townengine/apps/lua/game.c

#include "twn_game_api.h"
#include "state.h"

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

#include <malloc.h>


/* require will go through physicsfs exclusively so that scripts can be in the data dir */
static int physfs_loader(lua_State *L) {
    const char *name = luaL_checkstring(L, 1);
    char *final_path = NULL;
    SDL_asprintf(&final_path, "%s.lua", name);

    if (!file_exists(final_path)) {
        char *error_message = NULL;
        SDL_asprintf(&error_message, "could not find module %s in filesystem", name);
        lua_pushstring(L, error_message);
        free(error_message);

        free(final_path);
        return 1;
    }

    unsigned char *buf = NULL;
    int64_t buf_size = file_to_bytes(final_path, &buf);
    free(final_path);

    luaL_loadbuffer(L, (char *)buf, buf_size, name);
    free(buf);

    return 1;
}


static Rect table_to_rect(lua_State *L, int idx, const char *name) {
    /* types are checked here to help prevent unexpected results */
    Rect rect;
    int is_num;

    lua_getfield(L, idx, "x");
    rect.x = (float)lua_tonumberx(L, -1, &is_num);
    if (!is_num)
        luaL_error(L, "bad field 'x' in '%s' (number expected, got %s)", name, luaL_typename(L, -1));
    lua_pop(L, 1);

    lua_getfield(L, idx, "y");
    rect.y = (float)lua_tonumberx(L, -1, &is_num);
    if (!is_num)
        luaL_error(L, "bad field 'y' in '%s' (number expected, got %s)", name, luaL_typename(L, -1));
    lua_pop(L, 1);

    lua_getfield(L, idx, "w");
    rect.w = (float)lua_tonumberx(L, -1, &is_num);
    if (!is_num)
        luaL_error(L, "bad field 'w' in '%s' (number expected, got %s)", name, luaL_typename(L, -1));
    lua_pop(L, 1);

    lua_getfield(L, idx, "h");
    rect.h = (float)lua_tonumberx(L, -1, &is_num);
    if (!is_num)
        luaL_error(L, "bad field 'h' in '%s' (number expected, got %s)", name, luaL_typename(L, -1));
    lua_pop(L, 1);

    return rect;
}


static Color table_to_color(lua_State *L, int idx) {
    Color color;

    lua_getfield(L, idx, "r");
    color.r = (uint8_t)lua_tointeger(L, -1);
    lua_pop(L, 1);

    lua_getfield(L, idx, "g");
    color.g = (uint8_t)lua_tointeger(L, -1);
    lua_pop(L, 1);

    lua_getfield(L, idx, "b");
    color.b = (uint8_t)lua_tointeger(L, -1);
    lua_pop(L, 1);

    lua_getfield(L, idx, "a");
    color.a = (uint8_t)lua_tointeger(L, -1);
    lua_pop(L, 1);

    return color;
}


/* sprite(data [table]) */
/* data should contain the following fields: */
/*
 * path [string]
 * rect [table]
 * texture_region [table], optional
 * color [table], optional
 * rotation [number], optional
 * flip_x [boolean], optional
 * flip_y [boolean], optional
 * stretch [boolean], optional
 */
static int b_sprite(lua_State *L) {
    luaL_checktype(L, 1, LUA_TTABLE);

    PushSpriteArgs args = { 0 };

    lua_getfield(L, 1, "path");
    const char *field_path = lua_tostring(L, -1);
    if (field_path == NULL)
        luaL_error(L, "bad field 'path' in 'data' (string expected, got %s)", luaL_typename(L, -1));
    args.path = field_path;

    lua_getfield(L, 1, "rect");
    if (!lua_istable(L, -1))
        luaL_error(L, "bad field 'rect' in 'data' (table expected, got %s)", luaL_typename(L, -1));
    args.rect = table_to_rect(L, -1, "data.rect");

    lua_getfield(L, 1, "texture_region");
    if (lua_istable(L, -1)) {
        args.texture_region_opt = table_to_rect(L, -1, "data.texture_region");
        args.texture_region_opt_set = true;
    }

    lua_getfield(L, 1, "color");
    if (lua_istable(L, -1)) {
        args.color_opt = table_to_color(L, -1);
        args.color_opt_set = true;
    }

    lua_getfield(L, 1, "rotation");
    if (lua_isnumber(L, -1)) {
        args.rotation_opt = (float)lua_tonumber(L, -1);
        args.rotation_opt_set = true;
    }

    lua_getfield(L, 1, "flip_x");
    if (lua_isboolean(L, -1)) {
        args.flip_x_opt = lua_toboolean(L, -1);
        args.flip_x_opt_set = true;
    }

    lua_getfield(L, 1, "flip_y");
    if (lua_isboolean(L, -1)) {
        args.flip_y_opt = lua_toboolean(L, -1);
        args.flip_y_opt_set = true;
    }

    lua_getfield(L, 1, "stretch");
    if (lua_isboolean(L, -1)) {
        args.stretch_opt = lua_toboolean(L, -1);
        args.stretch_opt_set = true;
    }

    push_sprite(args);
    return 0;
}


/* rectangle(data [table]) */
/* data should contain the following fields: */
/*
 * rect [table]
 * color [table], optional, defaults to white
 */
static int b_rectangle(lua_State *L) {
    luaL_checktype(L, 1, LUA_TTABLE);

    lua_getfield(L, 1, "rect");
    if (!lua_istable(L, -1))
        luaL_error(L, "bad field 'rect' in 'data' (table expected, got %s)", luaL_typename(L, -1));
    Rect rect = table_to_rect(L, -1, "data.rect");

    Color color = { 255, 255, 255, 255 };
    lua_getfield(L, 1, "color");
    if (lua_istable(L, -1))
        color = table_to_color(L, -1);

    push_rectangle(rect, color);
    return 0;
}


/* text(data [table]) */
/* data should contain the following fields: */
/*
 * string [string]
 * position [table]
 * height_px [number], optional, defaults to 22
 * color [table], optional, defaults to black
 * font_path [string]
 */
static int b_text(lua_State *L) {
    luaL_checktype(L, 1, LUA_TTABLE);

    lua_getfield(L, 1, "string");
    const char *string = lua_tostring(L, -1);
    if (string == NULL)
        luaL_error(L, "bad field 'string' in 'data' (string expected, got %s)", luaL_typename(L, -1));

    lua_getfield(L, 1, "position");
    if (!lua_istable(L, -1))
        luaL_error(L, "bad field 'position' in 'data' (table expected, got %s)", luaL_typename(L, -1));
    lua_getfield(L, -1, "x");
    float x = (float)lua_tonumber(L, -1);
    lua_getfield(L, -2, "y");
    float y = (float)lua_tonumber(L, -1);

    lua_getfield(L, 1, "height_px");
    int is_num;
    int height_px = (int)lua_tointegerx(L, -1, &is_num);
    if (!is_num)
        height_px = 22;

    lua_getfield(L, 1, "color");
    Color color = { 0, 0, 0, 255 };
    if (lua_istable(L, -1))
        color = table_to_color(L, -1);

    lua_getfield(L, 1, "font_path");
    const char *font_path = lua_tostring(L, -1);
    if (font_path == NULL)
        luaL_error(L, "bad field 'font_path' in 'data' (string expected, got %s)", luaL_typename(L, -1));

    push_text(string, (Vec2) { x, y }, height_px, color, font_path);
    return 0;
}


void game_tick(void) {
    if (ctx.initialization_needed) {
        if (!ctx.udata)
            ctx.udata = ccalloc(1, sizeof (State));

        State *state = ctx.udata;

        /* let's init lua */
        /* state existed already */
        if (state->L != NULL) {
            lua_close(state->L);
        }
        state->L = luaL_newstate();

        /* fakey version of luaL_openlibs() that excludes file i/o */
        {
            static const luaL_Reg loaded_libs[] = {
               { LUA_GNAME, luaopen_base },
               { LUA_LOADLIBNAME, luaopen_package },
               { LUA_COLIBNAME, luaopen_coroutine },
               { LUA_TABLIBNAME, luaopen_table },
               { LUA_OSLIBNAME, luaopen_os },
               { LUA_STRLIBNAME, luaopen_string },
               { LUA_MATHLIBNAME, luaopen_math },
               { LUA_UTF8LIBNAME, luaopen_utf8 },
               { LUA_DBLIBNAME, luaopen_debug },
               { NULL, NULL },
            };

            for (const luaL_Reg *lib = loaded_libs; lib->func; ++lib) {
                luaL_requiref(state->L, lib->name, lib->func, true);
                lua_pop(state->L, 1); /* already stored, don't need the copy */
            }
        }

        /* package.searchers = { physfs_loader } */
        lua_getglobal(state->L, "package");
        lua_newtable(state->L);
        lua_setfield(state->L, -2, "searchers");

        lua_getfield(state->L, -1, "searchers");
        lua_pushcfunction(state->L, physfs_loader);
        lua_seti(state->L, -2, 1);

        /* pop package, package.searchers */
        lua_pop(state->L, 2);

        /* binding */
        lua_register(state->L, "sprite", b_sprite);
        lua_register(state->L, "rectangle", b_rectangle);
        lua_register(state->L, "text", b_text);

        /* now finally get to running the code */
        state->game_buf_size = file_to_bytes("/scripts/game.lua", &state->game_buf);
        if (luaL_loadbuffer(state->L, (char *)state->game_buf, state->game_buf_size, "game.lua") == LUA_OK) {
            if (lua_pcall(state->L, 0, 0, 0) != LUA_OK) {
                log_critical("%s", lua_tostring(state->L, -1));
                lua_pop(state->L, 1);
            }
        }
        /* from this point we have access to everything defined in lua */
    }

    State *state = ctx.udata;

    lua_getglobal(state->L, "game_tick");
    if (lua_pcall(state->L, 0, 0, 0) != LUA_OK) {
        log_critical("%s", lua_tostring(state->L, -1));
        lua_pop(state->L, 1);
    }
}


void game_end(void) {
    State *state = ctx.udata;
    free(state->game_buf);
    lua_close(state->L);
    free(state);
}