⛓️ Chain functions as arrays

chain.ts

export type Fn<Input = any, Output = any> = (input: Input) => Output;

export type Chain<Fns extends Fn[]> =
  // We chain two functions at one time
  Fns extends [infer Fn1, infer Fn2, ...infer RestFns]
    ? // Make sure two elements are functions
      Fn1 extends Fn<infer Fn1Argument>
      ? Fn2 extends Fn<infer Fn2Argument>
        ? RestFns extends Fn[]
          ? // Rest of the elements exist
            [Fn<Fn1Argument, Fn2Argument>, ...Chain<[Fn2, ...RestFns]>]
          : // Only two elements
            [Fn<Fn1Argument, Fn2Argument>, Fn2]
        : // Second element not a function
          [Fn1]
      : // First element not a function
        never
    : // Seems like we don't have two elements
    Fns extends [infer Fn]
    ? [Fn]
    : // The only element is not a function
      never;

// Try chaining functions in an array on this function.
function chain<Fns extend Fn[]>(...fns: Fns & Chain<Fns>) {}