import { isFunction, isUndefined } from 'underscore';
import { cloneImpl, isLensClass } from '../src-cjs/constants.js';
import CustomStep from './custom_step.js';
import fusion from './fusion.js';
import Optic from './optic.js';
import OpticArray from './optic_array.js';
import { getIterator, handleNoniterableValue, index_maybe, isLens } from './utils.js';
// Polyfill support for lenses to standard JavaScript types
import './stdlib_support/object.js';
import './stdlib_support/array.js';
import './stdlib_support/map.js';
/**
* @typedef {Object} OptionalThrow
* @property {*} [orThrow] The value to `throw` in case of an error.
*/
/**
* @typedef {Object} FallbackBindingResult
* @property {Function} [or] The function to return if the slot does not contain a function.
*/
/**
* @typedef {Object} Maybe
* @property {*} [just] The contained value
* @see Haskell's "Maybe" data type
*
* @description
* The presence of `just` as a property indicates the "Just" construction of
* the Maybe monad — the presence of a value (even if `undefined`). A Maybe
* without a `just` property is the "Nothing" construction.
*/
/**
* @extends Optic
* @property {Array.<*>} keys Indexing/subscripting values to be applied successively to subjects of this lens
*/
class Lens extends Optic {
/**
* @summary Class for operating immutably on a specific "slot" in complex data
* @extends Optic
* @param {...*} key A value to use in an application of subscripting (i.e. square bracket operator)
*
* @description
* A Lens constructed as `let l = new Lens('address', 'street', 0)` represents
* a certain slot within a complex subject value. If we had a record
* ```js
* const record = {
* address: {
* street: ["123 Somewhere Ln.", "Apt. 42"]
* }
* };
* ```
* then applying our lens with `l.get(record)` would evaluate to "123 Somewhere Ln.".
*
* **NOTE:** If a *key* of a Lens is a negative number and
* the container accessed at that level is an Array, the negtive index works
* like `Array.prototype.slice`, counting from the end of the Array.
*
* But Lenses offer more functionality than retrieval of values from a deeply
* structured value — they can create a minimally cloned value deeply equal
* to the subject but for the slot targeted by the lens and strictly equal
* but for the slot targeted by the lens and the nodes in the input subject
* traversed to reach that slot in the subject's tree.
*
* When constructing a modified clone, it is possible that some step of the
* Lens will target a slot within a container-not-existing-in-subject. In this
* case, the container to be created is intuited from the key that would
* access it: an Array if the key is a number, otherwise an Object. Alternative
* container construction can be specified via {@link Factory} or {@link Step}.
*
* Typically, instances are constructed by calling the Function exported
* from `natural-lenses` (if `require`d) or its default export (if `import`ed),
* conventionally named `lens`.
*/
constructor(...keys) {
super();
this.keys = keys;
}
/**
* @inheritdoc
*/
thence(...keys) {
return new Lens(...this.keys, ...keys);
}
/**
* @summary Get a combination of presence and value of this slot
* @param {*} subject The data to query
* @param {...*} tail Additional subject for repeated application
* @return {Maybe.<*>} Empty Object if this slot is not present in *subject*,
* otherwise Object with `just` property containing value of this slot in *subject*
*
* @description
* This implements the Maybe monad (familiar from Haskell), where Nothing is
* represented as an empty Object and Just is represented as an Object with a
* `just` property containing the value in the slot.
*
* If *tail* is given and getting this slot from from *subject* yields a
* Lens (as indicated by a truthy `lens.isLens` property), then `#get_maybe()`
* is called on that Lens, passing the spread of *tail*. If the value of
* this slot is *not* a Lens, the result is an empty Object.
*/
get_maybe(subject, ...tail) {
let cur = subject;
for (let i = 0; i < this.keys.length; i++) {
const k = this.keys[i];
const next_maybe = (function() {
if (k instanceof CustomStep) {
return k.get_maybe(cur);
} else {
return index_maybe(cur, k);
}
}());
if ('just' in next_maybe) {
cur = next_maybe.just;
} else {
return {}
}
}
if (tail.length > 0) {
return isLens(cur) ? cur.get_maybe(...tail) : {};
}
return {just: cur};
}
/**
* @template T
* @summary Clone *subject*, setting the value of this slot within the clone
* @param {T} subject The input structured data
* @param {*} newVal The new value to inject into the slot identified by this lens
* @return {T} A minimally changed clone of *subject* with *newVal* in this slot
*
* @description
* "Minimally changed" means that reference-copies are used wherever possible
* while leaving subject unchanged, and that setting the slot to the strict-
* equal value it already has results in returning subject.
*/
setInClone(subject, newVal) {
const slots = new Array(this.keys.length);
let cur = subject;
for (let i = 0; i < this.keys.length; i++) {
const k = this.keys[i];
const slot = slots[i] = makeSlot(cur, k);
const next_maybe = slot.get_maybe();
if ('just' in next_maybe) {
cur = next_maybe.just;
} else if (i + 1 < this.keys.length) {
cur = this._constructFor(i + 1);
}
}
if (slots[slots.length - 1].get() === newVal) {
return subject;
}
cur = newVal;
for (let i = slots.length - 1; i >= 0; i--) {
cur = slots[i].cloneAndSet(cur);
}
return cur;
}
/**
* @template T
* @summary Clone the input, transforming the value within this slot with a function
* @param {T} subject The input structured data
* @param {function(*): *} fn The function that transforms the slot value
* @param {Object} [opts]
* @param {Boolean} opts.addMissinng=false Whether to add the slot if missing in subject
* @return {T} A minimally changed clone of *subject* with *fn* applied to the value in this slot
*
* @description
* If this slot is missing in subject, fn will not be called unless *addMissing*
* is true, in which case fn will be called with undefined.
*
* "Minimally changed" means that reference-copies are used wherever possible
* while leaving subject unchanged, and that setting the slot to the strict-
* equal value it already has results in returning subject.
*/
xformInClone(subject, fn, {addMissing = false} = {}) {
const slots = new Array(this.keys.length);
let cur = subject;
for (let i = 0; i < this.keys.length; i++) {
const k = this.keys[i];
const slot = slots[i] = makeSlot(cur, k);
const next_maybe = slot.get_maybe();
if ('just' in next_maybe) {
cur = next_maybe.just;
} else if (addMissing) {
if (i + 1 < this.keys.length) {
cur = this._constructFor(i + 1);
}
} else {
return subject;
}
}
if (slots.length) {
const prevVal = slots[slots.length - 1].get();
cur = fn(prevVal);
if (cur === prevVal) {
return subject;
}
for (let i = slots.length - 1; i >= 0; i--) {
cur = slots[i].cloneAndSet(cur);
}
} else {
cur = fn(subject);
}
return cur;
}
/**
* @template T
* @summary Clone the input, transforming or deleting the Maybe value of this slot with a function
* @param {T} subject The input structured data
* @param {function(Maybe): Maybe} fn The function transforming the {@link Maybe} value of the slot
* @return {T} A minimally changed clone of *subject* with this slot transformed per *fn*
*
* @description
* The value given to *fn* will be the result of {@link Lens#get_maybe}, which
* indicates absence of this slot in *subject* by omitting the `just` property,
* which otherwise contains the value of this slot in *subject*. The value
* returned by *fn* is the result that should be returned by calling
* {@link Lens#get_maybe} of this slot on the modified clone: if no `just`
* property is returned by *fn*, the slot is deleted from the clone, and
* the value of the `just` property is otherwise set for this slot in the
* clone.
*
* This implements what would, in Haskell, be described as:
*
* Json -> (Maybe Json -> Maybe Json) -> Json
*
* "Minimally changed" means that reference-copies are used wherever possible
* while leaving subject unchanged, and that setting the slot to the strict-
* equal value it already has results in returning subject.
*/
xformInClone_maybe(subject, fn) {
const slots = new Array(this.keys.length);
let cur = subject, present = true;
for (let i = 0; i < this.keys.length; i++) {
const k = this.keys[i];
const slot = slots[i] = makeSlot(cur, k);
const next_maybe = slot.get_maybe();
if ('just' in next_maybe) {
cur = next_maybe.just;
} else {
present = false;
if (i + 1 < this.keys.length) {
cur = this._constructFor(i + 1);
}
}
}
if (slots.length) {
const prevVal = slots[slots.length - 1].get();
const maybe_val = fn(present ? {just: prevVal} : {});
const setting = 'just' in maybe_val;
if (present && !setting) {
cur = slots[slots.length - 1].cloneOmitting();
if (cur === slots[slots.length - 1].subject) {
return subject;
}
for (let i = slots.length - 2; i >= 0; i--) {
cur = slots[i].cloneAndSet(cur);
}
} else if (setting) {
if (present && prevVal === maybe_val.just) {
return subject;
}
cur = maybe_val.just;
for (let i = slots.length - 1; i >= 0; i--) {
cur = slots[i].cloneAndSet(cur);
}
} else {
return subject;
}
} else {
cur = fn({just: subject}).just;
}
return cur;
}
/**
* @summary DRYly bind a Function to the Object from which it was obtained
* @param {*} subject The input structured data
* @param {Object} [options]
* @param {boolean} [options.bindNow=true] Bind to the target of this lens with *subject* now rather than when the result function is invoked
* @param {*} [options.orThrow] {@link OptionalThrow} if the slot referenced does not contain a Function; has precedence over *or*
* @param {Function} [options.or] {@link FallbackBindingResult}, a Function to return if the slot referenced does not contain a Function
* @return {Function} A Function bound to the previous object in the chain used to access the Function, or `function() {}` if no such function found
*
* The return value of this method is *always* a Function; if the slot identified
* by this Lens is not present in *subject* or does not contain a Function,
* the trivial function (`function () {}` or equivalent) will be returned.
*
* @description
* Use this to avoid the dreaded Javascript binding repetition of
* `x.y.z.fn.bind(x.y.z)`. Instead, use `lens('y', 'z', 'fn').bound(x)`.
*/
bound(subject, {bindNow = true, orThrow, or} = {}) {
const lens = this;
function lookUpPlayers() {
const lCopy = new Lens(...lens.keys), mname = lCopy.keys.pop();
const mSubj = lCopy.get(subject), fn = (function() {
try {return mSubj[mname];} catch (e) {}
}());
return {mSubj, fn};
}
if (bindNow) {
const {mSubj, fn} = lookUpPlayers();
if (isFunction(fn)) {
return fn.bind(mSubj);
}
if (orThrow) {
throw orThrow;
} else if (!isUndefined(or)) {
return or;
}
return function() {};
} else return function (...args) {
const {mSubj, fn} = lookUpPlayers();
if (isFunction(fn)) {
return fn.apply(mSubj, args);
}
if (orThrow) {
throw orThrow;
} else if (!isUndefined(or)) {
return or.apply(undefined, args);
}
};
}
/**
* Combine the effects of multiple Lenses
*
* It is preferred to use {@link module:natural-lenses#fuse}
*/
static fuse(...lenses) {
if (!lenses.every(l => l.constructor === Lens)) {
throw "Expected all arguments to be exactly Lens (no derived classes)";
}
return new Lens(...lenses.flatMap(l => l.keys));
}
/*
* @package
* @summary Construct a container for a clone given the depth
*/
_constructFor(depth) {
const key = this.keys[depth];
if (key instanceof CustomStep) {
return key.construct();
}
return (typeof key === 'number') ? [] : {};
}
}
class Slot {
constructor(target, key) {
this.target = target;
this.key = key;
}
get() {
return this.get_maybe().just;
}
get_maybe() {
return index_maybe(this.target, this.key);
}
cloneAndSet(val) {
const rval = this.cloneTarget({set: [this.key, val]});
return rval;
}
cloneOmitting() {
const rval = this.cloneTarget({spliceOut: this.key});
return rval;
}
cloneTarget(opDesc /* {set, spliceOut} */ = {}) {
let target = this.target;
if (!target) {
target = (typeof key === 'number') ? [] : {};
}
return target[cloneImpl](opDesc);
}
}
class CSSlot {
constructor(target, customStep) {
this.target = target;
this.customStep = customStep;
}
get() {
return this.get_maybe().just;
}
get_maybe() {
return this.customStep.get_maybe(this.target);
}
cloneAndSet(val) {
return this.customStep.updatedClone(this.target, {just: val});
}
cloneOmitting() {
return this.customStep.updatedClone(this.target, {});
}
}
// Monkey-patch Optic here with `thence` to avoid cyclic dependency in optic.js
let fuse = null;
/**
* @function Optic#thence
* @summary Build a "deeper" lens/optic
* @param {...*} key A value to use in an application of subscripting (i.e. square bracket operator)
* @returns {Lens|OpticArray} An Optic that fuses this optic with a Lens looking at finer detail
*
* @description
* This method creates a new Optic that looks at finer detail than the Optic
* on which it was called. It either actually or effectively fuses a new
* {@link Lens} to the right of this optic, as with [fuse]{@link module:natural-lenses#fuse}.
*/
Optic.prototype.thence = function(...keys) {
fuse = fuse || fusion({ Lens, OpticArray});
return fuse(this, new Lens(...keys));
}
function makeSlot(cur, k) {
return new ((k instanceof CustomStep) ? CSSlot : Slot)(cur, k);
}
export default Lens;