X-Git-Url: https://git.ladys.computer/Pisces/blobdiff_plain/2989f964f0325a2d9c9294a8d3dab722313d5518..6e6d4e3261c1c943fe44fa9e381bcf8bf1441fd6:/string.js

diff --git a/string.js b/string.js
index d65d294..eb6f6fb 100644
--- a/string.js
+++ b/string.js
@@ -1,14 +1,252 @@
 // ♓🌟 Piscēs ∷ string.js
 // ====================================================================
 //
-// Copyright © 2022 Lady [@ Lady’s Computer].
+// Copyright © 2022–2023 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 { getPrototype, objectCreate } from "./object.js";
+import {
+  defineOwnProperties,
+  getOwnPropertyDescriptors,
+  getPrototype,
+  objectCreate,
+  setPrototype,
+} from "./object.js";
+import { type } from "./value.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 getFlags =
+    Object.getOwnPropertyDescriptor(rePrototype, "flags").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 the flags present on this Matcher.
+     *
+     * ※ This needs to be defined because the internal RegExp object
+     * may have flags which are not yet recognized by ♓🌟 Piscēs.
+     */
+    get flags() {
+      return call(getFlags, this.#regExp, []);
+    }
+
+    /** 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 matcherConstructor = defineOwnProperties(
+    class extends RegExp {
+      constructor(...args) {
+        return new Matcher(...args);
+      }
+    },
+    {
+      name: { value: "Matcher" },
+      length: { value: 1 },
+    },
+  );
+  const matcherPrototype = defineOwnProperties(
+    matcherConstructor.prototype,
+    getOwnPropertyDescriptors(Matcher.prototype),
+    { constructor: { value: matcherConstructor } },
+  );
+
+  return { Matcher: matcherConstructor };
+})();
 
 export const {
   /**
@@ -94,7 +332,8 @@ export const {
    * An iterator object for iterating over code values (either code
    * units or codepoints) in a string.
    *
-   * ※ This constructor is not exposed.
+   * ※ This class is not exposed, although its methods are (through
+   * the prototypes of string code value iterator objects).
    */
   const StringCodeValueIterator = class extends identity {
     #allowSurrogates;
@@ -199,21 +438,21 @@ export const {
 
   return {
     codeUnits: ($) =>
-      new StringCodeValueIterator(call(arrayIterator, $, [])),
+      new StringCodeValueIterator(call(arrayIterator, `${$}`, [])),
     codepoints: ($) =>
       new StringCodeValueIterator(
-        call(stringIterator, $, []),
+        call(stringIterator, `${$}`, []),
         true,
       ),
     scalarValues: ($) =>
       new StringCodeValueIterator(
-        call(stringIterator, $, []),
+        call(stringIterator, `${$}`, []),
         false,
       ),
     scalarValueString: ($) =>
       stringFromCodepoints(...objectCreate(
         scalarValueIterablePrototype,
-        { source: { value: $ } },
+        { source: { value: `${$}` } },
       )),
   };
 })();
@@ -478,3 +717,11 @@ export const stripLeadingAndTrailingASCIIWhitespace = (() => {
  * 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 = ($) => `${$}`;