/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed 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 com.android.ant;

import org.apache.tools.ant.BuildException;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;

/**
 * A base class for ant tasks that use a single dependency file to control (re)execution.
 */
public abstract class SingleDependencyTask extends BuildTypedTask {

    private DependencyGraph mDependencies;

    protected abstract String getExecTaskName();

    protected interface InputPathFactory {
        InputPath createPath(File file, Set<String> extensionsToCheck);
    }

    private final static InputPathFactory sDefaultFactory = new InputPathFactory() {
        @Override
        public InputPath createPath(File file, Set<String> extensionsToCheck) {
            return new InputPath(file, extensionsToCheck);
        }
    };

    /**
     * Creates a list of {@link InputPath} from a list of {@link File} and an optional list of
     * extensions. All the {@link InputPath} will share the same extension restrictions.
     * @param paths the list of path
     * @param extensionsToCheck A set of extensions. Only files with an extension in this set will
     *             be considered for a modification check. All deleted/created files will still be
     *             checked. If this is null, all files will be checked for modification date
     * @return a list of {@link InputPath}
     */
    protected static List<InputPath> getInputPaths(List<File> paths,
            Set<String> extensionsToCheck, InputPathFactory factory) {
        List<InputPath> result = new ArrayList<InputPath>(paths.size());

        if (factory == null ) {
            factory = sDefaultFactory;
        }

        for (File f : paths) {
            result.add(factory.createPath(f, extensionsToCheck));
        }

        return result;
    }

    /**
     * Set up the dependency graph by passing it the location of the ".d" file, and the new input
     * paths.
     * @param dependencyFile path to the dependency file to use
     * @param the new input paths for this new compilation.
     * @return true if the dependency graph was successfully initialized
     */
    protected boolean initDependencies(String dependencyFile, List<InputPath> inputPaths) {
        if (hasBuildTypeChanged()) {
            // we don't care about deps, we need to execute the task no matter what.
            return true;
        }

        File depFile = new File(dependencyFile);
        if (depFile.exists()) {
            mDependencies = new DependencyGraph(dependencyFile, inputPaths);
            return true;
        } else {
            return false;
        }
    }

    /**
     * Wrapper check to see if we need to execute this task at all
     * @return true if the DependencyGraph reports that our prereqs or targets
     *         have changed since the last run
     */
    protected boolean dependenciesHaveChanged() {
        if (hasBuildTypeChanged()) {
            // if this is not a new build, display that build type change is forcing running
            // the task.
            if (isNewBuild() == false) {
                String execName = getExecTaskName();
                if (execName == null) {
                    System.out.println(
                            "Current build type is different than previous build: forced task run.");
                } else {
                    System.out.println(
                            "Current build type is different than previous build: forced " +
                            execName + " run.");
                }
            }
            return true;
        }

        assert mDependencies != null : "Dependencies have not been initialized";
        return mDependencies.dependenciesHaveChanged(true /*printStatus*/);
    }

    protected void generateDependencyFile(String depFilePath,
            List<InputPath> inputs, String outputFile) {
        File depFile = new File(depFilePath);

        try {
            PrintStream ps = new PrintStream(depFile);

            // write the output file.
            ps.print(outputFile);
            ps.println(" : \\");

            //write the input files
            int count = inputs.size();
            for (int i = 0 ; i < count ; i++) {
                InputPath input = inputs.get(i);
                File file = input.getFile();
                if (file.isDirectory()) {
                    writeContent(ps, file, input);
                } else {
                    ps.print(file.getAbsolutePath());
                    ps.println(" \\");
                }
            }

            ps.close();
        } catch (FileNotFoundException e) {
            new BuildException(e);
        }
    }

    private void writeContent(PrintStream ps, File file, InputPath input) {
        if (input.ignores(file)) {
            return;
        }

        File[] files = file.listFiles();
        if (files != null) {
            for (File f : files) {
                if (f.isDirectory()) {
                    writeContent(ps, f, input);
                } else if (input.ignores(f) == false) {
                    ps.print(f.getAbsolutePath());
                    ps.println(" \\");
                }
            }
        }
    }
}