package io.dropwizard.util;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.URL;
import java.nio.charset.Charset;

Since:
2.0/**
 * @since 2.0
 */
public final class Resources {
    private Resources() {
    }

    
Returns a URL pointing to resourceName if the resource is found using the context class loader. In simple environments, the context class loader will find resources from the class path. In environments where different threads can have different class loaders, for example app servers, the context class loader will typically have been set to an appropriate loader for the current thread. 
In the unusual case where the context class loader is null, the class loader that loaded this class (Resources) will be used instead. 
Throws:
IllegalArgumentException – if the resource is not found/**
     * Returns a {@code URL} pointing to {@code resourceName} if the resource is found using the
     * {@linkplain Thread#getContextClassLoader() context class loader}. In simple environments, the
     * context class loader will find resources from the class path. In environments where different
     * threads can have different class loaders, for example app servers, the context class loader
     * will typically have been set to an appropriate loader for the current thread.
     *
     * <p>In the unusual case where the context class loader is null, the class loader that loaded
     * this class ({@code Resources}) will be used instead.
     *
     * @throws IllegalArgumentException if the resource is not found
     */
    public static URL getResource(String resourceName) {
        final ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();
        final ClassLoader loader = contextClassLoader == null ? Resources.class.getClassLoader() : contextClassLoader;
        final URL url = loader.getResource(resourceName);
        if (url == null) {
            throw new IllegalArgumentException("resource " + resourceName + " not found.");
        }
        return url;
    }

    
Reads all bytes from a URL into a byte array.
Params:
url – the URL to read from
Throws:
IOException – if an I/O error occurs
Returns:
a byte array containing all the bytes from the URL/**
     * Reads all bytes from a URL into a byte array.
     *
     * @param url the URL to read from
     * @return a byte array containing all the bytes from the URL
     * @throws IOException if an I/O error occurs
     */
    public static byte[] toByteArray(URL url) throws IOException {
        try (InputStream inputStream = url.openStream()) {
            return ByteStreams.toByteArray(inputStream);
        }
    }

    
Reads all characters from a URL into a String, using the given character set. 
Params:
url –     the URL to read from
charset – the charset used to decode the input stream; see StandardCharsets for helpful predefined constants
Throws:
IOException – if an I/O error occurs.
Returns:
a string containing all the characters from the URL/**
     * Reads all characters from a URL into a {@link String}, using the given character set.
     *
     * @param url     the URL to read from
     * @param charset the charset used to decode the input stream; see {@link java.nio.charset.StandardCharsets} for helpful
     *                predefined constants
     * @return a string containing all the characters from the URL
     * @throws IOException if an I/O error occurs.
     */
    public static String toString(URL url, Charset charset) throws IOException {
        try (InputStream inputStream = url.openStream()) {
            return CharStreams.toString(new InputStreamReader(inputStream, charset));
        }
    }

    
Copies all bytes from a URL to an output stream.
Params:
from – the URL to read from
to – the output stream
Throws:
IOException – if an I/O error occurs/**
     * Copies all bytes from a URL to an output stream.
     *
     * @param from the URL to read from
     * @param to the output stream
     * @throws IOException if an I/O error occurs
     */
    public static void copy(URL from, OutputStream to) throws IOException {
        try (InputStream inputStream = from.openStream()) {
            ByteStreams.copy(inputStream, to);
        }
    }
}