/*
 * Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0, which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.jvnet.mimepull;

import java.io.IOException;
import java.util.NoSuchElementException;
import java.util.List;

InternetHeaders is a utility class that manages RFC822 style headers. Given an RFC822 format message stream, it reads lines until the blank line that indicates end of header. The input stream is positioned at the start of the body. The lines are stored within the object and can be extracted as either Strings or Header objects. 


This class is mostly intended for service providers. MimeMessage
and MimeBody use this class for holding their headers. 


 A note on RFC822 and MIME headers


RFC822 and MIME header fields must contain only
US-ASCII characters. If a header contains non US-ASCII characters,
it must be encoded as per the rules in RFC 2047. The MimeUtility
class provided in this package can be used to to achieve this.
Callers of the setHeader, addHeader, and
addHeaderLine methods are responsible for enforcing
the MIME requirements for the specified headers.  In addition, these
header fields must be folded (wrapped) before being sent if they
exceed the line length limitation for the transport (1000 bytes for
SMTP).  Received headers may have been folded.  The application is
responsible for folding and unfolding headers as appropriate. 

Author:
John Mani, Bill Shannon/**
 * InternetHeaders is a utility class that manages RFC822 style
 * headers. Given an RFC822 format message stream, it reads lines
 * until the blank line that indicates end of header. The input stream
 * is positioned at the start of the body. The lines are stored
 * within the object and can be extracted as either Strings or
 * {@link Header} objects. <p>
 * <p/>
 * This class is mostly intended for service providers. MimeMessage
 * and MimeBody use this class for holding their headers. <p>
 * <p/>
 * <hr> <strong>A note on RFC822 and MIME headers</strong><p>
 * <p/>
 * RFC822 and MIME header fields <strong>must</strong> contain only
 * US-ASCII characters. If a header contains non US-ASCII characters,
 * it must be encoded as per the rules in RFC 2047. The MimeUtility
 * class provided in this package can be used to to achieve this.
 * Callers of the <code>setHeader</code>, <code>addHeader</code>, and
 * <code>addHeaderLine</code> methods are responsible for enforcing
 * the MIME requirements for the specified headers.  In addition, these
 * header fields must be folded (wrapped) before being sent if they
 * exceed the line length limitation for the transport (1000 bytes for
 * SMTP).  Received headers may have been folded.  The application is
 * responsible for folding and unfolding headers as appropriate. <p>
 *
 * @author John Mani
 * @author Bill Shannon
 */
final class InternetHeaders {

    private final FinalArrayList<Hdr> headers = new FinalArrayList<Hdr>();

    
Read and parse the given RFC822 message stream till the
blank line separating the header from the body. Store the
header lines inside this InternetHeaders object. 


Note that the header lines are added into this InternetHeaders
object, so any existing headers in this object will not be
affected.
Params:
lis – RFC822 input stream/**
     * Read and parse the given RFC822 message stream till the
     * blank line separating the header from the body. Store the
     * header lines inside this InternetHeaders object. <p>
     * <p/>
     * Note that the header lines are added into this InternetHeaders
     * object, so any existing headers in this object will not be
     * affected.
     *
     * @param	lis RFC822 input stream
     */
    InternetHeaders(MIMEParser.LineInputStream lis) {
        // Read header lines until a blank line. It is valid
        // to have BodyParts with no header lines.
        String line;
        String prevline = null;	// the previous header line, as a string
        // a buffer to accumulate the header in, when we know it's needed
        StringBuilder lineBuffer = new StringBuilder();

        try {
            //while ((line = lis.readLine()) != null) {
            do {
                line = lis.readLine();
                if (line != null &&
                        (line.startsWith(" ") || line.startsWith("\t"))) {
                    // continuation of header
                    if (prevline != null) {
                        lineBuffer.append(prevline);
                        prevline = null;
                    }
                    lineBuffer.append("\r\n");
                    lineBuffer.append(line);
                } else {
                    // new header
                    if (prevline != null) {
                        addHeaderLine(prevline);
                    } else if (lineBuffer.length() > 0) {
                        // store previous header first
                        addHeaderLine(lineBuffer.toString());
                        lineBuffer.setLength(0);
                    }
                    prevline = line;
                }
            } while (line != null && line.length() > 0);
        } catch (IOException ioex) {
            throw new MIMEParsingException("Error in input stream", ioex);
        }
    }

    
Return all the values for the specified header. The
values are String objects.  Returns null
if no headers with the specified name exist.
Params:
name – header name
Returns:
		array of header values, or null if none/**
     * Return all the values for the specified header. The
     * values are String objects.  Returns <code>null</code>
     * if no headers with the specified name exist.
     *
     * @param	name header name
     * @return		array of header values, or null if none
     */
    List<String> getHeader(String name) {
        // XXX - should we just step through in index order?
        FinalArrayList<String> v = new FinalArrayList<String>(); // accumulate return values

        int len = headers.size();
        for( int i=0; i<len; i++ ) {
            Hdr h = (Hdr) headers.get(i);
            if (name.equalsIgnoreCase(h.name)) {
                v.add(h.getValue());
            }
        }
        return (v.size() == 0) ? null : v;
    }

    
Return all the headers as an Enumeration of Header objects. 
Returns:
	Header objects/**
     * Return all the headers as an Enumeration of
     * {@link Header} objects.
     *
     * @return	Header objects
     */
    FinalArrayList<? extends Header> getAllHeaders() {
        return headers; // conceptually it should be read-only, but for performance reason I'm not wrapping it here
    }

    
Add an RFC822 header line to the header store.
If the line starts with a space or tab (a continuation line),
add it to the last header line in the list. 


Note that RFC822 headers can only contain US-ASCII characters
Params:
line – 	raw RFC822 header line/**
     * Add an RFC822 header line to the header store.
     * If the line starts with a space or tab (a continuation line),
     * add it to the last header line in the list. <p>
     * <p/>
     * Note that RFC822 headers can only contain US-ASCII characters
     *
     * @param	line	raw RFC822 header line
     */
    void addHeaderLine(String line) {
        try {
            char c = line.charAt(0);
            if (c == ' ' || c == '\t') {
                Hdr h = (Hdr) headers.get(headers.size() - 1);
                h.line += "\r\n" + line;
            } else {
                headers.add(new Hdr(line));
            }
        } catch (StringIndexOutOfBoundsException e) {
            // line is empty, ignore it
        } catch (NoSuchElementException e) {
            // XXX - vector is empty?
        }
    }

}

/*
 * A private utility class to represent an individual header.
 */

class Hdr implements Header {

    String name;    // the canonicalized (trimmed) name of this header
    // XXX - should name be stored in lower case?
    String line;    // the entire RFC822 header "line"

    /*
     * Constructor that takes a line and splits out
     * the header name.
     */
    Hdr(String l) {
        int i = l.indexOf(':');
        if (i < 0) {
            // should never happen
            name = l.trim();
        } else {
            name = l.substring(0, i).trim();
        }
        line = l;
    }

    /*
     * Constructor that takes a header name and value.
     */
    Hdr(String n, String v) {
        name = n;
        line = n + ": " + v;
    }

    /*
     * Return the "name" part of the header line.
     */
    @Override
    public String getName() {
        return name;
    }

    /*
     * Return the "value" part of the header line.
     */
    @Override
    public String getValue() {
        int i = line.indexOf(':');
        if (i < 0) {
            return line;
        }

        int j;
        if (name.equalsIgnoreCase("Content-Description")) {
            // Content-Description should retain the folded whitespace after header unfolding -
            // rf. RFC2822 section 2.2.3, rf. RFC2822 section 3.2.3
            for (j = i + 1; j < line.length(); j++) {
                char c = line.charAt(j);
                if (!(/*c == ' ' ||*/c == '\t' || c == '\r' || c == '\n')) {
                    break;
                }
            }
        } else {
            // skip whitespace after ':'
            for (j = i + 1; j < line.length(); j++) {
                char c = line.charAt(j);
                if (!(c == ' ' || c == '\t' || c == '\r' || c == '\n')) {
                    break;
                }
            }
        }
        return line.substring(j);
    }
}