    @SuppressWarnings("rawtypes")
    public boolean areIndirectInputsModified(File resource) {
        HashSet indirectResources = getAttribute(resource, INDIRECT_KEY, HashSet.class);
        if (indirectResources != null) {
            for (Object file: indirectResources) {
                if (getResourceStatus(file) != ResourceStatus.UNMODIFIED)
                    return true;
            }
        }
            
        return false;
    }

    /**
     * Callers who use this will want to use registerInput et al instead 
     * of registerInputsAndProcess, as the latter will not return all resources
     * that should be processed.
     */
    @SuppressWarnings({ "rawtypes", "unchecked" })
    public void associateIndirectInput(Resource<File> resource, File indirectInput) {
        
        File resourceFile = resource.getResource();
        
        if (!isProcessedResource(resourceFile))
            throw new IllegalStateException("Resource " + resourceFile + " hasn't been marked as processed");
        
        // easy way to add an input
        registerInput(indirectInput);
                
        HashSet indirectResources = getResourceAttribute(state, resourceFile, INDIRECT_KEY, HashSet.class);
        if (indirectResources == null) {
            indirectResources = new HashSet<>();
            setResourceAttribute(resourceFile, INDIRECT_KEY, indirectResources);
        }
        
        indirectResources.add(indirectInput);
    }
}