package org.jsoup.helper;

import org.jsoup.Connection;
import org.jsoup.internal.ControllableInputStream;
import org.jsoup.internal.Normalizer;
import org.jsoup.internal.StringUtil;
import org.jsoup.nodes.Comment;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.nodes.Node;
import org.jsoup.nodes.XmlDeclaration;
import org.jsoup.parser.Parser;
import org.jsoup.parser.StreamParser;
import org.jsoup.select.Elements;
import org.jspecify.annotations.Nullable;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.Reader;
import java.io.UncheckedIOException;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.SeekableByteChannel;
import java.nio.charset.Charset;
import java.nio.charset.IllegalCharsetNameException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Locale;
import java.util.Random;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.zip.GZIPInputStream;

import static org.jsoup.internal.SharedConstants.DefaultBufferSize;

/**
 * Internal static utilities for handling data.
 *
 */
@SuppressWarnings("CharsetObjectCanBeUsed")
public final class DataUtil {
    private static final Pattern charsetPattern = Pattern.compile("(?i)\\bcharset=\\s*(?:[\"'])?([^\\s,;\"']*)");
    public static final Charset UTF_8 = Charset.forName("UTF-8"); // Don't use StandardCharsets, as those only appear in Android API 19, and we target 10.
    static final String defaultCharsetName = UTF_8.name(); // used if not found in header or meta charset
    private static final int firstReadBufferSize = 1024 * 5;
    private static final char[] mimeBoundaryChars =
            "-_1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".toCharArray();
    static final int boundaryLength = 32;

    private DataUtil() {}

    /**
     * Loads and parses a file to a Document, with the HtmlParser. Files that are compressed with gzip (and end in {@code .gz} or {@code .z})
     * are supported in addition to uncompressed files.
     *
     * @param file file to load
     * @param charsetName (optional) character set of input; specify {@code null} to attempt to autodetect. A BOM in
     *     the file will always override this setting.
     * @param baseUri base URI of document, to resolve relative links against
     * @return Document
     * @throws IOException on IO error
     */
    public static Document load(File file, @Nullable String charsetName, String baseUri) throws IOException {
        return load(file.toPath(), charsetName, baseUri);
    }

    /**
     * Loads and parses a file to a Document. Files that are compressed with gzip (and end in {@code .gz} or {@code .z})
     * are supported in addition to uncompressed files.
     *
     * @param file file to load
     * @param charsetName (optional) character set of input; specify {@code null} to attempt to autodetect. A BOM in
     *     the file will always override this setting.
     * @param baseUri base URI of document, to resolve relative links against
     * @param parser alternate {@link Parser#xmlParser() parser} to use.

     * @return Document
     * @throws IOException on IO error
     * @since 1.14.2
     */
    public static Document load(File file, @Nullable String charsetName, String baseUri, Parser parser) throws IOException {
        return load(file.toPath(), charsetName, baseUri, parser);
    }

    /**
     * Loads and parses a file to a Document, with the HtmlParser. Files that are compressed with gzip (and end in {@code .gz} or {@code .z})
     * are supported in addition to uncompressed files.
     *
     * @param path file to load
     * @param charsetName (optional) character set of input; specify {@code null} to attempt to autodetect. A BOM in
     *     the file will always override this setting.
     * @param baseUri base URI of document, to resolve relative links against
     * @return Document
     * @throws IOException on IO error
     */
    public static Document load(Path path, @Nullable String charsetName, String baseUri) throws IOException {
        return load(path, charsetName, baseUri, Parser.htmlParser());
    }

    /**
     * Loads and parses a file to a Document. Files that are compressed with gzip (and end in {@code .gz} or {@code .z})
     * are supported in addition to uncompressed files.
     *
     * @param path file to load
     * @param charsetName (optional) character set of input; specify {@code null} to attempt to autodetect. A BOM in
     * the file will always override this setting.
     * @param baseUri base URI of document, to resolve relative links against
     * @param parser alternate {@link Parser#xmlParser() parser} to use.

     * @return Document
     * @throws IOException on IO error
     * @since 1.17.2
     */
    public static Document load(Path path, @Nullable String charsetName, String baseUri, Parser parser) throws IOException {
        return parseInputStream(openStream(path), charsetName, baseUri, parser);
    }

    /**
     * Returns a {@link StreamParser} that will parse the supplied file progressively.
     * Files that are compressed with gzip (and end in {@code .gz} or {@code .z})
     * are supported in addition to uncompressed files.
     *
     * @param path file to load
     * @param charset (optional) character set of input; specify {@code null} to attempt to autodetect from metadata.
     * A BOM in the file will always override this setting.
     * @param baseUri base URI of document, to resolve relative links against
     * @param parser alternate {@link Parser#xmlParser() parser} to use.

     * @return Document
     * @throws IOException on IO error
     * @since 1.18.2
     * @see Connection.Response#streamParser()
     */
    public static StreamParser streamParser(Path path, @Nullable Charset charset, String baseUri, Parser parser) throws IOException {
        StreamParser streamer = new StreamParser(parser);
        String charsetName = charset != null? charset.name() : null;
        DataUtil.CharsetDoc charsetDoc = DataUtil.detectCharset(openStream(path), charsetName, baseUri, parser);
        BufferedReader reader = new BufferedReader(new InputStreamReader(charsetDoc.input, charsetDoc.charset), DefaultBufferSize);
        streamer.parse(reader, baseUri); // initializes the parse and the document, but does not step() it

        return streamer;
    }

    /** Open an input stream from a file; if it's a gzip file, returns a GZIPInputStream to unzip it. */
    private static ControllableInputStream openStream(Path path) throws IOException {
        final SeekableByteChannel byteChannel = Files.newByteChannel(path);
        InputStream stream = Channels.newInputStream(byteChannel);
        String name = Normalizer.lowerCase(path.getFileName().toString());
        if (name.endsWith(".gz") || name.endsWith(".z")) {
            final boolean zipped = (stream.read() == 0x1f && stream.read() == 0x8b); // gzip magic bytes
            byteChannel.position(0); // reset to start of file
            if (zipped) {
                stream = new GZIPInputStream(stream);
            }
        }
        return ControllableInputStream.wrap(stream, 0);
    }

    /**
     * Parses a Document from an input steam.
     * @param in input stream to parse. The stream will be closed after reading.
     * @param charsetName character set of input (optional)
     * @param baseUri base URI of document, to resolve relative links against
     * @return Document
     * @throws IOException on IO error
     */
    public static Document load(InputStream in, @Nullable String charsetName, String baseUri) throws IOException {
        return parseInputStream(ControllableInputStream.wrap(in, 0), charsetName, baseUri, Parser.htmlParser());
    }

    /**
     * Parses a Document from an input steam, using the provided Parser.
     * @param in input stream to parse. The stream will be closed after reading.
     * @param charsetName character set of input (optional)
     * @param baseUri base URI of document, to resolve relative links against
     * @param parser alternate {@link Parser#xmlParser() parser} to use.
     * @return Document
     * @throws IOException on IO error
     */
    public static Document load(InputStream in, @Nullable String charsetName, String baseUri, Parser parser) throws IOException {
        return parseInputStream(ControllableInputStream.wrap(in, 0), charsetName, baseUri, parser);
    }

    /**
     * Writes the input stream to the output stream. Doesn't close them.
     * @param in input stream to read from
     * @param out output stream to write to
     * @throws IOException on IO error
     */
    static void crossStreams(final InputStream in, final OutputStream out) throws IOException {
        final byte[] buffer = new byte[DefaultBufferSize];
        int len;
        while ((len = in.read(buffer)) != -1) {
            out.write(buffer, 0, len);
        }
    }

    /** A struct to return a detected charset, and a document (if fully read). */
    static class CharsetDoc {
        Charset charset;
        InputStream input;
        @Nullable Document doc;

        CharsetDoc(Charset charset, @Nullable Document doc, InputStream input) {
            this.charset = charset;
            this.input = input;
            this.doc = doc;
        }
    }

    static Document parseInputStream(@Nullable ControllableInputStream input, @Nullable String charsetName, String baseUri, Parser parser) throws IOException {
        if (input == null) // empty body // todo reconsider?
            return new Document(baseUri);

        final Document doc;
        CharsetDoc charsetDoc = null;
        try {
            charsetDoc = detectCharset(input, charsetName, baseUri, parser);
            doc = parseInputStream(charsetDoc, baseUri, parser);
        } finally {
            if (charsetDoc != null)
                charsetDoc.input.close();
        }
        return doc;
    }

    static CharsetDoc detectCharset(ControllableInputStream input, @Nullable String charsetName, String baseUri, Parser parser) throws IOException {
        Document doc = null;
        // read the start of the stream and look for a BOM or meta charset:
        // look for BOM - overrides any other header or input
        String bomCharset = detectCharsetFromBom(input); // resets / consumes appropriately
        if (bomCharset != null)
            charsetName = bomCharset;

        if (charsetName == null) { // read ahead and determine from meta. safe first parse as UTF-8
            int origMax = input.max();
            input.max(firstReadBufferSize);
            input.mark(firstReadBufferSize);
            input.allowClose(false); // ignores closes during parse, in case we need to rewind
            try {
                Reader reader = new InputStreamReader(input, UTF_8); // input is currently capped to firstReadBufferSize
                doc = parser.parseInput(reader, baseUri);
                input.reset();
                input.max(origMax); // reset for a full read if required
            } catch (UncheckedIOException e) {
                throw e.getCause();
            } finally {
                input.allowClose(true);
            }

            // look for <meta http-equiv="Content-Type" content="text/html;charset=gb2312"> or HTML5 <meta charset="gb2312">
            Elements metaElements = doc.select("meta[http-equiv=content-type], meta[charset]");
            String foundCharset = null; // if not found, will keep utf-8 as best attempt
            for (Element meta : metaElements) {
                if (meta.hasAttr("http-equiv"))
                    foundCharset = getCharsetFromContentType(meta.attr("content"));
                if (foundCharset == null && meta.hasAttr("charset"))
                    foundCharset = meta.attr("charset");
                if (foundCharset != null)
                    break;
            }

            // look for <?xml encoding='ISO-8859-1'?>
            if (foundCharset == null && doc.childNodeSize() > 0) {
                Node first = doc.childNode(0);
                XmlDeclaration decl = null;
                if (first instanceof XmlDeclaration)
                    decl = (XmlDeclaration) first;
                else if (first instanceof Comment) {
                    Comment comment = (Comment) first;
                    if (comment.isXmlDeclaration())
                        decl = comment.asXmlDeclaration();
                }
                if (decl != null && decl.name().equalsIgnoreCase("xml")) {
                    foundCharset = decl.attr("encoding");
                }
            }
            foundCharset = validateCharset(foundCharset);
            if (foundCharset != null && !foundCharset.equalsIgnoreCase(defaultCharsetName)) { // need to re-decode. (case-insensitive check here to match how validate works)
                foundCharset = foundCharset.trim().replaceAll("[\"']", "");
                charsetName = foundCharset;
                doc = null;
            } else if (input.baseReadFully()) { // if we have read fully, and the charset was correct, keep that current parse
                input.close(); // the parser tried to close it
            } else {
                doc = null;
            }
        } else { // specified by content type header (or by user on file load)
            Validate.notEmpty(charsetName, "Must set charset arg to character set of file to parse. Set to null to attempt to detect from HTML");
        }

        // finally: prepare the return struct
        if (charsetName == null)
            charsetName = defaultCharsetName;
        Charset charset = charsetName.equals(defaultCharsetName) ? UTF_8 : Charset.forName(charsetName);
        return new CharsetDoc(charset, doc, input);
    }

    static Document parseInputStream(CharsetDoc charsetDoc, String baseUri, Parser parser) throws IOException {
        // if doc != null it was fully parsed during charset detection; so just return that
        if (charsetDoc.doc != null)
            return charsetDoc.doc;

        final InputStream input = charsetDoc.input;
        Validate.notNull(input);
        final Document doc;
        final Charset charset = charsetDoc.charset;
        try (Reader reader = new InputStreamReader(input, charset)) {
            try {
                doc = parser.parseInput(reader, baseUri);
            } catch (UncheckedIOException e) {
                // io exception when parsing (not seen before because reading the stream as we go)
                throw e.getCause();
            }
            doc.outputSettings().charset(charset);
            if (!charset.canEncode()) {
                // some charsets can read but not encode; switch to an encodable charset and update the meta el
                doc.charset(UTF_8);
            }
        }
        return doc;
    }

    /**
     * Read the input stream into a byte buffer. To deal with slow input streams, you may interrupt the thread this
     * method is executing on. The data read until being interrupted will be available.
     * @param inStream the input stream to read from
     * @param maxSize the maximum size in bytes to read from the stream. Set to 0 to be unlimited.
     * @return the filled byte buffer
     * @throws IOException if an exception occurs whilst reading from the input stream.
     */
    public static ByteBuffer readToByteBuffer(InputStream inStream, int maxSize) throws IOException {
        return ControllableInputStream.readToByteBuffer(inStream, maxSize);
    }

    static ByteBuffer emptyByteBuffer() {
        return ByteBuffer.allocate(0);
    }

    /**
     * Parse out a charset from a content type header. If the charset is not supported, returns null (so the default
     * will kick in.)
     * @param contentType e.g. "text/html; charset=EUC-JP"
     * @return "EUC-JP", or null if not found. Charset is trimmed and uppercased.
     */
    static @Nullable String getCharsetFromContentType(@Nullable String contentType) {
        if (contentType == null) return null;
        Matcher m = charsetPattern.matcher(contentType);
        if (m.find()) {
            String charset = m.group(1).trim();
            charset = charset.replace("charset=", "");
            return validateCharset(charset);
        }
        return null;
    }

    private @Nullable static String validateCharset(@Nullable String cs) {
        if (cs == null || cs.length() == 0) return null;
        cs = cs.trim().replaceAll("[\"']", "");
        try {
            if (Charset.isSupported(cs)) return cs;
            cs = cs.toUpperCase(Locale.ENGLISH);
            if (Charset.isSupported(cs)) return cs;
        } catch (IllegalCharsetNameException e) {
            // if all this charset matching fails.... we just take the default
        }
        return null;
    }

    /**
     * Creates a random string, suitable for use as a mime boundary
     */
    static String mimeBoundary() {
        final StringBuilder mime = StringUtil.borrowBuilder();
        final Random rand = new Random();
        for (int i = 0; i < boundaryLength; i++) {
            mime.append(mimeBoundaryChars[rand.nextInt(mimeBoundaryChars.length)]);
        }
        return StringUtil.releaseBuilder(mime);
    }

    private static @Nullable String detectCharsetFromBom(ControllableInputStream input) throws IOException {
        byte[] bom = new byte[4];
        input.mark(bom.length);
        //noinspection ResultOfMethodCallIgnored
        input.read(bom, 0, 4);
        input.reset();

        // 16 and 32 decoders consume the BOM to determine be/le; utf-8 should be consumed here
        if (bom[0] == 0x00 && bom[1] == 0x00 && bom[2] == (byte) 0xFE && bom[3] == (byte) 0xFF || // BE
            bom[0] == (byte) 0xFF && bom[1] == (byte) 0xFE && bom[2] == 0x00 && bom[3] == 0x00) { // LE
            return "UTF-32"; // and I hope it's on your system
        } else if (bom[0] == (byte) 0xFE && bom[1] == (byte) 0xFF || // BE
            bom[0] == (byte) 0xFF && bom[1] == (byte) 0xFE) {
            return "UTF-16"; // in all Javas
        } else if (bom[0] == (byte) 0xEF && bom[1] == (byte) 0xBB && bom[2] == (byte) 0xBF) {
            input.read(bom, 0, 3); // consume the UTF-8 BOM
            return "UTF-8"; // in all Javas
        }
        return null;
    }
}