/*******************************************************************************
 * Copyright (c) 2014, 2015 Cisco Systems, Inc. and others.  All rights reserved.
 *  
 *  This program and the accompanying materials are made available under the
 *  terms of the Eclipse Public License v1.0 which accompanies this distribution,
 *  and is available at http://www.eclipse.org/legal/epl-v10.html
 *  
 *******************************************************************************/
package com.cisco.yangide.editor.editors.text.help;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.nio.charset.StandardCharsets;

import org.eclipse.core.runtime.FileLocator;
import org.eclipse.core.runtime.IPath;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.Path;
import org.eclipse.core.runtime.SubMonitor;
import org.eclipse.osgi.util.NLS;

import com.cisco.yangide.editor.YangEditorPlugin;

/**
 * Loader of help info for YANG language types, keywords, etc.
 * 
 * @author Kirill Karmakulov
 * @date Oct 16, 2014
 */
public class YangLanguageHelpLoader {

    /**
     * Possible kinds of YANG definitions
     */
    public enum DefinitionKind {

        TYPE("types"), //$NON-NLS-1$
        KEYWORD("keywords"); //$NON-NLS-1$

        final String subdir;

        DefinitionKind(String subdir) {
            this.subdir = subdir;
        }
    }

    protected final String definition;
    protected final IPath path;

    public YangLanguageHelpLoader(String definition, DefinitionKind kind) {
        this.definition = definition;
        path = new Path("help").append(kind.subdir).append(definition).addFileExtension("txt"); //$NON-NLS-1$ //$NON-NLS-2$
    }

    /**
     * Reads an internal help file, packs it inside an HTML, and returns the result as a string.
     */
    public String get(IProgressMonitor monitor) {
        SubMonitor subMonitor = SubMonitor.convert(monitor, 2); // There's no way to discover size
                                                                // of the help file; so, the best
                                                                // guess is a 2-step process: read
                                                                // the file contents, construct an
                                                                // HTML that contains it.
        URL url = null;
        try {
            url = FileLocator.find(YangEditorPlugin.getDefault().getBundle(), path, null);
            if (url != null) {
                try (InputStream inputStream = url.openStream();
                        BufferedReader r = new BufferedReader(
                                new InputStreamReader(inputStream, StandardCharsets.UTF_8))) {
                    StringBuilder sb = new StringBuilder();
                    for (String str = null; (str = r.readLine()) != null;) {
                        sb.append(str).append("\n"); // line breaks are important if the help file //$NON-NLS-1$
                                                     // contains <pre> HTML tags
                    }
                    subMonitor.worked(1); // reading completed
                    String wrapHtmlText = HelpCompositionUtils.wrapHtmlText(sb.toString(), definition);
                    subMonitor.worked(1); // HTML construction completed
                    return wrapHtmlText;
                }
            }
        } catch (IOException e) {
            YangEditorPlugin.logError("Failed to load help contents from " + url, e); //$NON-NLS-1$
        } finally {
            subMonitor.done();
        }
        return null;
    }

}