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/*
 * Copyright 2017-2022 John Snow Labs
 *
 * 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.johnsnowlabs.ml.tensorflow.sentencepiece;

import java.io.*;

class NativeLibLoader {

    /**
     * Create a temp file that copies the resource from current JAR archive
     * 
     * The file from JAR is copied into system temp file.
     * The temporary file is deleted after exiting.
     * Method uses String as filename because the pathname is "abstract", not system-dependent.
     * 
     * The restrictions of {@link File#createTempFile(String, String)} apply to
     * {@code path}.
     *
     * @param path Path to the resources in the jar
     * @return The created temp file.
     * @throws IOException              When the temp file could not be created
     * @throws IllegalArgumentException When the file name contains invalid letters
     */
    static String createTempFileFromResource(String path) throws IOException, IllegalArgumentException {
        // Obtain filename from path
        if (!path.startsWith("/")) {
            throw new IllegalArgumentException("The path has to be absolute (start with '/').");
        }

        String[] parts = path.split("/");
        String filename = (parts.length > 1) ? parts[parts.length - 1] : null;

        // Split filename to prexif and suffix (extension)
        String prefix = "";
        String suffix = null;
        if (filename != null) {
            parts = filename.split("\\.", 2);
            prefix = parts[0];
            suffix = (parts.length > 1) ? "." + parts[parts.length - 1] : null; // Thanks, davs! :-)
        }

        // Check if the filename is okay
        if (filename == null || prefix.length() < 3) {
            throw new IllegalArgumentException("The filename has to be at least 3 characters long.");
        }
        // Prepare temporary file
        File temp = File.createTempFile(prefix, suffix);
        temp.deleteOnExit();

        if (!temp.exists()) {
            throw new FileNotFoundException("File " + temp.getAbsolutePath() + " does not exist.");
        }

        // Prepare buffer for data copying
        byte[] buffer = new byte[1024];
        int readBytes;

        // Open and check input stream
        InputStream is = NativeLibLoader.class.getResourceAsStream(path);
        if (is == null) {
            throw new FileNotFoundException("File " + path + " was not found inside JAR.");
        }

        // Open output stream and copy data between source file in JAR and the temporary file
        OutputStream os = new FileOutputStream(temp);
        try {
            while ((readBytes = is.read(buffer)) != -1) {
                os.write(buffer, 0, readBytes);
            }
        } finally {
            // If read/write fails, close streams safely before throwing an exception
            os.close();
            is.close();
        }
        return temp.getAbsolutePath();
    }
}