sequence-js/src/comparer/sync.ts

import { Converter } from "../types.js";
import { Nullable } from "../utils.js";
import { fromSync } from "./async.js";
import { Comparer, ComparisonOrComparer, Comparison, AsyncComparer } from "./types.js";

export function isComparer<T>(obj: any): obj is Comparer<T> {
  return obj instanceof BaseComparer;
}

export function asComparer<T>(comparer: ComparisonOrComparer<T>) {
  return typeof comparer === "function" ? createComparer(comparer) : comparer;
}

export function asComparison<T>(comparer: ComparisonOrComparer<T>) {
  return typeof comparer === "function" ? comparer : comparer.comparison();
}

export function createComparer<T = any>(comparison: Comparison<T>): Comparer<T> {
  return new SimpleComparer(comparison);
}

export function createComparerUsing<T = any, U = any>(projection: Converter<T, U>, comparison?: ComparisonOrComparer<U>): Comparer<T> {
  return new MappedComparer(projection, comparison);
}

export function reverseComparison<T>(comparison: Comparison<T>): Comparison<T> {
  return (a, b) => comparison(b, a);
}

export function combineNullableComparers<T>(comparers: Nullable<ComparisonOrComparer<T>>[]) {
  let result = defaultComparer;

  for (const comparer of comparers) {
    if (!comparer) {
      continue;
    }

    result = result.then(asComparer(comparer));
  }

  return result === defaultComparer ? undefined : result;
}

export abstract class BaseComparer<T> implements Comparer<T> {
  #cachedBoundComparison: Comparison<T> | undefined;

  public abstract compare(a: T, b: T): number;

  public comparison(): Comparison<T> {
    return this.#cachedBoundComparison ??= this.compare.bind(this);
  }

  public reverse(): Comparer<T> {
    return new ReversedComparer(this);
  }

  public then(comparer: Comparer<T>): Comparer<T> {
    return new ThenComparer(this, comparer);
  }

  public thenCompare(comparison: Comparison<T>): Comparer<T> {
    return this.then(createComparer(comparison));
  }

  public thenCompareUsing<U>(projection: Converter<T, U>, comparison?: ComparisonOrComparer<U>): Comparer<T> {
    return this.then(createComparerUsing(projection, comparison));
  }

  public toAsync(): AsyncComparer<T> {
    return fromSync<T>(this);
  }

  public nullAwareComparer(): Comparer<Nullable<T>> {
    return new NullAwareComparer(this);
  }
}

class SimpleComparer<T> extends BaseComparer<T> {
  readonly #comparison: Comparison<T>;

  public constructor(comparison: Comparison<T>) {
    super();

    this.#comparison = comparison;
  }

  public override compare(a: T, b: T) {
    return this.#comparison(a, b);
  }

  public override comparison() {
    return this.#comparison;
  }
}

class MappedComparer<T, U> extends BaseComparer<T> {
  readonly #projection: Converter<T, U>;
  readonly #comparison: Comparer<U>;

  public constructor(projection: Converter<T, U>, comparison?: ComparisonOrComparer<U>) {
    super();

    this.#projection = projection;
    this.#comparison = comparison ? asComparer(comparison) : defaultComparer;
  }

  public override compare(a: T, b: T) {
    return this.#comparison.compare(this.#projection(a), this.#projection(b));
  }
}

class ReversedComparer<T> extends BaseComparer<T> {
  readonly #base: Comparer<T>;

  public constructor(base: Comparer<T>) {
    super();

    this.#base = base;
  }

  public override compare(a: T, b: T): number {
    return this.#base.compare(b, a);
  }

  public override reverse(): Comparer<T> {
    return this.#base;
  }
}

class ThenComparer<T> extends BaseComparer<T> {
  readonly #base: Comparer<T>;
  readonly #comparer: Comparer<T>;

  public constructor(base: Comparer<T>, comparer: Comparer<T>) {
    super();

    this.#base = base;
    this.#comparer = comparer;
  }

  public override compare(a: T, b: T) {
    return this.#base.compare(a, b) || this.#comparer.compare(a, b);
  }
}

export const defaultComparer: Comparer<any> = new class DefaultComparer extends BaseComparer<any> {
  public override compare(a: any, b: any): number {
    if (a === undefined) {
      if (b === undefined) {
        return 0;
      }

      return 1;
    }

    if (b === undefined) {
      return -1;
    }

    const aStr = `${a}`, bStr = `${b}`;

    return aStr > bStr ? 1 : aStr < bStr ? -1 : 0;
  }
};

export function getDefaultComparer<T>(): Comparer<T> {
  return defaultComparer;
}

class NullAwareComparer<T> extends BaseComparer<Nullable<T>> {
  readonly #base: Comparer<T>;

  constructor(baseComparer: Comparer<T>) {
    super();

    this.#base = baseComparer;
  }

  public override compare(a: Nullable<T>, b: Nullable<T>): number {
    if (a === undefined) {
      if (b === undefined) {
        return 0;
      }

      return 1;
    }

    if (b === undefined) {
      return -1;
    }

    if (a === null) {
      if (b === null) {
        return 0;
      }

      return 1;
    }

    if (b === null) {
      return -1;
    }

    return this.#base.compare(a, b);
  }

  public override nullAwareComparer(): Comparer<Nullable<T>> {
    return this;
  }
}

export function nullAwareComparer<T>(baseComparer: Comparer<T>): Comparer<Nullable<T>> {
  return new NullAwareComparer(baseComparer);
}

export const stringComparer: Comparer<string> = new class StringComparer extends BaseComparer<string> {
  public override compare(a: string, b: string): number {
    return a.localeCompare(b);
  }
};

export const numberComparer: Comparer<number> = new class NumberComparer extends BaseComparer<number> {
  public override compare(a: number, b: number): number {
    return a - b;
  }
};

export const bigintComparer: Comparer<bigint> = new class BigIntComparer extends BaseComparer<bigint> {
  public override compare(a: bigint, b: bigint): number {
    return Number(a - b);
  }
};

export const booleanComparer: Comparer<boolean> = new class BooleanComparer extends BaseComparer<boolean> {
  public override compare(a: boolean, b: boolean): number {
    return Number(a) - Number(b);
  }
};

export const dateComparer: Comparer<Date> = new class DateComparer extends BaseComparer<Date> {
  public override compare(a: Date, b: Date): number {
    return a.getTime() - b.getTime();
  }
};