"use strict";
// Third Party
const include = require("include")(__dirname);
const stream = require("lodash/fp");
// Third Party Aliases
const concat = stream.concat;
const curry = stream.curry;
const each = stream.each;
const filter = stream.filter;
const find = stream.find;
const flow = stream.flow;
const get = stream.get;
const isEqual = stream.isEqual;
const map = stream.map;
const negate = stream.negate;
const reduce = stream.reduce;
// Project
const invokeIn = include("src/invokeIn");
/**
* The {@link Either} type is intended for handling disjointed, but related values such as the result or exceptional
* behavior of some function. It is a disjunction similar to <code>Validation</code>. The key difference of the
* {@link Either} type is the focus on the single error as opposed to aggregating many errors. Much like
* <code>Validation</code>, {@link Either} is right-biased.
* @param {*} value - Value to wrap.
* @return {Either} {@link Either} wrapped <code>value</code>.
* @example <caption>Via <code>new</code></caption>
*
* const v1 = new Right(value);
* const v2 = new Left(otherValue);
*
* @example <caption>Via function</caption>
*
* const v3 = Right.from(value);
* const v4 = Left.from(otherValue);
*
* @example <caption>Via Either function</caption>
*
* const fs = require("fs");
* const Either = require("lodash-fantasy/data/Either");
*
* function readFileSyncSafe(filePath, options) {
* let result = null;
*
* try {
* result = Either.Right.from(fs.readFileSync(filePath, options));
* } catch (error) {
* result = Either.Left.from(error);
* }
*
* return result;
* }
*
* module.exports = getValue;
*/
class Either {
/**
* @static
* @property {Right} Right - Either right.
*/
static get Right() {
return Right;
}
/**
* @static
* @property {Left} Left - Either left.
*/
static get Left() {
return Left;
}
/**
* Returns a {@link Either} that resolves all of the eithers in the collection into a single Either.
* @static
* @member
* @param {Either[]} eithers - Collection of eithers.
* @return {Either} A {@link Either} representing all {@link Right} values or a singular {@link Left}.
* @example
*
* const e1 = fs.readFileSync(filePath1);
* // => Right(contents1)
*
* const e2 = fs.readFileSync(filePath2);
* // => Right(contents2)
*
* const e3 = fs.readFileSync(filePath3);
* // => Left(error3)
*
* const e4 = fs.readFileSync(filePath4);
* // => Left(error4)
*
* Either.all([e1, e2]);
* // => Right([contents1, contents2])
*
* Either.all([e1, e2, e3]);
* // => Left(error3)
*
* Either.all([e1, e2, e3, e4]);
* // => Left(error3)
*/
static all(eithers) {
return find(Either.isLeft, eithers) || Either.of(stream(eithers).map(get("value")).reduce(concat, []));
}
/**
* Returns the first {@link Right} in the collection or finally a {@link Left}.
* @static
* @member
* @param {Either[]} eithers - Collection of eithers.
* @return {Either} First {@link Right} or finally a {@link Left}.
* @example
*
* const e1 = fs.readFileSync(filePath1);
* // => Right(contents1)
*
* const e2 = fs.readFileSync(filePath2);
* // => Right(contents2)
*
* const e3 = fs.readFileSync(filePath3);
* // => Left(error3)
*
* const e4 = fs.readFileSync(filePath4);
* // => Left(error4)
*
* Either.any([e1, e2]);
* // => Right(contents1)
*
* Either.any([e2, e3]);
* // => Right(contents2)
*
* Either.any([e3, e4]);
* // => Left(error3)
*/
static any(either) {
return find(Either.isRight, either) || find(Either.isLeft, either);
}
/**
* Creates a new {@link Either} from a <code>value</code>. If the <code>value</code> is already a {@link Either}
* instance, the <code>value</code> is returned unchanged. Otherwise, a new {@link Right} is made with the
* <code>value</code>.
* @static
* @member
* @param {*} value - Value to wrap in a {@link Either}.
* @return {Either} {@link Either} when is the <code>value</code> already wrapped or {@link Right} wrapped
* <code>value</code>.
*
* Either.from();
* // => Right()
*
* Either.from(true);
* // => Right(true)
*
* Either.from(Right.from(value));
* // => Right(value)
*
* Either.from(Left.from(error));
* // => Left(error)
*/
static from(value) {
return this.isEither(value) ? value : this.of(value);
}
/**
* Determines whether or not the value is a {@link Either}.
* @static
* @member
* @param {*} value - Value to check.
* @return {Boolean} <code>true</code> for {@link Either}; <code>false</code> for anything else.
* @example
*
* isEither();
* // => false
*
* isEither(Right.from());
* // => true
*
* isEither(Left.from(error));
* // => true
*/
static isEither(value) {
return value instanceof Either;
}
/**
* Determines whether or not the value is a {@link Left}.
* @static
* @member
* @param {*} value - Value to check.
* @return {Boolean} <code>true</code> for {@link Left}; <code>false</code> for {@link Right}.
* @example
*
* isLeft();
* // => false
*
* isLeft(Left.from(error));
* // => true
*
* isLeft(Right.from());
* // => false
*/
static isLeft(value) {
return value instanceof Left;
}
/**
* Determines whether or not the value is a {@link Right}.
* @static
* @member
* @param {*} value - Value to check.
* @return {Boolean} <code>true</code> for {@link Right}; <code>false</code> for {@link Left}.
* @example
*
* isRight();
* // => false
*
* isRight(Right.from());
* // => true
*
* isRight(Left.from(error));
* // => false
*/
static isRight(value) {
return value instanceof Right;
}
/**
* Wraps the <code>value</code> in a {@link Right}. No parts of <code>value</code> are checked.
* @static
* @member
* @param {*} value - Value to wrap.
* @return {Right} {@link Right} wrapped <code>value</code>.
* @example
*
* Either.of();
* // => Right()
*
* Either.of(true);
* // => Right(true)
*
* Either.of(Right.from(value));
* // => Right(Right(value))
*
* Either.of(Left.from(error));
* // => Right(Left(error))
*/
static of(value) {
return new Right(value);
}
/**
* Tries to invoke a <code>supplier</code>. The result of the <code>supplier</code> is returned in a {@link Right}.
* If an exception is thrown, the error is returned in a {@link Left}. The <code>function</code> takes no arguments.
* @static
* @member
* @param {Supplier} supplier - Function to invoke.
* @return {Either} {@link Right} wrapped supplier result or {@link Left} wrapped <code>error</code>.
* @example
*
* Either.try(normalFunction);
* // => Right(returnValue)
*
* Either.try(throwableFunction);
* // => Left(error)
*/
static try(method) {
try {
return Right.from(method());
} catch (error) {
return Left.from(error);
}
}
constructor(value) {
this.value = value;
}
/**
* Applies the function contained in the instance of a {@link Right} to the value contained in the provided
* {@link Right}, producing a {@link Right} containing the result. If the instance is a {@link Left}, the result
* is the {@link Left} instance. If the instance is a {@link Right} and the provided {@link Either} is {@link Left},
* the result is the provided {@link Left}.
* @abstract
* @function ap
* @memberof Either
* @instance
* @param {Either} other - Value to apply to the function wrapped in the {@link Right}.
* @return {Either} {@link Right} wrapped applied function or {@link Left}.
* @example <caption>Right#ap</caption>
*
* const findPerson = curryN(3, Person.find); // Person.find(name, birthdate, address)
*
* Right.from(findPerson) // => Right(findPerson)
* .ap(Right.try(getName())) // => Right(name)
* .ap(Right.try(getBirthdate())) // => Right(birthdate)
* .ap(Right.try(getAddress())) // => Right(address)
* .ifRight(console.log); // => Log Person.find() response
*/
/**
* Transforms a {@link Either} by applying the first function to the contained value for a {@link Left} or the
* second function for a {@link Right}. The result of each map is wrapped in the corresponding type.
* @abstract
* @function bimap
* @memberof Either
* @instance
* @param {Function} failureMap - Map to apply to the {@link Left}.
* @param {Function} successMap - Map to apply to the {@link Right}.
* @return {Either} {@link Either} wrapped value mapped with the corresponding mapping function.
* @example
*
* // Using lodash/fp/get
* Either.try(loadFile)
* .bimap(get("message"), parseFile)
* // ... other actions in workflow
*/
/**
* Applies the provided function to the value contained for a {@link Right}. The function should return the value
* wrapped in a {@link Either}. If the instance is a {@link Left}, the function is ignored and then instance is
* returned unchanged.
* @abstract
* @function chain
* @memberof Either
* @instance
* @param {Chain.<Either>} method - The function to invoke with the value.
* @return {Either} {@link Either} wrapped value returned by the provided <code>method</code>.
* @example <caption>Right#chain</caption>
*
* // Using lodash/fp/curry and getOr
* const getConfigOption = curry((path, config) => Either.Right.from(getOr(
* Either.Left.from(`Value not found at "${path}"`),
* path,
* config
* )));
*
* Either.of(config)
* .chain(getConfigOption("path.to.option"))
*/
/**
* Determines whether or not the <code>other</code> is equal in value to the current (<code>this</code>). This is
* <strong>not</strong> a reference check.
* @param {*} other - Other value to check.
* @return {Boolean} <code>true</code> if the two Eithers are equal; <code>false</code> if not equal.
* @example <caption>Reflexivity</caption>
*
* v1.equals(v1) === true;
* // => true
*
* @example <caption>Symmetry</caption>
*
* v1.equals(v2) === v2.equals(v1);
* // => true
*
* @example <caption>Transitivity</caption>
*
* (v1.equals(v2) === v2.equals(v3)) && v1.equals(v3)
* // => true
*/
equals(other) {
return isEqual(this, other);
}
/**
* Extends the Either. This is used for workflow continuation where the context has shifted.
* @abstract
* @function extend
* @memberof Either
* @instance
* @param {Extend.<Either>} - method - The function to invoke with the value.
* @return {Either}
* @example <caption>Workflow continuation</caption>
*
* // Workflow from makeRequest.js
* const makeRequest = requestOptions => requestAsPromise(requestOptions)
* .then(Right.from)
* .catch(Left.from);
*
* // Workflow from savePerson.js
* const savePerson = curry((requestOptions, eitherPerson) => eitherPerson
* .map(Person.from)
* .map(person => set("body", person, requestOptions))
* .map(makeRequest)
* );
*
* // Workflow from processResponse.js
* const processResponse = eitherResponse => eitherResponse
* .ifLeft(console.error)
* .ifRight(console.log);
*
* Either.of(person)
* .extend(savePerson({ method: "POST" }))
* .extend(processResponse);
*/
/**
* Returns the value if the instance is a {@link Right} otherwise the <code>null</code>.
* @function get
* @memberof Either
* @instance
* @return {*}
* @example <caption>Right#get</caption>
*
* Right.from(value).get();
* // => value
*
* @example <caption>Left#get</caption>
*
* Left.from(error).get();
* // => null
*/
/**
* Applies the provided function to the value contain for a {@link Left}. Any return value from the function is
* ignored. If the instance is a {@link Right}, the function is ignored and the instance is returned.
* @abstract
* @function ifLeft
* @memberof Either
* @instance
* @param {Consumer} method - The function to invoke with the value.
* @return {Either} Current instance.
* @example <caption>Right#ifLeft</caption>
*
* Right.from(value).ifLeft(doSomething); // void
* // => Right(value)
*
* @example <caption>Left#ifLeft</caption>
*
* Left.from(error).ifLeft(doSomething); // doSomething(error)
* // => Left(error)
*/
/**
* Applies the provided function to the value contain for a {@link Right}. Any return value from the function is
* ignored. If the instance is a {@link Left}, the function is ignored and the instance is returned.
* @abstract
* @function ifRight
* @memberof Either
* @instance
* @param {Consumer} method - The function to invoke with the value.
* @return {Either} Current instance.
* @example <caption>Right#ifRight</caption>
*
* Right.from(value).ifRight(doSomething); // doSomething(value)
* // => Right(value)
*
* @example <caption>Left#ifRight</caption>
*
* Left.from(error).ifRight(doSomething); // void
* // => Left(error)
*/
/**
* Determines whether or not the instance is a {@link Left}.
* @return {Boolean} <code>true</code> if the instance is a {@link Left}; <code>false</code> is not.
* @example <caption>Right#isLeft</caption>
*
* Right.from(value).isLeft();
* // => false
*
* @example <caption>Left#isLeft</caption>
*
* Left.from(error).isLeft();
* // => true
*/
isLeft() {
return this instanceof Left;
}
/**
* Determines whether or not the instance is a {@link Right}.
* @return {Boolean} <code>true</code> if the instance is a {@link Right}; <code>false</code> is not.
* @example <caption>Right</caption>
*
* Right.from(value).isLeft();
* // => true
*
* @example <caption>Left#isRight</caption>
*
* Left.from(error).isLeft();
* // => false
*/
isRight() {
return this instanceof Right;
}
/**
* Applies the provided function to the value contained for a {@link Right} which is, in turn, wrapped in a
* {@link Right}. If the instance is a {@link Left}, the function is ignored and then instance is returned unchanged.
* @abstract
* @function map
* @memberof Either
* @instance
* @param {Function} method - The function to invoke with the value.
* @return {Either} {@link Either} wrapped value mapped with the provided <code>method</code>.
* @example
*
* // Using lodash/fp/flow and sort
* Right.from([1, 3, 2]).map(flow(sort, join(", ")));
* // => Right("1, 2, 3")
*
* Left.from(error).map(flow(sort, join(", ")));
* // => Left(error)
*/
/**
* @see Either.of
*/
of(value) {
return Either.of(value);
}
/**
* Returns the value if the instance is a {@link Right} otherwise returns the value supplied if the instance is a
* {@link Left}.
* @abstract
* @function orElse
* @memberof Either
* @instance
* @param {Consumer} method - The function to invoke with the value.
* @return {*}
* @example <caption>Right#orElse</caption>
*
* Right.from(value).orElse(otherValue);
* // => value
*
* @example <caption>Left#orElse</caption>
*
* Left.from(error).orElse(otherValue);
* // => otherValue
*/
/**
* Return the value if the instance is a {@link Right} otherwise returns the value from the function provided.
* @abstract
* @function orElseGet
* @memberof Either
* @instance
* @param {Supplier} method - The function supplying the optional value.
* @return {*}
* @example <caption>Right#orElseGet</caption>
*
* Right.from(value).orElseGet(getOtherValue);
* // => value
*
* @example <caption>Left#orElseGet</caption>
*
* Left.from(error).orElse(getOtherValue);
* // => otherValue
*/
/**
* Returns the value if the instance is a {@link Right} otheriwse throws the <code>Error</code> supplied by the
* function provided. The function receives the value of the {@link Left} as its argument.
* @abstract
* @function orElseThrow
* @memberof Either
* @instance
* @param {Function} method - The function to invoke with the value.
* @return {*}
* @throws {Error} returned by the provided function.
* @example <caption>Right#orElseThrow</caption>
*
* Right.from(value).orElseThrow(createException);
* // => value
*
* @example <caption>Left#orElseThrow</caption>
*
* Left.from(error).orElseThrow(createException); // throw createException(error)
*/
/**
* Converts the Either to a {@link Maybe}. {@link Right} becomes {@link Just} and {@link Left} becomes
* {@link Nothing}.
* @abstract
* @function toMaybe
* @memberof Either
* @instance
* @param {Maybe} maybe - Maybe implementation.
* @return {Maybe} {@link Maybe} wrapped <code>value</code>.
* @example <caption>Right#toMaybe</caption>
*
* Right.from(value).toMaybe(Maybe);
* // => Maybe.Just(value);
*
* @example <caption>Left#toMaybe</caption>
*
* Left.from(error).toMaybe(Maybe);
* // => Maybe.Nothing();
*/
/**
* Converts the Either to a <code>Promise</code> using the provided <code>Promise</code> implementation.
* @abstract
* @function toPromise
* @memberof Either
* @instance
* @param {Promise} promise - Promise implementation.
* @return {Promise} <code>Promise</code> wrapped <code>value</code>.
* @example <caption>Right#toPromise</caption>
*
* const Bluebird = require("bluebird");
*
* Right.from(value).toPromise(Bluebird);
* // => Promise.resolve(value);
*
* @example <caption>Left#toPromise</caption>
*
* const Bluebird = require("bluebird");
*
* Left.from(error).toPromise(Bluebird);
* // => Promise.reject(error);
*/
/**
* Returns a <code>String</code> representation of the {@link Either}.
* @abstract
* @function toString
* @memberof Either
* @instance
* @return {String} <code>String</code> representation.
* @example <caption>Right#toString</caption>
*
* Right.from(1).toString();
* // => "Either.Right(1)"
*
* @example <caption>Left#toString</caption>
*
* Left.from(error).toString();
* // => "Either.Left(error)"
*/
/**
* Converts the Either to a {@link Validation}. {@link Right} becomes {@link Success} and {@link Left} becomes
* {@link Failure}.
* @abstract
* @function toValidation
* @memberof Either
* @instance
* @param {Validation} validation - Validation implementation.
* @return {Validation} {@link Validation} wrapped <code>value</code>.
* @example <caption>Right#toValidation</caption>
*
* Right.from(value).toValidation(Validation);
* // => Validation.Success(value);
*
* @example <caption>Left#toValidation</caption>
*
* Left.from(error).toValidation(Validation);
* // => Validation.Failure();
*/
}
/**
* Iterates over a collection of eithers and invokes the <code>iteratee</code> for each {@link Either}. The
* <code>iteratee</code> is invoked with one argument: <code>(value)</code>. Iteratee functions may exit iteration
* early by explicitly returning a {@link Left}.
* @static
* @member
* @param {Consumer} iteratee - The function to invoke per iteration.
* @param {Either[]} values - Collection of Eithers over which to iterate.
* @return {Either[]} Current {@link Either} collection.
* @example
*
* const optionalValues = [
* getValue(path1, source), // => Right(value1)
* getValue(path2, source), // => Right(value2)
* getValue(path3, source), // => Left()
* getValue(path4, source) // => Left()
* ];
*
* Either.each(eitherValue => eitherValue.ifRight(console.log), optionalValues);
* // => Right(value1)
* // => Right(value2)
*/
Either.each = curry((iteratee, values) => each(
flow(iteratee, negate(Either.isLeft)),
values
));
/**
* Determines whether or not the <code>other</code> is equal in value to the current (<code>this</code>). This is
* <strong>not</strong> a reference check.
* @static
* @member
* @param {*} other - Other value to check.
* @return {Boolean} <code>true</code> if the two validations are equal; <code>false</code> if not equal.
* @example <caption>Reflexivity</caption>
*
* Either.equals(v1, v1) === true;
* // => true
*
* @example <caption>Symmetry</caption>
*
* Either(v1, v2) === Either.equals(v2, v1);
* // => true
*
* @example <caption>Transitivity</caption>
*
* (Either.equals(v1, v2) === Either.equals(v2, v3)) && Either.equals(v1, v3)
* // => true
*/
Either.equals = isEqual;
/**
* Iterates over a collection of values, returning an array of all values the <code>predicate</code> for which returns
* truthy. The <code>predicate</code> is invoked with one argument: <code>(value)</code>.
* @static
* @member
* @param {Predicate} predicate - The function to invoke per iteration.
* @param {Eithers[]} values - Collection of values over which to iterate.
* @return {Eithers[]} Filtered {@link Either} collection.
* @example <caption>Filter and log failures</caption>
*
* const optionalValues = [
* getValue(path1, config), // => Right(value1)
* getValue(path2, config), // => Right(value2)
* getValue(path3, config), // => Left()
* getValue(path4, config) // => Left()
* ];
*
* Either.filter(Either.isRight, optionalValues);
* // => [Right(value1), Right(value2)]
*/
Either.filter = filter;
/**
* Creates an array of values by invoking {@link Either#map} with the <code>iteratee</code> for each {@link Either} in
* the collection. The iteratee is invoked with one argument: <code>(value)</code>.
* @static
* @member
* @param {Function} iteratee - The function to invoke per iteration.
* @param {Either[]} values - Collection of values over which to iterate.
* @return {Either[]} Mapped {@link Either} collection.
* @example <caption>Mapping each Either's value</caption>
*
* const optionalValues = [
* getValue(path1, config), // => Right(1.5)
* getValue(path2, config), // => Right(2.25)
* getValue(path3, config), // => Left(error1)
* getValue(path4, config) // => Left(error2)
* ];
*
* Either.mapIn(Math.floor, optionalValues);
* // => [Right(1), Right(2), Left(error1), Left(error2)]
*/
Either.mapIn = curry((iteratee, values) => map(invokeIn("map", iteratee), values));
/**
* Creates an array of values by running each {@link Either} in collection through the <code>iteratee</code>. The
* iteratee is invoked with one argument: <code>(value)</code>.
* @static
* @member
* @param {Function} iteratee - The function to invoke per iteration.
* @param {Either[]} values - Collection of values over which to iterate.
* @return {Either[]} Mapped collection.
* @example <caption>Mapping all values to promises</caption>
*
* const optionalValues = [
* getValue(path1, config), // => Right(value1)
* getValue(path2, config), // => Right(value2)
* getValue(path3, config), // => Left(error1)
* getValue(path4, config) // => Left(error2)
* ];
*
* Either.map(Either.toPromise, optionalValues);
* // => [Promise.resolve(price1), Promise.resolve(price2), Promise.reject(error1), Promise.reject(error2)]
*/
Either.map = map;
/**
* Reduces collection to a value which is the accumulated result of running each value in the <code>values</code>
* collection through the <code>iteratee</code>, where each successive invocation is supplied the return value of the
* previous. The iteratee is invoked with two arguments: <code>(accumulator, value)</code>.
* @static
* @member
* @param {Reduction} iteratee - The function to invoke per iteration.
* @param {*} accumulator - The initial value.
* @param {Either[]} values - Collection of values over which to iterate.
* @return {*} Accumulator.
* @example
*
* const eitherValues = [
* getValue(path1, config), // => Right(value1)
* getValue(path2, config), // => Right(value2)
* getValue(path3, config), // => Left(error1)
* getValue(path4, config) // => Left(error2)
* ];
*
* // Using lodash/fp/concat
* Either.reduce(
* (result, value) => value.isRight() ? concat(result, value.get()) : result,
* [],
* eitherValues
* );
* // => [value1, value2]
*/
Either.reduce = reduce;
/**
* Converts a {@link Either} to a {@link Maybe}. {@link Right} becomes a {@link Just} and {@link Left} becomes
* {@link Nothing}.
* @static
* @member
* @param {Maybe} maybe - Maybe implementation.
* @param {Either} value - Either to convert.
* @return {Maybe} {@link Maybe} wrapped <code>value</code>.
* @example <caption>Right to Just</caption>
*
* Either.toMaybe(Maybe, Right.from(value));
* // => Maybe.Just(value);
*
* @example <caption>Left to Nothing</caption>
*
* Either.toMaybe(Maybe, Left.from(error));
* // => Maybe.Nothing();
*/
Either.toMaybe = invokeIn("toMaybe");
/**
* Converts a validation to a <code>Promise</code> using the provided <code>Promise</code> implementation.
* @static
* @member
* @param {Promise} promise - Promise implementation.
* @param {Either} value - Either to convert.
* @return {Promise} <code>Promise</code> wrapped <code>value</code>.
* @example <caption>Convert with bluebird's implementation of Promise</caption>
*
* const toBluebird = Either.toPromise(require("bluebird"));
*
* toBluebird(Right.from(value));
* // => Promise.resolve(value);
*
* toBluebird(Left.from(error));
* // => Promise.reject(error);
*/
Either.toPromise = invokeIn("toPromise");
/**
* Converts a {@link Either} to a {@link Validation}. {@link Right} becomes a {@link Success} and {@link Left} becomes
* {@link Failure}.
* @static
* @member
* @param {Validation} validation - Validation implementation.
* @param {Either} value - Either to convert.
* @return {Validation} {@link Validation} wrapped <code>value</code>.
* @example <caption>Right to Success</caption>
*
* Either.toValidation(Validation, Right.from(value));
* // => Validation.Success(value);
*
* @example <caption>Left to Failure</caption>
*
* Either.toValidation(Validation, Left.from(error));
* // => Validation.Failure();
*/
Either.toValidation = invokeIn("toValidation");
/**
* @extends Either
* @inheritdoc
*/
class Left extends Either {
/**
* Creates a new {@link Left} from a <code>value</code>. If the <code>value</code> is already a {@link Either}
* instance, the <code>value</code> is returned unchanged. Otherwise, a new {@link Left} is made with the
* <code>value</code>.
* @static
* @param {*} value - Value to wrap in a {@link Left}.
* @return {Either} {@link Either} when is the <code>value</code> already wrapped or {@link Left} wrapped
* <code>value</code>.
* @example <caption>Left from nothing</caption>
*
* Left.from();
* // => Left()
*
* @example <caption>Left from arbitrary value</caption>
*
* Left.from(error);
* // => Left(error)
*
* @example <caption>Left from Right</caption>
*
* Left.from(Right.from(value));
* // => Right.from(value)
*
* @example <caption>Left from another Left</caption>
*
* Left.from(Left.from(error));
* // => Left(error)
*/
static from(value) {
return Either.isEither(value) ?
value :
new Left(value);
}
constructor(value) {
super(value);
}
ap() {
return this;
}
bimap(leftMap) {
return Left.from(leftMap(this.value));
}
chain() {
return this;
}
extend() {
return this;
}
get() {
return null;
}
ifLeft(method) {
method();
return this;
}
ifRight() {
return this;
}
map() {
return this;
}
orElse(value) {
return value;
}
orElseGet(method) {
return method();
}
orElseThrow(method) {
throw method(this.value);
}
toMaybe(maybe) {
return new maybe.Nothing();
}
toPromise(promise) {
return promise.reject(this.value);
}
toString() {
return `Either.Left(${this.value})`;
}
toValidation(validation) {
return new validation.Failure(this.value);
}
}
/**
* @extends Either
* @inheritdoc
*/
class Right extends Either {
/**
* Creates a new {@link Right} from a <code>value</code>. If the <code>value</code> is already a {@link Either}
* instance, the <code>value</code> is returned unchanged. Otherwise, a new {@link Right} is made with the
* <code>value</code>.
* @static
* @param {*} value - Value to wrap in a {@link Right}.
* @return {Either} {@link Either} when is the <code>value</code> already wrapped or {@link Right} wrapped
* <code>value</code>.
* @example <caption>Right from nothing</caption>
*
* Right.from();
* // => Right()
*
* @example <caption>Right from arbitrary value</caption>
*
* Right.from(true);
* // => Right(true)
*
* @example <caption>Right from another Right</caption>
*
* Right.from(Right.from(value));
* // => Right(value)
*
* @example <caption>Right from Left</caption>
*
* Right.from(Left.from(error));
* // => Left(error)
*/
static from(value) {
return Either.isEither(value) ?
value :
new Right(value);
}
constructor(value) {
super(value);
}
ap(other) {
return other.map(this.value);
}
bimap(leftMap, rightMap) {
return Right.from(rightMap(this.value));
}
chain(method) {
return Either.from(method(this.value));
}
extend(method) {
return Either.from(method(this));
}
get() {
return this.value;
}
ifLeft() {
return this;
}
ifRight(method) {
method(this.value);
return this;
}
map(method) {
return Right.of(method(this.value));
}
orElse() {
return this.value;
}
orElseGet() {
return this.value;
}
orElseThrow() {
return this.value;
}
toMaybe(maybe) {
return new maybe.Just(this.value);
}
toPromise(promise) {
return promise.resolve(this.value);
}
toString() {
return `Either.Right(${this.value})`;
}
toValidation(validation) {
return new validation.Success(this.value);
}
}
module.exports = Either;