-- INTERNAL
-- definitions of BUILD and game types for the Lunatic Interpreter

_EDUKE32_LUNATIC = true

local ffi = require("ffi")

---=== Duke3D engine and game definitions ===---
ffi.cdef[[
#pragma pack(push,1)
typedef struct
{
    const int16_t wallptr, wallnum;
    int32_t ceilingz, floorz;
    int16_t ceilingstat, floorstat;
    int16_t ceilingpicnum, ceilingheinum;
    int8_t ceilingshade;
    uint8_t ceilingpal, ceilingxpanning, ceilingypanning;
    int16_t floorpicnum, floorheinum;
    int8_t floorshade;
    uint8_t floorpal, floorxpanning, floorypanning;
    uint8_t visibility, filler;
    int16_t lotag, hitag, extra;
} sectortype;

typedef struct
{
    int32_t x, y;
    const int16_t point2, nextwall, nextsector;
    int16_t cstat;
    int16_t picnum, overpicnum;
    int8_t shade;
    uint8_t pal, xrepeat, yrepeat, xpanning, ypanning;
    int16_t lotag, hitag, extra;
} walltype;

typedef struct
{
    int32_t x, y, z;
    int16_t cstat, picnum;
    int8_t shade;
    uint8_t pal, clipdist, filler;
    uint8_t xrepeat, yrepeat;
    int8_t xoffset, yoffset;
    const int16_t sectnum, statnum;
    int16_t ang, owner, xvel, yvel, zvel;
    int16_t lotag, hitag, extra;
} spritetype;

typedef struct {
    const uint32_t mdanimtims;
    const int16_t mdanimcur;
    int16_t angoff, pitch, roll;
    int32_t xoff, yoff, zoff;
    uint8_t flags;
    uint8_t xpanning, ypanning;
    const uint8_t filler;
    float alpha;
    const int32_t _do_not_use1;
    const int32_t _do_not_use2;
} spriteext_t;

typedef struct {
    int32_t x, y, z;
} vec3_t;

typedef struct {
    vec3_t pos;
    int16_t hitsprite, hitwall, hitsect;
} hitdata_t;

typedef struct {
    char r,g,b,f;
} palette_t;
#pragma pack(pop)
]]

local vec3_ct = ffi.typeof("vec3_t")
local hitdata_ct = ffi.typeof("hitdata_t")

---- engine data and functions ----

-- GLOBAL gv: provides access to C global *scalars* and safe functions
-- XXX: still exposes C library functions etc. contained in ffi.C.
--  Is this a problem?
local gv_ = {
    -- all non-scalars need to be explicitly listed here and access to them is
    -- redirected to the dummy empty table...
}

local dummy_empty_table = {}

-- this is for declarations of arrays or pointers
-- NOTE: don't declare multiple pointers on one line (like int32_t *a, *b;)!
local function decl(str)
    for varname in string.gmatch(str, "([%a_][%w_]*)[[(;]") do
--        print("protect "..varname)
        gv_[varname] = dummy_empty_table
    end

    ffi.cdef(str)
end

ffi.cdef[[int32_t engine_main_arrays_are_static, engine_v8;]]

-- NOTE TO SELF: This is not C, never EVER write
--    if (x)
-- when checking a C variable x for 'thuthiness'
if (ffi.C.engine_main_arrays_are_static ~= 0) then
--    print('main arrays are static');
    decl[[
    sectortype sector[];
    walltype wall[];
    spritetype sprite[];
    spriteext_t spriteext[];
    ]]
else
--    print('main arrays are pointers');
    decl[[
    sectortype *sector;
    walltype *wall;
    spritetype *sprite;
    spriteext_t *spriteext;
    ]]
end

if (ffi.C.engine_v8 == 0) then
    -- V7
    ffi.cdef[[
enum
{
    MAXSECTORS = 1024,
    MAXWALLS = 8192,
    MAXSPRITES = 4096,
}
]]
else
    -- V8
    ffi.cdef[[
enum
{
    MAXSECTORS = 4096,
    MAXWALLS = 16384,
    MAXSPRITES = 16384,
}
]]
end

ffi.cdef[[
enum {
    MAXSTATUS = 1024,

    MAXBUNCHES = 256,
    CEILING = 0,
    FLOOR = 1,

    CLIPMASK0 = (1<<16)+1,  // blocking
    CLIPMASK1 = (256<<16)+64,  // hittable
};
]]

ffi.cdef[[
const int16_t numsectors, numwalls;
const int32_t numyaxbunches;
]]

decl[[
const int16_t headspritesect[MAXSECTORS+1], headspritestat[MAXSTATUS+1];
const int16_t prevspritesect[MAXSPRITES], prevspritestat[MAXSPRITES];
const int16_t nextspritesect[MAXSPRITES], nextspritestat[MAXSPRITES];

const int16_t headsectbunch[2][MAXBUNCHES], nextsectbunch[2][MAXSECTORS];

int16_t yax_getbunch(int16_t i, int16_t cf);

int32_t hitscan(const vec3_t *sv, int16_t sectnum, int32_t vx, int32_t vy, int32_t vz,
                hitdata_t *hitinfo, uint32_t cliptype);
]]

-- array -> element flattening inside structs,
-- e.g. int32_t a[4] --> int32_t _a0, _a1, _a2, _a3;
local function repeat_n_elts(type, namebase, num)
    local strbuf = { "const "..type.." " }

    for i=1,num do
        local str = namebase..tostring(i-1)
        if (i < num) then
            str = str..","
        end
        strbuf[#strbuf+1] = str
    end
    strbuf[#strbuf+1] = ";"

    return table.concat(strbuf)
end

---- game structs ----
ffi.cdef[[
enum dukeinv_t {
    GET_STEROIDS,
    GET_SHIELD,
    GET_SCUBA,
    GET_HOLODUKE,
    GET_JETPACK,
    GET_DUMMY1,
    GET_ACCESS,
    GET_HEATS,
    GET_DUMMY2,
    GET_FIRSTAID,
    GET_BOOTS,
    GET_MAX
};

enum dukeweapon_t {
    KNEE_WEAPON,
    PISTOL_WEAPON,
    SHOTGUN_WEAPON,
    CHAINGUN_WEAPON,
    RPG_WEAPON,
    HANDBOMB_WEAPON,
    SHRINKER_WEAPON,
    DEVISTATOR_WEAPON,
    TRIPBOMB_WEAPON,
    FREEZE_WEAPON,
    HANDREMOTE_WEAPON,
    GROW_WEAPON,
    MAX_WEAPONS
};

enum {
    MAXPLAYERS = 16,
};
]]

ffi.cdef([[
#pragma pack(push,1)
// TODO: still need to make some fields read-only
// NOTE: must not expose arrays in structs!!!
typedef struct
{
]]
..repeat_n_elts("int32_t", "_t", 14)..
[[
//    const int32_t t_data[14];  // 56b sometimes used to hold offsets to con code
    int16_t picnum,ang,extra,owner; //8b
    int16_t movflag,tempang,timetosleep; //6b

    int32_t flags, bposx,bposy,bposz; //16b
    int32_t floorz,ceilingz,lastvx,lastvy; //16b
    int32_t lasttransport; //4b

    const int16_t lightId, lightcount, lightmaxrange, cgg; //8b
    int16_t actorstayput, dispicnum, shootzvel; // 6b
]]
..repeat_n_elts("int8_t", "_d", 8)..
[[
//    const int8_t _do_not_use[8];
} actor_t;

typedef struct {
    vec3_t pos, opos, vel, npos;
    int32_t bobposx, bobposy;
    int32_t truefz, truecz, player_par;
    int32_t randomflamex, exitx, exity;
    int32_t runspeed, max_player_health, max_shield_amount;

    uint32_t interface_toggle_flag;

    uint8_t palette;

    uint16_t max_actors_killed, actors_killed;
    uint16_t gotweapon, zoom;
]]
..repeat_n_elts("int16_t", "_lx", 64)..repeat_n_elts("int16_t", "_ly", 64)..
[[
//    int16_t loogiex[64], loogiey[64];
    int16_t sbs, sound_pitch;

    int16_t ang, oang, angvel, cursectnum, look_ang, last_extra, subweapon;
]]
..repeat_n_elts("int16_t", "_ma", ffi.C.MAX_WEAPONS)
..repeat_n_elts("int16_t", "_aa", ffi.C.MAX_WEAPONS)
..repeat_n_elts("int16_t", "_ia", ffi.C.GET_MAX)..
[[
//    int16_t max_ammo_amount[MAX_WEAPONS], ammo_amount[MAX_WEAPONS], inv_amount[GET_MAX];
    int16_t wackedbyactor, pyoff, opyoff;

    int16_t horiz, horizoff, ohoriz, ohorizoff;
    int16_t newowner, jumping_counter, airleft;
    int16_t fta, ftq, access_wallnum, access_spritenum;
    int16_t got_access, weapon_ang, visibility;
    int16_t somethingonplayer, on_crane, i, one_parallax_sectnum;
    int16_t random_club_frame, one_eighty_count;
    int16_t dummyplayersprite, extra_extra8;
    int16_t actorsqu, timebeforeexit, customexitsound, last_pissed_time;
]]
..repeat_n_elts("int16_t", "_w", ffi.C.MAX_WEAPONS)..
[[
//    int16_t weaprecs[MAX_WEAPONS];
    int16_t weapon_sway, crack_time, bobcounter;

    int16_t orotscrnang, rotscrnang, dead_flag;   // JBF 20031220: added orotscrnang
    int16_t holoduke_on, pycount;

    uint8_t max_secret_rooms, secret_rooms;
    uint8_t frag, fraggedself, quick_kick, last_quick_kick;
    uint8_t return_to_center, reloading, weapreccnt;
    uint8_t aim_mode, auto_aim, weaponswitch, movement_lock, team;
    uint8_t tipincs, hbomb_hold_delay, frag_ps, kickback_pic;

    uint8_t gm, on_warping_sector, footprintcount, hurt_delay;
    uint8_t hbomb_on, jumping_toggle, rapid_fire_hold, on_ground;
    uint8_t inven_icon, buttonpalette, over_shoulder_on, show_empty_weapon;

    uint8_t jetpack_on, spritebridge, lastrandomspot;
    uint8_t scuba_on, footprintpal, heat_on, invdisptime;

    uint8_t holster_weapon, falling_counter, footprintshade;
    uint8_t refresh_inventory, last_full_weapon;

    uint8_t toggle_key_flag, knuckle_incs, knee_incs, access_incs;
    uint8_t walking_snd_toggle, palookup, hard_landing, fist_incs;

    int8_t numloogs, loogcnt, scream_voice, transporter_hold;
    int8_t last_weapon, cheat_phase, weapon_pos, wantweaponfire, curr_weapon;

    palette_t pals;
]]
..repeat_n_elts("char", "_n", 32)..
[[
//    char name[32];
} DukePlayer_t;

typedef struct {
    uint32_t bits; // 4b
    int16_t fvel, svel; // 4b
    int8_t avel, horz; // 2b
    int8_t extbits, filler; // 2b
} input_t;

typedef struct {
    DukePlayer_t *ps;
    input_t *sync;

    int32_t netsynctime;
    int16_t ping, filler;
    int32_t pcolor, pteam;
    uint8_t frags[MAXPLAYERS], wchoice[MAX_WEAPONS];

    char vote, gotvote, pingcnt, playerquitflag;
    char user_name[32];
    uint32_t revision;
} playerdata_t;
#pragma pack(pop)

enum
{
    MAXMOUSEBUTTONS = 10,
    MAXMOUSEAXES = 2,
    MAXJOYBUTTONS = (32+4),
    MAXJOYAXES = 8,
    NUMGAMEFUNCTIONS = 56,
};

typedef struct {
    vec3_t camera;
    int32_t const_visibility,uw_framerate;
    int32_t camera_time,folfvel,folavel,folx,foly,fola;
    int32_t reccnt,crosshairscale;

    int32_t runkey_mode,statusbarscale,mouseaiming,weaponswitch,drawweapon;   // JBF 20031125
    int32_t democams,color,msgdisptime,statusbarmode;
    int32_t m_noexits,noexits,autovote,automsg,idplayers;
    int32_t team, viewbob, weaponsway, althud, weaponscale, textscale;

    int32_t entered_name,screen_tilting,shadows,fta_on,executions,auto_run;
    int32_t coords,tickrate,levelstats,m_coop,coop,screen_size,lockout,crosshair;
    int32_t playerai,angleinterpolation,obituaries;

    int32_t respawn_monsters,respawn_items,respawn_inventory,recstat,monsters_off,brightness;
    int32_t m_respawn_items,m_respawn_monsters,m_respawn_inventory,m_recstat,m_monsters_off,detail;
    int32_t m_ffire,ffire,m_player_skill,m_level_number,m_volume_number,multimode;
    int32_t player_skill,level_number,volume_number,m_marker,marker,mouseflip;

    int32_t configversion;

    int16_t cameraang, camerasect, camerahoriz;
    int16_t pause_on,from_bonus;
    int16_t camerasprite,last_camsprite;
    int16_t last_level,secretlevel, bgstretch;

    struct {
        int32_t UseJoystick;
        int32_t UseMouse;
        int32_t AutoAim;
        int32_t ShowOpponentWeapons;
        int32_t MouseDeadZone,MouseBias;
        int32_t SmoothInput;

        // JBF 20031211: Store the input settings because
        // (currently) jmact can't regurgitate them
        int32_t MouseFunctions[MAXMOUSEBUTTONS][2];
        int32_t MouseDigitalFunctions[MAXMOUSEAXES][2];
        int32_t MouseAnalogueAxes[MAXMOUSEAXES];
        int32_t MouseAnalogueScale[MAXMOUSEAXES];
        int32_t JoystickFunctions[MAXJOYBUTTONS][2];
        int32_t JoystickDigitalFunctions[MAXJOYAXES][2];
        int32_t JoystickAnalogueAxes[MAXJOYAXES];
        int32_t JoystickAnalogueScale[MAXJOYAXES];
        int32_t JoystickAnalogueDead[MAXJOYAXES];
        int32_t JoystickAnalogueSaturate[MAXJOYAXES];
        uint8_t KeyboardKeys[NUMGAMEFUNCTIONS][2];

        //
        // Sound variables
        //
        int32_t FXDevice;
        int32_t MusicDevice;
        int32_t FXVolume;
        int32_t MusicVolume;
        int32_t SoundToggle;
        int32_t MusicToggle;
        int32_t VoiceToggle;
        int32_t AmbienceToggle;

        int32_t NumVoices;
        int32_t NumChannels;
        int32_t NumBits;
        int32_t MixRate;

        int32_t ReverseStereo;

        //
        // Screen variables
        //

        int32_t ScreenMode;

        int32_t ScreenWidth;
        int32_t ScreenHeight;
        int32_t ScreenBPP;

        int32_t ForceSetup;
        int32_t NoAutoLoad;

        int32_t scripthandle;
        int32_t setupread;

        int32_t CheckForUpdates;
        int32_t LastUpdateCheck;
        int32_t useprecache;
    } config;

    char overhead_on,last_overhead,showweapons;
    char god,warp_on,cashman,eog,showallmap;
    char show_help,scrollmode,noclip;
    char ridecule[10][40];
    char savegame[10][22];
    char pwlockout[128],rtsname[128];
    char display_bonus_screen;
    char show_level_text;
} user_defs;
]])

decl[[
const char *g_sizes_of_what[];
int32_t g_sizes_of[];
actor_t actor[MAXSPRITES];
user_defs ud;
playerdata_t g_player[MAXPLAYERS];
]]

-- functions
ffi.cdef[[
int32_t ksqrt(uint32_t num);
]]

ffi.cdef "double gethitickms(void);"

local ffiC = ffi.C

-- sanity-check struct type sizes
for i=0,6 do
    assert(ffi.sizeof(ffi.typeof(ffi.string(ffiC.g_sizes_of_what[i])))
           == ffiC.g_sizes_of[i])
end

--- default defines
local con = require("con_lang")

for i=1,#con.labels do
    local strbuf = {"enum {"}

    for label, val in pairs(con.labels[i]) do
        strbuf[#strbuf+1] = string.format("%s = %d,", label, val)
    end
    strbuf[#strbuf+1] = "};"

    ffi.cdef(table.concat(strbuf))
end


---=== Set up restricted global environment ===---

-- _G tweaks -- pull in only 'safe' stuff
local G_ = {}  -- our soon-to-be global environment
local oG = _G  -- old genv, to access thrown-out functions later in this chunk

G_.coroutine = coroutine
G_.assert = assert
G_.tostring = tostring
G_.tonumber = tonumber
--rawget
G_.xpcall = xpcall
G_.ipairs = ipairs
G_.print = print
G_.pcall = pcall
--gcinfo --DEPRECATED
--module
--setfenv
--require
--rawset
--jit
G_.bit = bit
--package
G_.error = error
--debug
--loadfile
--rawequal
--load
G_.unpack = unpack
G_.pairs = pairs
G_.table = table
G_._VERSION = _VERSION
--newproxy --NOT STD?
--collectgarbage
--dofile
G_.next = next
G_.math = math
--loadstring
--_G
G_.select = select
G_.string = string
G_.type = type
--getmetatable
--getfenv
--setmetatable

G_._G = G_

-- http://lua-users.org/wiki/SandBoxes says "potentially unsafe"
-- as it allows to see implementations of functions.
local string_dump = string.dump
string.dump = nil

--- non-default data and functions
G_._EDUKE32_LUNATIC = _EDUKE32_LUNATIC
G_.gameevent = gameevent  -- included in lunatic.c
G_.gameactor = gameactor  -- included in lunatic.c


---=== Lunatic interpreter setup ===---

local lunacon = require("lunacon")


-- change the environment of this chunk to the table G_
setfenv(1, G_)


-- print keys and values of a table
local function printkv(label, table)
    print('========== Keys and values of '..label)
    for k,v in pairs(table) do
        print(k .. ': ' .. tostring(v))
    end
    print('----------')
end

--printkv('_G AFTER SETFENV', _G)


---=== Restricted access to C variables from Lunatic ===---

-- error(..., 2) is to blame the caller and get its line numbers

local tmpmt = {
    __index = function() error('dummy variable: read access forbidden', 2) end,
    __newindex = function() error('dummy variable: write access forbidden', 2) end,
    __metatable = true,  -- forbid setting the metatable
}
oG.setmetatable(dummy_empty_table, tmpmt)

gv = gv_
local tmpmt = {
    __index = ffiC,
    __newindex = function() error("cannot create new or write into existing fields of 'gv'", 2) end,
    __metatable = true,
}
oG.setmetatable(gv, tmpmt)

---- indirect C array access ----
sector = {}
local tmpmt = {
    __index = function(tab, key)
                  if (key >= 0 and key < ffiC.numsectors) then return ffiC.sector[key] end
                  error('out-of-bounds sector[] read access', 2)
              end,

    __newindex = function(tab, key, val) error('cannot write directly to sector[] struct', 2) end,
    __metatable = true,
}
oG.setmetatable(sector, tmpmt)

wall = {}
local tmpmt = {
    __index = function(tab, key)
                  if (key >= 0 and key < ffiC.numwalls) then return ffiC.wall[key] end
                  error('out-of-bounds wall[] read access', 2)
              end,

    __newindex = function(tab, key, val) error('cannot write directly to wall[] struct', 2) end,
    __metatable = true,
}
oG.setmetatable(wall, tmpmt)

-- create a safe indirection for a ffi.C array
local function creategtab(ctab, maxidx, name)
    local tab = {}
    local tmpmt = {
        __index = function(tab, key)
                      if (key>=0 and key < maxidx) then
                          return ctab[key]
                      end
                      error('out-of-bounds '..name..' read access', 2)
                  end,
        __newindex = function(tab, key, val)
                         error('cannot write directly to '..name, 2)
                     end,
        __metatable = true,
    }
    oG.setmetatable(tab, tmpmt)
    return tab
end

sprite = creategtab(ffiC.sprite, ffiC.MAXSPRITES, 'sprite[] struct')
spriteext = creategtab(ffiC.spriteext, ffiC.MAXSPRITES, 'spriteext[] struct')
headspritesect = creategtab(ffiC.headspritesect, ffiC.MAXSECTORS, 'headspritesect[]')
-- TODO: allow sprite freelist access via the status list for CON compatibility?
headspritestat = creategtab(ffiC.headspritestat, ffiC.MAXSTATUS, 'headspritestat[]')
nextspritesect = creategtab(ffiC.nextspritesect, ffiC.MAXSPRITES, 'nextspritesect[]')
nextspritestat = creategtab(ffiC.nextspritestat, ffiC.MAXSPRITES, 'nextspritestat[]')
prevspritesect = creategtab(ffiC.prevspritesect, ffiC.MAXSPRITES, 'prevspritesect[]')
prevspritestat = creategtab(ffiC.prevspritestat, ffiC.MAXSPRITES, 'prevspritestat[]')

actor = creategtab(ffiC.actor, ffiC.MAXSPRITES, 'actor[]')

function TEMP_getvollev()  -- REMOVE
    return ffiC.ud.volume_number+1, ffiC.ud.level_number+1
end

---- per-sector/per-statnum sprite iterators ----
local function iter_spritesofsect(sect, i)
    if (i < 0) then
        i = ffiC.headspritesect[sect]
    else
        i = ffiC.nextspritesect[i]
    end

    if (i >= 0) then return i end
end

function spritesofsect(sect)
    if (sect < 0 or sect >= ffiC.numsectors) then
        error("passed invalid sectnum to spritesofsect iterator", 2)
    end

    return iter_spritesofsect, sect, -1
end

local function iter_spritesofstat(stat, i)
    if (i < 0) then
        i = ffiC.headspritestat[stat]
    else
        i = ffiC.nextspritestat[i]
    end

    if (i >= 0) then return i end
end

function spritesofstat(stat)
    if (stat < 0 or stat >= ffiC.MAXSTATUS) then
        error("passed invalid statnum to spritesofstat iterator", 2)
    end

    return iter_spritesofstat, stat, -1
end

-- TROR iterators
local function iter_sectorsofbunch(cf, i)
    if (i < 0) then
        i = ffiC.headsectbunch[cf][-i-1];
    else
        i = ffiC.nextsectbunch[cf][i];
    end

    if (i >= 0) then return i end
end

function sectorsofbunch(bunchnum, cf)
    if (bunchnum < 0 or bunchnum >= ffiC.numyaxbunches) then
        error("passed invalid bunchnum to sectorsofbunch iterator", 2)
    end
    if (cf ~= 0 and cf ~= 1) then
        error("passed invalid 'cf' to sectorsofbunch iterator, must be 0 or 1", 2)
    end

    return iter_sectorsofbunch, cf, -bunchnum-1
end

function getbunch(sectnum, cf)
    if (sectnum < 0 or sectnum >= ffiC.numsectors) then
        error('passed out-of-bounds sector number'..sectnum, 2)
    end
    if (cf ~= 0 and cf ~= 1) then
        error("passed invalid 'cf' to getbunch, must be 0 or 1", 2)
    end

    return ffiC.yax_getbunch(sectnum, cf)
end


---=== Engine functions, wrapped for Lua convenience ===---
-- returns a hitdata_ct
function hitscan(x,y,z, sectnum, vx,vy,vz, cliptype)
    if (sectnum < 0 or sectnum >= ffiC.numsectors) then
        error('passed out-of-bounds sector number'..sectnum, 2)
    end

    local vec = vec3_ct(x,y,z)
    local hitdata = hitdata_ct()

    ffiC.hitscan(vec, sectnum, vx,vy,vz, hitdata, cliptype)
    return hitdata
end

---=== Game variables ===---

-- gamevarNames[name] is true if that gamevar was declared
local gamevarNames = {}

-- code for prohibiting initial assignments to create new variables,
-- based on 14.2 of PiL
function gamevar(name, initval)  -- aka 'declare'
    if (type(name) ~= "string") then
        error("First argument to 'gamevar' must be a string", 2);
    end

    if (not string.match(name, "^[%a_][%w_]*$")) then
        error("First argument to 'gamevar' must be a valid identifier", 2);
    end

    if (gamevarNames[name]) then
        error(string.format("Duplicate declaration of identifier '%s'", name), 2)
    end

    if (oG.rawget(G_, name) ~= nil) then
        error(string.format("Identifier name '%s' is already used in the global environment", name), 2)
    end

    gamevarNames[name] = true
    oG.rawset(G_, name, initval or false)
end


---=== Serialization, from PiL with modifications ===---
local function basicSerialize(o)
    if (type(o) == "number") then
        if (o ~= o) then return "0/0" end  -- nan
        if (o == 1/0) then return "1/0" end  -- inf
        if (o == -1/0) then return "-1/0" end  -- -inf

        return tostring(o)
    elseif (type(o) == "boolean") then
        return tostring(o)
    elseif (type(o) == "string") then
        return string.format("%q", o)
    end
end

-- will contain all gamevar tables as keys (and true as value)
local tmpgvtabs = {}

local function save(name, value, saved, strings)
    saved = saved or {}       -- initial value

    strings[#strings+1] = name .. "="

    local str = basicSerialize(value)

    if (str ~= nil) then
        strings[#strings+1] = str .. "\n"
    elseif (type(value) == "table") then
        if (saved[value]) then    -- value already saved?
            strings[#strings+1] = saved[value] .. "\n"  -- use its previous name
        else
            saved[value] = name   -- save name for next time
            strings[#strings+1] = "{}\n"  -- create a new table

            for k,v in pairs(value) do      -- save its fields
                local keystr = basicSerialize(k)
                if (keystr == nil) then
                    error("cannot save a " .. type(k) .. " as key of a table", 2);
                end
                local fieldname = string.format("%s[%s]", name, keystr)
                if (type(v)=="table" and not tmpgvtabs[v]) then
                    error("cannot save \""..name..
                          "\": gamevar tables may only contain tables that are also gamevars", 2)
                end
                save(fieldname, v, saved, strings)
            end
        end
    else
        error("cannot save \""..name.."\", a " .. type(value), 2)
    end
end

local function serializeGamevars()
    local saved = {}
    local strings = {}

    for gvname,_ in pairs(gamevarNames) do
        if (type(G_[gvname])=="table") then
            tmpgvtabs[G_[gvname]] = true
        end
    end

    -- TODO: catch errors in save()
    for gvname,_ in pairs(gamevarNames) do
        save(gvname, G_[gvname], saved, strings)
    end
    strings[#strings+1] = "\n"

    tmpgvtabs = {}

    return table.concat(strings)
end

local function loadGamevarsString(string)
--[=[
    for gvname,_ in pairs(gamevarNames) do
        G_[gvname] = nil;
    end
    gamevarNames = {};  -- clear gamevars
--]=]

    assert(oG.loadstring(string))()
end


-- REMOVE this for release
DBG_ = {}
DBG_.printkv = printkv
DBG_.loadstring = oG.loadstring
DBG_.serializeGamevars = serializeGamevars
DBG_.loadGamevarsString = loadGamevarsString


---=== Finishing environment setup ===---

--printkv('_G AFTER DECLS', _G)


-- PiL 14.2 continued
-- We need this at the end because we were previously doing just that!
-- XXX: but user modules will want to do "function thisfunc() ... "
oG.setmetatable(
    G_, {
        __newindex = function (_, n)
            error("attempt to write to undeclared variable "..n, 2)
        end,
        __index = function (_, n)
            error("attempt to read undeclared variable "..n, 2)
        end,
        })

-- Change the environment of the running Lua thread so that everything
-- what we've set up will be available when this chunk is left.
-- In particular, we need the functions defined after setting this chunk's
-- environment earlier.
oG.setfenv(0, _G)