| 1 | 'use strict'; |
| 2 | |
| 3 | //------------------------------------------------------------------------------ |
| 4 | // Requirements |
| 5 | //------------------------------------------------------------------------------ |
| 6 | |
| 7 | //------------------------------------------------------------------------------ |
| 8 | // Helpers |
| 9 | //------------------------------------------------------------------------------ |
| 10 | |
| 11 | /** |
| 12 | * Checks whether or not a given segment is reachable. |
| 13 | * @param {CodePathSegment} segment A segment to check. |
| 14 | * @returns {boolean} `true` if the segment is reachable. |
| 15 | */ |
| 16 | function isReachable(segment) { |
| 17 | return segment.reachable; |
| 18 | } |
| 19 | |
| 20 | //------------------------------------------------------------------------------ |
| 21 | // Public Interface |
| 22 | //------------------------------------------------------------------------------ |
| 23 | |
| 24 | /** |
| 25 | * A code path segment. |
| 26 | */ |
| 27 | class CodePathSegment { |
| 28 | /** |
| 29 | * @param {string} id An identifier. |
| 30 | * @param {CodePathSegment[]} allPrevSegments An array of the previous segments. |
| 31 | * This array includes unreachable segments. |
| 32 | * @param {boolean} reachable A flag which shows this is reachable. |
| 33 | */ |
| 34 | constructor(id, allPrevSegments, reachable) { |
| 35 | /** |
| 36 | * The identifier of this code path. |
| 37 | * Rules use it to store additional information of each rule. |
| 38 | * @type {string} |
| 39 | */ |
| 40 | this.id = id; |
| 41 | |
| 42 | /** |
| 43 | * An array of the next segments. |
| 44 | * @type {CodePathSegment[]} |
| 45 | */ |
| 46 | this.nextSegments = []; |
| 47 | |
| 48 | /** |
| 49 | * An array of the previous segments. |
| 50 | * @type {CodePathSegment[]} |
| 51 | */ |
| 52 | this.prevSegments = allPrevSegments.filter(isReachable); |
| 53 | |
| 54 | /** |
| 55 | * An array of the next segments. |
| 56 | * This array includes unreachable segments. |
| 57 | * @type {CodePathSegment[]} |
| 58 | */ |
| 59 | this.allNextSegments = []; |
| 60 | |
| 61 | /** |
| 62 | * An array of the previous segments. |
| 63 | * This array includes unreachable segments. |
| 64 | * @type {CodePathSegment[]} |
| 65 | */ |
| 66 | this.allPrevSegments = allPrevSegments; |
| 67 | |
| 68 | /** |
| 69 | * A flag which shows this is reachable. |
| 70 | * @type {boolean} |
| 71 | */ |
| 72 | this.reachable = reachable; |
| 73 | |
| 74 | // Internal data. |
| 75 | Object.defineProperty(this, 'internal', { |
| 76 | value: { |
| 77 | used: false, |
| 78 | loopedPrevSegments: [], |
| 79 | }, |
| 80 | }); |
| 81 | } |
| 82 | |
| 83 | /** |
| 84 | * Checks a given previous segment is coming from the end of a loop. |
| 85 | * @param {CodePathSegment} segment A previous segment to check. |
| 86 | * @returns {boolean} `true` if the segment is coming from the end of a loop. |
| 87 | */ |
| 88 | isLoopedPrevSegment(segment) { |
| 89 | return this.internal.loopedPrevSegments.includes(segment); |
| 90 | } |
| 91 | |
| 92 | /** |
| 93 | * Creates the root segment. |
| 94 | * @param {string} id An identifier. |
| 95 | * @returns {CodePathSegment} The created segment. |
| 96 | */ |
| 97 | static newRoot(id) { |
| 98 | return new CodePathSegment(id, [], true); |
| 99 | } |
| 100 | |
| 101 | /** |
| 102 | * Creates a segment that follows given segments. |
| 103 | * @param {string} id An identifier. |
| 104 | * @param {CodePathSegment[]} allPrevSegments An array of the previous segments. |
| 105 | * @returns {CodePathSegment} The created segment. |
| 106 | */ |
| 107 | static newNext(id, allPrevSegments) { |
| 108 | return new CodePathSegment( |
| 109 | id, |
| 110 | CodePathSegment.flattenUnusedSegments(allPrevSegments), |
| 111 | allPrevSegments.some(isReachable), |
| 112 | ); |
| 113 | } |
| 114 | |
| 115 | /** |
| 116 | * Creates an unreachable segment that follows given segments. |
| 117 | * @param {string} id An identifier. |
| 118 | * @param {CodePathSegment[]} allPrevSegments An array of the previous segments. |
| 119 | * @returns {CodePathSegment} The created segment. |
| 120 | */ |
| 121 | static newUnreachable(id, allPrevSegments) { |
| 122 | const segment = new CodePathSegment( |
| 123 | id, |
| 124 | CodePathSegment.flattenUnusedSegments(allPrevSegments), |
| 125 | false, |
| 126 | ); |
| 127 | |
| 128 | /* |
| 129 | * In `if (a) return a; foo();` case, the unreachable segment preceded by |
| 130 | * the return statement is not used but must not be remove. |
| 131 | */ |
| 132 | CodePathSegment.markUsed(segment); |
| 133 | |
| 134 | return segment; |
| 135 | } |
| 136 | |
| 137 | /** |
| 138 | * Creates a segment that follows given segments. |
| 139 | * This factory method does not connect with `allPrevSegments`. |
| 140 | * But this inherits `reachable` flag. |
| 141 | * @param {string} id An identifier. |
| 142 | * @param {CodePathSegment[]} allPrevSegments An array of the previous segments. |
| 143 | * @returns {CodePathSegment} The created segment. |
| 144 | */ |
| 145 | static newDisconnected(id, allPrevSegments) { |
| 146 | return new CodePathSegment(id, [], allPrevSegments.some(isReachable)); |
| 147 | } |
| 148 | |
| 149 | /** |
| 150 | * Makes a given segment being used. |
| 151 | * |
| 152 | * And this function registers the segment into the previous segments as a next. |
| 153 | * @param {CodePathSegment} segment A segment to mark. |
| 154 | * @returns {void} |
| 155 | */ |
| 156 | static markUsed(segment) { |
| 157 | if (segment.internal.used) { |
| 158 | return; |
| 159 | } |
| 160 | segment.internal.used = true; |
| 161 | |
| 162 | let i; |
| 163 | |
| 164 | if (segment.reachable) { |
| 165 | for (i = 0; i < segment.allPrevSegments.length; ++i) { |
| 166 | const prevSegment = segment.allPrevSegments[i]; |
| 167 | |
| 168 | prevSegment.allNextSegments.push(segment); |
| 169 | prevSegment.nextSegments.push(segment); |
| 170 | } |
| 171 | } else { |
| 172 | for (i = 0; i < segment.allPrevSegments.length; ++i) { |
| 173 | segment.allPrevSegments[i].allNextSegments.push(segment); |
| 174 | } |
| 175 | } |
| 176 | } |
| 177 | |
| 178 | /** |
| 179 | * Marks a previous segment as looped. |
| 180 | * @param {CodePathSegment} segment A segment. |
| 181 | * @param {CodePathSegment} prevSegment A previous segment to mark. |
| 182 | * @returns {void} |
| 183 | */ |
| 184 | static markPrevSegmentAsLooped(segment, prevSegment) { |
| 185 | segment.internal.loopedPrevSegments.push(prevSegment); |
| 186 | } |
| 187 | |
| 188 | /** |
| 189 | * Replaces unused segments with the previous segments of each unused segment. |
| 190 | * @param {CodePathSegment[]} segments An array of segments to replace. |
| 191 | * @returns {CodePathSegment[]} The replaced array. |
| 192 | */ |
| 193 | static flattenUnusedSegments(segments) { |
| 194 | const done = Object.create(null); |
| 195 | const retv = []; |
| 196 | |
| 197 | for (let i = 0; i < segments.length; ++i) { |
| 198 | const segment = segments[i]; |
| 199 | |
| 200 | // Ignores duplicated. |
| 201 | if (done[segment.id]) { |
| 202 | continue; |
| 203 | } |
| 204 | |
| 205 | // Use previous segments if unused. |
| 206 | if (!segment.internal.used) { |
| 207 | for (let j = 0; j < segment.allPrevSegments.length; ++j) { |
| 208 | const prevSegment = segment.allPrevSegments[j]; |
| 209 | |
| 210 | if (!done[prevSegment.id]) { |
| 211 | done[prevSegment.id] = true; |
| 212 | retv.push(prevSegment); |
| 213 | } |
| 214 | } |
| 215 | } else { |
| 216 | done[segment.id] = true; |
| 217 | retv.push(segment); |
| 218 | } |
| 219 | } |
| 220 | |
| 221 | return retv; |
| 222 | } |
| 223 | } |
| 224 | |
| 225 | module.exports = CodePathSegment; |