Implement Option

2024-05-21 15:40:45 +02:00
parent ede55607e9
commit e09f4364b5
3 changed files with 184 additions and 0 deletions
@@ -0,0 +1,113 @@
+import logger from 'log'
+import {Result} from './result'
+
+const log = logger('option')
+
+export class Option<T> {
+    // *****************************************************************************************************************
+    // Constructors
+    private constructor(
+        private readonly data: T | null,
+        private readonly _state: State,
+    ) {}
+    public static some<T>(data: T) : Option<T> {
+        return new Option(data, State.Some)
+    }
+    public static none<T>() : Option<T> {
+        return new Option<T>(null, State.None)
+    }
+
+    // *****************************************************************************************************************
+    // some
+    public is_some() : boolean {
+        return this._state === State.Some
+    }
+    public is_some_and(f: (data: T) => boolean) : boolean {
+        return this._state === State.Some && f(this.data as T)
+    }
+    public expect(msg: string) : T {
+        log.trace("expect")
+
+        if (this._state === State.Some) {
+            return this.data as T
+        }
+
+        log.warn(msg)
+        throw new Error(msg)
+    }
+    public unwrap() : T {
+        log.trace("unwrap")
+        return this.expect("called unwrap on a None value")
+    }
+    public unwrap_or(default_: T) : T {
+        if (this._state === State.Some) return this.data as T
+        return default_
+    }
+    public unwrap_or_else(f: () => T) : T {
+        if (this._state === State.Some) return this.data as T
+        return f()
+    }
+
+    //  *****************************************************************************************************************
+    // none
+    public is_none() : boolean {
+        return this._state === State.None
+    }
+
+    //  *****************************************************************************************************************
+    // map
+    public map<U>(f: (data: T) => U) : Option<U> {
+        if (this._state === State.Some) return Option.some(f(this.data as T))
+        return Option.none()
+    }
+    public map_or<U>(default_: U, f: (data: T) => U) : U {
+        if (this._state === State.Some) return f(this.data as T)
+        return default_
+    }
+    public map_or_else<U>(default_: () => U, f: (data: T) => U) : U {
+        if (this._state === State.Some) return f(this.data as T)
+        return default_()
+    }
+    public ok_or<E>(err: E) : Result<T, E> {
+        if (this._state === State.Some) return Result.ok(this.data as T)
+        return Result.error(err)
+    }
+    public ok_or_else<E>(err: () => E) : Result<T, E> {
+        if (this._state === State.Some) return Result.ok(this.data as T)
+        return Result.error(err())
+    }
+    public and<U>(optb: Option<U>) : Option<U> {
+        if (this._state === State.Some) return optb
+        return Option.none()
+    }
+    public and_then<U>(f: (data: T) => Option<U>) : Option<U> {
+        if (this._state === State.Some) return f(this.data as T)
+        return Option.none()
+    }
+    public filter(f: (data: T) => boolean) : Option<T> {
+        if (this._state === State.Some && f(this.data as T)) return this
+        return Option.none()
+    }
+    public or(optb: Option<T>) : Option<T> {
+        if (this._state === State.Some) return this
+        return optb
+    }
+    public or_else(f: () => Option<T>) : Option<T> {
+        if (this._state === State.Some) return this
+        return f()
+    }
+    public xor(optb: Option<T>) : Option<T> {
+        if (this._state === optb._state) return Option.none()
+        else if (this._state === State.Some) return this
+        return optb
+    }
+
+    public get state() : State {
+        return this._state
+    }
+}
+
+export enum State {
+    Some,
+    None,
+}