[Pisces] / string.js

// ♓🌟 Piscēs ∷ string.js
// ====================================================================
//
// Copyright © 2022 Lady [@ Lady’s Computer].
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at <https://mozilla.org/MPL/2.0/>.

import { bind, call, identity, makeCallable } from "./function.js";
import {
  defineOwnProperties,
  getPrototype,
  objectCreate,
  setPrototype,
} from "./object.js";

export const {
  /**
   * A RegExp·like object which only matches entire strings, and may
   * have additional constraints specified.
   *
   * Matchers are callable objects and will return true if they are
   * called with a string that they match, and false otherwise.
   * Matchers will always return false if called with nonstrings,
   * although other methods like `exec` coerce their arguments and may
   * still return true.
   */
  Matcher,
} = (() => {
  const RE = RegExp;
  const { prototype: rePrototype } = RE;
  const { exec: reExec, toString: reToString } = rePrototype;
  const getDotAll =
    Object.getOwnPropertyDescriptor(rePrototype, "dotAll").get;
  const getGlobal =
    Object.getOwnPropertyDescriptor(rePrototype, "global").get;
  const getHasIndices =
    Object.getOwnPropertyDescriptor(rePrototype, "hasIndices").get;
  const getIgnoreCase =
    Object.getOwnPropertyDescriptor(rePrototype, "ignoreCase").get;
  const getMultiline =
    Object.getOwnPropertyDescriptor(rePrototype, "multiline").get;
  const getSource =
    Object.getOwnPropertyDescriptor(rePrototype, "source").get;
  const getSticky =
    Object.getOwnPropertyDescriptor(rePrototype, "sticky").get;
  const getUnicode =
    Object.getOwnPropertyDescriptor(rePrototype, "unicode").get;

  const Matcher = class extends identity {
    #constraint;
    #regExp;

    /**
     * Constructs a new Matcher from the provided source.
     *
     * If the provided source is a regular expression, then it must
     * have the unicode flag set. Otherwise, it is interpreted as the
     * string source of a regular expression with the unicode flag set.
     *
     * Other flags are taken from the provided regular expression
     * object, if any are present.
     *
     * A name for the matcher may be provided as the second argument.
     *
     * A callable constraint on acceptable inputs may be provided as a
     * third argument. If provided, it will be called with three
     * arguments whenever a match appears successful: first, the string
     * being matched, second, the match result, and third, the Matcher
     * object itself. If the return value of this call is falsey, then
     * the match will be considered a failure.
     *
     * ☡ If the provided source regular expression uses nongreedy
     * quantifiers, it may not match the whole string even if a match
     * with the whole string is possible. Surround the regular
     * expression with `^(?:` and `)$` if you don’t want nongreedy
     * regular expressions to fail when shorter matches are possible.
     */
    constructor(source, name = undefined, constraint = null) {
      super(
        ($) => {
          if (typeof $ !== "string") {
            // The provided value is not a string.
            return false;
          } else {
            // The provided value is a string. Set the `lastIndex` of
            // the regular expression to 0 and see if the first attempt
            // at a match matches the whole string and passes the
            // provided constraint (if present).
            regExp.lastIndex = 0;
            const result = call(reExec, regExp, [$]);
            return result?.[0] === $ &&
              (constraint === null || constraint($, result, this));
          }
        },
      );
      const regExp = this.#regExp = (() => {
        try {
          call(reExec, source, [""]); // throws if source not a RegExp
        } catch {
          return new RE(`${source}`, "u");
        }
        const unicode = call(getUnicode, source, []);
        if (!unicode) {
          // The provided regular expression does not have a unicode
          // flag.
          throw new TypeError(
            `Piscēs: Cannot create Matcher from non‐Unicode RegExp: ${source}`,
          );
        } else {
          // The provided regular expression has a unicode flag.
          return new RE(source);
        }
      })();
      if (constraint !== null && typeof constraint !== "function") {
        throw new TypeError(
          "Piscēs: Cannot construct Matcher: Constraint is not callable.",
        );
      } else {
        this.#constraint = constraint;
        return defineOwnProperties(
          setPrototype(this, matcherPrototype),
          {
            lastIndex: {
              configurable: false,
              enumerable: false,
              value: 0,
              writable: false,
            },
            name: {
              value: name != null
                ? `${name}`
                : `Matcher(${call(reToString, regExp, [])})`,
            },
          },
        );
      }
    }

    /** Gets whether the dotAll flag is present on this Matcher. */
    get dotAll() {
      return call(getDotAll, this.#regExp, []);
    }

    /**
     * Executes this Matcher on the provided value and returns the
     * result if there is a match, or null otherwise.
     *
     * Matchers only match if they can match the entire value on the
     * first attempt.
     *
     * ☡ The match result returned by this method will be the same as
     * that passed to the constraint function—and may have been
     * modified by said function prior to being returned.
     */
    exec($) {
      const regExp = this.#regExp;
      const constraint = this.#constraint;
      const string = `${$}`;
      regExp.lastIndex = 0;
      const result = call(reExec, regExp, [string]);
      if (
        result?.[0] === string &&
        (constraint === null || constraint(string, result, this))
      ) {
        // The entire string was matched and the constraint, if
        // present, returned a truthy value.
        return result;
      } else {
        // The entire string was not matched or the constraint returned
        // a falsey value.
        return null;
      }
    }

    /** Gets whether the global flag is present on this Matcher. */
    get global() {
      return call(getGlobal, this.#regExp, []);
    }

    /** Gets whether the hasIndices flag is present on this Matcher. */
    get hasIndices() {
      return call(getHasIndices, this.#regExp, []);
    }

    /** Gets whether the ignoreCase flag is present on this Matcher. */
    get ignoreCase() {
      return call(getIgnoreCase, this.#regExp, []);
    }

    /** Gets whether the multiline flag is present on this Matcher. */
    get multiline() {
      return call(getMultiline, this.#regExp, []);
    }

    /** Gets the regular expression source for this Matcher. */
    get source() {
      return call(getSource, this.#regExp, []);
    }

    /** Gets whether the sticky flag is present on this Matcher. */
    get sticky() {
      return call(getSticky, this.#regExp, []);
    }

    /**
     * Gets whether the unicode flag is present on this Matcher.
     *
     * ※ This will always be true.
     */
    get unicode() {
      return call(getUnicode, this.#regExp, []);
    }
  };
  const matcherPrototype = setPrototype(
    Matcher.prototype,
    rePrototype,
  );

  return { Matcher };
})();

export const {
  /**
   * Returns the result of converting the provided value to A·S·C·I·I
   * lowercase.
   */
  asciiLowercase,

  /**
   * Returns the result of converting the provided value to A·S·C·I·I
   * uppercase.
   */
  asciiUppercase,
} = (() => {
  const {
    toLowerCase: stringToLowercase,
    toUpperCase: stringToUppercase,
  } = String.prototype;
  return {
    asciiLowercase: ($) =>
      stringReplaceAll(
        `${$}`,
        /[A-Z]/gu,
        makeCallable(stringToLowercase),
      ),
    asciiUppercase: ($) =>
      stringReplaceAll(
        `${$}`,
        /[a-z]/gu,
        makeCallable(stringToUppercase),
      ),
  };
})();

export const {
  /**
   * Returns an iterator over the code units in the string
   * representation of the provided value.
   */
  codeUnits,

  /**
   * Returns an iterator over the codepoints in the string
   * representation of the provided value.
   */
  codepoints,

  /**
   * Returns an iterator over the scalar values in the string
   * representation of the provided value.
   *
   * Codepoints which are not valid Unicode scalar values are replaced
   * with U+FFFF.
   */
  scalarValues,

  /**
   * Returns the result of converting the provided value to a string of
   * scalar values by replacing (unpaired) surrogate values with
   * U+FFFD.
   */
  scalarValueString,
} = (() => {
  const {
    iterator: iteratorSymbol,
    toStringTag: toStringTagSymbol,
  } = Symbol;
  const { [iteratorSymbol]: arrayIterator } = Array.prototype;
  const arrayIteratorPrototype = Object.getPrototypeOf(
    [][iteratorSymbol](),
  );
  const { next: arrayIteratorNext } = arrayIteratorPrototype;
  const iteratorPrototype = Object.getPrototypeOf(
    arrayIteratorPrototype,
  );
  const { [iteratorSymbol]: stringIterator } = String.prototype;
  const stringIteratorPrototype = Object.getPrototypeOf(
    ""[iteratorSymbol](),
  );
  const { next: stringIteratorNext } = stringIteratorPrototype;

  /**
   * An iterator object for iterating over code values (either code
   * units or codepoints) in a string.
   *
   * ※ This class is not exposed, although its methods are (through
   * the prototypes of string code value iterator objects).
   */
  const StringCodeValueIterator = class extends identity {
    #allowSurrogates;
    #baseIterator;

    /**
     * Constructs a new string code value iterator from the provided
     * base iterator.
     *
     * If the provided base iterator is an array iterator, this is a
     * code unit iterator.  If the provided iterator is a string
     * iterator and surrogates are allowed, this is a codepoint
     * iterator. If the provided iterator is a string iterator and
     * surrogates are not allowed, this is a scalar value iterator.
     */
    constructor(baseIterator, allowSurrogates = true) {
      super(objectCreate(stringCodeValueIteratorPrototype));
      this.#allowSurrogates = !!allowSurrogates;
      this.#baseIterator = baseIterator;
    }

    /** Provides the next code value in the iterator. */
    next() {
      const baseIterator = this.#baseIterator;
      switch (getPrototype(baseIterator)) {
        case arrayIteratorPrototype: {
          // The base iterator is iterating over U·C·S characters.
          const {
            value: ucsCharacter,
            done,
          } = call(arrayIteratorNext, baseIterator, []);
          return done
            ? { value: undefined, done: true }
            : { value: getCodeUnit(ucsCharacter, 0), done: false };
        }
        case stringIteratorPrototype: {
          // The base iterator is iterating over Unicode characters.
          const {
            value: character,
            done,
          } = call(stringIteratorNext, baseIterator, []);
          if (done) {
            // The base iterator has been exhausted.
            return { value: undefined, done: true };
          } else {
            // The base iterator provided a character; yield the
            // codepoint.
            const codepoint = getCodepoint(character, 0);
            return {
              value: this.#allowSurrogates || codepoint <= 0xD7FF ||
                  codepoint >= 0xE000
                ? codepoint
                : 0xFFFD,
              done: false,
            };
          }
        }
        default: {
          // Should not be possible!
          throw new TypeError(
            "Piscēs: Unrecognized base iterator type in %StringCodeValueIterator%.",
          );
        }
      }
    }
  };

  const {
    next: stringCodeValueIteratorNext,
  } = StringCodeValueIterator.prototype;
  const stringCodeValueIteratorPrototype = objectCreate(
    iteratorPrototype,
    {
      next: {
        configurable: true,
        enumerable: false,
        value: stringCodeValueIteratorNext,
        writable: true,
      },
      [toStringTagSymbol]: {
        configurable: true,
        enumerable: false,
        value: "String Code Value Iterator",
        writable: false,
      },
    },
  );
  const scalarValueIterablePrototype = {
    [iteratorSymbol]() {
      return {
        next: bind(
          stringCodeValueIteratorNext,
          new StringCodeValueIterator(
            call(stringIterator, this.source, []),
            false,
          ),
          [],
        ),
      };
    },
  };

  return {
    codeUnits: ($) =>
      new StringCodeValueIterator(call(arrayIterator, `${$}`, [])),
    codepoints: ($) =>
      new StringCodeValueIterator(
        call(stringIterator, `${$}`, []),
        true,
      ),
    scalarValues: ($) =>
      new StringCodeValueIterator(
        call(stringIterator, `${$}`, []),
        false,
      ),
    scalarValueString: ($) =>
      stringFromCodepoints(...objectCreate(
        scalarValueIterablePrototype,
        { source: { value: `${$}` } },
      )),
  };
})();

/**
 * Returns an iterator over the codepoints in the string representation
 * of the provided value according to the algorithm of
 * String::[Symbol.iterator].
 */
export const characters = makeCallable(
  String.prototype[Symbol.iterator],
);

/**
 * Returns the character at the provided position in the string
 * representation of the provided value according to the algorithm of
 * String::codePointAt.
 */
export const getCharacter = ($, pos) => {
  const codepoint = getCodepoint($, pos);
  return codepoint == null
    ? undefined
    : stringFromCodepoints(codepoint);
};

/**
 * Returns the code unit at the provided position in the string
 * representation of the provided value according to the algorithm of
 * String::charAt.
 */
export const getCodeUnit = makeCallable(String.prototype.charCodeAt);

/**
 * Returns the codepoint at the provided position in the string
 * representation of the provided value according to the algorithm of
 * String::codePointAt.
 */
export const getCodepoint = makeCallable(String.prototype.codePointAt);

/**
 * Returns the index of the first occurrence of the search string in
 * the string representation of the provided value according to the
 * algorithm of String::indexOf.
 */
export const getFirstSubstringIndex = makeCallable(
  String.prototype.indexOf,
);

/**
 * Returns the index of the last occurrence of the search string in the
 * string representation of the provided value according to the
 * algorithm of String::lastIndexOf.
 */
export const getLastSubstringIndex = makeCallable(
  String.prototype.lastIndexOf,
);

/**
 * Returns the result of joining the provided iterable.
 *
 * If no separator is provided, it defaults to ",".
 *
 * If a value is nullish, it will be stringified as the empty string.
 */
export const join = (() => {
  const { join: arrayJoin } = Array.prototype;
  const join = ($, separator = ",") =>
    call(arrayJoin, [...$], [`${separator}`]);
  return join;
})();

export const {
  /**
   * Returns a string created from the raw value of the tagged template
   * literal.
   *
   * ※ This is an alias for String.raw.
   */
  raw: rawString,

  /**
   * Returns a string created from the provided code units.
   *
   * ※ This is an alias for String.fromCharCode.
   */
  fromCharCode: stringFromCodeUnits,

  /**
   * Returns a string created from the provided codepoints.
   *
   * ※ This is an alias for String.fromCodePoint.
   */
  fromCodePoint: stringFromCodepoints,
} = String;

/**
 * Returns the result of splitting the provided value on A·S·C·I·I
 * whitespace.
 */
export const splitOnASCIIWhitespace = ($) =>
  stringSplit(stripAndCollapseASCIIWhitespace($), " ");

/**
 * Returns the result of splitting the provided value on commas,
 * trimming A·S·C·I·I whitespace from the resulting tokens.
 */
export const splitOnCommas = ($) =>
  stringSplit(
    stripLeadingAndTrailingASCIIWhitespace(
      stringReplaceAll(
        `${$}`,
        /[\n\r\t\f ]*,[\n\r\t\f ]*/gu,
        ",",
      ),
    ),
    ",",
  );

/**
 * Returns the result of catenating the string representations of the
 * provided values, returning a new string according to the algorithm
 * of String::concat.
 */
export const stringCatenate = makeCallable(String.prototype.concat);

/**
 * Returns whether the string representation of the provided value ends
 * with the provided search string according to the algorithm of
 * String::endsWith.
 */
export const stringEndsWith = makeCallable(String.prototype.endsWith);

/**
 * Returns whether the string representation of the provided value
 * contains the provided search string according to the algorithm of
 * String::includes.
 */
export const stringIncludes = makeCallable(String.prototype.includes);

/**
 * Returns the result of matching the string representation of the
 * provided value with the provided matcher according to the algorithm
 * of String::match.
 */
export const stringMatch = makeCallable(String.prototype.match);

/**
 * Returns the result of matching the string representation of the
 * provided value with the provided matcher according to the algorithm
 * of String::matchAll.
 */
export const stringMatchAll = makeCallable(String.prototype.matchAll);

/**
 * Returns the normalized form of the string representation of the
 * provided value according to the algorithm of String::matchAll.
 */
export const stringNormalize = makeCallable(
  String.prototype.normalize,
);

/**
 * Returns the result of padding the end of the string representation
 * of the provided value padded until it is the desired length
 * according to the algorithm of String::padEnd.
 */
export const stringPadEnd = makeCallable(String.prototype.padEnd);

/**
 * Returns the result of padding the start of the string representation
 * of the provided value padded until it is the desired length
 * according to the algorithm of String::padStart.
 */
export const stringPadStart = makeCallable(String.prototype.padStart);

/**
 * Returns the result of repeating the string representation of the
 * provided value the provided number of times according to the
 * algorithm of String::repeat.
 */
export const stringRepeat = makeCallable(String.prototype.repeat);

/**
 * Returns the result of replacing the string representation of the
 * provided value with the provided replacement, using the provided
 * matcher and according to the algorithm of String::replace.
 */
export const stringReplace = makeCallable(String.prototype.replace);

/**
 * Returns the result of replacing the string representation of the
 * provided value with the provided replacement, using the provided
 * matcher and according to the algorithm of String::replaceAll.
 */
export const stringReplaceAll = makeCallable(
  String.prototype.replaceAll,
);

/**
 * Returns the result of searching the string representation of the
 * provided value using the provided matcher and according to the
 * algorithm of String::search.
 */
export const stringSearch = makeCallable(String.prototype.search);

/**
 * Returns a slice of the string representation of the provided value
 * according to the algorithm of String::slice.
 */
export const stringSlice = makeCallable(String.prototype.slice);

/**
 * Returns the result of splitting of the string representation of the
 * provided value on the provided separator according to the algorithm
 * of String::split.
 */
export const stringSplit = makeCallable(String.prototype.split);

/**
 * Returns whether the string representation of the provided value
 * starts with the provided search string according to the algorithm of
 * String::startsWith.
 */
export const stringStartsWith = makeCallable(
  String.prototype.startsWith,
);

/**
 * Returns the `[[StringData]]` of the provided value.
 *
 * ☡ This function will throw if the provided object does not have a
 * `[[StringData]]` internal slot.
 */
export const stringValue = makeCallable(String.prototype.valueOf);

/**
 * Returns the result of stripping leading and trailing A·S·C·I·I
 * whitespace from the provided value and collapsing other A·S·C·I·I
 * whitespace in the string representation of the provided value.
 */
export const stripAndCollapseASCIIWhitespace = ($) =>
  stripLeadingAndTrailingASCIIWhitespace(
    stringReplaceAll(
      `${$}`,
      /[\n\r\t\f ]+/gu,
      " ",
    ),
  );

/**
 * Returns the result of stripping leading and trailing A·S·C·I·I
 * whitespace from the string representation of the provided value.
 */
export const stripLeadingAndTrailingASCIIWhitespace = (() => {
  const { exec: reExec } = RegExp.prototype;
  return ($) =>
    call(reExec, /^[\n\r\t\f ]*([^]*?)[\n\r\t\f ]*$/u, [$])[1];
})();

/**
 * Returns a substring of the string representation of the provided
 * value according to the algorithm of String::substring.
 */
export const substring = makeCallable(String.prototype.substring);

/**
 * Returns the result of converting the provided value to a string.
 *
 * ☡ This method throws for symbols and other objects without a string
 * representation.
 */
export const toString = ($) => `${$}`;