AlkantarClanX12
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'use strict'
const Method = require('./method')
const Role = require('./role')
const util = require('./util')
const kCache = Symbol('cache')
const kDefaultMethod = Symbol('defaultMethod')
const kMethods = Symbol('methods')
const kNoNext = Symbol('noNext')
module.exports = function genfun (opts) {
function gf () {
if (!gf[kMethods].length && gf[kDefaultMethod]) {
return gf[kDefaultMethod].func.apply(this, arguments)
} else {
return gf.applyGenfun(this, arguments)
}
}
Object.setPrototypeOf(gf, Genfun.prototype)
gf[kMethods] = []
gf[kCache] = {key: [], methods: [], state: STATES.UNINITIALIZED}
if (opts && typeof opts === 'function') {
gf.add(opts)
} else if (opts && opts.default) {
gf.add(opts.default)
}
if (opts && opts.name) {
Object.defineProperty(gf, 'name', {
value: opts.name
})
}
if (opts && opts.noNextMethod) {
gf[kNoNext] = true
}
return gf
}
class Genfun extends Function {}
Genfun.prototype.isGenfun = true
const STATES = {
UNINITIALIZED: 0,
MONOMORPHIC: 1,
POLYMORPHIC: 2,
MEGAMORPHIC: 3
}
const MAX_CACHE_SIZE = 32
/**
* Defines a method on a generic function.
*
* @function
* @param {Array-like} selector - Selector array for dispatching the method.
* @param {Function} methodFunction - Function to execute when the method
* successfully dispatches.
*/
Genfun.prototype.add = function addMethod (selector, func) {
if (!func && typeof selector === 'function') {
func = selector
selector = []
}
selector = [].slice.call(selector)
for (var i = 0; i < selector.length; i++) {
if (!selector.hasOwnProperty(i)) {
selector[i] = Object.prototype
}
}
this[kCache] = {key: [], methods: [], state: STATES.UNINITIALIZED}
let method = new Method(this, selector, func)
if (selector.length) {
this[kMethods].push(method)
} else {
this[kDefaultMethod] = method
}
return this
}
/**
* Removes a previously-defined method on `genfun` that matches
* `selector` exactly.
*
* @function
* @param {Genfun} genfun - Genfun to remove a method from.
* @param {Array-like} selector - Objects to match on when finding a
* method to remove.
*/
Genfun.prototype.rm = function removeMethod () {
throw new Error('not yet implemented')
}
/**
* Returns true if there are methods that apply to the given arguments on
* `genfun`. Additionally, makes sure the cache is warmed up for the given
* arguments.
*
*/
Genfun.prototype.hasMethod = function hasMethod () {
const methods = this.getApplicableMethods(arguments)
return !!(methods && methods.length)
}
/**
* This generic function is called when `genfun` has been called and no
* applicable method was found. The default method throws an `Error`.
*
* @function
* @param {Genfun} genfun - Generic function instance that was called.
* @param {*} newthis - value of `this` the genfun was called with.
* @param {Array} callArgs - Arguments the genfun was called with.
*/
module.exports.noApplicableMethod = module.exports()
module.exports.noApplicableMethod.add([], (gf, thisArg, args) => {
let msg =
'No applicable method found when called with arguments of types: (' +
[].map.call(args, (arg) => {
return (/\[object ([a-zA-Z0-9]+)\]/)
.exec(({}).toString.call(arg))[1]
}).join(', ') + ')'
let err = new Error(msg)
err.genfun = gf
err.thisArg = thisArg
err.args = args
throw err
})
/*
* Internal
*/
Genfun.prototype.applyGenfun = function applyGenfun (newThis, args) {
let applicableMethods = this.getApplicableMethods(args)
if (applicableMethods.length === 1 || this[kNoNext]) {
return applicableMethods[0].func.apply(newThis, args)
} else if (applicableMethods.length > 1) {
let idx = 0
const nextMethod = function nextMethod () {
if (arguments.length) {
// Replace args if passed in explicitly
args = arguments
Array.prototype.push.call(args, nextMethod)
}
const next = applicableMethods[idx++]
if (idx >= applicableMethods.length) {
Array.prototype.pop.call(args)
}
return next.func.apply(newThis, args)
}
Array.prototype.push.call(args, nextMethod)
return nextMethod()
} else {
return module.exports.noApplicableMethod(this, newThis, args)
}
}
Genfun.prototype.getApplicableMethods = function getApplicableMethods (args) {
if (!args.length || !this[kMethods].length) {
return this[kDefaultMethod] ? [this[kDefaultMethod]] : []
}
let applicableMethods
let maybeMethods = cachedMethods(this, args)
if (maybeMethods) {
applicableMethods = maybeMethods
} else {
applicableMethods = computeApplicableMethods(this, args)
cacheArgs(this, args, applicableMethods)
}
return applicableMethods
}
function cacheArgs (genfun, args, methods) {
if (genfun[kCache].state === STATES.MEGAMORPHIC) { return }
var key = []
var proto
for (var i = 0; i < args.length; i++) {
proto = cacheableProto(genfun, args[i])
if (proto) {
key[i] = proto
} else {
return null
}
}
genfun[kCache].key.unshift(key)
genfun[kCache].methods.unshift(methods)
if (genfun[kCache].key.length === 1) {
genfun[kCache].state = STATES.MONOMORPHIC
} else if (genfun[kCache].key.length < MAX_CACHE_SIZE) {
genfun[kCache].state = STATES.POLYMORPHIC
} else {
genfun[kCache].state = STATES.MEGAMORPHIC
}
}
function cacheableProto (genfun, arg) {
var dispatchable = util.dispatchableObject(arg)
if (Object.hasOwnProperty.call(dispatchable, Role.roleKeyName)) {
for (var j = 0; j < dispatchable[Role.roleKeyName].length; j++) {
var role = dispatchable[Role.roleKeyName][j]
if (role.method.genfun === genfun) {
return null
}
}
}
return Object.getPrototypeOf(dispatchable)
}
function cachedMethods (genfun, args) {
if (genfun[kCache].state === STATES.UNINITIALIZED ||
genfun[kCache].state === STATES.MEGAMORPHIC) {
return null
}
var protos = []
var proto
for (var i = 0; i < args.length; i++) {
proto = cacheableProto(genfun, args[i])
if (proto) {
protos[i] = proto
} else {
return
}
}
for (i = 0; i < genfun[kCache].key.length; i++) {
if (matchCachedMethods(genfun[kCache].key[i], protos)) {
return genfun[kCache].methods[i]
}
}
}
function matchCachedMethods (key, protos) {
if (key.length !== protos.length) { return false }
for (var i = 0; i < key.length; i++) {
if (key[i] !== protos[i]) {
return false
}
}
return true
}
function computeApplicableMethods (genfun, args) {
args = [].slice.call(args)
let discoveredMethods = []
function findAndRankRoles (object, hierarchyPosition, index) {
var roles = Object.hasOwnProperty.call(object, Role.roleKeyName)
? object[Role.roleKeyName]
: []
roles.forEach(role => {
if (role.method.genfun === genfun && index === role.position) {
if (discoveredMethods.indexOf(role.method) < 0) {
Method.clearRank(role.method)
discoveredMethods.push(role.method)
}
Method.setRankHierarchyPosition(role.method, index, hierarchyPosition)
}
})
// When a discovered method would receive more arguments than
// were specialized, we pretend all extra arguments have a role
// on Object.prototype.
if (util.isObjectProto(object)) {
discoveredMethods.forEach(method => {
if (method.minimalSelector <= index) {
Method.setRankHierarchyPosition(method, index, hierarchyPosition)
}
})
}
}
args.forEach((arg, index) => {
getPrecedenceList(util.dispatchableObject(arg))
.forEach((obj, hierarchyPosition) => {
findAndRankRoles(obj, hierarchyPosition, index)
})
})
let applicableMethods = discoveredMethods.filter(method => {
return (args.length === method._rank.length &&
Method.isFullySpecified(method))
})
applicableMethods.sort((a, b) => Method.score(a) - Method.score(b))
if (genfun[kDefaultMethod]) {
applicableMethods.push(genfun[kDefaultMethod])
}
return applicableMethods
}
/*
* Helper function for getting an array representing the entire
* inheritance/precedence chain for an object by navigating its
* prototype pointers.
*/
function getPrecedenceList (obj) {
var precedenceList = []
var nextObj = obj
while (nextObj) {
precedenceList.push(nextObj)
nextObj = Object.getPrototypeOf(nextObj)
}
return precedenceList
}