/*
 * xml.c:  xml helper code shared among the Subversion libraries.
 *
 * ====================================================================
 *    Licensed to the Apache Software Foundation (ASF) under one
 *    or more contributor license agreements.  See the NOTICE file
 *    distributed with this work for additional information
 *    regarding copyright ownership.  The ASF licenses this file
 *    to you under the Apache License, Version 2.0 (the
 *    "License"); you may not use this file except in compliance
 *    with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing,
 *    software distributed under the License is distributed on an
 *    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *    KIND, either express or implied.  See the License for the
 *    specific language governing permissions and limitations
 *    under the License.
 * ====================================================================
 */


#include <string.h>
#include <assert.h>

#include "svn_private_config.h"         /* for SVN_HAVE_OLD_EXPAT */
#include "svn_hash.h"
#include "svn_pools.h"
#include "svn_xml.h"
#include "svn_error.h"
#include "svn_ctype.h"

#include "private/svn_utf_private.h"
#include "private/svn_subr_private.h"

#ifdef SVN_HAVE_OLD_EXPAT
#include <xmlparse.h>
#else
#include <expat.h>
#endif

#ifndef XML_VERSION_AT_LEAST
#define XML_VERSION_AT_LEAST(major,minor,patch)                  \
(((major) < XML_MAJOR_VERSION)                                       \
 || ((major) == XML_MAJOR_VERSION && (minor) < XML_MINOR_VERSION)    \
 || ((major) == XML_MAJOR_VERSION && (minor) == XML_MINOR_VERSION && \
     (patch) <= XML_MICRO_VERSION))
#endif /* XML_VERSION_AT_LEAST */

#ifdef XML_UNICODE
#error Expat is unusable -- it has been compiled for wide characters
#endif

const char *
svn_xml__compiled_version(void)
{
  static const char xml_version_str[] = APR_STRINGIFY(XML_MAJOR_VERSION)
                                        "." APR_STRINGIFY(XML_MINOR_VERSION)
                                        "." APR_STRINGIFY(XML_MICRO_VERSION);

  return xml_version_str;
}

const char *
svn_xml__runtime_version(void)
{
  const char *expat_version = XML_ExpatVersion();

  if (!strncmp(expat_version, "expat_", 6))
    expat_version += 6;

  return expat_version;
}


/* The private internals for a parser object. */
struct svn_xml_parser_t
{
  /** the expat parser */
  XML_Parser parser;

  /** the SVN callbacks to call from the Expat callbacks */
  svn_xml_start_elem start_handler;
  svn_xml_end_elem end_handler;
  svn_xml_char_data data_handler;

  /** the user's baton for private data */
  void *baton;

  /** if non-@c NULL, an error happened while parsing */
  svn_error_t *error;

  /** where this object is allocated, so we can free it easily */
  apr_pool_t *pool;

};


/*** XML character validation ***/

svn_boolean_t
svn_xml_is_xml_safe(const char *data, apr_size_t len)
{
  const char *end = data + len;
  const char *p;

  if (! svn_utf__is_valid(data, len))
    return FALSE;

  for (p = data; p < end; p++)
    {
      unsigned char c = *p;

      if (svn_ctype_iscntrl(c))
        {
          if ((c != SVN_CTYPE_ASCII_TAB)
              && (c != SVN_CTYPE_ASCII_LINEFEED)
              && (c != SVN_CTYPE_ASCII_CARRIAGERETURN)
              && (c != SVN_CTYPE_ASCII_DELETE))
            return FALSE;
        }
    }
  return TRUE;
}


/*** XML escaping. ***/

/* ### ...?
 *
 * If *OUTSTR is @c NULL, set *OUTSTR to a new stringbuf allocated
 * in POOL, else append to the existing stringbuf there.
 */
static void
xml_escape_cdata(svn_stringbuf_t **outstr,
                 const char *data,
                 apr_size_t len,
                 apr_pool_t *pool)
{
  const char *end = data + len;
  const char *p = data, *q;

  if (*outstr == NULL)
    *outstr = svn_stringbuf_create_empty(pool);

  while (1)
    {
      /* Find a character which needs to be quoted and append bytes up
         to that point.  Strictly speaking, '>' only needs to be
         quoted if it follows "]]", but it's easier to quote it all
         the time.

         So, why are we escaping '\r' here?  Well, according to the
         XML spec, '\r\n' gets converted to '\n' during XML parsing.
         Also, any '\r' not followed by '\n' is converted to '\n'.  By
         golly, if we say we want to escape a '\r', we want to make
         sure it remains a '\r'!  */
      q = p;
      while (q < end && *q != '&' && *q != '<' && *q != '>' && *q != '\r')
        q++;
      svn_stringbuf_appendbytes(*outstr, p, q - p);

      /* We may already be a winner.  */
      if (q == end)
        break;

      /* Append the entity reference for the character.  */
      if (*q == '&')
        svn_stringbuf_appendcstr(*outstr, "&amp;");
      else if (*q == '<')
        svn_stringbuf_appendcstr(*outstr, "&lt;");
      else if (*q == '>')
        svn_stringbuf_appendcstr(*outstr, "&gt;");
      else if (*q == '\r')
        svn_stringbuf_appendcstr(*outstr, "&#13;");

      p = q + 1;
    }
}

/* Essentially the same as xml_escape_cdata, with the addition of
   whitespace and quote characters. */
static void
xml_escape_attr(svn_stringbuf_t **outstr,
                const char *data,
                apr_size_t len,
                apr_pool_t *pool)
{
  const char *end = data + len;
  const char *p = data, *q;

  if (*outstr == NULL)
    *outstr = svn_stringbuf_create_ensure(len, pool);

  while (1)
    {
      /* Find a character which needs to be quoted and append bytes up
         to that point. */
      q = p;
      while (q < end && *q != '&' && *q != '<' && *q != '>'
             && *q != '"' && *q != '\'' && *q != '\r'
             && *q != '\n' && *q != '\t')
        q++;
      svn_stringbuf_appendbytes(*outstr, p, q - p);

      /* We may already be a winner.  */
      if (q == end)
        break;

      /* Append the entity reference for the character.  */
      if (*q == '&')
        svn_stringbuf_appendcstr(*outstr, "&amp;");
      else if (*q == '<')
        svn_stringbuf_appendcstr(*outstr, "&lt;");
      else if (*q == '>')
        svn_stringbuf_appendcstr(*outstr, "&gt;");
      else if (*q == '"')
        svn_stringbuf_appendcstr(*outstr, "&quot;");
      else if (*q == '\'')
        svn_stringbuf_appendcstr(*outstr, "&apos;");
      else if (*q == '\r')
        svn_stringbuf_appendcstr(*outstr, "&#13;");
      else if (*q == '\n')
        svn_stringbuf_appendcstr(*outstr, "&#10;");
      else if (*q == '\t')
        svn_stringbuf_appendcstr(*outstr, "&#9;");

      p = q + 1;
    }
}


void
svn_xml_escape_cdata_stringbuf(svn_stringbuf_t **outstr,
                               const svn_stringbuf_t *string,
                               apr_pool_t *pool)
{
  xml_escape_cdata(outstr, string->data, string->len, pool);
}


void
svn_xml_escape_cdata_string(svn_stringbuf_t **outstr,
                            const svn_string_t *string,
                            apr_pool_t *pool)
{
  xml_escape_cdata(outstr, string->data, string->len, pool);
}


void
svn_xml_escape_cdata_cstring(svn_stringbuf_t **outstr,
                             const char *string,
                             apr_pool_t *pool)
{
  xml_escape_cdata(outstr, string, (apr_size_t) strlen(string), pool);
}


void
svn_xml_escape_attr_stringbuf(svn_stringbuf_t **outstr,
                              const svn_stringbuf_t *string,
                              apr_pool_t *pool)
{
  xml_escape_attr(outstr, string->data, string->len, pool);
}


void
svn_xml_escape_attr_string(svn_stringbuf_t **outstr,
                           const svn_string_t *string,
                           apr_pool_t *pool)
{
  xml_escape_attr(outstr, string->data, string->len, pool);
}


void
svn_xml_escape_attr_cstring(svn_stringbuf_t **outstr,
                            const char *string,
                            apr_pool_t *pool)
{
  xml_escape_attr(outstr, string, (apr_size_t) strlen(string), pool);
}


const char *
svn_xml_fuzzy_escape(const char *string, apr_pool_t *pool)
{
  const char *end = string + strlen(string);
  const char *p = string, *q;
  svn_stringbuf_t *outstr;
  char escaped_char[6];   /* ? \ u u u \0 */

  for (q = p; q < end; q++)
    {
      if (svn_ctype_iscntrl(*q)
          && ! ((*q == '\n') || (*q == '\r') || (*q == '\t')))
        break;
    }

  /* Return original string if no unsafe characters found. */
  if (q == end)
    return string;

  outstr = svn_stringbuf_create_empty(pool);
  while (1)
    {
      q = p;

      /* Traverse till either unsafe character or eos. */
      while ((q < end)
             && ((! svn_ctype_iscntrl(*q))
                 || (*q == '\n') || (*q == '\r') || (*q == '\t')))
        q++;

      /* copy chunk before marker */
      svn_stringbuf_appendbytes(outstr, p, q - p);

      if (q == end)
        break;

      /* Append an escaped version of the unsafe character.

         ### This format was chosen for consistency with
         ### svn_utf__cstring_from_utf8_fuzzy().  The two functions
         ### should probably share code, even though they escape
         ### different characters.
      */
      apr_snprintf(escaped_char, sizeof(escaped_char), "?\\%03u",
                   (unsigned char) *q);
      svn_stringbuf_appendcstr(outstr, escaped_char);

      p = q + 1;
    }

  return outstr->data;
}


/*** Map from the Expat callback types to the SVN XML types. ***/

static void expat_start_handler(void *userData,
                                const XML_Char *name,
                                const XML_Char **atts)
{
  svn_xml_parser_t *svn_parser = userData;

  (*svn_parser->start_handler)(svn_parser->baton, name, atts);

#if XML_VERSION_AT_LEAST(1, 95, 8)
  /* Stop XML parsing if svn_xml_signal_bailout() was called.
     We cannot do this in svn_xml_signal_bailout() because Expat
     documentation states that XML_StopParser() must be called only from
     callbacks. */
  if (svn_parser->error)
    (void) XML_StopParser(svn_parser->parser, 0 /* resumable */);
#endif
}

static void expat_end_handler(void *userData, const XML_Char *name)
{
  svn_xml_parser_t *svn_parser = userData;

  (*svn_parser->end_handler)(svn_parser->baton, name);

#if XML_VERSION_AT_LEAST(1, 95, 8)
  /* Stop XML parsing if svn_xml_signal_bailout() was called.
     We cannot do this in svn_xml_signal_bailout() because Expat
     documentation states that XML_StopParser() must be called only from
     callbacks. */
  if (svn_parser->error)
    (void) XML_StopParser(svn_parser->parser, 0 /* resumable */);
#endif
}

static void expat_data_handler(void *userData, const XML_Char *s, int len)
{
  svn_xml_parser_t *svn_parser = userData;

  (*svn_parser->data_handler)(svn_parser->baton, s, (apr_size_t)len);

#if XML_VERSION_AT_LEAST(1, 95, 8)
  /* Stop XML parsing if svn_xml_signal_bailout() was called.
     We cannot do this in svn_xml_signal_bailout() because Expat
     documentation states that XML_StopParser() must be called only from
     callbacks. */
  if (svn_parser->error)
    (void) XML_StopParser(svn_parser->parser, 0 /* resumable */);
#endif
}

#if XML_VERSION_AT_LEAST(1, 95, 8)
static void expat_entity_declaration(void *userData,
                                     const XML_Char *entityName,
                                     int is_parameter_entity,
                                     const XML_Char *value,
                                     int value_length,
                                     const XML_Char *base,
                                     const XML_Char *systemId,
                                     const XML_Char *publicId,
                                     const XML_Char *notationName)
{
  svn_xml_parser_t *svn_parser = userData;

  /* Stop the parser if an entity declaration is hit. */
  XML_StopParser(svn_parser->parser, 0 /* resumable */);
}
#else
/* A noop default_handler. */
static void expat_default_handler(void *userData, const XML_Char *s, int len)
{
}
#endif

/*** Making a parser. ***/

static apr_status_t parser_cleanup(void *data)
{
  svn_xml_parser_t *svn_parser = data;

  /* Free Expat parser. */
  if (svn_parser->parser)
    {
      XML_ParserFree(svn_parser->parser);
      svn_parser->parser = NULL;
    }
  return APR_SUCCESS;
}

svn_xml_parser_t *
svn_xml_make_parser(void *baton,
                    svn_xml_start_elem start_handler,
                    svn_xml_end_elem end_handler,
                    svn_xml_char_data data_handler,
                    apr_pool_t *pool)
{
  svn_xml_parser_t *svn_parser;
  XML_Parser parser = XML_ParserCreate(NULL);

  XML_SetElementHandler(parser,
                        start_handler ? expat_start_handler : NULL,
                        end_handler ? expat_end_handler : NULL);
  XML_SetCharacterDataHandler(parser,
                              data_handler ? expat_data_handler : NULL);

#if XML_VERSION_AT_LEAST(1, 95, 8)
  XML_SetEntityDeclHandler(parser, expat_entity_declaration);
#else
  XML_SetDefaultHandler(parser, expat_default_handler);
#endif

  svn_parser = apr_pcalloc(pool, sizeof(*svn_parser));

  svn_parser->parser = parser;
  svn_parser->start_handler = start_handler;
  svn_parser->end_handler = end_handler;
  svn_parser->data_handler = data_handler;
  svn_parser->baton = baton;
  svn_parser->pool = pool;

  /* store our parser info as the UserData in the Expat parser */
  XML_SetUserData(parser, svn_parser);

  /* Register pool cleanup handler to free Expat XML parser on cleanup,
     if svn_xml_free_parser() was not called explicitly. */
  apr_pool_cleanup_register(svn_parser->pool, svn_parser,
                            parser_cleanup, apr_pool_cleanup_null);

  return svn_parser;
}


/* Free a parser */
void
svn_xml_free_parser(svn_xml_parser_t *svn_parser)
{
  apr_pool_cleanup_run(svn_parser->pool, svn_parser, parser_cleanup);
}


svn_error_t *
svn_xml_parse(svn_xml_parser_t *svn_parser,
              const char *buf,
              apr_size_t len,
              svn_boolean_t is_final)
{
  svn_error_t *err;
  int success;

  /* Parse some xml data */
  success = XML_Parse(svn_parser->parser, buf, (int) len, is_final);

  /* Did an error occur somewhere *inside* the expat callbacks? */
  if (svn_parser->error)
    {
      /* Kill all parsers and return the error */
      svn_xml_free_parser(svn_parser);
      return svn_parser->error;
    }

  /* If expat choked internally, return its error. */
  if (! success)
    {
      /* Line num is "int" in Expat v1, "long" in v2; hide the difference. */
      long line = XML_GetCurrentLineNumber(svn_parser->parser);

      err = svn_error_createf
        (SVN_ERR_XML_MALFORMED, NULL,
         _("Malformed XML: %s at line %ld"),
         XML_ErrorString(XML_GetErrorCode(svn_parser->parser)), line);

      /* Kill all parsers and return the expat error */
      svn_xml_free_parser(svn_parser);
      return err;
    }

  return SVN_NO_ERROR;
}


void svn_xml_signal_bailout(svn_error_t *error,
                            svn_xml_parser_t *svn_parser)
{
  /* This will cause the current XML_Parse() call to finish quickly! */
  XML_SetElementHandler(svn_parser->parser, NULL, NULL);
  XML_SetCharacterDataHandler(svn_parser->parser, NULL);
#if XML_VERSION_AT_LEAST(1, 95, 8)
  XML_SetEntityDeclHandler(svn_parser->parser, NULL);
#endif
  /* Once outside of XML_Parse(), the existence of this field will
     cause svn_delta_parse()'s main read-loop to return error. */
  svn_parser->error = error;
}


/*** Attribute walking. ***/

const char *
svn_xml_get_attr_value(const char *name, const char *const *atts)
{
  while (atts && (*atts))
    {
      if (strcmp(atts[0], name) == 0)
        return atts[1];
      else
        atts += 2; /* continue looping */
    }

  /* Else no such attribute name seen. */
  return NULL;
}


/*** Printing XML ***/

void
svn_xml_make_header2(svn_stringbuf_t **str, const char *encoding,
                     apr_pool_t *pool)
{

  if (*str == NULL)
    *str = svn_stringbuf_create_empty(pool);
  svn_stringbuf_appendcstr(*str, "<?xml version=\"1.0\"");
  if (encoding)
    {
      encoding = apr_psprintf(pool, " encoding=\"%s\"", encoding);
      svn_stringbuf_appendcstr(*str, encoding);
    }
  svn_stringbuf_appendcstr(*str, "?>\n");
}


/*** Creating attribute hashes. ***/

/* Combine an existing attribute list ATTS with a HASH that itself
   represents an attribute list.  Iff PRESERVE is true, then no value
   already in HASH will be changed, else values from ATTS will
   override previous values in HASH. */
static void
amalgamate(const char **atts,
           apr_hash_t *ht,
           svn_boolean_t preserve,
           apr_pool_t *pool)
{
  const char *key;

  if (atts)
    for (key = *atts; key; key = *(++atts))
      {
        const char *val = *(++atts);
        size_t keylen;
        assert(key != NULL);
        /* kff todo: should we also insist that val be non-null here?
           Probably. */

        keylen = strlen(key);
        if (preserve && ((apr_hash_get(ht, key, keylen)) != NULL))
          continue;
        else
          apr_hash_set(ht, apr_pstrndup(pool, key, keylen), keylen,
                       val ? apr_pstrdup(pool, val) : NULL);
      }
}


apr_hash_t *
svn_xml_ap_to_hash(va_list ap, apr_pool_t *pool)
{
  apr_hash_t *ht = apr_hash_make(pool);
  const char *key;

  while ((key = va_arg(ap, char *)) != NULL)
    {
      const char *val = va_arg(ap, const char *);
      svn_hash_sets(ht, key, val);
    }

  return ht;
}


apr_hash_t *
svn_xml_make_att_hash(const char **atts, apr_pool_t *pool)
{
  apr_hash_t *ht = apr_hash_make(pool);
  amalgamate(atts, ht, 0, pool);  /* third arg irrelevant in this case */
  return ht;
}


void
svn_xml_hash_atts_overlaying(const char **atts,
                             apr_hash_t *ht,
                             apr_pool_t *pool)
{
  amalgamate(atts, ht, 0, pool);
}


void
svn_xml_hash_atts_preserving(const char **atts,
                             apr_hash_t *ht,
                             apr_pool_t *pool)
{
  amalgamate(atts, ht, 1, pool);
}


/*** Making XML tags. ***/


void
svn_xml_make_open_tag_hash(svn_stringbuf_t **str,
                           apr_pool_t *pool,
                           enum svn_xml_open_tag_style style,
                           const char *tagname,
                           apr_hash_t *attributes)
{
  apr_hash_index_t *hi;
  apr_size_t est_size = strlen(tagname) + 4 + apr_hash_count(attributes) * 30;

  if (*str == NULL)
    *str = svn_stringbuf_create_ensure(est_size, pool);

  svn_stringbuf_appendcstr(*str, "<");
  svn_stringbuf_appendcstr(*str, tagname);

  for (hi = apr_hash_first(pool, attributes); hi; hi = apr_hash_next(hi))
    {
      const void *key;
      void *val;

      apr_hash_this(hi, &key, NULL, &val);
      assert(val != NULL);

      svn_stringbuf_appendcstr(*str, "\n   ");
      svn_stringbuf_appendcstr(*str, key);
      svn_stringbuf_appendcstr(*str, "=\"");
      svn_xml_escape_attr_cstring(str, val, pool);
      svn_stringbuf_appendcstr(*str, "\"");
    }

  if (style == svn_xml_self_closing)
    svn_stringbuf_appendcstr(*str, "/");
  svn_stringbuf_appendcstr(*str, ">");
  if (style != svn_xml_protect_pcdata)
    svn_stringbuf_appendcstr(*str, "\n");
}


void
svn_xml_make_open_tag_v(svn_stringbuf_t **str,
                        apr_pool_t *pool,
                        enum svn_xml_open_tag_style style,
                        const char *tagname,
                        va_list ap)
{
  apr_pool_t *subpool = svn_pool_create(pool);
  apr_hash_t *ht = svn_xml_ap_to_hash(ap, subpool);

  svn_xml_make_open_tag_hash(str, pool, style, tagname, ht);
  svn_pool_destroy(subpool);
}


void
svn_xml_make_open_tag(svn_stringbuf_t **str,
                      apr_pool_t *pool,
                      enum svn_xml_open_tag_style style,
                      const char *tagname,
                      ...)
{
  va_list ap;

  va_start(ap, tagname);
  svn_xml_make_open_tag_v(str, pool, style, tagname, ap);
  va_end(ap);
}


void svn_xml_make_close_tag(svn_stringbuf_t **str,
                            apr_pool_t *pool,
                            const char *tagname)
{
  if (*str == NULL)
    *str = svn_stringbuf_create_empty(pool);

  svn_stringbuf_appendcstr(*str, "</");
  svn_stringbuf_appendcstr(*str, tagname);
  svn_stringbuf_appendcstr(*str, ">\n");
}