const { lua, lauxlib, lualib, to_luastring } = require('fengari')
const interop = require('./vm/interop')
const defaultExtensions = [
require('./vm/extension/agent'),
require('./vm/extension/base'),
require('./vm/extension/context'),
require('./vm/extension/crypto'),
require('./vm/extension/json')
]
/**
* Operate VM module. Responsible for initalizing the VM state and evaluating
* and executing Lua code in the VM.
*
* @class
*/
class VM {
/**
* Initliazes a new VM state.
*
* @return {VM}
*/
constructor(opts = {}) {
const extensions = opts.extensions || []
this.agent = opts.agent
this._vm = lauxlib.luaL_newstate()
lualib.luaL_openlibs(this._vm)
defaultExtensions.concat(extensions)
.forEach(ext => this.extend(ext))
}
/**
* Extends the VM state with the given module or modules.
*
* @param {Extension|Array} extension Extension class or array
* @return {VM}
*/
extend(extension) {
if (Array.isArray(extension)) {
extension.forEach(ext => this.extend(ext))
}
extension.extend(this)
return this
}
/**
* Returns the value from the specified path on the VM state.
*
* @param {String|Array} path Lua path
* @return {String|Number|Object|Array|Function}
*/
get(path, opts = {}) {
if (typeof path === 'string') {
return this.get(path.split('.'), opts)
}
path.forEach((p, i) => {
let type
if (i === 0) {
type = lua.lua_getglobal(this._vm, to_luastring(p))
} else {
type = lua.lua_getfield(this._vm, -1, to_luastring(p))
}
if (type < 0) this._throwError();
})
return interop.tojs(this._vm, -1)
}
/**
* Sets the value at the specified path on the VM state.
*
* @param {String|Array} path Lua path
* @param {String|Number|Object|Array} value Value
* @param {Object} opts Options
* @return {VM}
*/
set(path, value, opts = {}) {
if (opts.force) return this.setDeep(path, value)
if (typeof path === 'string') {
return this.set(path.split('.'), value)
}
path.forEach((p, i) => {
let type
if (i === path.length-1) {
if (value && typeof value === 'object' && Object.keys(value).length === 0) {
lua.lua_createtable(this._vm, 0, 0)
} else {
interop.push(this._vm, value)
}
}
if (i === 0) {
if (path.length === 1) {
lua.lua_setglobal(this._vm, to_luastring(p))
} else {
type = lua.lua_getglobal(this._vm, to_luastring(p))
}
} else {
if (i === path.length-1) {
lua.lua_setfield(this._vm, -2, to_luastring(p))
} else {
type = lua.lua_getfield(this._vm, -1, to_luastring(p))
}
}
if (i < path.length-1 && (![5,7].includes(type))) {
throw new Error('Invalid Lua path.')
} else if (type <= 0) {
this._throwError()
}
})
lua.lua_settop(this._vm, 0)
return this
}
/**
* Sets the value at the specified deeply nested path on the VM state.
*
* @param {String|Array} path Lua path
* @param {String|Number|Object|Array} value Value
* @return {VM}
*/
setDeep(path, value) {
if (typeof path === 'string') {
return this.setDeep(path.split('.'), value)
}
for (const [i, p] of path.entries()) {
let type
if (i === path.length-1) {
return this.set(path, value)
}
lua.lua_createtable(this._vm, 0, 0)
if (i === 0) {
lua.lua_setglobal(this._vm, to_luastring(p))
type = lua.lua_getglobal(this._vm, to_luastring(p))
} else if (i < path.length-1) {
lua.lua_setfield(this._vm, -2, to_luastring(p))
type = lua.lua_getfield(this._vm, -1, to_luastring(p))
}
if (type <= 0) this._throwError();
}
}
/**
* Sets a JavaScript function at the specified path on the VM state.
* Automatically detects if the function is an `AsyncFunction`, and if so
* handles yielding and resuming from Lua.
*
* @param {String|Array} path Lua path
* @param {Function} callback JavaScript function
* @param {Object} opts Options
* @return {VM}
*/
setFunction(path, callback, opts = {}) {
this.set(path, function(vm) {
let nargs = lua.lua_gettop(vm)
let args = new Array(Math.max(0, nargs))
if (nargs > 0) {
for (let i = 0; i < nargs; i++) {
args[i] = interop.tojs(vm, i+1)
}
}
// If AsyncFunction attempt to pause and resume Lua execution
if (opts.async || callback.constructor.name === 'AsyncFunction') {
Promise.resolve(callback(...args))
.then(r => {
interop.push(vm, r)
lua.lua_resume(vm, null, 1)
})
.catch(err => {
lauxlib.luaL_error(vm, to_luastring(err.message))
})
lua.lua_yield(vm, 0)
// Otherwise, just call the function
} else {
const r = callback(...args)
interop.push(vm, r)
return 1
}
}, opts)
return this
}
/**
* Evaluates the given script within the VM state and returns the result.
*
* @param {String} code Lua code string
* @return {String|Number|Object|Array|Function}
*/
eval(code, opts = {}) {
this.exec(code)
return interop.tojs(this._vm, -1)
}
/**
* Evaluates the given script within the VM state and returns the modified
* state.
*
* @param {String} code Lua code string
* @return {VM}
*/
exec(code) {
let status
lua.lua_settop(this._vm, 0)
status = lauxlib.luaL_dostring(this._vm, to_luastring(code))
if (status !== 0) this._throwError();
return this
}
/**
* Calls a function within the VM state at the given lua path and returns the
* result.
*
* @param {String|Array} path Lua path
* @param {Array} args Function arguments
* @return {String|Number|Object|Array|Function}
*/
call(path, args = [], opts = {}) {
if (typeof path === 'string') {
return this.call(path.split('.'), args)
}
let status
path.forEach((p, i) => {
let type,
_path = to_luastring(p);
if (i === 0) {
type = lua.lua_getglobal(this._vm, _path)
} else {
type = lua.lua_getfield(this._vm, -1, _path)
}
if (type <= 0) this._throwError();
})
lauxlib.luaL_checkstack(this._vm, args.length, null)
args.forEach(a => interop.push(this._vm, a))
status = lua.lua_pcall(this._vm, args.length, 1, 0)
if (status !== 0) this._throwError();
return interop.tojs(this._vm, -1)
}
/**
* Generic error handler
* @private
*/
_throwError() {
const err = lua.lua_tojsstring(this._vm, -1)
throw new Error(`Lua Error: ${ err }`);
}
}
module.exports = VMSource