/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */

package org.apache.tools.ant.taskdefs;

import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Vector;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.ProjectHelper;
import org.apache.tools.ant.ProjectHelperRepository;
import org.apache.tools.ant.Task;
import org.apache.tools.ant.types.Resource;
import org.apache.tools.ant.types.ResourceCollection;
import org.apache.tools.ant.types.resources.FileProvider;
import org.apache.tools.ant.types.resources.FileResource;
import org.apache.tools.ant.types.resources.URLProvider;
import org.apache.tools.ant.types.resources.URLResource;
import org.apache.tools.ant.types.resources.Union;
import org.apache.tools.ant.util.FileUtils;

/**
 * Task to import another build file into the current project.
 * <p>
 * It must be 'top level'. On execution it will read another Ant file
 * into the same Project.
 * </p>
 * <p>
 * <b>Important</b>: Trying to understand how relative file references
 * resolved in deep/complex build hierarchies - such as what happens
 * when an imported file imports another file can be difficult. Use absolute references for
 * enhanced build file stability, especially in the imported files.
 * </p>
 * <p>Examples:</p>
 * <pre>
 * &lt;import file="../common-targets.xml"/&gt;
 * </pre>
 * <p>Import targets from a file in a parent directory.</p>
 * <pre>
 * &lt;import file="${deploy-platform}.xml"/&gt;
 * </pre>
 * <p>Import the project defined by the property <code>deploy-platform</code>.</p>
 *
 * @since Ant1.6
 * @ant.task category="control"
 */
public class ImportTask extends Task {
    private String file;
    private boolean optional;
    private String targetPrefix = ProjectHelper.USE_PROJECT_NAME_AS_TARGET_PREFIX;
    private String prefixSeparator = ".";
    private final Union resources = new Union();
    private static final FileUtils FILE_UTILS = FileUtils.getFileUtils();

    public ImportTask() {
        resources.setCache(true);
    }

    /**
     * sets the optional attribute
     *
     * @param optional if true ignore files that are not present,
     *                 default is false
     */
    public void setOptional(boolean optional) {
        this.optional = optional;
    }

    /**
     * the name of the file to import. How relative paths are resolved is still
     * in flux: use absolute paths for safety.
     * @param file the name of the file
     */
    public void setFile(String file) {
        // I don't think we can use File - different rules
        // for relative paths.
        this.file = file;
    }

    /**
     * The prefix to use when prefixing the imported target names.
     *
     * @param prefix String
     * @since Ant 1.8.0
     */
    public void setAs(String prefix) {
        targetPrefix = prefix;
    }

    /**
     * The separator to use between prefix and target name, default is
     * ".".
     *
     * @param s String
     * @since Ant 1.8.0
     */
    public void setPrefixSeparator(String s) {
        prefixSeparator = s;
    }

    /**
     * The resource to import.
     *
     * @param r ResourceCollection
     * @since Ant 1.8.0
     */
    public void add(ResourceCollection r) {
        resources.add(r);
    }

    public void execute() {
        if (file == null && resources.size() == 0) {
            throw new BuildException("import requires file attribute or"
                                     + " at least one nested resource");
        }
        if (getOwningTarget() == null
            || !"".equals(getOwningTarget().getName())) {
            throw new BuildException("import only allowed as a top-level task");
        }

        ProjectHelper helper =
                (ProjectHelper) getProject().
                    getReference(ProjectHelper.PROJECTHELPER_REFERENCE);

        if (helper == null) {
            // this happens if the projecthelper was not registered with the project.
            throw new BuildException("import requires support in ProjectHelper");
        }

        Vector<Object> importStack = helper.getImportStack();

        if (importStack.size() == 0) {
            // this happens if ant is used with a project
            // helper that doesn't set the import.
            throw new BuildException("import requires support in ProjectHelper");
        }

        if (getLocation() == null || getLocation().getFileName() == null) {
            throw new BuildException("Unable to get location of import task");
        }

        Union resourcesToImport = new Union(getProject(), resources);
        Resource fromFileAttribute = getFileAttributeResource();
        if (fromFileAttribute != null) {
            resources.add(fromFileAttribute);
        }
        for (Resource r : resourcesToImport) {
            importResource(helper, r);
        }
    }

    private void importResource(ProjectHelper helper,
                                Resource importedResource) {
        Vector<Object> importStack = helper.getImportStack();

        getProject().log("Importing file " + importedResource + " from "
                         + getLocation().getFileName(), Project.MSG_VERBOSE);

        if (!importedResource.isExists()) {
            String message =
                "Cannot find " + importedResource + " imported from "
                + getLocation().getFileName();
            if (optional) {
                getProject().log(message, Project.MSG_VERBOSE);
                return;
            } else {
                throw new BuildException(message);
            }
        }

        if (!isInIncludeMode() &&
            hasAlreadyBeenImported(importedResource, importStack)) {
            getProject().log(
                "Skipped already imported file:\n   "
                + importedResource + "\n", Project.MSG_VERBOSE);
            return;
        }

        // nested invocations are possible like an imported file
        // importing another one
        String oldPrefix = ProjectHelper.getCurrentTargetPrefix();
        boolean oldIncludeMode = ProjectHelper.isInIncludeMode();
        String oldSep = ProjectHelper.getCurrentPrefixSeparator();
        try {
            String prefix;
            if (isInIncludeMode() && oldPrefix != null
                && targetPrefix != null) {
                prefix = oldPrefix + oldSep + targetPrefix;
            } else if (isInIncludeMode()) {
                prefix = targetPrefix;
            } else if (!ProjectHelper.USE_PROJECT_NAME_AS_TARGET_PREFIX.equals(targetPrefix)) {
                prefix = targetPrefix;
            } else {
                prefix = oldPrefix;
            }
            setProjectHelperProps(prefix, prefixSeparator,
                                  isInIncludeMode());

            ProjectHelper subHelper = ProjectHelperRepository.getInstance().getProjectHelperForBuildFile(
                    importedResource);

            // push current stacks into the sub helper
            subHelper.getImportStack().addAll(helper.getImportStack());
            subHelper.getExtensionStack().addAll(helper.getExtensionStack());
            getProject().addReference(ProjectHelper.PROJECTHELPER_REFERENCE, subHelper);

            subHelper.parse(getProject(), importedResource);

            // push back the stack from the sub helper to the main one
            getProject().addReference(ProjectHelper.PROJECTHELPER_REFERENCE, helper);
            helper.getImportStack().clear();
            helper.getImportStack().addAll(subHelper.getImportStack());
            helper.getExtensionStack().clear();
            helper.getExtensionStack().addAll(subHelper.getExtensionStack());
        } catch (BuildException ex) {
            throw ProjectHelper.addLocationToBuildException(
                ex, getLocation());
        } finally {
            setProjectHelperProps(oldPrefix, oldSep, oldIncludeMode);
        }
    }

    private Resource getFileAttributeResource() {
        // Paths are relative to the build file they're imported from,
        // *not* the current directory (same as entity includes).

        if (file != null) {
            if (isExistingAbsoluteFile(file)) {
                return new FileResource(FILE_UTILS.normalize(file));
            }

            File buildFile =
                new File(getLocation().getFileName()).getAbsoluteFile();
            if (buildFile.exists()) {
                File buildFileParent = new File(buildFile.getParent());
                File importedFile =
                    FILE_UTILS.resolveFile(buildFileParent, file);
                return new FileResource(importedFile);
            }
            // maybe this import tasks is inside an imported URL?
            try {
                URL buildFileURL = new URL(getLocation().getFileName());
                URL importedFile = new URL(buildFileURL, file);
                return new URLResource(importedFile);
            } catch (MalformedURLException ex) {
                log(ex.toString(), Project.MSG_VERBOSE);
            }
            throw new BuildException("failed to resolve " + file
                                     + " relative to "
                                     + getLocation().getFileName());
        }
        return null;
    }

    private boolean isExistingAbsoluteFile(String name) {
        File f = new File(name);
        return f.isAbsolute() && f.exists();
    }

    private boolean hasAlreadyBeenImported(Resource importedResource,
                                           Vector<Object> importStack) {
        File importedFile = null;
        FileProvider fp = importedResource.as(FileProvider.class);
        if (fp != null) {
            importedFile = fp.getFile();
        }
        URL importedURL = null;
        URLProvider up = importedResource.as(URLProvider.class);
        if (up != null) {
            importedURL = up.getURL();
        }
        for (Object o : importStack) {
            if (isOneOf(o, importedResource, importedFile, importedURL)) {
                return true;
            }
        }
        return false;
    }

    private boolean isOneOf(Object o, Resource importedResource,
                            File importedFile, URL importedURL) {
        if (o.equals(importedResource) || o.equals(importedFile)
            || o.equals(importedURL)) {
            return true;
        }
        if (o instanceof Resource) {
            if (importedFile != null) {
                FileProvider fp = ((Resource) o).as(FileProvider.class);
                if (fp != null && fp.getFile().equals(importedFile)) {
                    return true;
                }
            }
            if (importedURL != null) {
                URLProvider up = ((Resource) o).as(URLProvider.class);
                if (up != null && up.getURL().equals(importedURL)) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Whether the task is in include (as opposed to import) mode.
     *
     * <p>In include mode included targets are only known by their
     * prefixed names and their depends lists get rewritten so that
     * all dependencies get the prefix as well.</p>
     *
     * <p>In import mode imported targets are known by an adorned as
     * well as a prefixed name and the unadorned target may be
     * overwritten in the importing build file.  The depends list of
     * the imported targets is not modified at all.</p>
     *
     * @return boolean
     * @since Ant 1.8.0
     */
    protected final boolean isInIncludeMode() {
        return "include".equals(getTaskType());
    }

    /**
     * Sets a bunch of Thread-local ProjectHelper properties.
     *
     * @param prefix String
     * @param prefixSep String
     * @param inIncludeMode boolean
     * @since Ant 1.8.0
     */
    private static void setProjectHelperProps(String prefix,
                                              String prefixSep,
                                              boolean inIncludeMode) {
        ProjectHelper.setCurrentTargetPrefix(prefix);
        ProjectHelper.setCurrentPrefixSeparator(prefixSep);
        ProjectHelper.setInIncludeMode(inIncludeMode);
    }
}
