unsafe.ts

export type Unsafe<T> = Error | T;

export function match<T, TResult>(input: Unsafe<T>, succ: (t: T) => TResult, err: (err: Error) => TResult): TResult {
    if (input instanceof Error) {
        return err(input);
    }
    return succ(input as T);
}

export function matcher<T>(input: Unsafe<T>): IMatcher<T> {
    return new Matcher(input);
}

interface IRightMatcherContext<TResult> {
    left(act: (err: Error) => TResult): TResult;
}

class RightMatcherContext<T, TResult> implements IRightMatcherContext<TResult> {

    private right: (t: T) => TResult;
    private input: Unsafe<T>;

    constructor(input: Unsafe<T>, right: (t: T) => TResult) {
        this.right = right;
        this.input = input;
    }

    public left(act: (err: Error) => TResult): TResult {
        return match(this.input, this.right, act);
    }
}

interface IMatcher<T> {
    ifLeft(act: (err: Error) => void): void;
    ifRight(act: (t: T) => void): void;

    right<TResult>(act: (t: T) => TResult): RightMatcherContext<T, TResult>;
}

class Matcher<T> implements IMatcher<T> {
    private input: Unsafe<T>;

    constructor(input: Unsafe<T>) {
        this.input = input;
    }

    public ifLeft(act: (err: Error) => void): void {
        if (this.input instanceof Error) {
            act(this.input);
        }
    }

    public ifRight(act: (t: T) => void): void {
        if (!(this.input instanceof Error)) {
            act(this.input as T);
        }
    }

    public right<TResult>(act: (t: T) => TResult): RightMatcherContext<T, TResult> {
        throw new Error("Method not implemented.");
    }
}