// ScraperInputStream.java
// (C) 2005, 2006 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
// first published 2005 on http://www.anomic.de
//
// This is a part of YaCy, a peer-to-peer based web search engine
//
// $LastChangedDate$
// $LastChangedRevision$
// $LastChangedBy$
//
// LICENSE
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

package net.yacy.document.parser.html;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
import java.nio.charset.StandardCharsets;
import java.util.Properties;

import net.yacy.cora.document.id.DigestURL;
import net.yacy.cora.util.CommonPattern;
import net.yacy.document.VocabularyScraper;


public class ScraperInputStream extends InputStream implements ScraperListener {

    private static final int MODE_PRESCAN = 0;
    private static final int MODE_PRESCAN_FINISHED = 1;
    private int mode = 1;

    private static final long preBufferSize = 4096;
    private long preRead = 0;
    private final BufferedInputStream bufferedIn;

    private String detectedCharset;
    private boolean charsetChanged = false;
    private boolean endOfHead = false;

    private Reader reader;
    private Writer writer;

    public ScraperInputStream(
            final InputStream inStream,
            final String inputStreamCharset,
            final VocabularyScraper vocabularyScraper,
            final DigestURL rooturl,
            final Transformer transformer,
            final boolean passbyIfBinarySuspect,
            final int maxLinks,
            final int timezoneOffset
    ) {
        // create a input stream for buffereing
        this.bufferedIn = new BufferedInputStream(inStream, (int) preBufferSize);
        this.bufferedIn.mark((int) preBufferSize);

        final ContentScraper scraper = new ContentScraper(rooturl, maxLinks, vocabularyScraper, timezoneOffset);
        scraper.registerHtmlFilterEventListener(this);

        try {
	    this.reader = (inputStreamCharset == null) ? new InputStreamReader(this) : new InputStreamReader(this,inputStreamCharset);
	} catch (final UnsupportedEncodingException e) {
		this.reader = new InputStreamReader(this, StandardCharsets.UTF_8);
	}
        this.writer = new TransformerWriter(null,null,scraper,transformer,passbyIfBinarySuspect);
    }

    private static String extractCharsetFromMimetypeHeader(final String mimeType) {
        if (mimeType == null) return null;

        final String[] parts = CommonPattern.SEMICOLON.split(mimeType);
        if (parts == null || parts.length <= 1) return null;

        for (int i=1; i < parts.length; i++) {
            final String param = parts[i].trim();
            if (param.startsWith("charset=")) {
                String charset = param.substring("charset=".length()).trim();
                if (charset.length() > 0 && (charset.charAt(0) == '\"' || charset.charAt(0) == '\'')) charset = charset.substring(1);
                if (charset.endsWith("\"") || charset.endsWith("'")) charset = charset.substring(0,charset.length()-1);
                return charset.trim();
            }
        }

        return null;
    }

    @Override
    public void scrapeTag0(final String tagname, final Properties tagopts) {
        if (tagname == null || tagname.isEmpty()) return;

        if (tagname.equalsIgnoreCase("meta")) {
            if (tagopts.containsKey("http-equiv")) {
                final String value = tagopts.getProperty("http-equiv");
                if (value.equalsIgnoreCase("Content-Type")) {
                    // parse lines like <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
                    final String contentType = tagopts.getProperty("content","");
                    this.detectedCharset = extractCharsetFromMimetypeHeader(contentType);
                    if (this.detectedCharset != null && this.detectedCharset.length() > 0) {
                        this.charsetChanged = true;
                    } else if (tagopts.containsKey("charset")) {
                        // sometimes the charset property is configured as extra attribut. try it ...
                        this.detectedCharset = tagopts.getProperty("charset");
                        this.charsetChanged = true;
                    }
                }
            }
        }
    }

    @Override
    public void scrapeTag1(final String tagname, final Properties tagopts, final char[] text) {
        if (tagname == null || tagname.isEmpty()) return;

        if (tagname.equalsIgnoreCase("head")) {
            this.endOfHead = true;
        }
    }

    public String detectCharset() throws IOException {
        this.mode = MODE_PRESCAN;

        // loop until we have detected the header element or the charset data
        int c;
        while ((c = this.reader.read())!= -1) {
            this.writer.write(c);
            if (this.charsetChanged) break; // thats enough
        }

        // free writer
        this.writer = null;
        // don't close writer here, otherwise it will shutdown our source stream

        // reset the buffer if not already done
        if (this.mode != MODE_PRESCAN_FINISHED) {
            this.mode++;
            this.bufferedIn.reset();
        }

        // return scanning result
        return (this.charsetChanged) ? this.detectedCharset : null;
    }

    @Override
    public int read() throws IOException {
        // mode 0 is called from within the detectCharset function
        if (this.mode == MODE_PRESCAN) {
            if (this.endOfHead || this.charsetChanged || this.preRead >= preBufferSize - 1) {
                return -1;
            }
            this.preRead++;
        }
        return this.bufferedIn.read();
    }

    @Override
    public synchronized void close() throws IOException {
        if (this.writer != null) this.writer.close();
    }

}