/*
 * Copyright 2004-2008 H2 Group. Multiple-Licensed under the H2 License, 
 * Version 1.0, and under the Eclipse Public License, Version 1.0
 * (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.build.doc;

import java.io.File;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;

import org.h2.util.IOUtils;
import org.h2.util.StartBrowser;
import org.h2.util.StringUtils;

/**
 * The link checker makes sure that each link in the documentation
 * points to an existing target.
 */
public class LinkChecker {

    private static final boolean OPEN_EXTERNAL_LINKS = false;
    private static final String[] IGNORE_MISSING_LINKS_TO = new String[]{
        "SysProperties", "ErrorCode"
    };
    
    private HashMap targets = new HashMap();
    private HashMap links = new HashMap();

    /**
     * This method is called when executing this application from the command
     * line.
     * 
     * @param args the command line parameters
     */
    public static void main(String[] args) throws Exception {
        new LinkChecker().run(args);
    }

    private void run(String[] args) throws Exception {
        String dir = "docs";
        for (int i = 0; i < args.length; i++) {
            if ("-dir".equals(args[i])) {
                dir = args[++i];
            }
        }
        process(dir);
        listExternalLinks();
        listBadLinks();
    }

    private void listExternalLinks() {
        for (Iterator it = links.keySet().iterator(); it.hasNext();) {
            String link = (String) it.next();
            if (link.startsWith("http")) {
                if (link.indexOf("//localhost") > 0) {
                    continue;
                }
                if (OPEN_EXTERNAL_LINKS) {
                    StartBrowser.openURL(link);
                }
                // System.out.println("External Link: " + link);
            }
        }
    }

    private void listBadLinks() throws Exception {
        ArrayList errors = new ArrayList();
        for (Iterator it = links.keySet().iterator(); it.hasNext();) {
            String link = (String) it.next();
            if (!link.startsWith("http") && !link.endsWith("h2.pdf")
                    && link.indexOf("_ja.") < 0) {
                if (targets.get(link) == null) {
                    errors.add(links.get(link) + ": missing link " + link);
                }
            }
        }
        for (Iterator it = links.keySet().iterator(); it.hasNext();) {
            String link = (String) it.next();
            if (!link.startsWith("http")) {
                targets.remove(link);
            }
        }
        for (Iterator it = targets.keySet().iterator(); it.hasNext();) {
            String name = (String) it.next();
            if (targets.get(name).equals("name")) {
                boolean ignore = false;
                for (int i = 0; i < IGNORE_MISSING_LINKS_TO.length; i++) {
                    if (name.indexOf(IGNORE_MISSING_LINKS_TO[i]) >= 0) {
                        ignore = true;
                        break;
                    }
                }
                if (!ignore) {
                    errors.add("No link to " + name);
                }
            }
        }
        Collections.sort(errors);
        for (int i = 0; i < errors.size(); i++) {
            System.out.println(errors.get(i));
        }
        if (errors.size() > 0) {
            throw new Exception("Problems where found by the Link Checker");
        }
    }

    private void process(String path) throws Exception {
        if (path.endsWith("/CVS") || path.endsWith("/.svn")) {
            return;
        }
        File file = new File(path);
        if (file.isDirectory()) {
            String[] list = file.list();
            for (int i = 0; i < list.length; i++) {
                process(path + "/" + list[i]);
            }
        } else {
            processFile(path);
        }
    }

    private void processFile(String path) throws Exception {
        targets.put(path, "file");
        String lower = StringUtils.toLowerEnglish(path);
        if (!lower.endsWith(".html") && !lower.endsWith(".htm")) {
            return;
        }
        String fileName = new File(path).getName();
        String parent = path.substring(0, path.lastIndexOf('/'));
        String html = IOUtils.readStringAndClose(new FileReader(path), -1);
        int idx = -1;
        while (true) {
            idx = html.indexOf(" id=\"", idx + 1);
            if (idx < 0) {
                break;
            }
            int start = idx + 4;
            int end = html.indexOf("\"", start + 1);
            if (end < 0) {
                error(fileName, "expected \" after id= " + html.substring(idx, idx + 100));
            }
            String ref = html.substring(start + 1, end);
            targets.put(path + "#" + ref, "id");
        }
        idx = -1;
        while (true) {
            idx = html.indexOf("<a ", idx + 1);
            if (idx < 0) {
                break;
            }
            int equals = html.indexOf("=", idx);
            if (equals < 0) {
                error(fileName, "expected = after <a at " + html.substring(idx, idx + 100));
            }
            String type = html.substring(idx + 2, equals).trim();
            int start = html.indexOf("\"", idx);
            if (start < 0) {
                error(fileName, "expected \" after <a at " + html.substring(idx, idx + 100));
            }
            int end = html.indexOf("\"", start + 1);
            if (end < 0) {
                error(fileName, "expected \" after <a at " + html.substring(idx, idx + 100));
            }
            String ref = html.substring(start + 1, end);
            if (type.equals("href")) {
                if (ref.startsWith("http:") || ref.startsWith("https:")) {
                    // ok
                } else if (ref.startsWith("javascript:")) {
                    ref = null;
                    // ok
                } else if (ref.length() == 0) {
                    ref = null;
                    // ok
                } else if (ref.startsWith("#")) {
                    ref = path + ref;
                } else {
                    String p = parent;
                    while (ref.startsWith(".")) {
                        if (ref.startsWith("./")) {
                            ref = ref.substring(2);
                        } else if (ref.startsWith("../")) {
                            ref = ref.substring(3);
                            p = p.substring(0, p.lastIndexOf('/'));
                        }
                    }
                    ref = p + "/" + ref;
                }
                if (ref != null) {
                    links.put(ref, path);
                }
            } else if (type.equals("name")) {
                targets.put(path + "#" + ref, "name");
            } else {
                error(fileName, "unsupported <a ?: " + html.substring(idx, idx + 100));
            }
        }
    }

    private void error(String fileName, String string) {
        System.out.println("ERROR with " + fileName + ": " + string);
    }

}
