Leveret Lua Evaluation Commons

levlua.js

const commons = {
	initialize: function (ctx) {
		const newCtx = {};

		// Create a shallow copy of the provided context.
		for(var key in ctx) {
			newCtx[key] = ctx[key];
		}

		// Since fengari-web is primarily a browser library,
		// we need to shim browser-specific things. Temporarily, at least.
		newCtx.window = {
			dispatchEvent: () => { }
		}

		// Fetch and evaluate Fengari.
		const fengariSrc = http.request("https://github.com/fengari-lua/fengari-web/releases/download/v0.1.4/fengari-web.js").data
		new Function("window = this.window;" + fengariSrc).call({ window: newCtx });

		this.fengari = newCtx.fengari;
	},

	createLuaContext: function () {
		if (!this.fengari) this.initialize();

		const L = this.fengari.lauxlib.luaL_newstate();

		this.fengari.lualib.luaL_openlibs(L);
		this.fengari.interop.luaopen_js(L);
		this.fengari.lua.lua_setglobal(L, "js");

		return L;
	},

	replacePrintFunction: function (L, callback) {
		if (!this.fengari) this.initialize();

		const buffer = [];
		const lua = this.fengari.lua;

		// Printer function.
		// Taken directly from the Fengari source.
		let print = (L) => {
			let n = lua.lua_gettop(L);
			lua.lua_getglobal(L, this.fengari.to_luastring("tostring", true));

			let linebuf = [];
			for (let i = 1; i <= n; i++) {
				lua.lua_pushvalue(L, -1);
				lua.lua_pushvalue(L, i);
				lua.lua_call(L, 1, 1);
				let s = lua.lua_tolstring(L, -1);
				if (s === null)
					return this.fengari.lauxlib.luaL_error(L,
						this.fengari.to_luastring("'tostring' must return a string to 'print'"));

				if (i > 1) linebuf.push("\t");
				linebuf.push(this.fengari.to_jsstring(s));

				lua.lua_pop(L, 1);
			}

			callback(linebuf.join(""));

			return 0;
		};

		// Finally, replace "print" within the context.
		lua.lua_pushjsfunction(L, print);
		lua.lua_setglobal(L, "print");

		return buffer
	},

	parseInput: function (input) {
		let code, args;

		// Parse code block if exists.
		let parsed = input.match(/^(.*?)`{3}([\S]+)?\n([\s\S]+)`{3}$/mi);
		if (parsed) {
			// Args precede the code block.
			args = parsed[1].trim();
			code = parsed[3];
		} // Otherwise treat the entire input as code.
		else code = input;

		return { code, args }
	},

	runLua: function (L, code) {
		if (!this.fengari) this.initialize();

		const lua = this.fengari.lua;
		const result = this.fengari.lauxlib
			.luaL_loadstring(L, this.fengari.to_luastring(code));

		if (result === 0) {
			if (lua.lua_gettop(L) > 0) {
				const type = lua.lua_type(L, -1);
				if (type == lua.LUA_TFUNCTION) {
					lua.lua_call(L, 0, 1);
				}
			}
		}
	},

	getStackTrace: function (L) {
		const lua = this.fengari.lua;

		const buf = [];
		const top = lua.lua_gettop(L);
		const bottom = 1;

		lua.lua_getglobal(L, "tostring");
		for (let i = top; i >= bottom; i--) {
			lua.lua_pushvalue(L, -1);
			lua.lua_pushvalue(L, i);
			lua.lua_pcall(L, 1, 1, 0);
			const str = this.fengari.interop.tojs(L, -1);
			if (str) {
				buf.push(str);
			} else {
				buf.push(this.fengari.lauxlib.luaL_typename(L, i));
			}
			lua.lua_pop(L, 1);
		}
		lua.lua_pop(L, 1);

		return buf;
	}
}

return commons;