FilesystemModuleProvider.java

package org.dynjs.runtime.modules;

import org.dynjs.runtime.ExecutionContext;
import org.dynjs.runtime.builtins.Require;

import java.io.File;
import java.io.IOException;
import java.util.List;

/**
 * Implementation of <code>ModuleProvider</code> which loads from the
 * filesystem based upon the context's load-paths.
 * 
 * @author Lance Ball
 * @author Bob McWhirter
 */
public class FilesystemModuleProvider extends ModuleProvider {

    private final Require nativeRequire;

    public FilesystemModuleProvider(Require require) {
        this.nativeRequire = require;
    }

    @Override
    public boolean load(ExecutionContext context, String moduleID) {
        File file = new File(moduleID);
        if (file.exists()) {
            final String parent = file.getParent();
            nativeRequire.addLoadPath(parent);
            try {
                context.getRuntime().newRunner().withContext(context).withSource(file).execute();
                nativeRequire.removeLoadPath(parent);
                return true;
            } catch (IOException e) {
                System.err.println("There was an error loading the module " + moduleID + ". Error message: " + e.getMessage());
                e.printStackTrace();
            }
        }
        return false;
    }

    @Override
    public String generateModuleID(ExecutionContext context, String moduleName) {
        File moduleFile = findFile(nativeRequire.getLoadPaths(), moduleName);
        if (moduleFile != null && moduleFile.exists()) {
            try {
                return moduleFile.getCanonicalPath();
            } catch(IOException e) {
                System.err.println("There was an error generating id of module " + moduleName + ". Error message: " + e.getMessage());
                return moduleFile.getAbsolutePath();
            }
        }
        return null;
    }

    /**
     * Finds the module file based on the known load paths.
     * 
     * @param loadPaths the list of load paths to search
     * @param moduleName the name of the module to find
     * @return the File if found, else null
     */
    protected File findFile(List<String> loadPaths, String moduleName) {
        String fileName = normalizeName(moduleName);
        File file = new File( moduleName );
        if ( file.isAbsolute() ) {
            if ( file.exists() ) {
                return file;
            }
        }
        for (String loadPath : loadPaths) {
            // require('foo');
            file = new File(loadPath, fileName);
            // foo.js is in the require path
            if (file.exists()) break;
        }
        return file;
    }

}