/************************************************************************
*
* Copyright 2020 by Sean Conner.  All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
*
* Comments, questions and criticisms can be sent to: sean@conman.org
*
*************************************************************************/

#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#include <ctype.h>
#include <limits.h>

#include <lua.h>
#include <lauxlib.h>

#if !defined(LUA_VERSION_NUM) || LUA_VERSION_NUM < 503
#  error You need to compile against Lua 5.3 or higher
#endif

/**************************************************************************/

enum
{
  UPV_ENTITY = 1,
  UPV_UTF8   = 2,
};

struct _yycontext;

static int  readchars   (struct _yycontext *,char *,size_t);
static void tagi        (struct _yycontext *,char const *);
static void tagb        (struct _yycontext *,char const *);
static void endtag      (struct _yycontext *);
static void setfield    (struct _yycontext *,char const *);
static void deentifyn   (struct _yycontext *,char const *,int);
static void deentify    (struct _yycontext *,char const *);

#define YY_CTX_LOCAL
#define YY_PARSE(T) static T
#define YY_CTX_MEMBERS  \
  size_t       len;     \
  char const  *buffer;  \
  lua_State   *L;       \
  luaL_Buffer  buf;     \
  bool         pre;
#define YY_INPUT(yy,buf,result,max) result = readchars(yy,buf,max);

#include "html.i"

/**************************************************************************/

static int readchars(yycontext *yy,char *dest,size_t dlen)
{
  size_t xfer;

  if (dlen > INT_MAX)
    dlen = INT_MAX;

  xfer = dlen < yy->len ? dlen : yy->len;

  memcpy(dest,yy->buffer,xfer);
  yy->len    -= xfer;
  yy->buffer += xfer;

  return (int)xfer;
}

/**************************************************************************/

static void tagi(yycontext *yy,char const *tag)
{
  lua_createtable(yy->L,0,0);
  lua_pushstring(yy->L,tag);
  lua_setfield(yy->L,-2,"tag");
  lua_pushboolean(yy->L,true);
  lua_setfield(yy->L,-2,"inline");
  lua_createtable(yy->L,0,0);
  lua_setfield(yy->L,-2,"attributes");
}

/**************************************************************************/

static void tagb(yycontext *yy,char const *tag)
{
  lua_createtable(yy->L,0,0);
  lua_pushstring(yy->L,tag);
  lua_setfield(yy->L,-2,"tag");
  lua_pushboolean(yy->L,true);
  lua_setfield(yy->L,-2,"block");
  lua_createtable(yy->L,0,0);
  lua_setfield(yy->L,-2,"attributes");
}

/**************************************************************************/

static void endtag(yycontext *yy)
{
  lua_pushinteger(yy->L,luaL_len(yy->L,-2) + 1);
  lua_insert(yy->L,-2);
  lua_settable(yy->L,-3);
}

/**************************************************************************/

static void setfield(yycontext *yy,char const *name)
{
  lua_pushstring(yy->L,name);
  lua_insert(yy->L,-2);
  lua_getfield(yy->L,-3,"attributes");
  lua_insert(yy->L,-3);
  lua_settable(yy->L,-3);
  lua_pop(yy->L,1);
}

/**************************************************************************/

static void deentifyn(yycontext *yy,char const *num,int base)
{
  lua_Integer v = strtoul(num,NULL,base);
  lua_getfield(yy->L,lua_upvalueindex(UPV_UTF8),"char");
  lua_pushinteger(yy->L,v);
  lua_call(yy->L,1,1);
  luaL_addvalue(&yy->buf);
}

/**************************************************************************/

static void deentify(yycontext *yy,char const *label)
{
  lua_getfield(yy->L,lua_upvalueindex(UPV_ENTITY),label);
  luaL_addvalue(&yy->buf);
}

/**************************************************************************/

static int parse(lua_State *L)
{
  yycontext yyctx;
  int       rc;

  lua_settop(L,1);
  lua_createtable(L,0,0);

  memset(&yyctx,0,sizeof(yyctx));
  yyctx.buffer = luaL_checklstring(L,1,&yyctx.len);
  yyctx.L      = L;
  rc           = yyparse(&yyctx);
  yyrelease(&yyctx);

  if (rc == 0)
    lua_pushnil(L);
  return 1;
}

/**************************************************************************/

int luaopen_org_conman_app_mod_blog_html(lua_State *L)
{
  lua_getglobal(L,"require");
  lua_pushliteral(L,"org.conman.const.entity");
  lua_call(L,1,1);

  lua_getglobal(L,"require");
  lua_pushliteral(L,"utf8");
  lua_call(L,1,1);

  lua_pushcclosure(L,parse,2);
  return 1;
}
<!DOCTYPE html><html><head><meta charset="utf-8" /><meta name="viewport" content="width=device-width, initial-scale=1.0"><link rel="canonical" href="gemini://gemini.conman.org/extensions/mod_blog/html.c" /><title>gemini://gemini.conman.org/extensions/mod_blog/html.c</title><style>.c{max-width:80em;margin-left:auto;margin-right:auto;}.l{margin:0;color:lightgray;}.m{margin-top:0;margin-bottom:0;}.b{display:list-item;list-style-type:disc;list-style-position:inside;}</style></head><body><p class="l">-- Leo's gemini proxy</p><p class="l">-- Connecting to gemini.conman.org:1965...</p><p class="l">-- Connected</p><p class="l">-- Sending request</p><p class="l">-- Meta line: 20 text/plain; charset=us-ascii</p><p class="l">-- Response ended</p><p class="l">-- Page fetched on Sat May 18 21:24:07 2024</p></body></html>