"use strict";

const {
    LUA_MULTRET,
    LUA_OPBNOT,
    LUA_OPEQ,
    LUA_OPLE,
    LUA_OPLT,
    LUA_OPUNM,
    LUA_REGISTRYINDEX,
    LUA_RIDX_GLOBALS,
    LUA_VERSION_NUM,
    constant_types: {
        LUA_NUMTAGS,
        LUA_TBOOLEAN,
        LUA_TCCL,
        LUA_TFUNCTION,
        LUA_TLCF,
        LUA_TLCL,
        LUA_TLIGHTUSERDATA,
        LUA_TLNGSTR,
        LUA_TNIL,
        LUA_TNONE,
        LUA_TNUMFLT,
        LUA_TNUMINT,
        LUA_TSHRSTR,
        LUA_TTABLE,
        LUA_TTHREAD,
        LUA_TUSERDATA
    },
    thread_status: { LUA_OK },
    from_userstring,
    to_luastring,
} = require('./defs.js');
const { api_check } = require('./llimits.js');
const ldebug    = require('./ldebug.js');
const ldo       = require('./ldo.js');
const { luaU_dump } = require('./ldump.js');
const lfunc     = require('./lfunc.js');
const lobject   = require('./lobject.js');
const lstate    = require('./lstate.js');
const {
    luaS_bless,
    luaS_new,
    luaS_newliteral
} = require('./lstring.js');
const ltm       = require('./ltm.js');
const { LUAI_MAXSTACK } = require('./luaconf.js');
const lvm       = require('./lvm.js');
const ltable    = require('./ltable.js');
const { ZIO } = require('./lzio.js');
const TValue    = lobject.TValue;
const CClosure  = lobject.CClosure;

const api_incr_top = function(L) {
    L.top++;
    api_check(L, L.top <= L.ci.top, "stack overflow");
};

const api_checknelems = function(L, n) {
    api_check(L, n < (L.top - L.ci.funcOff), "not enough elements in the stack");
};

const fengari_argcheck = function(c) {
    if (!c) throw TypeError("invalid argument");
};

const fengari_argcheckinteger = function(n) {
    fengari_argcheck(typeof n === "number" && (n|0) === n);
};

const isvalid = function(o) {
    return o !== lobject.luaO_nilobject;
};

const lua_version = function(L) {
    if (L === null) return LUA_VERSION_NUM;
    else return L.l_G.version;
};

const lua_atpanic = function(L, panicf) {
    let old = L.l_G.panic;
    L.l_G.panic = panicf;
    return old;
};

const lua_atnativeerror = function(L, errorf) {
    let old = L.l_G.atnativeerror;
    L.l_G.atnativeerror = errorf;
    return old;
};

// Return value for idx on stack
const index2addr = function(L, idx) {
    let ci = L.ci;
    if (idx > 0) {
        let o = ci.funcOff + idx;
        api_check(L, idx <= ci.top - (ci.funcOff + 1), "unacceptable index");
        if (o >= L.top) return lobject.luaO_nilobject;
        else return L.stack[o];
    } else if (idx > LUA_REGISTRYINDEX) {
        api_check(L, idx !== 0 && -idx <= L.top, "invalid index");
        return L.stack[L.top + idx];
    } else if (idx === LUA_REGISTRYINDEX) {
        return L.l_G.l_registry;
    } else { /* upvalues */
        idx = LUA_REGISTRYINDEX - idx;
        api_check(L, idx <= lfunc.MAXUPVAL + 1, "upvalue index too large");
        if (ci.func.ttislcf()) /* light C function? */
            return lobject.luaO_nilobject; /* it has no upvalues */
        else {
            return idx <= ci.func.value.nupvalues ? ci.func.value.upvalue[idx - 1] : lobject.luaO_nilobject;
        }
    }
};

// Like index2addr but returns the index on stack; doesn't allow pseudo indices
const index2addr_ = function(L, idx) {
    let ci = L.ci;
    if (idx > 0) {
        let o = ci.funcOff + idx;
        api_check(L, idx <= ci.top - (ci.funcOff + 1), "unacceptable index");
        if (o >= L.top) return null;
        else return o;
    } else if (idx > LUA_REGISTRYINDEX) {
        api_check(L, idx !== 0 && -idx <= L.top, "invalid index");
        return L.top + idx;
    } else { /* registry or upvalue */
        throw Error("attempt to use pseudo-index");
    }
};

const lua_checkstack = function(L, n) {
    let res;
    let ci = L.ci;
    api_check(L, n >= 0, "negative 'n'");
    if (L.stack_last - L.top > n) /* stack large enough? */
        res = true;
    else { /* no; need to grow stack */
        let inuse = L.top + lstate.EXTRA_STACK;
        if (inuse > LUAI_MAXSTACK - n)  /* can grow without overflow? */
            res = false;  /* no */
        else { /* try to grow stack */
            ldo.luaD_growstack(L, n);
            res = true;
        }
    }

    if (res && ci.top < L.top + n)
        ci.top = L.top + n;  /* adjust frame top */

    return res;
};

const lua_xmove = function(from, to, n) {
    if (from === to) return;
    api_checknelems(from, n);
    api_check(from, from.l_G === to.l_G, "moving among independent states");
    api_check(from, to.ci.top - to.top >= n, "stack overflow");
    from.top -= n;
    for (let i = 0; i < n; i++) {
        to.stack[to.top] = new lobject.TValue();
        lobject.setobj2s(to, to.top, from.stack[from.top + i]);
        delete from.stack[from.top + i];
        to.top++;
    }
};

/*
** basic stack manipulation
*/

/*
** convert an acceptable stack index into an absolute index
*/
const lua_absindex = function(L, idx) {
    return (idx > 0 || idx <= LUA_REGISTRYINDEX)
        ? idx
        : (L.top - L.ci.funcOff) + idx;
};

const lua_gettop = function(L) {
    return L.top - (L.ci.funcOff + 1);
};

const lua_pushvalue = function(L, idx) {
    lobject.pushobj2s(L, index2addr(L, idx));
    api_check(L, L.top <= L.ci.top, "stack overflow");
};

const lua_settop = function(L, idx) {
    let func = L.ci.funcOff;
    let newtop;
    if (idx >= 0) {
        api_check(L, idx <= L.stack_last - (func + 1), "new top too large");
        newtop = func + 1 + idx;
    } else {
        api_check(L, -(idx + 1) <= L.top - (func + 1), "invalid new top");
        newtop = L.top + idx + 1; /* 'subtract' index (index is negative) */
    }
    ldo.adjust_top(L, newtop);
};

const lua_pop = function(L, n) {
    lua_settop(L, -n - 1);
};

const reverse = function(L, from, to) {
    for (; from < to; from++, to--) {
        let fromtv = L.stack[from];
        let temp = new TValue(fromtv.type, fromtv.value);
        lobject.setobjs2s(L, from, to);
        lobject.setobj2s(L, to, temp);
    }
};

/*
** Let x = AB, where A is a prefix of length 'n'. Then,
** rotate x n === BA. But BA === (A^r . B^r)^r.
*/
const lua_rotate = function(L, idx, n) {
    let t = L.top - 1;
    let pIdx = index2addr_(L, idx);
    let p = L.stack[pIdx];
    api_check(L, isvalid(p) && idx > LUA_REGISTRYINDEX, "index not in the stack");
    api_check(L, (n >= 0 ? n : -n) <= (t - pIdx + 1), "invalid 'n'");
    let m = n >= 0 ? t - n : pIdx - n - 1;  /* end of prefix */
    reverse(L, pIdx, m);
    reverse(L, m + 1, L.top - 1);
    reverse(L, pIdx, L.top - 1);
};

const lua_copy = function(L, fromidx, toidx) {
    let from = index2addr(L, fromidx);
    index2addr(L, toidx).setfrom(from);
};

const lua_remove = function(L, idx) {
    lua_rotate(L, idx, -1);
    lua_pop(L, 1);
};

const lua_insert = function(L, idx) {
    lua_rotate(L, idx, 1);
};

const lua_replace = function(L, idx) {
    lua_copy(L, -1, idx);
    lua_pop(L, 1);
};

/*
** push functions (JS -> stack)
*/

const lua_pushnil = function(L) {
    L.stack[L.top] = new TValue(LUA_TNIL, null);
    api_incr_top(L);
};

const lua_pushnumber = function(L, n) {
    fengari_argcheck(typeof n === "number");
    L.stack[L.top] = new TValue(LUA_TNUMFLT, n);
    api_incr_top(L);
};

const lua_pushinteger = function(L, n) {
    fengari_argcheckinteger(n);
    L.stack[L.top] = new TValue(LUA_TNUMINT, n);
    api_incr_top(L);
};

const lua_pushlstring = function(L, s, len) {
    fengari_argcheckinteger(len);
    let ts;
    if (len === 0) {
        s = to_luastring("", true);
        ts = luaS_bless(L, s);
    } else {
        s = from_userstring(s);
        api_check(L, s.length >= len, "invalid length to lua_pushlstring");
        ts = luaS_new(L, s.subarray(0, len));
    }
    lobject.pushsvalue2s(L, ts);
    api_check(L, L.top <= L.ci.top, "stack overflow");
    return ts.value;
};

const lua_pushstring = function (L, s) {
    if (s === undefined || s === null) {
        L.stack[L.top] = new TValue(LUA_TNIL, null);
        L.top++;
    } else {
        let ts = luaS_new(L, from_userstring(s));
        lobject.pushsvalue2s(L, ts);
        s = ts.getstr(); /* internal copy */
    }
    api_check(L, L.top <= L.ci.top, "stack overflow");
    return s;
};

const lua_pushvfstring = function (L, fmt, argp) {
    fmt = from_userstring(fmt);
    return lobject.luaO_pushvfstring(L, fmt, argp);
};

const lua_pushfstring = function (L, fmt, ...argp) {
    fmt = from_userstring(fmt);
    return lobject.luaO_pushvfstring(L, fmt, argp);
};

/* Similar to lua_pushstring, but takes a JS string */
const lua_pushliteral = function (L, s) {
    if (s === undefined || s === null) {
        L.stack[L.top] = new TValue(LUA_TNIL, null);
        L.top++;
    } else {
        fengari_argcheck(typeof s === "string");
        let ts = luaS_newliteral(L, s);
        lobject.pushsvalue2s(L, ts);
        s = ts.getstr(); /* internal copy */
    }
    api_check(L, L.top <= L.ci.top, "stack overflow");

    return s;
};

const lua_pushcclosure = function(L, fn, n) {
    fengari_argcheck(typeof fn === "function");
    fengari_argcheckinteger(n);
    if (n === 0)
        L.stack[L.top] = new TValue(LUA_TLCF, fn);
    else {
        api_checknelems(L, n);
        api_check(L, n <= lfunc.MAXUPVAL, "upvalue index too large");
        let cl = new CClosure(L, fn, n);
        for (let i=0; i<n; i++)
            cl.upvalue[i].setfrom(L.stack[L.top - n + i]);
        for (let i=1; i<n; i++)
            delete L.stack[--L.top];
        if (n>0)
            --L.top;
        L.stack[L.top].setclCvalue(cl);
    }
    api_incr_top(L);
};

const lua_pushjsclosure = lua_pushcclosure;

const lua_pushcfunction = function(L, fn) {
    lua_pushcclosure(L, fn, 0);
};

const lua_pushjsfunction = lua_pushcfunction;

const lua_pushboolean = function(L, b) {
    L.stack[L.top] = new TValue(LUA_TBOOLEAN, !!b);
    api_incr_top(L);
};

const lua_pushlightuserdata = function(L, p) {
    L.stack[L.top] = new TValue(LUA_TLIGHTUSERDATA, p);
    api_incr_top(L);
};

const lua_pushthread = function(L) {
    L.stack[L.top] = new TValue(LUA_TTHREAD, L);
    api_incr_top(L);
    return L.l_G.mainthread === L;
};

const lua_pushglobaltable = function(L) {
    lua_rawgeti(L, LUA_REGISTRYINDEX, LUA_RIDX_GLOBALS);
};

/*
** set functions (stack -> Lua)
*/

/*
** t[k] = value at the top of the stack (where 'k' is a string)
*/
const auxsetstr = function(L, t, k) {
    let str = luaS_new(L, from_userstring(k));
    api_checknelems(L, 1);
    lobject.pushsvalue2s(L, str); /* push 'str' (to make it a TValue) */
    api_check(L, L.top <= L.ci.top, "stack overflow");
    lvm.settable(L, t, L.stack[L.top - 1], L.stack[L.top - 2]);
    /* pop value and key */
    delete L.stack[--L.top];
    delete L.stack[--L.top];
};

const lua_setglobal = function(L, name) {
    auxsetstr(L, ltable.luaH_getint(L.l_G.l_registry.value, LUA_RIDX_GLOBALS), name);
};

const lua_setmetatable = function(L, objindex) {
    api_checknelems(L, 1);
    let mt;
    let obj = index2addr(L, objindex);
    if (L.stack[L.top - 1].ttisnil())
        mt = null;
    else {
        api_check(L, L.stack[L.top - 1].ttistable(), "table expected");
        mt = L.stack[L.top - 1].value;
    }

    switch (obj.ttnov()) {
        case LUA_TUSERDATA:
        case LUA_TTABLE: {
            obj.value.metatable = mt;
            break;
        }
        default: {
            L.l_G.mt[obj.ttnov()] = mt;
            break;
        }
    }

    delete L.stack[--L.top];
    return true;
};

const lua_settable = function(L, idx) {
    api_checknelems(L, 2);
    let t = index2addr(L, idx);
    lvm.settable(L, t, L.stack[L.top - 2], L.stack[L.top - 1]);
    delete L.stack[--L.top];
    delete L.stack[--L.top];
};

const lua_setfield = function(L, idx, k) {
    auxsetstr(L, index2addr(L, idx), k);
};

const lua_seti = function(L, idx, n) {
    fengari_argcheckinteger(n);
    api_checknelems(L, 1);
    let t = index2addr(L, idx);
    L.stack[L.top] = new TValue(LUA_TNUMINT, n);
    api_incr_top(L);
    lvm.settable(L, t, L.stack[L.top - 1], L.stack[L.top - 2]);
    /* pop value and key */
    delete L.stack[--L.top];
    delete L.stack[--L.top];
};

const lua_rawset = function(L, idx) {
    api_checknelems(L, 2);
    let o = index2addr(L, idx);
    api_check(L, o.ttistable(), "table expected");
    let k = L.stack[L.top - 2];
    let v = L.stack[L.top - 1];
    if (v.ttisnil()) {
        ltable.luaH_delete(L, o.value, k);
    } else {
        let slot = ltable.luaH_set(L, o.value, k);
        slot.setfrom(v);
    }
    ltable.invalidateTMcache(o.value);
    delete L.stack[--L.top];
    delete L.stack[--L.top];
};

const lua_rawseti = function(L, idx, n) {
    fengari_argcheckinteger(n);
    api_checknelems(L, 1);
    let o = index2addr(L, idx);
    api_check(L, o.ttistable(), "table expected");
    ltable.luaH_setint(o.value, n, L.stack[L.top - 1]);
    delete L.stack[--L.top];
};

const lua_rawsetp = function(L, idx, p) {
    api_checknelems(L, 1);
    let o = index2addr(L, idx);
    api_check(L, o.ttistable(), "table expected");
    let k = new TValue(LUA_TLIGHTUSERDATA, p);
    let v = L.stack[L.top - 1];
    if (v.ttisnil()) {
        ltable.luaH_delete(L, o.value, k);
    } else {
        let slot = ltable.luaH_set(L, o.value, k);
        slot.setfrom(v);
    }
    delete L.stack[--L.top];
};

/*
** get functions (Lua -> stack)
*/

const auxgetstr = function(L, t, k) {
    let str = luaS_new(L, from_userstring(k));
    lobject.pushsvalue2s(L, str);
    api_check(L, L.top <= L.ci.top, "stack overflow");
    lvm.luaV_gettable(L, t, L.stack[L.top - 1], L.top - 1);
    return L.stack[L.top - 1].ttnov();
};

const lua_rawgeti = function(L, idx, n) {
    let t = index2addr(L, idx);
    fengari_argcheckinteger(n);
    api_check(L, t.ttistable(), "table expected");
    lobject.pushobj2s(L, ltable.luaH_getint(t.value, n));
    api_check(L, L.top <= L.ci.top, "stack overflow");
    return L.stack[L.top - 1].ttnov();
};

const lua_rawgetp = function(L, idx, p) {
    let t = index2addr(L, idx);
    api_check(L, t.ttistable(), "table expected");
    let k = new TValue(LUA_TLIGHTUSERDATA, p);
    lobject.pushobj2s(L, ltable.luaH_get(L, t.value, k));
    api_check(L, L.top <= L.ci.top, "stack overflow");
    return L.stack[L.top - 1].ttnov();
};

const lua_rawget = function(L, idx) {
    let t = index2addr(L, idx);
    api_check(L, t.ttistable(t), "table expected");
    lobject.setobj2s(L, L.top - 1, ltable.luaH_get(L, t.value, L.stack[L.top - 1]));
    return L.stack[L.top - 1].ttnov();
};

// narray and nrec are mostly useless for this implementation
const lua_createtable = function(L, narray, nrec) {
    let t = new lobject.TValue(LUA_TTABLE, ltable.luaH_new(L));
    L.stack[L.top] = t;
    api_incr_top(L);
};

const luaS_newudata = function(L, size) {
    return new lobject.Udata(L, size);
};

const lua_newuserdata = function(L, size) {
    let u = luaS_newudata(L, size);
    L.stack[L.top] = new lobject.TValue(LUA_TUSERDATA, u);
    api_incr_top(L);
    return u.data;
};

const aux_upvalue = function(L, fi, n) {
    fengari_argcheckinteger(n);
    switch(fi.ttype()) {
        case LUA_TCCL: {  /* C closure */
            let f = fi.value;
            if (!(1 <= n && n <= f.nupvalues)) return null;
            return {
                name: to_luastring("", true),
                val: f.upvalue[n-1]
            };
        }
        case LUA_TLCL: {  /* Lua closure */
            let f = fi.value;
            let p = f.p;
            if (!(1 <= n && n <= p.upvalues.length)) return null;
            let name = p.upvalues[n-1].name;
            return {
                name: name ? name.getstr() : to_luastring("(*no name)", true),
                val: f.upvals[n-1]
            };
        }
        default: return null;  /* not a closure */
    }
};

const lua_getupvalue = function(L, funcindex, n) {
    let up = aux_upvalue(L, index2addr(L, funcindex), n);
    if (up) {
        let name = up.name;
        let val = up.val;
        lobject.pushobj2s(L, val);
        api_check(L, L.top <= L.ci.top, "stack overflow");
        return name;
    }
    return null;
};

const lua_setupvalue = function(L, funcindex, n) {
    let fi = index2addr(L, funcindex);
    api_checknelems(L, 1);
    let aux = aux_upvalue(L, fi, n);
    if (aux) {
        let name = aux.name;
        let val = aux.val;
        val.setfrom(L.stack[L.top-1]);
        delete L.stack[--L.top];
        return name;
    }
    return null;
};

const lua_newtable = function(L) {
    lua_createtable(L, 0, 0);
};

const lua_register = function(L, n, f) {
    lua_pushcfunction(L, f);
    lua_setglobal(L, n);
};

const lua_getmetatable = function(L, objindex) {
    let obj = index2addr(L, objindex);
    let mt;
    let res = false;
    switch (obj.ttnov()) {
        case LUA_TTABLE:
        case LUA_TUSERDATA:
            mt = obj.value.metatable;
            break;
        default:
            mt = L.l_G.mt[obj.ttnov()];
            break;
    }

    if (mt !== null && mt !== undefined) {
        L.stack[L.top] = new TValue(LUA_TTABLE, mt);
        api_incr_top(L);
        res = true;
    }

    return res;
};

const lua_getuservalue = function(L, idx) {
    let o = index2addr(L, idx);
    api_check(L, o.ttisfulluserdata(), "full userdata expected");
    let uv = o.value.uservalue;
    L.stack[L.top] = new TValue(uv.type, uv.value);
    api_incr_top(L);
    return L.stack[L.top - 1].ttnov();
};

const lua_gettable = function(L, idx) {
    let t = index2addr(L, idx);
    lvm.luaV_gettable(L, t, L.stack[L.top - 1], L.top - 1);
    return L.stack[L.top - 1].ttnov();
};

const lua_getfield = function(L, idx, k) {
    return auxgetstr(L, index2addr(L, idx), k);
};

const lua_geti = function(L, idx, n) {
    let t = index2addr(L, idx);
    fengari_argcheckinteger(n);
    L.stack[L.top] = new TValue(LUA_TNUMINT, n);
    api_incr_top(L);
    lvm.luaV_gettable(L, t, L.stack[L.top - 1], L.top - 1);
    return L.stack[L.top - 1].ttnov();
};

const lua_getglobal = function(L, name) {
    return auxgetstr(L, ltable.luaH_getint(L.l_G.l_registry.value, LUA_RIDX_GLOBALS), name);
};

/*
** access functions (stack -> JS)
*/

const lua_toboolean = function(L, idx) {
    let o = index2addr(L, idx);
    return !o.l_isfalse();
};

const lua_tolstring = function(L, idx) {
    let o = index2addr(L, idx);

    if (!o.ttisstring()) {
        if (!lvm.cvt2str(o)) {  /* not convertible? */
            return null;
        }
        lobject.luaO_tostring(L, o);
    }
    return o.svalue();
};

const lua_tostring =  lua_tolstring;

const lua_tojsstring = function(L, idx) {
    let o = index2addr(L, idx);

    if (!o.ttisstring()) {
        if (!lvm.cvt2str(o)) {  /* not convertible? */
            return null;
        }
        lobject.luaO_tostring(L, o);
    }
    return o.jsstring();
};

const lua_todataview = function(L, idx) {
    let u8 = lua_tolstring(L, idx);
    return new DataView(u8.buffer, u8.byteOffset, u8.byteLength);
};

const lua_rawlen = function(L, idx) {
    let o = index2addr(L, idx);
    switch (o.ttype()) {
        case LUA_TSHRSTR:
        case LUA_TLNGSTR:
            return o.vslen();
        case LUA_TUSERDATA:
            return o.value.len;
        case LUA_TTABLE:
            return ltable.luaH_getn(o.value);
        default:
            return 0;
    }
};

const lua_tocfunction = function(L, idx) {
    let o = index2addr(L, idx);
    if (o.ttislcf() || o.ttisCclosure()) return o.value;
    else return null;  /* not a C function */
};

const lua_tointeger = function(L, idx) {
    let n = lua_tointegerx(L, idx);
    return n === false ? 0 : n;
};

const lua_tointegerx = function(L, idx) {
    return lvm.tointeger(index2addr(L, idx));
};

const lua_tonumber = function(L, idx) {
    let n = lua_tonumberx(L, idx);
    return n === false ? 0 : n;
};

const lua_tonumberx = function(L, idx) {
    return lvm.tonumber(index2addr(L, idx));
};

const lua_touserdata = function(L, idx) {
    let o = index2addr(L, idx);
    switch (o.ttnov()) {
        case LUA_TUSERDATA:
            return o.value.data;
        case LUA_TLIGHTUSERDATA:
            return o.value;
        default: return null;
    }
};

const lua_tothread = function(L, idx) {
    let o = index2addr(L, idx);
    return o.ttisthread() ? o.value : null;
};

const lua_topointer = function(L, idx) {
    let o = index2addr(L, idx);
    switch (o.ttype()) {
        case LUA_TTABLE:
        case LUA_TLCL:
        case LUA_TCCL:
        case LUA_TLCF:
        case LUA_TTHREAD:
        case LUA_TUSERDATA: /* note: this differs in behaviour to reference lua implementation */
        case LUA_TLIGHTUSERDATA:
            return o.value;
        default:
            return null;
    }
};


/* A proxy is a function that the same lua value to the given lua state. */

/* Having a weakmap of created proxies was only way I could think of to provide an 'isproxy' function */
const seen = new WeakMap();

/* is the passed object a proxy? is it from the given state? (if passed) */
const lua_isproxy = function(p, L) {
    let G = seen.get(p);
    if (!G)
        return false;
    return (L === null) || (L.l_G === G);
};

/* Use 'create_proxy' helper function so that 'L' is not in scope */
const create_proxy = function(G, type, value) {
    let proxy = function(L) {
        api_check(L, L instanceof lstate.lua_State && G === L.l_G, "must be from same global state");
        L.stack[L.top] = new TValue(type, value);
        api_incr_top(L);
    };
    seen.set(proxy, G);
    return proxy;
};

const lua_toproxy = function(L, idx) {
    let tv = index2addr(L, idx);
    /* pass broken down tv incase it is an upvalue index */
    return create_proxy(L.l_G, tv.type, tv.value);
};


const lua_compare = function(L, index1, index2, op) {
    let o1 = index2addr(L, index1);
    let o2 = index2addr(L, index2);

    let i = 0;

    if (isvalid(o1) && isvalid(o2)) {
        switch (op) {
            case LUA_OPEQ: i = lvm.luaV_equalobj(L, o1, o2); break;
            case LUA_OPLT: i = lvm.luaV_lessthan(L, o1, o2); break;
            case LUA_OPLE: i = lvm.luaV_lessequal(L, o1, o2); break;
            default: api_check(L, false, "invalid option");
        }
    }

    return i;
};

const lua_stringtonumber = function(L, s) {
    let tv = new TValue();
    let sz = lobject.luaO_str2num(s, tv);
    if (sz !== 0) {
        L.stack[L.top] = tv;
        api_incr_top(L);
    }
    return sz;
};

const f_call = function(L, ud) {
    ldo.luaD_callnoyield(L, ud.funcOff, ud.nresults);
};

const lua_type = function(L, idx) {
    let o = index2addr(L, idx);
    return isvalid(o) ?  o.ttnov() : LUA_TNONE;
};

const lua_typename = function(L, t) {
    api_check(L, LUA_TNONE <= t && t < LUA_NUMTAGS, "invalid tag");
    return ltm.ttypename(t);
};

const lua_iscfunction = function(L, idx) {
    let o = index2addr(L, idx);
    return o.ttislcf(o) || o.ttisCclosure();
};

const lua_isnil = function(L, n) {
    return lua_type(L, n) === LUA_TNIL;
};

const lua_isboolean = function(L, n) {
    return lua_type(L, n) === LUA_TBOOLEAN;
};

const lua_isnone = function(L, n) {
    return lua_type(L, n) === LUA_TNONE;
};

const lua_isnoneornil = function(L, n) {
    return lua_type(L, n) <= 0;
};

const lua_istable = function(L, idx) {
    return index2addr(L, idx).ttistable();
};

const lua_isinteger = function(L, idx) {
    return index2addr(L, idx).ttisinteger();
};

const lua_isnumber = function(L, idx) {
    return lvm.tonumber(index2addr(L, idx)) !== false;
};

const lua_isstring = function(L, idx) {
    let o = index2addr(L, idx);
    return o.ttisstring() || lvm.cvt2str(o);
};

const lua_isuserdata = function(L, idx) {
    let o = index2addr(L, idx);
    return o.ttisfulluserdata(o) || o.ttislightuserdata();
};

const lua_isthread = function(L, idx) {
    return lua_type(L, idx) === LUA_TTHREAD;
};

const lua_isfunction = function(L, idx) {
    return lua_type(L, idx) === LUA_TFUNCTION;
};

const lua_islightuserdata = function(L, idx) {
    return lua_type(L, idx) === LUA_TLIGHTUSERDATA;
};

const lua_rawequal = function(L, index1, index2) {
    let o1 = index2addr(L, index1);
    let o2 = index2addr(L, index2);
    return isvalid(o1) && isvalid(o2) ? lvm.luaV_equalobj(null, o1, o2) : 0;
};

const lua_arith = function(L, op) {
    if (op !== LUA_OPUNM && op !== LUA_OPBNOT)
        api_checknelems(L, 2);  /* all other operations expect two operands */
    else {  /* for unary operations, add fake 2nd operand */
        api_checknelems(L, 1);
        lobject.pushobj2s(L, L.stack[L.top-1]);
        api_check(L, L.top <= L.ci.top, "stack overflow");
    }
    /* first operand at top - 2, second at top - 1; result go to top - 2 */
    lobject.luaO_arith(L, op, L.stack[L.top - 2], L.stack[L.top - 1], L.stack[L.top - 2]);
    delete L.stack[--L.top];  /* remove second operand */
};

/*
** 'load' and 'call' functions (run Lua code)
*/

const default_chunkname = to_luastring("?");
const lua_load = function(L, reader, data, chunkname, mode) {
    if (!chunkname) chunkname = default_chunkname;
    else chunkname = from_userstring(chunkname);
    if (mode !== null) mode = from_userstring(mode);
    let z = new ZIO(L, reader, data);
    let status = ldo.luaD_protectedparser(L, z, chunkname, mode);
    if (status === LUA_OK) {  /* no errors? */
        let f = L.stack[L.top - 1].value; /* get newly created function */
        if (f.nupvalues >= 1) {  /* does it have an upvalue? */
            /* get global table from registry */
            let gt = ltable.luaH_getint(L.l_G.l_registry.value, LUA_RIDX_GLOBALS);
            /* set global table as 1st upvalue of 'f' (may be LUA_ENV) */
            f.upvals[0].setfrom(gt);
        }
    }
    return status;
};

const lua_dump = function(L, writer, data, strip) {
    api_checknelems(L, 1);
    let o = L.stack[L.top -1];
    if (o.ttisLclosure())
        return luaU_dump(L, o.value.p, writer, data, strip);
    return 1;
};

const lua_status = function(L) {
    return L.status;
};

const lua_setuservalue = function(L, idx) {
    api_checknelems(L, 1);
    let o = index2addr(L, idx);
    api_check(L, o.ttisfulluserdata(), "full userdata expected");
    o.value.uservalue.setfrom(L.stack[L.top - 1]);
    delete L.stack[--L.top];
};

const checkresults = function(L,na,nr) {
    api_check(L, nr === LUA_MULTRET || (L.ci.top - L.top >= (nr) - (na)),
        "results from function overflow current stack size");
};

const lua_callk = function(L, nargs, nresults, ctx, k) {
    api_check(L, k === null || !(L.ci.callstatus & lstate.CIST_LUA), "cannot use continuations inside hooks");
    api_checknelems(L, nargs + 1);
    api_check(L, L.status === LUA_OK, "cannot do calls on non-normal thread");
    checkresults(L, nargs, nresults);
    let func = L.top - (nargs + 1);
    if (k !== null && L.nny === 0) { /* need to prepare continuation? */
        L.ci.c_k = k;
        L.ci.c_ctx = ctx;
        ldo.luaD_call(L, func, nresults);
    } else { /* no continuation or no yieldable */
        ldo.luaD_callnoyield(L, func, nresults);
    }

    if (nresults === LUA_MULTRET && L.ci.top < L.top)
        L.ci.top = L.top;
};

const lua_call = function(L, n, r) {
    lua_callk(L, n, r, 0, null);
};

const lua_pcallk = function(L, nargs, nresults, errfunc, ctx, k) {
    api_check(L, k === null || !(L.ci.callstatus & lstate.CIST_LUA), "cannot use continuations inside hooks");
    api_checknelems(L, nargs + 1);
    api_check(L, L.status === LUA_OK, "cannot do calls on non-normal thread");
    checkresults(L, nargs, nresults);
    let status;
    let func;
    if (errfunc === 0)
        func = 0;
    else {
        func = index2addr_(L, errfunc);
    }
    let funcOff = L.top - (nargs + 1); /* function to be called */
    if (k === null || L.nny > 0) { /* no continuation or no yieldable? */
        let c = {
            funcOff: funcOff,
            nresults: nresults /* do a 'conventional' protected call */
        };
        status = ldo.luaD_pcall(L, f_call, c, funcOff, func);
    } else { /* prepare continuation (call is already protected by 'resume') */
        let ci = L.ci;
        ci.c_k = k;  /* prepare continuation (call is already protected by 'resume') */
        ci.c_ctx = ctx;  /* prepare continuation (call is already protected by 'resume') */
        /* save information for error recovery */
        ci.extra = funcOff;
        ci.c_old_errfunc = L.errfunc;
        L.errfunc = func;
        ci.callstatus &= ~lstate.CIST_OAH | L.allowhook;
        ci.callstatus |= lstate.CIST_YPCALL;  /* function can do error recovery */
        ldo.luaD_call(L, funcOff, nresults);  /* do the call */
        ci.callstatus &= ~lstate.CIST_YPCALL;
        L.errfunc = ci.c_old_errfunc;
        status = LUA_OK;
    }

    if (nresults === LUA_MULTRET && L.ci.top < L.top)
        L.ci.top = L.top;

    return status;
};

const lua_pcall = function(L, n, r, f) {
    return lua_pcallk(L, n, r, f, 0, null);
};

/*
** miscellaneous functions
*/

const lua_error = function(L) {
    api_checknelems(L, 1);
    ldebug.luaG_errormsg(L);
};

const lua_next = function(L, idx) {
    let t = index2addr(L, idx);
    api_check(L, t.ttistable(), "table expected");
    L.stack[L.top] = new TValue();
    let more = ltable.luaH_next(L, t.value, L.top - 1);
    if (more) {
        api_incr_top(L);
        return 1;
    } else {
        delete L.stack[L.top];
        delete L.stack[--L.top];
        return 0;
    }
};

const lua_concat = function(L, n) {
    api_checknelems(L, n);
    if (n >= 2)
        lvm.luaV_concat(L, n);
    else if (n === 0) {
        lobject.pushsvalue2s(L, luaS_bless(L, to_luastring("", true)));
        api_check(L, L.top <= L.ci.top, "stack overflow");
    }
};

const lua_len = function(L, idx) {
    let t = index2addr(L, idx);
    let tv = new TValue();
    lvm.luaV_objlen(L, tv, t);
    L.stack[L.top] = tv;
    api_incr_top(L);
};

const getupvalref = function(L, fidx, n) {
    let fi = index2addr(L, fidx);
    api_check(L, fi.ttisLclosure(), "Lua function expected");
    let f = fi.value;
    fengari_argcheckinteger(n);
    api_check(L, 1 <= n && n <= f.p.upvalues.length, "invalid upvalue index");
    return {
        f: f,
        i: n - 1
    };
};

const lua_upvalueid = function(L, fidx, n) {
    let fi = index2addr(L, fidx);
    switch (fi.ttype()) {
        case LUA_TLCL: {  /* lua closure */
            let ref = getupvalref(L, fidx, n);
            return ref.f.upvals[ref.i];
        }
        case LUA_TCCL: {  /* C closure */
            let f = fi.value;
            api_check(L, n|0 === n && 1 <= n && n <= f.nupvalues, "invalid upvalue index");
            return f.upvalue[n - 1];
        }
        default: {
            api_check(L, false, "closure expected");
            return null;
        }
    }
};

const lua_upvaluejoin = function(L, fidx1, n1, fidx2, n2) {
    let ref1 = getupvalref(L, fidx1, n1);
    let ref2 = getupvalref(L, fidx2, n2);
    let up2 = ref2.f.upvals[ref2.i];
    ref1.f.upvals[ref1.i] = up2;
};

// This functions are only there for compatibility purposes
const lua_gc = function () {};

const lua_getallocf = function () {
    console.warn("lua_getallocf is not available");
    return 0;
};

const lua_setallocf = function () {
    console.warn("lua_setallocf is not available");
    return 0;
};

const lua_getextraspace = function () {
    console.warn("lua_getextraspace is not available");
    return 0;
};

module.exports.api_incr_top          = api_incr_top;
module.exports.api_checknelems       = api_checknelems;
module.exports.lua_absindex          = lua_absindex;
module.exports.lua_arith             = lua_arith;
module.exports.lua_atpanic           = lua_atpanic;
module.exports.lua_atnativeerror     = lua_atnativeerror;
module.exports.lua_call              = lua_call;
module.exports.lua_callk             = lua_callk;
module.exports.lua_checkstack        = lua_checkstack;
module.exports.lua_compare           = lua_compare;
module.exports.lua_concat            = lua_concat;
module.exports.lua_copy              = lua_copy;
module.exports.lua_createtable       = lua_createtable;
module.exports.lua_dump              = lua_dump;
module.exports.lua_error             = lua_error;
module.exports.lua_gc                = lua_gc;
module.exports.lua_getallocf         = lua_getallocf;
module.exports.lua_getextraspace     = lua_getextraspace;
module.exports.lua_getfield          = lua_getfield;
module.exports.lua_getglobal         = lua_getglobal;
module.exports.lua_geti              = lua_geti;
module.exports.lua_getmetatable      = lua_getmetatable;
module.exports.lua_gettable          = lua_gettable;
module.exports.lua_gettop            = lua_gettop;
module.exports.lua_getupvalue        = lua_getupvalue;
module.exports.lua_getuservalue      = lua_getuservalue;
module.exports.lua_insert            = lua_insert;
module.exports.lua_isboolean         = lua_isboolean;
module.exports.lua_iscfunction       = lua_iscfunction;
module.exports.lua_isfunction        = lua_isfunction;
module.exports.lua_isinteger         = lua_isinteger;
module.exports.lua_islightuserdata   = lua_islightuserdata;
module.exports.lua_isnil             = lua_isnil;
module.exports.lua_isnone            = lua_isnone;
module.exports.lua_isnoneornil       = lua_isnoneornil;
module.exports.lua_isnumber          = lua_isnumber;
module.exports.lua_isproxy           = lua_isproxy;
module.exports.lua_isstring          = lua_isstring;
module.exports.lua_istable           = lua_istable;
module.exports.lua_isthread          = lua_isthread;
module.exports.lua_isuserdata        = lua_isuserdata;
module.exports.lua_len               = lua_len;
module.exports.lua_load              = lua_load;
module.exports.lua_newtable          = lua_newtable;
module.exports.lua_newuserdata       = lua_newuserdata;
module.exports.lua_next              = lua_next;
module.exports.lua_pcall             = lua_pcall;
module.exports.lua_pcallk            = lua_pcallk;
module.exports.lua_pop               = lua_pop;
module.exports.lua_pushboolean       = lua_pushboolean;
module.exports.lua_pushcclosure      = lua_pushcclosure;
module.exports.lua_pushcfunction     = lua_pushcfunction;
module.exports.lua_pushfstring       = lua_pushfstring;
module.exports.lua_pushglobaltable   = lua_pushglobaltable;
module.exports.lua_pushinteger       = lua_pushinteger;
module.exports.lua_pushjsclosure     = lua_pushjsclosure;
module.exports.lua_pushjsfunction    = lua_pushjsfunction;
module.exports.lua_pushlightuserdata = lua_pushlightuserdata;
module.exports.lua_pushliteral       = lua_pushliteral;
module.exports.lua_pushlstring       = lua_pushlstring;
module.exports.lua_pushnil           = lua_pushnil;
module.exports.lua_pushnumber        = lua_pushnumber;
module.exports.lua_pushstring        = lua_pushstring;
module.exports.lua_pushthread        = lua_pushthread;
module.exports.lua_pushvalue         = lua_pushvalue;
module.exports.lua_pushvfstring      = lua_pushvfstring;
module.exports.lua_rawequal          = lua_rawequal;
module.exports.lua_rawget            = lua_rawget;
module.exports.lua_rawgeti           = lua_rawgeti;
module.exports.lua_rawgetp           = lua_rawgetp;
module.exports.lua_rawlen            = lua_rawlen;
module.exports.lua_rawset            = lua_rawset;
module.exports.lua_rawseti           = lua_rawseti;
module.exports.lua_rawsetp           = lua_rawsetp;
module.exports.lua_register          = lua_register;
module.exports.lua_remove            = lua_remove;
module.exports.lua_replace           = lua_replace;
module.exports.lua_rotate            = lua_rotate;
module.exports.lua_setallocf         = lua_setallocf;
module.exports.lua_setfield          = lua_setfield;
module.exports.lua_setglobal         = lua_setglobal;
module.exports.lua_seti              = lua_seti;
module.exports.lua_setmetatable      = lua_setmetatable;
module.exports.lua_settable          = lua_settable;
module.exports.lua_settop            = lua_settop;
module.exports.lua_setupvalue        = lua_setupvalue;
module.exports.lua_setuservalue      = lua_setuservalue;
module.exports.lua_status            = lua_status;
module.exports.lua_stringtonumber    = lua_stringtonumber;
module.exports.lua_toboolean         = lua_toboolean;
module.exports.lua_tocfunction       = lua_tocfunction;
module.exports.lua_todataview        = lua_todataview;
module.exports.lua_tointeger         = lua_tointeger;
module.exports.lua_tointegerx        = lua_tointegerx;
module.exports.lua_tojsstring        = lua_tojsstring;
module.exports.lua_tolstring         = lua_tolstring;
module.exports.lua_tonumber          = lua_tonumber;
module.exports.lua_tonumberx         = lua_tonumberx;
module.exports.lua_topointer         = lua_topointer;
module.exports.lua_toproxy           = lua_toproxy;
module.exports.lua_tostring          = lua_tostring;
module.exports.lua_tothread          = lua_tothread;
module.exports.lua_touserdata        = lua_touserdata;
module.exports.lua_type              = lua_type;
module.exports.lua_typename          = lua_typename;
module.exports.lua_upvalueid         = lua_upvalueid;
module.exports.lua_upvaluejoin       = lua_upvaluejoin;
module.exports.lua_version           = lua_version;
module.exports.lua_xmove             = lua_xmove;