/*
Copyright (c) Fabien Ninoles <fabien@tzone.org>
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.
3. Neither the name of the University nor the names of its contributors
   may be used to endorse or promote products derived from this software
   without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
*/

#include "jsonsax.h"

#include <assert.h>

#define CASE_IS_SPACE   \
    case ' ':           \
case '\n':              \
case '\t':              \
case '\r'

#define CASE_IS_DIGIT  \
    case '0':          \
case '1':              \
case '2':              \
case '3':              \
case '4':              \
case '5':              \
case '6':              \
case '7':              \
case '8':              \
case '9'


struct _jsonsax_state
{
  struct jsonsax_backend  m_backend;
  char                    m_lastchar;
  void*                   m_data;
};

#define JSONSAX_GETCHAR(state) \
  (state)->m_backend.m_getchar((state)->m_data)
#define JSONSAX_ONERROR(state, err) \
  (state)->m_backend.m_onerror((state)->m_data, err)
#define JSONSAX_ONSTART(state,type) \
  (state)->m_backend.m_onstart((state)->m_data, type)
#define JSONSAX_ONSTOP(state,type) \
  (state)->m_backend.m_onstop((state)->m_data, type)

static int jsonsax_parsevalue(struct _jsonsax_state* state);

static int _jsonsax_getc(struct _jsonsax_state* state)
{
  int c = JSONSAX_GETCHAR(state);
  if (c > 0)
  {
    state->m_lastchar = c;
    return 0;
  };
  return -1;
}

static int _jsonsax_trim(struct _jsonsax_state* state)
{
  do
    {
      switch(state->m_lastchar)
        {
        CASE_IS_SPACE:
          break;
        default:
          return 0;
        }
    }
  while(_jsonsax_getc(state) == 0);
  return -1;
}

static int jsonsax_getc(struct _jsonsax_state* state)
{
  int err = _jsonsax_getc(state);
  if (err == 0)
  {
    return _jsonsax_trim(state);
  }
  return err;
}

int jsonsax_parsearray(struct _jsonsax_state* state)
{
    assert(state->m_lastchar == '[');
    int err = jsonsax_getc(state);
    if (err != 0) return err;
    while(jsonsax_parsevalue(state))
    {
        switch(state->m_lastchar)
        {
        case ',':
          jsonsax_getc(state);
          break;
        case ']':
          JSONSAX_ONSTOP(state, EJSONSAX_ARRAY);
          jsonsax_getc(state);
          return 0;
        default:
          JSONSAX_ONERROR(state, -1);
          return -1;
        }
    }
    if (state->m_lastchar != ']')
    {
      JSONSAX_ONERROR(state, -1);
      return -1;
    }
    JSONSAX_ONSTOP(state, EJSONSAX_ARRAY);
    jsonsax_getc(state);
    return 0;
}

int jsonsax_parsestring(struct _jsonsax_state* state)
{
    assert(state->m_lastchar == '"');
    JSONSAX_ONSTART(state, EJSONSAX_STRING);
    while(jsonsax_getc(state) == 0)
    {
        switch(state->m_lastchar)
        {
        case '\\':
          jsonsax_getc(state);
          break;
        case '"':
          JSONSAX_ONSTOP(state, EJSONSAX_STRING);
          jsonsax_getc(state);
          return 0;
        }
    }
    return -1;
}

int jsonsax_parsenumber(struct _jsonsax_state* state)
{
    assert(state->m_lastchar == '-' ||
           state->m_lastchar == '0' ||
           state->m_lastchar == '1' ||
           state->m_lastchar == '2' ||
           state->m_lastchar == '3' ||
           state->m_lastchar == '4' ||
           state->m_lastchar == '5' ||
           state->m_lastchar == '6' ||
           state->m_lastchar == '7' ||
           state->m_lastchar == '8' ||
           state->m_lastchar == '9');

    JSONSAX_ONSTART(state, EJSONSAX_NUMBER);
    while(jsonsax_getc(state) == 0)
    {
        switch(state->m_lastchar)
        {
            // TODO: lookup for correct number format.
        case 'e':
        case '-':
        case '.':
        CASE_IS_DIGIT:
            break;
        default:
          JSONSAX_ONSTOP(state, EJSONSAX_NUMBER);
          return -1;
        }
    }
    return 0;
}

int jsonsax_parseconstant(struct _jsonsax_state* state,
                          const char* constant,
                          enum EJSONSAX_TYPE etype)
{
    assert(state->m_lastchar == constant[0]);
    ++constant;
    while(jsonsax_getc(state) == 0)
    {
      if (*constant == '\0') break;
      if (*constant != state->m_lastchar) break;
      constant++;
    }

    if (*constant == '\0')
    {
      JSONSAX_ONSTOP(state, etype);
      return 0;
    }
    else
    {
      JSONSAX_ONERROR(state, -1);
      return -1;
    }
}

int jsonsax_parsenull(struct _jsonsax_state* state)
{
  return jsonsax_parseconstant(state, "null", EJSONSAX_NULL);
}

int jsonsax_parsetrue(struct _jsonsax_state* state)
{
  return jsonsax_parseconstant(state, "true", EJSONSAX_TRUE);
}

int jsonsax_parsefalse(struct _jsonsax_state* state)
{
  return jsonsax_parseconstant(state, "false", EJSONSAX_FALSE);
}

int jsonsax_parsepair(struct _jsonsax_state* state)
{
    if (state->m_lastchar != '"')
    {
      JSONSAX_ONERROR(state, -1);
      return -1;
    }
    if (jsonsax_parsestring(state) != 0)
    {
      JSONSAX_ONERROR(state, -1);
      return -1;
    }
    if (state->m_lastchar != ':')
    {
      JSONSAX_ONERROR(state, -1);
      return -1;
    }
    if (jsonsax_getc(state) != 0)
    {
      JSONSAX_ONERROR(state, -1);
      return -1;
    }
    return jsonsax_parsevalue(state);
}

static int jsonsax_parseobject(struct _jsonsax_state* state)
{
    assert(state->m_lastchar == '{');
    JSONSAX_ONSTART(state, EJSONSAX_OBJECT);
    jsonsax_getc(state);
    while(jsonsax_parsepair(state) == 0)
    {
        switch(state->m_lastchar)
        {
        case ',':
          jsonsax_getc(state);
          break;
        case '}':
          JSONSAX_ONSTOP(state, EJSONSAX_OBJECT);
          jsonsax_getc(state);
          return 0;
        default:
          JSONSAX_ONERROR(state, -1);
          return -1;
        }
    }
    if (state->m_lastchar != '}')
    {
      JSONSAX_ONERROR(state, -1);
      return -1;
    }
    JSONSAX_ONSTOP(state, EJSONSAX_OBJECT);
    jsonsax_getc(state);
    return 0;
}

static int jsonsax_parsevalue(struct _jsonsax_state* state)
{
    switch(state->m_lastchar)
    {
    case '[':
        return jsonsax_parsearray(state);
    case '{':
        return jsonsax_parseobject(state);
    case '"':
        return jsonsax_parsestring(state);
    case '-':
    CASE_IS_DIGIT:
        return jsonsax_parsenumber(state);
    case 'n':
        return jsonsax_parsenull(state);
    case 't':
        return jsonsax_parsetrue(state);
    case 'f':
        return jsonsax_parsefalse(state);
    default:
        return -1;
    }
}

static int default_onevent(void* data, enum EJSONSAX_TYPE type)
{
  return 0;
}

static void default_onerror(void* data, int error)
{
  (void)data;
  (void)error;
}

int jsonsax_parse(struct jsonsax_backend* backend, void* data)
{
  assert(backend != 0);
  assert(backend->m_getchar != 0);
  struct _jsonsax_state state;
  state.m_backend.m_getchar = backend->m_getchar;
  state.m_backend.m_onstart = backend->m_onstart ? backend->m_onstart : default_onevent;
  state.m_backend.m_onstop  = backend->m_onstop  ? backend->m_onstop  : default_onevent;
  state.m_backend.m_onerror = backend->m_onerror ? backend->m_onerror : default_onerror;
  state.m_data = data;
  state.m_lastchar = '\0';
  int err = jsonsax_getc(&state);
  if (err != 0) return err;
  err = jsonsax_parsevalue(&state);
  return err;
}

#undef CASE_IS_DIGIT
#undef CASE_IS_SPACE