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- /**
- * @fileoverview The CodePathSegment class.
- * @author Toru Nagashima
- */
-
- "use strict";
-
- //------------------------------------------------------------------------------
- // Requirements
- //------------------------------------------------------------------------------
-
- const debug = require("./debug-helpers");
-
- //------------------------------------------------------------------------------
- // Helpers
- //------------------------------------------------------------------------------
-
- /**
- * Checks whether or not a given segment is reachable.
- * @param {CodePathSegment} segment A segment to check.
- * @returns {boolean} `true` if the segment is reachable.
- */
- function isReachable(segment) {
- return segment.reachable;
- }
-
- //------------------------------------------------------------------------------
- // Public Interface
- //------------------------------------------------------------------------------
-
- /**
- * A code path segment.
- *
- * Each segment is arranged in a series of linked lists (implemented by arrays)
- * that keep track of the previous and next segments in a code path. In this way,
- * you can navigate between all segments in any code path so long as you have a
- * reference to any segment in that code path.
- *
- * When first created, the segment is in a detached state, meaning that it knows the
- * segments that came before it but those segments don't know that this new segment
- * follows it. Only when `CodePathSegment#markUsed()` is called on a segment does it
- * officially become part of the code path by updating the previous segments to know
- * that this new segment follows.
- */
- class CodePathSegment {
-
- /**
- * Creates a new instance.
- * @param {string} id An identifier.
- * @param {CodePathSegment[]} allPrevSegments An array of the previous segments.
- * This array includes unreachable segments.
- * @param {boolean} reachable A flag which shows this is reachable.
- */
- constructor(id, allPrevSegments, reachable) {
-
- /**
- * The identifier of this code path.
- * Rules use it to store additional information of each rule.
- * @type {string}
- */
- this.id = id;
-
- /**
- * An array of the next reachable segments.
- * @type {CodePathSegment[]}
- */
- this.nextSegments = [];
-
- /**
- * An array of the previous reachable segments.
- * @type {CodePathSegment[]}
- */
- this.prevSegments = allPrevSegments.filter(isReachable);
-
- /**
- * An array of all next segments including reachable and unreachable.
- * @type {CodePathSegment[]}
- */
- this.allNextSegments = [];
-
- /**
- * An array of all previous segments including reachable and unreachable.
- * @type {CodePathSegment[]}
- */
- this.allPrevSegments = allPrevSegments;
-
- /**
- * A flag which shows this is reachable.
- * @type {boolean}
- */
- this.reachable = reachable;
-
- // Internal data.
- Object.defineProperty(this, "internal", {
- value: {
-
- // determines if the segment has been attached to the code path
- used: false,
-
- // array of previous segments coming from the end of a loop
- loopedPrevSegments: []
- }
- });
-
- /* c8 ignore start */
- if (debug.enabled) {
- this.internal.nodes = [];
- }/* c8 ignore stop */
- }
-
- /**
- * Checks a given previous segment is coming from the end of a loop.
- * @param {CodePathSegment} segment A previous segment to check.
- * @returns {boolean} `true` if the segment is coming from the end of a loop.
- */
- isLoopedPrevSegment(segment) {
- return this.internal.loopedPrevSegments.includes(segment);
- }
-
- /**
- * Creates the root segment.
- * @param {string} id An identifier.
- * @returns {CodePathSegment} The created segment.
- */
- static newRoot(id) {
- return new CodePathSegment(id, [], true);
- }
-
- /**
- * Creates a new segment and appends it after the given segments.
- * @param {string} id An identifier.
- * @param {CodePathSegment[]} allPrevSegments An array of the previous segments
- * to append to.
- * @returns {CodePathSegment} The created segment.
- */
- static newNext(id, allPrevSegments) {
- return new CodePathSegment(
- id,
- CodePathSegment.flattenUnusedSegments(allPrevSegments),
- allPrevSegments.some(isReachable)
- );
- }
-
- /**
- * Creates an unreachable segment and appends it after the given segments.
- * @param {string} id An identifier.
- * @param {CodePathSegment[]} allPrevSegments An array of the previous segments.
- * @returns {CodePathSegment} The created segment.
- */
- static newUnreachable(id, allPrevSegments) {
- const segment = new CodePathSegment(id, CodePathSegment.flattenUnusedSegments(allPrevSegments), false);
-
- /*
- * In `if (a) return a; foo();` case, the unreachable segment preceded by
- * the return statement is not used but must not be removed.
- */
- CodePathSegment.markUsed(segment);
-
- return segment;
- }
-
- /**
- * Creates a segment that follows given segments.
- * This factory method does not connect with `allPrevSegments`.
- * But this inherits `reachable` flag.
- * @param {string} id An identifier.
- * @param {CodePathSegment[]} allPrevSegments An array of the previous segments.
- * @returns {CodePathSegment} The created segment.
- */
- static newDisconnected(id, allPrevSegments) {
- return new CodePathSegment(id, [], allPrevSegments.some(isReachable));
- }
-
- /**
- * Marks a given segment as used.
- *
- * And this function registers the segment into the previous segments as a next.
- * @param {CodePathSegment} segment A segment to mark.
- * @returns {void}
- */
- static markUsed(segment) {
- if (segment.internal.used) {
- return;
- }
- segment.internal.used = true;
-
- let i;
-
- if (segment.reachable) {
-
- /*
- * If the segment is reachable, then it's officially part of the
- * code path. This loops through all previous segments to update
- * their list of next segments. Because the segment is reachable,
- * it's added to both `nextSegments` and `allNextSegments`.
- */
- for (i = 0; i < segment.allPrevSegments.length; ++i) {
- const prevSegment = segment.allPrevSegments[i];
-
- prevSegment.allNextSegments.push(segment);
- prevSegment.nextSegments.push(segment);
- }
- } else {
-
- /*
- * If the segment is not reachable, then it's not officially part of the
- * code path. This loops through all previous segments to update
- * their list of next segments. Because the segment is not reachable,
- * it's added only to `allNextSegments`.
- */
- for (i = 0; i < segment.allPrevSegments.length; ++i) {
- segment.allPrevSegments[i].allNextSegments.push(segment);
- }
- }
- }
-
- /**
- * Marks a previous segment as looped.
- * @param {CodePathSegment} segment A segment.
- * @param {CodePathSegment} prevSegment A previous segment to mark.
- * @returns {void}
- */
- static markPrevSegmentAsLooped(segment, prevSegment) {
- segment.internal.loopedPrevSegments.push(prevSegment);
- }
-
- /**
- * Creates a new array based on an array of segments. If any segment in the
- * array is unused, then it is replaced by all of its previous segments.
- * All used segments are returned as-is without replacement.
- * @param {CodePathSegment[]} segments The array of segments to flatten.
- * @returns {CodePathSegment[]} The flattened array.
- */
- static flattenUnusedSegments(segments) {
- const done = new Set();
-
- for (let i = 0; i < segments.length; ++i) {
- const segment = segments[i];
-
- // Ignores duplicated.
- if (done.has(segment)) {
- continue;
- }
-
- // Use previous segments if unused.
- if (!segment.internal.used) {
- for (let j = 0; j < segment.allPrevSegments.length; ++j) {
- const prevSegment = segment.allPrevSegments[j];
-
- if (!done.has(prevSegment)) {
- done.add(prevSegment);
- }
- }
- } else {
- done.add(segment);
- }
- }
-
- return [...done];
- }
- }
-
- module.exports = CodePathSegment;
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