//
//  ========================================================================
//  Copyright (c) 1995-2020 Mort Bay Consulting Pty Ltd and others.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.http2.hpack;

import org.eclipse.jetty.http.HostPortHttpField;
import org.eclipse.jetty.http.HttpField;
import org.eclipse.jetty.http.HttpFields;
import org.eclipse.jetty.http.HttpHeader;
import org.eclipse.jetty.http.HttpScheme;
import org.eclipse.jetty.http.HttpVersion;
import org.eclipse.jetty.http.MetaData;
import org.eclipse.jetty.http2.hpack.HpackException.SessionException;

public class MetaDataBuilder
{
    private final int _maxSize;
    private int _size;
    private Integer _status;
    private String _method;
    private HttpScheme _scheme;
    private HostPortHttpField _authority;
    private String _path;
    private long _contentLength = Long.MIN_VALUE;
    private HttpFields _fields = new HttpFields();
    private HpackException.StreamException _streamException;
    private boolean _request;
    private boolean _response;

    /**
     * @param maxHeadersSize The maximum size of the headers, expressed as total name and value characters.
     */
    protected MetaDataBuilder(int maxHeadersSize)
    {
        _maxSize = maxHeadersSize;
    }

    /**
     * Get the maxSize.
     *
     * @return the maxSize
     */
    public int getMaxSize()
    {
        return _maxSize;
    }

    /**
     * Get the size.
     *
     * @return the current size in bytes
     */
    public int getSize()
    {
        return _size;
    }

    public void emit(HttpField field) throws HpackException.SessionException
    {
        HttpHeader header = field.getHeader();
        String name = field.getName();
        if (name == null || name.length() == 0)
            throw new HpackException.SessionException("Header size 0");
        String value = field.getValue();
        int fieldSize = name.length() + (value == null ? 0 : value.length());
        _size += fieldSize + 32;
        if (_size > _maxSize)
            throw new HpackException.SessionException("Header size %d > %d", _size, _maxSize);

        if (field instanceof StaticTableHttpField)
        {
            StaticTableHttpField staticField = (StaticTableHttpField)field;
            switch (header)
            {
                case C_STATUS:
                    if (checkPseudoHeader(header, _status))
                        _status = (Integer)staticField.getStaticValue();
                    _response = true;
                    break;

                case C_METHOD:
                    if (checkPseudoHeader(header, _method))
                        _method = value;
                    _request = true;
                    break;

                case C_SCHEME:
                    if (checkPseudoHeader(header, _scheme))
                        _scheme = (HttpScheme)staticField.getStaticValue();
                    _request = true;
                    break;

                default:
                    throw new IllegalArgumentException(name);
            }
        }
        else if (header != null)
        {
            switch (header)
            {
                case C_STATUS:
                    if (checkPseudoHeader(header, _status))
                        _status = field.getIntValue();
                    _response = true;
                    break;

                case C_METHOD:
                    if (checkPseudoHeader(header, _method))
                        _method = value;
                    _request = true;
                    break;

                case C_SCHEME:
                    if (checkPseudoHeader(header, _scheme) && value != null)
                        _scheme = HttpScheme.CACHE.get(value);
                    _request = true;
                    break;

                case C_AUTHORITY:
                    if (checkPseudoHeader(header, _authority))
                    {
                        if (field instanceof HostPortHttpField)
                            _authority = (HostPortHttpField)field;
                        else if (value != null)
                            _authority = new AuthorityHttpField(value);
                    }
                    _request = true;
                    break;

                case HOST:
                    // :authority fields must come first.  If we have one, ignore the host header as far as authority goes.
                    if (_authority == null)
                    {
                        if (field instanceof HostPortHttpField)
                            _authority = (HostPortHttpField)field;
                        else if (value != null)
                            _authority = new AuthorityHttpField(value);
                    }
                    _fields.add(field);
                    break;

                case C_PATH:
                    if (checkPseudoHeader(header, _path))
                    {
                        if (value != null && value.length() > 0)
                            _path = value;
                        else
                            streamException("No Path");
                    }
                    _request = true;
                    break;

                case CONTENT_LENGTH:
                    _contentLength = field.getLongValue();
                    _fields.add(field);
                    break;

                case TE:
                    if ("trailers".equalsIgnoreCase(value))
                        _fields.add(field);
                    else
                        streamException("Unsupported TE value '%s'", value);
                    break;

                case CONNECTION:
                    if ("TE".equalsIgnoreCase(value))
                        _fields.add(field);
                    else
                        streamException("Connection specific field '%s'", header);
                    break;

                default:
                    if (name.charAt(0) == ':')
                        streamException("Unknown pseudo header '%s'", name);
                    else
                        _fields.add(field);
                    break;
            }
        }
        else
        {
            if (name.charAt(0) == ':')
                streamException("Unknown pseudo header '%s'", name);
            else
                _fields.add(field);
        }
    }

    protected void streamException(String messageFormat, Object... args)
    {
        HpackException.StreamException stream = new HpackException.StreamException(messageFormat, args);
        if (_streamException == null)
            _streamException = stream;
        else
            _streamException.addSuppressed(stream);
    }

    protected boolean checkPseudoHeader(HttpHeader header, Object value)
    {
        if (_fields.size() > 0)
        {
            streamException("Pseudo header %s after fields", header.asString());
            return false;
        }
        if (value == null)
            return true;
        streamException("Duplicate pseudo header %s", header.asString());
        return false;
    }

    public MetaData build() throws HpackException.StreamException
    {
        if (_streamException != null)
        {
            _streamException.addSuppressed(new Throwable());
            throw _streamException;
        }

        if (_request && _response)
            throw new HpackException.StreamException("Request and Response headers");

        HttpFields fields = _fields;
        try
        {
            if (_request)
            {
                if (_method == null)
                    throw new HpackException.StreamException("No Method");
                if (_scheme == null)
                    throw new HpackException.StreamException("No Scheme");
                if (_path == null)
                    throw new HpackException.StreamException("No Path");
                return new MetaData.Request(_method, _scheme, _authority, _path, HttpVersion.HTTP_2, fields, _contentLength);
            }
            if (_response)
            {
                if (_status == null)
                    throw new HpackException.StreamException("No Status");
                return new MetaData.Response(HttpVersion.HTTP_2, _status, fields, _contentLength);
            }

            return new MetaData(HttpVersion.HTTP_2, fields, _contentLength);
        }
        finally
        {
            _fields = new HttpFields(Math.max(16, fields.size() + 5));
            _request = false;
            _response = false;
            _status = null;
            _method = null;
            _scheme = null;
            _authority = null;
            _path = null;
            _size = 0;
            _contentLength = Long.MIN_VALUE;
        }
    }

    /**
     * Check that the max size will not be exceeded.
     *
     * @param length the length
     * @param huffman the huffman name
     * @throws SessionException in case of size errors
     */
    public void checkSize(int length, boolean huffman) throws SessionException
    {
        // Apply a huffman fudge factor
        if (huffman)
            length = (length * 4) / 3;
        if ((_size + length) > _maxSize)
            throw new HpackException.SessionException("Header too large %d > %d", _size + length, _maxSize);
    }
}
