/* OpenCOBOL Lua interface */
/* tectonics: cobc -c -I/usr/include/lua5.1 oclua.c */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

/* Include the Lua API header files. */
#include <lua.h>
#include <lauxlib.h>
#include <lualib.h>

/* Open the Lua engine and load all the default libraries */
lua_State *OCLUA_OPEN() {
    lua_State *oclua_state;
    oclua_state = lua_open();
    luaL_openlibs(oclua_state);
    return oclua_state;
}

int OCLUA_DO(lua_State *L, int which, const char *string, unsigned char *cobol, int coblen) {
    int result;
    int stacked;
    const char *retstr;
    int retlen;

    memset(cobol, ' ', coblen);
    result = ((which == 0) ? luaL_dostring(L, string) : luaL_dofile(L, string));
    if (result == 1) {
        /* error condition */
        return -1;
    } else {
        stacked = lua_gettop(L);
        if (stacked > 0) {
            /* populate cobol field with top of stack */
            retstr = lua_tolstring(L, stacked, &retlen);
            memcpy(cobol, retstr, (coblen > retlen) ? retlen : coblen);
        }
        /* return number of items on the stack */
        return stacked;
    }
}

/* by filename */
int OCLUA_DOFILE(lua_State *L, const char *filename, unsigned char *cobol, int coblen) {
    return OCLUA_DO(L, 1, filename, cobol, coblen);
}

/* by string */
int OCLUA_DOSTRING(lua_State *L, const char *string, unsigned char *cobol, int coblen) {
    return OCLUA_DO(L, 0, string, cobol, coblen);
}

/* retrieve stack item as string */
int OCLUA_GET(lua_State *L, int element, unsigned char *cobol, int coblen) {
    const char *retstr;
    int retlen;

    /* populate cobol field with top of stack */
    memset(cobol, ' ', coblen);
    retstr = lua_tolstring(L, element, &retlen);
    if (retstr == NULL) {
        return -1;
    } else {
        memcpy(cobol, retstr, (coblen > retlen) ? retlen : coblen);
        return retlen;
    }
}

/* check the stack, resize if needed, returns false if stack can't grow */
int OCLUA_STACK(lua_State *L, int extra) {
    return lua_checkstack(L, extra);
}

/* depth of Lua stack */
int OCLUA_DEPTH(lua_State *L) {
    return lua_gettop(L);
}

/* pop elements off stack */
int OCLUA_POP(lua_State *L, int elements) {
    lua_pop(L, elements);
    return lua_gettop(L);
}

/* close the engine */
void OCLUA_CLOSE(lua_State *L) {
    lua_close(L);
}