typescript(option): feat: added the base helpers

Signed-off-by: prescientmoon <git@moonythm.dev>

typescript/option/src/helpers.ts

@@ -0,0 +1,110 @@
+import { Option, Some, None } from './types'
+import { Binder, Folder, Mapper, Predicate, BackFolder } from './internalTypes'
+import Internals, { SomeClass } from './internals'
+
+export const isSome = <T>(option: Option<T>) =>
+    option instanceof Internals.SomeClass
+export const isNothing = <T>(option: Option<T>) =>
+    option instanceof Internals.NoneClass
+
+export const match = <T, U>(
+    option: Option<T>,
+    caseSome: (v: T) => U,
+    caseNone: () => U
+) => {
+    if (isSome(option)) {
+        return caseSome((option as SomeClass<T>)[Internals.someValue])
+    }
+
+    return caseNone()
+}
+
+export const bind = <T, U>(
+    binder: Binder<T, U>,
+    option: Option<T>
+): Option<U> => {
+    return match(option, binder, () => None)
+}
+
+export const map = <T, U>(
+    mapper: Mapper<T, U>,
+    option: Option<T>
+): Option<U> => {
+    return match(
+        option,
+        v => Some(mapper(v)),
+        () => None
+    )
+}
+
+export const count = <T>(option: Option<T>) => Number(isSome(option))
+
+export const exists = <T>(predicate: Predicate<T>, option: Option<T>) => {
+    return match(option, predicate, () => false)
+}
+
+export const filter = <T>(predicate: Predicate<T>, option: Option<T>) => {
+    return match(
+        option,
+        v => (predicate(v) ? Some(v) : None),
+        () => None
+    )
+}
+
+export const fold = <T, U>(
+    folder: Folder<T, U>,
+    initial: U,
+    option: Option<T>
+) => {
+    match(
+        option,
+        v => folder(initial, v),
+        () => initial
+    )
+}
+
+export const foldback = <T, U>(
+    folder: BackFolder<T, U>,
+    option: Option<T>,
+    initial: U
+) => {
+    return match(
+        option,
+        v => folder(v, initial),
+        () => initial
+    )
+}
+
+export const forall = <T>(predicate: Predicate<T>, option: Option<T>) => {
+    return match(option, predicate, () => true)
+}
+
+export const get = <T>(option: Option<T>) => {
+    return match(
+        option,
+        v => v,
+        () => {
+            throw new Error('Cannot get value from None')
+        }
+    )
+}
+
+export const iter = <T>(mapper: Mapper<T, void>, option: Option<T>) => {
+    match(option, mapper, () => {})
+}
+
+export const toArray = <T>(option: Option<T>) => {
+    return match(
+        option,
+        v => [v],
+        () => []
+    )
+}
+
+export const toNullable = <T>(option: Option<T>) => {
+    return match(
+        option,
+        v => v,
+        () => null
+    )
+}

typescript/option/src/index.ts

@@ -0,0 +1,2 @@
+export * from './helpers'
+export * from './types'

typescript/option/src/internalTypes.ts

@@ -0,0 +1,7 @@
+import { Option } from './types'
+
+export type Mapper<T, U> = (v: T) => U
+export type Binder<T, U> = Mapper<T, Option<U>>
+export type Predicate<T> = Mapper<T, boolean>
+export type Folder<T, U> = (s: U, v: T) => U
+export type BackFolder<T, U> = (v: T, s: U) => U

typescript/option/src/internals.ts

@@ -0,0 +1,17 @@
+export const isOption = Symbol('option')
+export const someValue = Symbol('value')
+
+export class SomeClass<T> {
+    public [isOption] = true
+    public [someValue]: T
+
+    public constructor(value: T) {
+        this[someValue] = value
+    }
+}
+
+export class NoneClass {
+    public [isOption] = true
+}
+
+export default { NoneClass, SomeClass, isOption, someValue }

typescript/option/src/types.ts

@@ -0,0 +1,6 @@
+import * as Internals from './internals'
+
+export type Option<T> = Internals.SomeClass<T> | Internals.NoneClass
+
+export const None = new Internals.NoneClass()
+export const Some = <T>(v: T) => new Internals.SomeClass(v)