/*
 * Copyright 2002-2020 the original author or authors.
 *
 * 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
 *
 *      https://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.alibaba.nacos.common.packagescan.resource;

import com.alibaba.nacos.common.packagescan.util.ResourceUtils;
import com.alibaba.nacos.common.packagescan.util.AbstractAssert;
import com.alibaba.nacos.common.utils.StringUtils;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLConnection;

/**
 * Copy from https://github.com/spring-projects/spring-framework.git, with less modifications
 * {@link Resource} implementation for {@code java.net.URL} locators.
 * Supports resolution as a {@code URL} and also as a {@code File} in
 * case of the {@code "file:"} protocol.
 *
 * @author Juergen Hoeller
 * @see URL
 * @since 28.12.2003
 */
public class UrlResource extends AbstractFileResolvingResource {

    /**
     * Original URI, if available; used for URI and File access.
     */

    private final URI uri;

    /**
     * Original URL, used for actual access.
     */
    private final URL url;

    /**
     * Cleaned URL (with normalized path), used for comparisons.
     */

    private volatile URL cleanedUrl;

    /**
     * Create a new {@code UrlResource} based on the given URI object.
     *
     * @param uri a URI
     * @throws MalformedURLException if the given URL path is not valid
     * @since 2.5
     */
    public UrlResource(URI uri) throws MalformedURLException {
        AbstractAssert.notNull(uri, "URI must not be null");
        this.uri = uri;
        this.url = uri.toURL();
    }

    /**
     * Create a new {@code UrlResource} based on the given URL object.
     *
     * @param url a URL
     */
    public UrlResource(URL url) {
        AbstractAssert.notNull(url, "URL must not be null");
        this.uri = null;
        this.url = url;
    }

    /**
     * Create a new {@code UrlResource} based on a URL path.
     *
     * <p>Note: The given path needs to be pre-encoded if necessary.
     *
     * @param path a URL path
     * @throws MalformedURLException if the given URL path is not valid
     * @see URL#URL(String)
     */
    public UrlResource(String path) throws MalformedURLException {
        AbstractAssert.notNull(path, "Path must not be null");
        this.uri = null;
        this.url = new URL(path);
        this.cleanedUrl = getCleanedUrl(this.url, path);
    }

    /**
     * Create a new {@code UrlResource} based on a URI specification.
     *
     * <p>The given parts will automatically get encoded if necessary.
     *
     * @param protocol the URL protocol to use (e.g. "jar" or "file" - without colon);
     *                 also known as "scheme"
     * @param location the location (e.g. the file path within that protocol);
     *                 also known as "scheme-specific part"
     * @throws MalformedURLException if the given URL specification is not valid
     * @see URI#URI(String, String, String)
     */
    public UrlResource(String protocol, String location) throws MalformedURLException {
        this(protocol, location, null);
    }

    /**
     * Create a new {@code UrlResource} based on a URI specification.
     *
     * <p>The given parts will automatically get encoded if necessary.
     *
     * @param protocol the URL protocol to use (e.g. "jar" or "file" - without colon);
     *                 also known as "scheme"
     * @param location the location (e.g. the file path within that protocol);
     *                 also known as "scheme-specific part"
     * @param fragment the fragment within that location (e.g. anchor on an HTML page,
     *                 as following after a "#" separator)
     * @throws MalformedURLException if the given URL specification is not valid
     * @see URI#URI(String, String, String)
     */
    public UrlResource(String protocol, String location, String fragment) throws MalformedURLException {
        try {
            this.uri = new URI(protocol, location, fragment);
            this.url = this.uri.toURL();
        } catch (URISyntaxException ex) {
            MalformedURLException exToThrow = new MalformedURLException(ex.getMessage());
            exToThrow.initCause(ex);
            throw exToThrow;
        }
    }

    /**
     * Determine a cleaned URL for the given original URL.
     *
     * @param originalUrl  the original URL
     * @param originalPath the original URL path
     * @return the cleaned URL (possibly the original URL as-is)
     * @see StringUtils#cleanPath
     */
    private static URL getCleanedUrl(URL originalUrl, String originalPath) {
        String cleanedPath = StringUtils.cleanPath(originalPath);
        if (!cleanedPath.equals(originalPath)) {
            try {
                return new URL(cleanedPath);
            } catch (MalformedURLException ex) {
                // Cleaned URL path cannot be converted to URL -> take original URL.
            }
        }
        return originalUrl;
    }

    /**
     * Lazily determine a cleaned URL for the given original URL.
     *
     * @see #getCleanedUrl(URL, String)
     */
    private URL getCleanedUrl() {
        URL cleanedUrl = this.cleanedUrl;
        if (cleanedUrl != null) {
            return cleanedUrl;
        }
        cleanedUrl = getCleanedUrl(this.url, (this.uri != null ? this.uri : this.url).toString());
        this.cleanedUrl = cleanedUrl;
        return cleanedUrl;
    }


    /**
     * This implementation opens an InputStream for the given URL.
     *
     * <p>It sets the {@code useCaches} flag to {@code false},
     * mainly to avoid jar file locking on Windows.
     *
     * @see URL#openConnection()
     * @see URLConnection#setUseCaches(boolean)
     * @see URLConnection#getInputStream()
     */
    @Override
    public InputStream getInputStream() throws IOException {
        URLConnection con = this.url.openConnection();
        ResourceUtils.useCachesIfNecessary(con);
        try {
            return con.getInputStream();
        } catch (IOException ex) {
            // Close the HTTP connection (if applicable).
            if (con instanceof HttpURLConnection) {
                ((HttpURLConnection) con).disconnect();
            }
            throw ex;
        }
    }

    /**
     * This implementation returns the underlying URL reference.
     */
    @Override
    public URL getUrl() {
        return this.url;
    }

    /**
     * This implementation returns the underlying URI directly,
     * if possible.
     */
    @Override
    public URI getUri() throws IOException {
        if (this.uri != null) {
            return this.uri;
        } else {
            return super.getUri();
        }
    }

    @Override
    public boolean isFile() {
        if (this.uri != null) {
            return super.isFile(this.uri);
        } else {
            return super.isFile();
        }
    }

    /**
     * This implementation returns a File reference for the underlying URL/URI,
     * provided that it refers to a file in the file system.
     *
     * @see ResourceUtils#getFile(URL, String)
     */
    @Override
    public File getFile() throws IOException {
        if (this.uri != null) {
            return super.getFile(this.uri);
        } else {
            return super.getFile();
        }
    }

    /**
     * This implementation creates a {@code UrlResource}, delegating to
     * {@link #createRelativeUrl(String)} for adapting the relative path.
     *
     * @see #createRelativeUrl(String)
     */
    @Override
    public Resource createRelative(String relativePath) throws MalformedURLException {
        return new UrlResource(createRelativeUrl(relativePath));
    }

    /**
     * This delegate creates a {@code java.net.URL}, applying the given path
     * relative to the path of the underlying URL of this resource descriptor.
     * A leading slash will get dropped; a "#" symbol will get encoded.
     *
     * @see #createRelative(String)
     * @since 5.2
     */
    protected URL createRelativeUrl(String relativePath) throws MalformedURLException {
        if (relativePath.startsWith("/")) {
            relativePath = relativePath.substring(1);
        }
        // # can appear in filenames, java.net.URL should not treat it as a fragment
        relativePath = StringUtils.replace(relativePath, "#", "%23");
        // Use the URL constructor for applying the relative path as a URL spec
        return new URL(this.url, relativePath);
    }

    /**
     * This implementation returns the name of the file that this URL refers to.
     *
     * @see URL#getPath()
     */
    @Override
    public String getFilename() {
        return StringUtils.getFilename(getCleanedUrl().getPath());
    }

    /**
     * This implementation returns a description that includes the URL.
     */
    @Override
    public String getDescription() {
        return "URL [" + this.url + "]";
    }


    /**
     * This implementation compares the underlying URL references.
     */
    @Override
    public boolean equals(Object other) {
        return (this == other || (other instanceof UrlResource
                && getCleanedUrl().equals(((UrlResource) other).getCleanedUrl())));
    }

    /**
     * This implementation returns the hash code of the underlying URL reference.
     */
    @Override
    public int hashCode() {
        return getCleanedUrl().hashCode();
    }

}
