/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* vim:expandtab:shiftwidth=4:tabstop=4:
 */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
/*
 * This interface allows any module to access the routine 
 * for MIME header parameter parsing (RFC 2231/5987)
 */

#include "nsISupports.idl"

[scriptable, uuid(9c9252a1-fdaf-40a2-9c2b-a3dc45e28dde)]
interface nsIMIMEHeaderParam : nsISupports {

  /** 
   * Given the value of a single header field  (such as
   * Content-Disposition and Content-Type) and the name of a parameter
   * (e.g. filename, name, charset), returns the value of the parameter.
   * The value is obtained by decoding RFC 2231/5987-style encoding,
   * RFC 2047-style encoding, and converting to UniChar(UTF-16)
   * from charset specified in RFC 2231/2047 encoding, UTF-8, 
   * <code>aFallbackCharset</code>, the locale charset as fallback if
   * <code>TryLocaleCharset</code> is set, and null-padding as last resort
   * if all else fails.
   *
   * <p> 
   * This method internally invokes <code>getParameterInternal</code>, 
   * However, it does not stop at decoding RFC 2231 (the task for
   * <code>getParameterInternal</code> but tries to cope
   * with several non-standard-compliant cases mentioned below.
   *
   * <p>
   * Note that a lot of MUAs put RFC 2047-encoded parameters. Unfortunately,
   * this includes Mozilla as of 2003-05-30. Even more standard-ignorant MUAs,
   * web servers and application servers put 'raw 8bit characters'. This will
   * try to cope with all these cases as gracefully as possible. Additionally,
   * it returns the language tag if the parameter is encoded per RFC 2231 and 
   * includes lang.
   *
   * <p>
   * Note that GetParameterHTTP skips some of the workarounds used for
   * mail (MIME) header fields, and thus SHOULD be used from non-mail
   * code.
   *
   *
   * @param  aHeaderVal        a header string to get the value of a parameter 
   *                           from.
   * @param  aParamName        the name of a MIME header parameter (e.g. 
   *                           filename, name, charset). If empty,  returns 
   *                           the first (possibly) _unnamed_ 'parameter'.
   * @param  aFallbackCharset  fallback charset to try if  the string after
   *                           RFC 2231/2047 decoding or the raw 8bit 
   *                           string is not UTF-8
   * @param  aTryLocaleCharset If set, makes yet another attempt 
   *                           with the locale charset.
   * @param  aLang             If non-null, assigns it to a pointer 
   *                           to a string containing the value of language 
   *                           obtained from RFC 2231 parsing. Caller has to 
   *                           free it.
   * @return the value of <code>aParamName</code> in Unichar(UTF-16).
   */
  AString getParameter(in ACString aHeaderVal,
                       in string aParamName,
                       in ACString aFallbackCharset,
                       in boolean aTryLocaleCharset, 
                       out string aLang);


  /**
   * Like getParameter, but disabling encodings and workarounds specific to
   * MIME (as opposed to HTTP).
   */
  AString getParameterHTTP(in ACString aHeaderVal,
                           in string aParamName,
                           in ACString aFallbackCharset,
                           in boolean aTryLocaleCharset, 
                           out string aLang);

  /** 
   * Given the value of a header field parameter using the encoding
   * defined in RFC 5987, decode the value into a Unicode string, and extract
   * the optional language parameter.
   *
   * <p> 
   * This function is purposefully picky; it will abort for all (most?)
   * invalid inputs. This is by design. In particular, it does not support
   * any character encodings other than UTF-8, in order not to promote
   * non-interoperable usage.
   *
   * <p>
   * Code that parses HTTP header fields (as opposed to MIME header fields)
   * should use this function.
   *
   * @param  aParamVal         a header field parameter to decode.
   * @param  aLang             will be set to the language part (possibly
   *                           empty).
   * @return the decoded parameter value.
   */
  AString decodeRFC5987Param(in ACString aParamVal, 
                             out ACString aLang);

  /** 
   * Given the value of a single header field  (such as
   * Content-Disposition and Content-Type) and the name of a parameter
   * (e.g. filename, name, charset), returns the value of the parameter 
   * after decoding RFC 2231-style encoding. 
   * <p>
   * For <strong>internal use only</strong>. The only other place where 
   * this needs to be  invoked  is  |MimeHeaders_get_parameter| in 
   * mailnews/mime/src/mimehdrs.cpp defined as 
   * char * MimeHeaders_get_parameter (const char *header_value, 
   *                                   const char *parm_name,
   *                                   char **charset, char **language)
   *
   * Otherwise, this method would have been made static.
   *
   * @param  aHeaderVal  a header string to get the value of a parameter from.
   * @param  aParamName  the name of a MIME header parameter (e.g. 
   *                     filename, name, charset). If empty,  returns 
   *                     the first (possibly) _unnamed_ 'parameter'.
   * @param  aCharset    If non-null, it gets assigned a new pointer
   *                     to a string containing the value of charset obtained
   *                     from RFC 2231 parsing. Caller has to free it.
   * @param  aLang       If non-null, it gets assigned a new pointer
   *                     to a string containing the value of language obtained
   *                     from RFC 2231 parsing. Caller has to free it.
   * @return             the value of <code>aParamName</code> after
   *                     RFC 2231 decoding but without charset conversion.
   */

  [noscript]
  string getParameterInternal(in string aHeaderVal,
                              in string aParamName,
                              out string aCharset,
                              out string aLang);


  /** 
   * Given a header value, decodes RFC 2047-style encoding and
   * returns the decoded header value in UTF-8 if either it's
   * RFC-2047-encoded or aDefaultCharset is given. Otherwise,
   * returns the input header value (in whatever encoding) 
   * as it is except that  RFC 822 (using backslash) quotation and 
   * CRLF (if aEatContinuation is set) are stripped away
   * <p>
   * For internal use only. The only other place where this needs to be 
   * invoked  is  <code>MIME_DecodeMimeHeader</code> in 
   * mailnews/mime/src/mimehdrs.cpp defined as
   * char * Mime_DecodeMimeHeader(char *header_val, const char *charset, 
   *                              bool override, bool eatcontinuation)
   *
   * @param aHeaderVal       a header value to decode
   * @param aDefaultCharset  MIME charset to use in place of MIME charset
   *                         specified in RFC 2047 style encoding
   *                         when <code>aOverrideCharset</code> is set.
   * @param aOverrideCharset When set, overrides MIME charset specified 
   *                         in RFC 2047 style encoding with <code>aDefaultCharset</code>
   * @param aEatContinuation When set, removes CR/LF
   * @return                 decoded header value
   */
  [noscript]
  ACString decodeRFC2047Header(in string aHeaderVal,
                               in string aDefaultCharset,
                               in boolean aOverrideCharset,
                               in boolean aEatContinuation);


  /** 
   * Given a header parameter, decodes RFC 2047 style encoding (if it's 
   * not obtained from RFC 2231 encoding),  converts it to
   * UTF-8 and returns the result in UTF-8 if an attempt to extract 
   * charset info. from a few different sources succeeds.
   * Otherwise,  returns the input header value (in whatever encoding) 
   * as it is except that  RFC 822 (using backslash) quotation is
   * stripped off.
   * <p>
   * For internal use only. The only other place where this needs to be 
   * invoked  is  <code>mime_decode_filename</code> in 
   * mailnews/mime/src/mimehdrs.cpp defined as
   * char * mime_decode_filename(char *name, const char *charset, 
   *                             MimeDisplayOptions *opt) 
   *
   * @param aParamValue      the value of a parameter to decode and convert
   * @param aCharset         charset obtained from RFC 2231 decoding  in which 
   *                         <code>aParamValue</code> is encoded. If null,
   *                         indicates that it needs to try RFC 2047, instead. 
   * @param aDefaultCharset  MIME charset to use when aCharset is null and
   *                         cannot be obtained per RFC 2047 (most likely 
   *                         because 'bare' string is  used.)  Besides, it 
   *                         overrides aCharset/MIME charset obtained from 
   *                         RFC 2047 if <code>aOverrideCharset</code>  is set.
   * @param aOverrideCharset When set, overrides MIME charset specified 
   *                         in RFC 2047 style encoding with 
   *                         <code>aDefaultCharset</code>
   * @return                 decoded parameter 
   */

  [noscript]
   ACString decodeParameter(in ACString aParamValue,
                            in string aCharset,
                            in string aDefaultCharset,
                            in boolean aOverrideCharset);
};

