/*
 * 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.jackrabbit.oak.commons;

import static java.io.File.createTempFile;
import static java.nio.charset.StandardCharsets.UTF_8;
import static org.apache.commons.io.FileUtils.forceDelete;
import static org.apache.commons.io.IOUtils.copyLarge;
import static org.apache.jackrabbit.oak.commons.sort.EscapeUtils.escapeLineBreak;
import static org.apache.jackrabbit.oak.commons.sort.EscapeUtils.unescapeLineBreaks;
import static org.apache.jackrabbit.oak.commons.sort.ExternalSort.mergeSortedFiles;
import static org.apache.jackrabbit.oak.commons.sort.ExternalSort.sortInBatch;

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.StandardCopyOption;
import java.util.Comparator;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Objects;
import java.util.Set;
import java.util.function.Function;

import org.apache.commons.io.FileUtils;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import org.slf4j.Logger;

/**
 * Simple File utils
 */
public final class FileIOUtils {

    private FileIOUtils() {
    }

    public final static Comparator<String> lexComparator = new Comparator<String>() {
        @Override public int compare(String s1, String s2) {
            return s1.compareTo(s2);
        }
    };

    /**
     * Sorts the given file externally using the {@link #lexComparator} and removes duplicates.
     *
     * @param file file whose contents needs to be sorted
     */
    public static void sort(File file) throws IOException {
        sort(file, lexComparator);
    }

    /**
     * Sorts the given file externally with the given comparator and removes duplicates.
     *
     * @param file file whose contents needs to be sorted
     * @param comparator to compare
     * @throws IOException
     */
    public static void sort(File file, Comparator<String> comparator) throws IOException {
        File sorted = createTempFile("file-io-utils-sort-", null);
        merge(sortInBatch(file, comparator, true), sorted, comparator);
        Files.move(sorted.toPath(), file.toPath(), StandardCopyOption.REPLACE_EXISTING);
    }

    /**
     * Merges a list of files after sorting with the {@link #lexComparator}.
     *
     * @param files files to merge
     * @param output merge output file
     * @throws IOException
     */
    public static void merge(List<File> files, File output) throws IOException {
        mergeSortedFiles(
            files,
            output, lexComparator, true);
    }

    /**
     * Merges a list of files after sorting with the given comparator.
     *
     * @param files files to merge
     * @param output merge output file
     * @throws IOException
     */
    public static void merge(List<File> files, File output, Comparator<String> comparator) throws IOException {
        mergeSortedFiles(
            files,
            output, comparator, true);
    }

    /**

     * Copies an input stream to a file.
     *
     * @param stream steam to copy
     * @return
     * @throws IOException
     */
    public static File copy(InputStream stream) throws IOException {
        File file = createTempFile("fleioutilscopy", null);
        copyInputStreamToFile(stream, file);
        return file;
    }

    /**
     * Appends the contents of the list of files to the given file and deletes the files
     * if the delete flag is enabled.
     *
     * If there is a scope for lines in the files containing line break characters it should be
     * ensured that the files are written with {@link #writeAsLine(BufferedWriter, String, boolean)}
     * with true to escape line break characters.
     * @param files
     * @param appendTo
     * @throws IOException
     */
    public static void append(List<File> files, File appendTo, boolean delete) throws IOException {

        try (OutputStream appendStream = new BufferedOutputStream(new FileOutputStream(appendTo, true))) {

            for (File f : files) {
                try (InputStream iStream = new FileInputStream(f)) {
                    copyLarge(iStream, appendStream);
                }
            }
        } finally {
            if (delete) {
                for (File f : files) {
                    f.delete();
                }
            }
        }
    }

    /**
     * Writes a string as a new line into the given buffered writer and optionally
     * escapes the line for line breaks.
     *
     * @param writer to write the string
     * @param str the string to write
     * @param escape whether to escape string for line breaks
     * @throws IOException
     */
    public static void writeAsLine(BufferedWriter writer, String str, boolean escape) throws IOException {
        if (escape) {
            writer.write(escapeLineBreak(str));
        } else {
            writer.write(str);
        }
        writer.newLine();
    }

    /**
     * Writes string from the given iterator to the given file and optionally
     * escape the written strings for line breaks.
     *
     * @param iterator the source of the strings
     * @param f file to write to
     * @param escape whether to escape for line breaks
     * @return count
     * @throws IOException
     */
    public static int writeStrings(Iterator<String> iterator, File f, boolean escape)
        throws IOException {
        return writeStrings(iterator, f, escape, null, "");
    }

    /**
     * Writes string from the given iterator to the given file and optionally
     * escape the written strings for line breaks.
     *
     * @param iterator the source of the strings
     * @param f file to write to
     * @param escape escape whether to escape for line breaks
     * @param logger logger to log progress
     * @param message message to log
     * @return
     * @throws IOException
     */
    public static int writeStrings(Iterator<String> iterator, File f, boolean escape,
        @Nullable Logger logger, @Nullable String message) throws IOException {
        return writeStrings(iterator, f, escape, Function.identity(), logger, message);
    }

    /**
     * Writes string from the given iterator to the given file and optionally
     * escape the written strings for line breaks.
     *
     * @param iterator the source of the strings
     * @param f file to write to
     * @param escape escape whether to escape for line breaks
     * @param transformer any transformation on the input
     * @param logger logger to log progress
     * @param message message to log
     * @return
     * @throws IOException
     */
    public static int writeStrings(Iterator<String> iterator, File f, boolean escape,
        @NotNull Function<String, String> transformer, @Nullable Logger logger, @Nullable String message) throws IOException {

        int count = 0;
        try (BufferedWriter writer = new BufferedWriter(new FileWriter(f, UTF_8))) {
            while (iterator.hasNext()) {
                writeAsLine(writer, transformer.apply(iterator.next()), escape);
                count++;
                if (logger != null) {
                    if (count % 100000 == 0) {
                        logger.info(Objects.toString(message, "") + count);
                    }
                }
            }
        }
        return count;
    }

    /**
     * Reads strings from the given stream into a set and optionally unescaping for line breaks.
     *
     * @param stream the source of the strings
     * @param unescape whether to unescape for line breaks
     * @return set
     * @throws IOException
     */
    public static Set<String> readStringsAsSet(InputStream stream, boolean unescape) throws IOException {
        Set<String> set = new HashSet<>();

        try (BufferedReader reader = new BufferedReader(new InputStreamReader(stream, UTF_8))) {
            String line;
            while ((line = reader.readLine()) != null) {
                if (unescape) {
                    set.add(unescapeLineBreaks(line));
                } else {
                    set.add(line);
                }
            }
        }
        return set;
    }

    /**
     * Composing iterator which unescapes for line breaks and delegates to the given comparator.
     * When using this it should be ensured that the data source has been correspondingly escaped.
     *
     * @param delegate the actual comparison iterator
     * @return comparator aware of line breaks
     */
    public static Comparator<String> lineBreakAwareComparator (Comparator<String> delegate) {
        return new FileIOUtils.TransformingComparator(delegate, new Function<String, String>() {
            @Nullable
            @Override
            public String apply(@Nullable String input) {
                return unescapeLineBreaks(input);
            }
        });
    }

    /**
     *
     * Copy the input stream to the given file. Delete the file in case of exception.
     *
     * @param source the input stream source
     * @param destination the file to write to
     * @throws IOException
     */
    public static void copyInputStreamToFile(final InputStream source, final File destination) throws IOException {
        boolean success = false;
        try {
            FileUtils.copyInputStreamToFile(source, destination);
            success = true;
        } finally {
            if (!success) {
                forceDelete(destination);
            }
        }
    }

    /**
     * Decorates the given comparator and applies the function before delegating to the decorated
     * comparator.
     */
    public static class TransformingComparator implements Comparator<String> {
        private Comparator<String> delegate;
        private Function<String, String> func;

        public TransformingComparator(Comparator<String> delegate, Function<String, String> func) {
            this.delegate = delegate;
            this.func = func;
        }

        @Override
        public int compare(String s1, String s2) {
            return delegate.compare(func.apply(s1), func.apply(s2));
        }
    }
}
