264 lines
8.6 KiB
JavaScript
264 lines
8.6 KiB
JavaScript
/**
|
|
* @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;
|